Brandon Fowler, Author at Machinist Guides

Bilateral Tolerance Guide [Examples & Explanation]

May 6, 2022December 4, 2021 by Brandon Fowler

What is a bilateral tolerance?

A bilateral tolerance is a plus or minus tolerance (+/-). It allows variation from the nominal size in both a positive and negative direction.

In most cases, the bilateral tolerance will be specified as equal in both directions such as 10.0mm +/- 0.5mm.

This is not always the case though and a bilateral tolerance does not need to have equal positive and negative tolerances. 10.0mm +0.2mm/-0.3mm would be an acceptable bilateral tolerance as well.

Here are some quick bilateral tolerance examples:

5.5″ +/- 0.25″
5.5″ +1.0″/-0.5″

25.5mm +0.1mm/-0.2mm
30.6mm +/- 0.3mm

Notice that in each of the examples there is allowed variation (tolerance) from the nominal size in both directions.

A tolerance of 25.5mm +0/-0.2mm would not be a bilateral tolerance because it has no tolerance in the positive direction. This would be an example of a unilateral tolerance.

Bilateral tolerance symbol

There is no GD&T symbol for a bilateral tolerance.

Per ASME Y14.5, the notation for a bilateral tolerance is to show a plus and a minus tolerance associated with a nominal dimension and neither of them is a zero.

Want to learn how to type GD&T symbols with no special fonts needed?

How to read a bilateral tolerance

Let’s start with our examples from above

5.5″ +/- 0.25″

5.5″ +1.0″/-0.5″
25.5mm +0.1mm/-0.2mm
30.6mm +/- 0.3mm

Now let’s break it down so you can see what the nominal size is as well as the top and bottom ends of the tolerance zone.

Nominal Size	Bottom of Tolerance	Top of Tolerance
5.5"	5.25"	5.75"
5.5"	5.0"	6.5"
25.5mm	25.3mm	25.6mm
30.6mm	30.3mm	30.9mm

Bilateral tolerance examples

Types of bilateral tolerances

Equal bilateral tolerance

An equal bilateral tolerance will have equal plus and minus tolerances such as 6.35 +/- 0.025 as shown in the example above.

Unequal bilateral tolerance

An unequal bilateral tolerance will have plus and minus tolerances that are not the same and neither is zero such as 17.0 +0.1/-0.2 as shown in the example above.

Bilateral tolerances compared to other tolerance types

Bilateral tolerance vs unilateral tolerance

A bilateral tolerance allows a tolerance in both directions.

A unilateral tolerance allows a tolerance in only one direction.

A bilateral tolerance is plus AND minus tolerance. A unilateral tolerance is a plus OR minus tolerance.

Here are some examples of unilateral tolerances:

10.0mm +0/+0.5mm
5.515″ +0.010″/+0.015″

2.325″ +0/-0.005″
4.5mm -0.2/-0.3mm

Bilateral tolerance vs limit tolerance

A bilateral tolerance specifies a nominal size and a plus/minus tolerance. These values are used to determine the tolerance range for a feature.

A limit tolerance skips the calculation step and simply gives you the tolerance range.

The table below shows bilateral tolerances with their equivalent limit tolerances.

Bilateral Tolerance	Limit Tolerance
10.0 +/-0.5	9.5 - 10.5
5.525 +0.025/-0.050	5.475 - 5.550
7.55 +/+0.15	7.40 - 7.70
2.324 +0.005/-0.010	2.314 - 2.329

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

For more information see these related articles:

Unilateral Tolerance Guide [Examples & Explanation]

May 6, 2022December 4, 2021 by Brandon Fowler

What is a unilateral tolerance?

Basically, a unilateral tolerance is a type of tolerance that is only allowed in one direction. Either an all plus tolerance or an all minus tolerance.

Here are some quick unilateral tolerance examples:

10.0mm +0/+0.5mm

5.515″ +0.010″/+0.015″
2.325″ +0/-0.005″
4.5mm -0.2/-0.3mm

Notice that in these examples, all of the allowed size variation is in one direction. The direction can be positive or negative and zero is allowed.

Unilateral tolerances are often used to specify dimensions that require a specific fit with a mating part.

Unilateral tolerance symbol

There is no GD&T symbol for a unilateral tolerance.

Per ASME Y14.5, the notation for a unilateral tolerance is to show a plus or a minus tolerance associated with a nominal dimension. It is acceptable for one of the specified tolerances to be zero.

Want to learn how to type GD&T symbols with no special fonts needed?

How to read a unilateral tolerance

Let’s start with our examples from above.

10.0mm +0/+0.5mm
5.515″ +0.010″/+0.015″
2.325″ +0/-0.005″

4.5mm -0.2/-0.3mm

Now let’s break it down so you can see what the nominal size is as well as the top and bottom ends of the tolerance zone.

Nominal Size	Bottom of Tolerance	Top of Tolerance
10.0mm	10.0mm	10.5mm
5.515"	5.525"	5.530"
2.325"	2.320"	2.325"
4.5mm	4.2mm	4.3mm

Regardless of what the nominal size is, the requirement for each of these unilateral tolerance examples would be that the dimension must fall within the top and bottom tolerance range.

Unilateral tolerances compared to other tolerance types

Unilateral tolerance vs bilateral tolerance

A bilateral tolerance allows a tolerance in both directions.

