# Circle dimensions with different bits

**URL:** <https://community.inventables.com/t/circle-dimensions-with-different-bits/35148>\
**Category:** Uncategorized\
**Created:** [March 11, 2017, 8:47pm UTC](https://community.inventables.com/t/circle-dimensions-with-different-bits/35148 "2017-03-11T20:47:39Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Traxxtar](https://yyz1.discourse-cdn.com/flex009/user_avatar/community.inventables.com/traxxtar/32/67235_2.png) [@Traxxtar](https://community.inventables.com/u/Traxxtar)\
**Post date:** [March 11, 2017, 8:47pm UTC](https://community.inventables.com/t/circle-dimensions-with-different-bits/35148/1 "2017-03-11T20:47:39Z")

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Mac Mini host using Easel w/3.3 driver, 1.0c GRBL firmware  
Machine is calibrated. When I send X or Y 100mm, it’s precisely 100mm in movement in both directions.

Problem: just trying to carve a single .25" hole.  
using 1/16 upcut bit, the hole is .15" too small  
using 1/8" upcut, the hole is .15" too small  
using 1/8" straight bit, the hole is .18" too small  
using 1/8" fishtail/upcut the hole is .2 too small  
using 1/8" engraving bit(don’t ask), the hole is a perfect.

The size of the hole is specified in Easel as .25" ‘Fill’ cut.

NO changes to anything other than the bit.

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**Author:** ![Traxxtar](https://yyz1.discourse-cdn.com/flex009/user_avatar/community.inventables.com/traxxtar/32/67235_2.png) [@Traxxtar](https://community.inventables.com/u/Traxxtar)\
**Post date:** [March 11, 2017, 9:19pm UTC](https://community.inventables.com/t/circle-dimensions-with-different-bits/35148/2 "2017-03-11T21:19:56Z")

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So here’s a ‘noob’ finding.

Just because the bit is 1/8" doesn’t mean the cutting diameter is 1/8"!! The 1/8" refers to the shank size. When you select 1/16, 1/8" bits in Easel, it appears to use exactly 1/16 or 1/8" as the cutting radius. That’s bogus.

If I measure the cutting part of the bit, the 1/8" bit is .118. When I specify an “Other” bit and use those measurements, the circles come out perfect.

Easel needs to be modified to make you measure your bits every time. I’ll never use the default bit sizes again!!!

Gee thanks, I just wasted $40 on some nice Katalox too finding this out.

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**Author:** ![Traxxtar](https://yyz1.discourse-cdn.com/flex009/user_avatar/community.inventables.com/traxxtar/32/67235_2.png) [@Traxxtar](https://community.inventables.com/u/Traxxtar)\
**Post date:** [March 11, 2017, 10:08pm UTC](https://community.inventables.com/t/circle-dimensions-with-different-bits/35148/4 "2017-03-11T22:08:48Z")

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Disagree that $40 was not wasted or that Easel defaults to shank measurements instead of actual cutting measurements?

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**Author:** ![JDM](https://yyz1.discourse-cdn.com/flex009/user_avatar/community.inventables.com/jdm/32/84169_2.png) [@JDM](https://community.inventables.com/u/JDM)\
**Post date:** [March 11, 2017, 10:28pm UTC](https://community.inventables.com/t/circle-dimensions-with-different-bits/35148/8 "2017-03-11T22:28:26Z")

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This is an issue for every CNC machine, CAM software package and manufacturer out there.

Easel defaults to standard bit sizes just like Meshcam, Fusion360, EstlCam and any other. You could order 10 bits from the same manufacturer and they could all be off a little.

I understand your frustration, though.

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**Author:** ![Traxxtar](https://yyz1.discourse-cdn.com/flex009/user_avatar/community.inventables.com/traxxtar/32/67235_2.png) [@Traxxtar](https://community.inventables.com/u/Traxxtar)\
**Post date:** [March 11, 2017, 11:17pm UTC](https://community.inventables.com/t/circle-dimensions-with-different-bits/35148/9 "2017-03-11T23:17:24Z")

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Thanks guys. Just a bit of a learning curve I suppose, that’s all.