Chamfering 101

September 4, 2020 3:41 pm

A chamfer is a specific type of edge. Chamfering is the process in developing that edge and what one could argue, a unique yet very common application. A chamfer edge is made up of a flat edge meeting a 45-degree angle.

A chamfer edge improves visual properties, but it is also a practical option for reasons other than appearance. This particular type of edge makes it less susceptible to damage and is sturdier than a filet and bevel edge. Additionally, chamfering is great for creating edges that can join seamlessly. For example, if two workpieces have to be welded together at a specific angle, it is easier for those edges to come together if they are chamfered and thus comply with any required dimensional accuracy.

A chamfer edge has two similar counterparts called bevel and fillet who offer similar functions, as they all produce a smooth edge. Chamfer, bevel, and fillet are often compared but they do not resemble one another much at all. They are alike in that their purpose is to smooth edges that can be extremely sharp and dangerous. Technically, all a deburring process. So, what’s the difference between the three? This can be easily articulated through a visual.

Image Credit: CNC Cookbook

The filet edge is a rounded (radiused) edge. And lastly a bevel edge is when the entire edge is flat, with no vertical wall to break it up (like the chamfer edge).

Chamfered holes

Chamfer holes most commonly created so that a certain assembly component can be inserted into the hole. This could be a bushing, a pin, a screw etc. For threaded holes, chamfering will prevent a raised burr from developing which would interfere with the mating part’s insertion. If say the part was inserted with a burr present, it could force the burr down and thus damage the thread.

“Cross-sections of countersunk holes of various chamfer angles” – Image Credit:

Chamfering best practices

Though chamfering can be done with a hand tool, it would be a primitive choice. Your best bet is to chamfer your edges with a chamfer mill. However, if you’re working on a hole you will be using a drill or spot drill  typically with a solid stainless steel or carbide body.

Sometimes it can be tempting to rely on the accuracy of the machine and think you can skip the finishing step, instead of using a setup meant for chamfering. Taking the risk of using tooling that isn’t meant for a chamfer job, simply isn’t worth the risk. There are many options available when it comes to chamfering mills and spot drills, so do your homework and invest in quality. You want to look for a chamfer tool is that is built to withstand optimized feeds and speeds, and for the tool to be multi-functional. For example, having inserts that work for both back and front chamfering won’t require very involved setup changes. Those types of features of a chamfer tool will save you time with sped up cycles and money because you won’t deal with broken inserts left and right. Lastly, the quality tools only add to delivering quality and competitive parts to your customers.

Tools to support your chamfering process

Dial indicating chamfer diameter gage

These internal and external chamfer tools will help you determine the top diameter of chamfered holes.

Starrett Reading Internal Chamfer Gauge

Starrett Inch Reading Dial Indicator Internal Chamfer Gage

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All surfaces are made of hardened tool steel. This internal gage will measure the largest diameter of any chamfer that features an angle within the range of the dial (maximum measurement is 0-1”). This tool comes with a padded case for safe keeping.

Starrett  External Chamfer Gauge

Starrett 685-3Z Inch Reading External Chamfer Gauge

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The only difference between this Starrett chamfer gage and the one before, besides this having a measuring range of 1” – 2” is that this chamfer gage is for external chamfer measuring.

Brencor Angle Range Dial Chamfer-Chek

Brencor 1090 0-1″ Capacity 0-90° Angle Range Dial Chamfer-Chek®


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Another chamfer gage option. This one weighing a bit more than the Starrett at 2 pounds. The same maximum measurement 0-1”. According to Amazon’s product review, this tool is ranked #2 in the chamfer gages category.


If you are not dealing with a countersink or hole, it is likely you can use a micrometer to meet your measuring needs. For example, measuring rectangular chamfer edge can be done with a depth micrometer. To really dig into those options, you can read our article What You Need to Know About Depth Micrometers. Here’s a peek of the micrometers recommended.

Starrett 440Z-6RL Vernier Depth Gauge

Starrett Depth Micrometer with Ratchet Stop and Locknut

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This complete set comes with 12 interchangeable rods that allow you to measure depths up to 12”. It comes with a ring-type knurled lock nut, ratchet as well as a speeder for stability and to apply uniform pressure and make quick adjustments for precise measurements.

Mitutoyo 129-149 Vernier Depth Gauge

Mitutoyo 129-149 Vernier Depth Gauge

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This set also comes with 12 interchangeable rods that allow for measurements up to 12” in depth. The diameter of the rods (0.157”) is slightly bigger than the Starrett model but will still allow you to measure almost any type of recess.


Some practical Machinist members mentioned how their eyes “aren’t what they used to be.” In regard to reading the gauges. If you can relate to that perhaps you’ll consider…

Headband Magnifier Headset

Headband Magnifier Headset

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This headset features real glass lenses and enough space to be worn over prescription glasses. The headset is made with an adjustable strap and form fitting comfort for extended periods of time.


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1 Comment

  • john f says:

    I did the turning of the knobs for the rebuild of the Bombe at Blechley Park. The knobs have
    knurled surfaces. The drawings do not mention any chamfering but I found the best looking result for
    a knurled knob to be 60 deg rather than the usual 45.

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