A unilateral tolerance allows a tolerance in only one direction.

A bilateral tolerance is plus AND minus. A unilateral tolerance is a plus OR minus tolerance.

If we take the unilateral tolerance from the picture above and convert it to a bilateral tolerance it could be either:

39.75 +/- 0.25
39.7 +0.3/-0.2

39.6 +0.4/-0.1

Notice that the important feature of the tolerance is that it has both a positive and negative tolerance. Neither side of the tolerance is zero.

Unilateral tolerance vs limit tolerance

A unilateral tolerance specifies a nominal size and a plus or minus tolerance. These values are used to determine the tolerance range for a feature.

A limit tolerance skips the calculation step and simply gives you the tolerance range. Instead of a nominal size and a tolerance, the top and bottom of the tolerance range are directly listed.

Let’s compare some unilateral and limit tolerances to see how they differ:

Unilateral Tolerance	Limit Tolerance
10.0 +0/-0.5	9.5 - 10.0
5.525 +0.025/+0.050	5.550 - 5.575
7.55 +0/+0.15	7.55 - 7.70
2.324 -0.005/-0.010	2.314 - 2.319

What is a unilateral tolerance used for?

A unilateral tolerance is most often used to specify a tolerance associated with a specific fit such as a clearance fit or interference fit.

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

For more information see these related articles:

Best CNC and Machining Books

Ultimate Guide to Measuring Caliper Accuracy

February 10, 2022November 25, 2021 by Brandon Fowler

Measuring calipers can be extremely capable measuring devices when in the right hands.

Knowing the limitations of your calipers and how you affect them is what will make you the “right hands” for the job.

I’m going to run you through the different aspects that affect caliper accuracy. I’ll start with the most basic topics and work from there so feel free to skip ahead if you already know about a subject.

Size of calipers

0-6" calipers

The most common type of measuring caliper is a 0-6” caliper. If you are working in metric, this will be a 0-300mm caliper.

There is some variety in what they are capable of but in general they will be able to measure inside, outside and depth measurements over a 6” measuring range.

Larger and smaller calipers

Calipers do come in many different size measuring ranges. They are used much less often but you will still run into them.

0-12” calipers are the next logical choice when it comes time to measure a bigger part. The reason you wouldn’t use them all the time is because they are big and can be awkward to use.

0-24” calipers have the same issue and are even more awkward. Typically, you would only use the larger calipers in a situation where you could not use a caliper.

There 0-4” and 0-8” varieties that can be found as well and all types of specialized measuring ranges can be special ordered.

Larger calipers will be more expensive than small calipers. The added expense is for accuracy. It gets much harder to maintain the accuracy seen in smaller calipers over larger measuring ranges.

Note: Calipers with larger measuring ranges tend to be less accurate. For example, the same Mitutoyo caliper in a 0-6” version has a specified accuracy of +/- 0.001” and the 0-24” version has an accuracy of +/- 0.002”. They are only half as accurate. This only gets worse when you realize larger calipers from lesser known manufacturers may be even less accurate.

Types of calipers

There are three main types of calipers. They are very similar with the main difference being how the actual measurement is read.

Vernier calipers

Often referred to as simply “verniers”, these calipers have multiple scales on the face of the tool that are used together to take your measurement reading.

Because they do not have any internal mechanisms, they are the most durable type of caliper and most likely to remain accurate.

Verniers are the most difficult type of caliper then it comes to reading a measurement, especially for beginners. While they are not necessarily difficult to use, they take a little more understanding than using a dial or digital caliper.

Dial calipers

Dial calipers use a geared system to spin a needle on a dial. They have an easy to ready scale on the body of the caliper. This scale is often in .100” increments. The distance between the rulings makes them easier to read compared to the small lines which are used on a vernier.

The scale reading is used with the reading from the needle on the dial face of the tool to calculate your measurement.

Dial and vernier calipers are very similar in cost. Both do not require batteries which means they are always ready to take a measurement.

Digital calipers

Digital calipers use electronic sensors to give a measurement reading. They are easily the simplest caliper to take a reading with.

The values get read off the LCD display like an alarm clock.

At one time they were very expensive and still somewhat are. In recent years, they have dropped in price and gotten more reliable. Tools made in China and other lower labor cost countries have improved in quality, though they can be hit or miss when compared to established tool and gauge companies.

There are many digital calipers available which are not nearly as accurate as they would lead you to believe. This is because their resolution is finer than their accuracy.

Typical accuracies for different types of calipers

A caliper should be accurate to .001”. There are cheap ones or shoddy quality ones that will fail to meet this accuracy but when most people think about calipers, they expect it to be accurate to .001”.

Accuracy is similar across the different types of 0-6” calipers and it may look like digital calipers have better resolution but that isn’t exactly true.

Often digital calipers will have displays that read out farther than they are accurate to. There isn’t any point taking a reading to 5 tenths of an inch or .0005” if the tool isn’t accurate to that level.

Be careful. Some digital calipers will make you think they are more accurate than they actually are.

How cost affects accuracy

Small calipers are easier to make than large ones at the same accuracy. To get a caliper accurate to .001” at 6” will be much easier than at 24”. This is why the cost goes up quickly for larger calipers or their accuracy goes down.

Some calipers will sacrifice accuracy to keep costs down. Some budget level calipers do not meet an accuracy of +/- 0.001” for a 0-6” caliper. Pay attention to the specified accuracy when comparing different tools.

Keep in mind that if something seems too good to be true then it probably is such as a cheap, large range caliper that claims accuracy to +/- 0.001”.

What tools are more accurate than a measuring caliper?

Micrometers are another tool frequently used by people who also use calipers to take measurements. The typical accuracy of a micrometer is a tenth of an inch or .0001”. This is 10x more accurate than a caliper.

Dial and test indicators are another type of tool used in machine shops. They usually have dial faces with a needle, or occasionally you will find digital versions.

The accuracy of these indicators varies from .001” for many dial indicators to .00001” for test indicators. Test indicators can be 1000x more accurate than dial indicators and calipers.

Accuracy vs resolution

Resolution is the how finely your tool will give for a reading. It is not how accurate it is.

Imagine you measure a box.

A less capable digital caliper may measure the length of the box at 6.5005”. The problem is that the caliper may only be accurate to +/- 0.001”. This means you could take that same caliper and measure the same box again, in the same exact location and get a reading of 6.4995” or 6.5015”

Tips for increasing your accuracy using calipers

Know what accuracy you need

The first step is knowing how accurate of a tool you need. You might not need a caliper at all. You might need a micrometer to measure down to a tenth (0.0001”). Maybe you can get away with using a good tape measure.

I don’t know. Only you can decide what accuracy you will need.

General advice would be to get a caliper with an accuracy of +/- 0.001” or better.

Be careful how you hold your caliper

You affect the accuracy of your caliper a lot.

You want to make sure that the jaws of your caliper sit flat when you take a measurement. If they are cock-eyed when you use them, the readings will be larger than the actual size.

Luckily, for outside measurements, such as the length or width of a part, this is easy to do. You can gently rock, again I said gently, and you will feel the caliper settle in when it sits flush.

Inside measurements are slightly more difficult because the jaws do not have a flat spot to settle into. Still, you will want to use the same rocking motion, but be even more careful with it.

Repeatability

No matter what type of measurement you plan to take, take multiple readings to develop an assurance that your measurement is accurate. It is not uncommon to take a measurement and get a reading, only to take two more measurements that are both 0.005” off.

At this point you would want to take more measurements to verify that your first measurement was indeed wrong. Maybe it was dirt, or you had the tool at an angle. Either way, verifying your repeatability will help you take more accurate measurements.

Depth measurements are easy to get wrong

Outside and inside measurements aren’t too bad but depth measurements are where things get tricky.

Not all calipers will have the ability to take depth measurements. However, for those that do it is easy to get bad readings when using them to take depth readings.

The shape of the caliper makes them top heavy which means they have a tendency to want to tilt. If your tool moves even just a small amount, it will throw your measurement off by quite a bit.

There are attachments that you can get for your caliper to help steady your tool when taking depth measurements, but they are not a perfect solution.

Another factor affecting accuracy is that the depth measuring rod on a caliper can easily get bent or otherwise out of alignment. This is a common occurrence and even brand-new calipers can come from the factory unable to make accurate depth measurements.

Depth measurements are the most difficult type of measurement to take with a caliper and also the most difficult aspect for a tool maker to build accurately.

Be consistent with your measurements

The amount of force you use when taking measurements with your calipers will change your readings. This is called your “touch”.

If you take a measurement using a small amount of pressure on the caliper and then do the same measurement squeezing the caliper shut and holding it with some force, you will see that your readings can easily vary by a thousandth or two (0.001”-0.002”).

The easiest way to practice being consistent with the force you use to take measurements is to check the same thing over and over.

Checking the accuracy of your caliper

Cheaper calipers can be accurate, but not every cheap caliper will be. Premium tools from Mitutoyo, Starrett or other well-known manufacturers can be off too, but the odds are much less likely.

The problem is that you won’t know the caliper is accurate until you check it. This process is called calibrating. If you don’t have access to everything you need to calibrate a caliper, a less precise version of the process would be called zeroing.

Zeroing your caliper

Zeroing your calipers requires you to close them all the way and reset the zero point.

Zeroing procedure

Make sure your tool is clean, especially the jaws of the caliper.

Slide the caliper closed.

For a digital caliper, hit the origin button – this will sometimes be labeled differently (such as Zero) based on the manufacturer of the caliper.

For a dial caliper, loosen the bezel lock screw, twist the dial until the needle reads zero and then lock the bezel lock screw again.

Once you have reset the zero location, make sure to verify it. Do this by opening the calipers up and then closing to the zero position again.

You want to verify that the caliper reads zero each time. The amount of pressure you put on the tool affects the measurement so make sure to use the same amount of force to close your caliper.

Consistent, gentle movements will help you get the most accurate readings out of your tool.

At this point you know your caliper is accurate at the zero location. What is not known is how that same caliper will measure at another location. It may be perfectly accurate at zero but off by ten thousandths or 0.010” at 6 inches.

This process is for your external jaws only and it is entirely possible that your jaws for measuring internal measurements such as holes may not be aligned with the external jaws. The zero location may be different for your internal and external jaws.

This is why ideally you would calibrate your calipers to verify their accuracy over the whole measuring range. Calibration requires additional equipment so many people won’t take the extra step.

What is important is to consider is what level of accuracy you need for your measurement.

Precision measuring tools = be gentle

These things are not hammers. You need to treat them gingerly. They won’t shatter into a million pieces when you set them on a bench but banging them or dropping them means you’re going to have a bad time.

The most common types of damage, all of which would affect accuracy are

Shock to the internal workings. This can cause excess drag in the mechanism or simply give bad measurements.
Damage to the jaws of the caliper such as nicks or burrs. Even a very small nick can cause your measurement to be off. The inside measurement jaws are more likely to be damaged than the outside measurement jaws.
The depth measuring rod can get bent or otherwise damaged and give bad readings. The rods tend to be long and thin which means it doesn’t take much force to damage them.

Calibration

Calibration involves taking a known length standard such as a set of gauge blocks and using them to check the accuracy of the caliper over its whole measuring range.

You would check the caliper at 0 inches, 6 inches and at random intervals between the two. This is the super simplified version of a calibration procedure. If you want a more detailed instruction, then check out our guide to caliper calibration.

For more information check out these related articles:

Beginner’s Guide To Reading Machine Shop Numbers & Values

June 25, 2022November 24, 2021 by Brandon Fowler

Confused? If you’re reading this page then I’m pretty sure you are. Dealing with numbers, values and calculations when machining or 3d printing can be hard for those just starting.

The lingo and terminology used by many people both online or at a new job can be hard to understand. My hope is that after this quick lesson in dealing with machine shop numbers, you will not only be comfortable reading your numbers and measurements but also will know how to perform some simple calculations using them.

Let's begin

First we need to understand what the numbers we are working with represent.

Whether they are a reading on a micrometer, a spec on a blueprint or a stack of gage blocks, the goal is the same.

We need to know how to read them and work with them.

Below is a graphic that shows the name (including machine shop lingo) for different values.

Pay attention to how far each number is from the decimal place when looking at the chart.

Please note that not everyone will be working down to millionths of an inch but I included them for reference. Many will only work down to the the values shown in this table.

Value	Machinist Lingo	Technical Math Term
0.001"	Thousandth or Thou	Thousandth of an Inch
0.0001"	Tenth	Ten Thousandth of an Inch

Keep in mind that all these numbers and terms apply to imperial units (inches).

How to say the value

Machine shops usually speak in terms of thousandths of an inch. Because of this when we describe the value to someone else we will read it a little different than you might expect.

As noted above, if we give the example of 7.489136″ a machinist would describe the value as 7 inch, 489 thousandths, 1 tenth, 36 millionths.

Read that last sentence over a couple times to really understand the terms your typical machine shop speaks in.

As a note, not all machine shops or hobbyists will deal in millionths of an inch and some might not even work with tenths but I have included them for reference.

Note: Thousandths of an inch is often abbreviated as “thou” especially when discussing values verbally.

Machine shop number reading examples

Below are some more examples to show how machinists communicate values:

Value	Machinist Lingo
1.325"	1 inch 325 thousandths
0.5001"	500 thousandths 1 tenth
0.021	21 thousandths
0.6532"	653 thousandths 2 tenths
9.792345"	9 inch 792 thousandths 3 tenths 45 millionths

Gage blocks

A common scenario for someone new in a machine shop is learning how to set up a stack of gage blocks.

I’m not going to show you how to pick the right gage blocks for your stack here. If you need those instructions then head over to Starrett’s website. They have great instructions that show you how to select your gage blocks and make a stack of a specific height.

The link also contains information related to the use and care of your gage blocks. Take care of your gage blocks people, those things are expensive.

How to setup calculations

Now I said I would show you how to work with these numbers, so let’s demonstrate how to do that.

The important part when dealing with numbers or values in a machine shop context is to line up the decimal point. Below you will see some examples of addition and subtraction of numbers:

Simple calculation examples

For practice, let’s list out how to say those answers!

Value	Machinist Lingo
1.610"	1 inch 610 thousandths
0.7206"	720 thousandths 6 tenths
0.6249"	624 thousandths 9 tenths

There aren’t any other special tricks here. Once you line up the decimal places everything else is just like you learned early in school. Also consider yourself lucky we have calculators.

That’s it. Now you should know how to speak in terms that a machinist would understand and use the values in simple calculations.

If you need more in depth training when it comes to machine shop math, check out the training linked below. It breaks all the hard subjects down into bite sized pieces to make them easy to understand.

Beginner’s Guide to Basic Dimensions

May 6, 2022November 24, 2021 by Brandon Fowler

Basic dimensions are shown on a blueprint enclosed in a box. But what do they mean?

Keep reading to find out.

What is a basic dimension?

A basic dimension is a theoretically exact size or location.

Basic dimensions do not have a tolerance applied to them, this includes any general tolerance blocks.

Instead a separate is listed on the drawing that uses the basic dimension.

An example of this would be a true position callout for a hole or set of holes. The basic dimension(s) specify the location of the hole.

The true position of the hole is calculated based on the difference of the actual location compared to the basic dimensions theoretically exact location.

What is a basic dimension used for?

Basic dimensions are used for calculations. They are used to calculate various geometric dimensioning and tolerancing (GD&T) characteristics such as true position, profile or angularity.

In the example above, the 120 degree callout and the 42 diameter bolt circle are the basic dimensions and the true position of 0.2 is the characteristic controlling the basic dimensions.

Using basic dimensions

How is a basic dimension shown on a drawing?

The symbol for a basic dimension is the dimension shown enclosed in a rectangular frame or box.

This is the convention identified in the blueprint drawing standard ASME Y14.5.

Some drawings may list a basic dimension not in a rectangular frame but instead the dimension will be followed by a Bsc. notation. This is more common on older drawings and does not change the way basic dimensions are used.

Basic dimension examples

Basic dimensions and tolerances

Can a basic dimension have a tolerance?

A basic dimension itself does not have a tolerance. General tolerance blocks do not apply to a basic dimension.

Instead its value is used to compute another characteristic such as angularity, profile or true position.

Basic dimensions compared to other types of dimensions

Basic dimension vs reference dimension

Basic dimensions are associated with another tolerance or dimension. While they don’t have a tolerance tied to themselves, they are used to calculate another toleranced feature such as the true position of a hole.

Reference dimensions are simply placed on a drawing or blueprint for reference. They have no tolerance associated with them. No matter how far off the given value a reference dimension is, it would never be cause for rejection.

A basic dimension being far off its nominal value would not be cause for rejection itself, but its effect on another feature referencing the basic dimension could be cause for rejection. So if a basic dimension was far off the nominal location, another tolerance would likely be out of spec.

Basic dimension vs regular dimension

Regular dimensions have a tolerance assigned to them. This can be directly assigned to the individual dimension or it can be the general tolerances. The regular dimension must fall within the limits of the tolerance.

A basic dimension is instead controlled by another characteristic. The basic dimension can vary by any amount but it must not deviate from the nominal value to the point that the other characteristic (true position callout, profile callout, etc.) is no longer within the specified limits.

How to measure a basic dimension

A basic dimension is measured just like any other dimension. The only difference is that the basic dimension doesn’t have a tolerance directly associated with it. Instead another dimension uses the basic dimension to calculate its value.

How to report basic dimensions

Do basic dimensions need to be listed on an inspection report?

While there isn’t a strict requirement anywhere to include them, I would recommend reporting their values on an inspection report.

The features have been measured and you likely already have the values. By recording them, you will provide more information and value for your customer.

You must report the feature control values such as true position, profile value, etc. that use the basic dimension to be calculated.

What about on FAIs?

The requirement for reporting basic dimensions is the same for first article inspection reports. Be aware that some customers may require them even though there is no requirement per AS9102.

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

For more information see these related articles:

Best Woods For CNC Routing

January 25, 2022November 23, 2021 by Brandon Fowler

Let’s say you have some extra time on your hands, and you decide to build your own computer. Countless people do this every year, so surely it can’t be too difficult to find the necessary materials, right?

Then you realize you’re going to need some basic electrical wiring. Would you go search through a pile of old electronics and rip out whatever you can find?

Of course not.

You’re going to go find something that is meant for your build.

The same goes for CNC routing. You can’t (or at least shouldn’t) use just any old piece of wood you see lying around.

To build a nice project, you’ll need quality material, and we are going to help you figure out which ones are right for your use. Picking the right wood is especially important when you are making things to sell with your CNC.

We do our best to run through as many different types of wood for CNC routing that we could come up with, but if you just want the short and sweet version to help you pick a wood to work with check out our list of the best woods below.

Category	Wood Type
Easiest wood for CNC routing (best for beginners)	Cherry
Best wood for CNC carving	Walnut
Best wood for CNC sign making	Cypress
Best cheap wood for CNC routing	Poplar
Best plywood for CNC routing	Birch

Below is a lengthy list of various types of woods that you can use for CNC woodworking.

While the list may not include absolutely every type of wood you might want to use, it does hit the main ones

The cost of the different woods will vary by region and availability, but we have tried our best to assign a relative cost score to them.

Cost rating system

Keep it simple right? We used a scale of 1-5 dollar signs

$ = cheaper woods

$$$$$ = very expensive woods

Alder

Cost: $

Alder wood is generally light and soft. Its structure is even with straight fibers. Highly pliant, alder wood is one of the preferred woods for furniture makers the world over.

Alder is pretty good for carving, though it can be a bit stringy at times.

Ash

Cost: $

Ash wood is strong, durable and generally light in color. It is coarse, but the grain is fairly straight. As a result of its strength and durability, ash wood has an array of uses but is commonly used in the making of tools, furniture and frames.

For routing, you might find moderate resistance with ash because it’s a stronger wood. Ash can tend to wear your cutters quicker than other, softer woods. If you’re going to use ash, make sure your cutters are sharp before you start.

Balsa

Cost: $

Balsa is the lightest and softest timber used commercially. Though it’s lightweight, balsa is also fairly coarse. It possesses an unusually high degree of buoyancy, and the wood is adaptable to a great number of special uses.

If you’re using softer balsa, it can be prone to tearing along the grain as the cutter goes past. It can also be hard to get a nicely finished edge with balsa.

Beech

Cost: $

Beech wood is known for its fine-textured straight and attractive grain, pliability, strength, and finishing ease. However, Beech wood has a fairly high shrinkage rate, which is why most beech wood ends up as paper.

When routing beech, you’ll likely want to have the router moving at a lower speed to avoid burning.

Birch

Cost: $

Birch is a stiff wood with light color and wavy grain.

When working with birch, you should go slow and take shallow passes. If routing in one direction causes a lot of splintering, turn the board around and go in the opposite direction. This hits the grain from a different direction. The splintering is caused by the bit digging into the grain. Going the other way stops that.

Birch plywood

Cost: $

For birch plywood, some good advice is to cut the chip load down to about half of what you would normally do.

You should also have your spindle speed as high as you can get it without overheating the cutting tool. For engraving, you will find that it is best to outline the toolpath first.

Cedar

Cost: $$

Cedar has a nice smell and good color, but the knots in the wood can make it a bit difficult to work with.

Also, because it’s a softer wood, you need to be careful with tear outs – this is a common problem with cedar. To avoid the tear-out issue, try doing multiple passes.

There are some who swear by soaking and freezing cedar before working with it as a way to get a better finished product.

Cherry

Cost: $$$$

Cherry wood is hard, durable, resistant to rot and decay, and has a pretty good ability to withstand shock.

It’s also easy to carve, cut, and mold.

Cherry is interesting because it is a relatively soft hardwood.

In other words, cherry wood is a fantastic option for CNC wood routing, and you’ll find that it is popular among hobbyists and professionals alike. Cherry has a reputation for being easy to work with due to its versatility.

Cyprus

Cost: $

Cypress wood is extremely soft, and a lot of woodworkers will tell you that this stuff carves like butter.

Cypress is a really great option if you’re looking at making signs. Cypress also holds up extremely well outdoors. It is a decay-resistant wood.

One downside to cypress would be that it can be a knotty wood, similar to cedar.

Elm

Cost: $$$

Elm wood has fairly open pores, which can lead to a lot of tear-outs if you’re not careful.

Some people also find Elm to be a bit stringy. However, elm is also known for being extremely tough, so if you can avoid tear-outs and your project isn’t too stringy, you will have your elm wood project for a long time to come.

Elm is a little pricier now than it used to be because “Dutch Elm Disease” wiped out a good portion of elms around the world.

Fir

Cost: $$

Fir has a nice consistent pattern and is pretty easy to work with.

Fir can have some issues with tear-outs, but most people can easily avoid these through climb cuts. Though Fir can splinter a bit, it isn’t known for having knots, which makes it easier to work with.

Mahogany

Cost: $$$$$

Many woodworkers the world over will consider genuine mahogany to be the best wood on the market.

It’s durable, stable, and looks beautiful. It’s a fairly hardwood but is easy to work with. Its mostly straight, open grains mean the wood rarely tears out.

When working with mahogany, you should go a bit slower in terms of your feeding, and don’t overload your carvers.

Maple

Cost: $$$$$

If you don’t have a ton of experience, maple can be a little bit difficult to work with.

The wood is extremely hard, so you’ll need very sharp cutters, though the maple will dull them while cutting.

You should also cut at a lower speed to prevent any burning. Though maple might be hard to work with, you’ll love the final product because it’s a beautiful wood.

MDF

Cost: $

Medium-density fiberboard is super cheap and versatile. MDF is basically sawdust and glue, so be prepared for a sandstorm when you’re working with it.

Still, people find MDF super easy to work with as it carves and cuts extremely easily.

Oak

Cost: $$$$

Oak is a heavy, hard wood that rarely breaks. Since it’s so hard, you want to be a little careful when it comes to cutting.

Make smaller passes, and take multiple passes, so you don’t break any of your bits. Also, watch out for any burning.

Paduak

Cost: $$$

You’ll really like the way padauk carves but be sure to bring a sharp bit. The reason people like to work with Padauk is that it has nice, straight grains.

One thing to watch out for when working with Padauk is the dust. When you start cutting this wood, you’ll get a lot of dust, so you might find a dust boot helpful.

Pine

Cost: $

Pine generally machines well, but sometimes certain cuts can get a little bit gummy on you.

Another thing about pine is that it’s a fuzzy wood, so it can be helpful to sand the wood down both before and after you work with it.

Making multiple passes can also reduce some of the fuzz. Pine may not be your first choice to work with, but you should learn how to machine pine because it’s reasonably cheap and available everywhere.

Pine plywood

Cost: $

Like with regular pine, again get a lot of fuzz. The benefit here, though, is that this stuff is so easy to find and it’s cheap.

Be sure not to cut too deep and take multiple passes when working with pine plywood. Patience will be key if you want the project to turn out well.

Poplar

Cost: $

Similar to pine, Poplar is widely available, cheap, and leaves behind a lot of fuzz.

So, like with Pine, be sure to sand the Poplar down well. You will also want to have sharp bits and a slower speeds and feeds to avoid any tearing.

Poplar will take paint really well, so if you’re working on a project that you’ll ultimately want to paint poplar might be your choice of wood.

Red gum

Cost: $$$

Due to its softness and low density, people generally find red gum easy to work with.

However, red gum does have interlocked fibers, so be careful to avoid tear-outs. Another criticism of red gum is that it can warp a lot when drying out.

Redwood

Cost: $$$

While Redwood is light but strong, it does splinter fairly easily. Make sure you’re using shallow cuts to avoid tear-outs.

If you’re just looking for a carving project, redwood will be fantastic due to its softness.

Spruce

Cost: $

Spruce is not really known for being great wood to route with. It splinters easily and can have hidden sap pockets that can’t be cut through and will make your bit super sticky.

With short fibers and many knots, you may find it difficult to work with spruce.

Walnut

Cost: $$$$

Walnut is a very popular wood when it comes to routing. It cuts well. If you have a sharp bit, then cutting through walnut is like passing a hot knife through butter.

Another great feature of walnut is that it is not really known to burn while routing. However, Walnut dust can be highly irritating, so be sure to protect your eyes. A dust collection system of some sort would be advised.

Western red cedar

Cost: $$$

Western red cedar has a really wide grain which can be helpful for routing. That said, this wood can easily tear out if you’re not careful. This red cedar can be a better option than regular cedar because it has fewer knots.

Another benefit of red cedar is that it is good to use for outdoor projects.

Yew

Cost: $$$$

Yew can be a tough wood to work with. For one, when yew trees grow, they can contort in a way to that creates a lot of cross-fibers, which can lead to tear-outs.

Additionally, Yew wood can come with a whole lot of knots that you’ll have to work around.

Things to consider when choosing your wood for CNC routing

Clean up

Some woods that create more fuzz – such as pine and poplar – are going to require additional sanding. You can’t just pull these woods off the machine and expect a finished product.

Other woods may not have fuzz, but the cutting action will create rough edges that have to be sanded out. Keep this in mind when creating a project timeline.

Additionally, some of these woods are heavy on the dust. All of the woods listed will create some dust, but some woods are worse than others. You’ll definitely need a shop vac or other form of dust collection in use, and it could be very helpful to have a dust boot.

Knots

A knot is a portion of a branch or limb that has become incorporated in the trunk of a tree. Knots can change the direction of the wood, which make the wood vulnerable to tear-outs.

Your machining parameters should be reduced when working with a knotted portion of the workpiece to avoid shock loading.

Before you can machine them, use 5-minute epoxy to lock loose and loosening knots into place and fill any gaps and voids. When the epoxy cures, you can saw, joint, or plane the wood without fear of knocking the knot out, or worse, sending it flying across the shop or hurting you or your machine.

Price

Depending on what wood you use, your project can skyrocket up in price.

The more exotic woods you use, the more expensive they will be.

Redwood, for example, only grows in a very specific location and environment, so that makes it rarer. Pine, on the other hand, is easily available so it’s cheap.

Expensive woods can be worth it if you’re making a nice project, but don’t spend a bunch of money on wood if you’re not sure how the project will turn out. It is best to practice with the cheap stuff until you get things more figured out.

When you do start moving up to more expensive woods, run some test cuts or small test projects to try out your setup before committing to a large project.

Where to buy wood for CNC routing

You can go to your local hardware store to check out their wood selection. Some stores will have scrap or damaged pcs that can be had for free or at a large discount.

This can be a good way to get material for a small project or for testing out cuts on different types of wood.

You can also find a lumber mill near you and see if they’ll sell you any wood. Oftentimes, lumber mills will have excess wood that they can’t use that they will sell you for cheap.

Break Edge – All About

May 6, 2022November 21, 2021 by Brandon Fowler

Table of Contents

What is a break edge?

A break edge means the removal of material, usually in the form of a chamfer or radius to remove the sharp edge.

Machining a surface will often leave a corner which can be dangerous for both the part and the part handler. Many times there will be a burr (raised piece of material), left on the edge which can be razor sharp. Using a deburring tool can break the edge to remove the sharp

A broken edge is usually specified as a maximum value or with no value at all. If no value is specified, the break edge has not been constrained sufficiently.

A break edge callout with no maximum size referenced would normally be assumed to be approximately .005-.010” though in some instances it could be larger.

What does a break edge look like?

Break edge on a physical part

In the brass cube below, notice how the corners have all the sharp edges removed. This is an example of a break edge.

Break edge on a blueprint

Break edge symbol

There is no GD&T symbol for a break edge. Break edges are also not referenced in the engineering drawing standard ASME Y14.5.

Break edge callouts are specified directly on the drawing to reference a certain surface or as a note e.g. “Break all sharp edges”.

At times, the break edge specification may be contained in the general tolerance block such as shown below.

Break edge note example

How to make a break edge

Break edge on wood

Using 180 grit fine sandpaper is the easiest way to create a break edge on a wooden workpiece. This can also be used together with a block plane to chamfer the edge and then soften it with a light sanding.

Break edge on metal

Because metal tends to be more durable, you have more choices for creating a break edge on your piece of metal.

You can use:

A chamfer deburring tool which is a specialty tool designed to remove burrs from the edges of parts

A file to knock the edge off a part
Sandpaper
A grinding wheel

A rotary tool such as a Dremel

Break edge on glass

To create a break edge on a piece of glass, use one of the following:

Diamond file

Grinding wheel
Rotary tool with diamond wheel

How to measure a break edge

Which measuring tools to use

The size of a break edge is measured the same as a standard chamfer or radius. If a measurement is required, a pocket comparator or eye loupe with a reticle are the most common inspection tools to use.

An optical comparator with or without an overlay could also be used. See the examples below to better understand how the size of a break edge would be determined.

How to measure the break edge based on your blueprint

On the left is a chamfered break edge. The size is measured from the left edge of the part to the intersection of the break edge and the top of the part. This is done in both the x and y directions (up and down, left and right).

On the right is a break edge created by a radius. The same measurement technique applies with the exception that the intersection would now be called the tangent point or point where the radius meets the straight edge.

Break edge compared to similar features

Break edge vs chamfer

The difference between a break edge dimension and a chamfer dimension is generally in the tolerancing of the two. A chamfer is usually thought of as being toleranced in a way that places tighter constraints on the feature.

Often a chamfer callout will have a tolerance associated with the angle and a break edge will not.

Break edge vs radius

A break edge can be a radius. Many times, the person or company machining the part will round the edge using a variety of techniques including tumbling, specialty tools or even sandpaper.

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

For more information see these related articles:

Beginner’s Guide to Blueprint Reading

Beginner’s Guide to GD&T Symbols

Best CNC Routers For Every Budget and Application

December 2, 2021November 19, 2021 by Brandon Fowler

Big to small, metal to wood, kits vs pre-built. There are CNC routers of all types available, but which one is right for your application?

We pick the best CNCs in a variety of categories to help you choose a quality tool that is built to last and provide the accuracy you expect. Get machining quickly with our guides.

Best Beginner CNC Routers

Just starting out?

Then keep things simple with our guide to the best starter CNCs for anyone testing the waters of CNC routing.

Best Woodworking CNCs

Want to make your own signs? Or maybe you want to be able to create some unique wooden wall art. Either way we got you covered with the best CNC routers for working with woods of all kinds.

Best CNCs for Small Spaces

Not everyone has a giant workshop. Some of us are just trying to get by machining widgets in our closet. If this is you then check our list of the best CNCs with small footprints.

Best Budget CNC Routers

Limited budget? No problem.

If you are working on a budget then we got the best value for money machines picked for you.

Learn More About CNC Coding

Guides to G codes. We got’em

More about M codes. Got that too.

Check out our list of CNC codes for guidance on every code you will need.

Best 3018 Series CNC Upgrades

Got one of the 3018 series CNCs?

Well then check out our list of awesome upgrades to make your machines more capable and your setups so much simpler.

Best CNC and Machining Books

Expand your knowledge with these essential references for anyone working with a CNC.

Includes books for everyone from beginner level to advanced.

Measuring Calipers

November 25, 2021November 18, 2021 by Brandon Fowler

Digital Calipers

Prices have dropped significantly in recent years meaning that many digital calipers are directly competing with your standard dial calipers. Find out which ones are the best of the best as well as check out our tips, tricks and calibration guides.

Dial Calipers

People have been taking precision measurement with dial calipers for decades. So why stop now? Check out our guide to dial calipers to figure out which ones are quality and which ones are just over priced. Lots of extra info so there is something for everyone.

Dial vs Digital Calipers

Analog vs Digital

Old School vs New School

Which caliper comes out on top and why? Read out comparison guide to find out.

Measuring Tools

Other

Best CNC and Machining Books

What is a bilateral tolerance?

Bilateral tolerance symbol

How to read a bilateral tolerance

Bilateral tolerance examples

Types of bilateral tolerances

Equal bilateral tolerance

Unequal bilateral tolerance

Bilateral tolerances compared to other tolerance types

Bilateral tolerance vs unilateral tolerance

Bilateral tolerance vs limit tolerance

Want to learn more?

Related articles

What is a unilateral tolerance?

Unilateral tolerance symbol

How to read a unilateral tolerance

Unilateral tolerances compared to other tolerance types

Unilateral tolerance vs bilateral tolerance

Unilateral tolerance vs limit tolerance

What is a unilateral tolerance used for?

Want to learn more?

Related articles

Size of calipers

0-6" calipers

Larger and smaller calipers

Types of calipers

Vernier calipers

Dial calipers

Digital calipers

Typical accuracies for different types of calipers

How cost affects accuracy

What tools are more accurate than a measuring caliper?

Accuracy vs resolution

Tips for increasing your accuracy using calipers

Know what accuracy you need

Be careful how you hold your caliper

Repeatability

Depth measurements are easy to get wrong

Be consistent with your measurements

Checking the accuracy of your caliper

Zeroing your caliper

Zeroing procedure

Precision measuring tools = be gentle

Calibration

Related articles

Let's begin

How to say the value

Machine shop number reading examples

Gage blocks

How to setup calculations

Simple calculation examples

Related articles

What is a basic dimension?

What is a basic dimension used for?

Using basic dimensions

How is a basic dimension shown on a drawing?

Basic dimension examples

Basic dimensions and tolerances

Can a basic dimension have a tolerance?

Basic dimensions compared to other types of dimensions

Basic dimension vs reference dimension

Basic dimension vs regular dimension

How to measure a basic dimension

How to report basic dimensions

Do basic dimensions need to be listed on an inspection report?

What about on FAIs?

Want to learn more?

Related articles

Cost rating system

Alder

Ash

Balsa

Beech

Birch

Birch plywood

Cedar

Cherry

Cyprus

Elm

Fir

Mahogany