# Changing bit size

**URL:** <https://forum.onefinitycnc.com/t/changing-bit-size/32749>\
**Category:** Uncategorized\
**Created:** [April 27, 2025, 5:39pm UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749 "2025-04-27T17:39:28Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Warrior1035](https://avatars.discourse-cdn.com/v4/letter/w/a88e4f/32.png) [@Warrior1035](https://forum.onefinitycnc.com/u/Warrior1035)\
**Post date:** [April 27, 2025, 5:39pm UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749/1 "2025-04-27T17:39:28Z")

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Question: after setting the xyz for a 1/8 bit then changing tool paths to a 1/4 inch do you only have to set the z or do something different when changing to a 1/4 in bit? Thanks

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**Author:** ![avacado](https://avatars.discourse-cdn.com/v4/letter/a/e47774/32.png) [@avacado](https://forum.onefinitycnc.com/u/avacado)\
**Post date:** [April 27, 2025, 6:22pm UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749/2 "2025-04-27T18:22:31Z")

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Never change the X/Y, only Z.

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**Author:** ![Warrior1035](https://avatars.discourse-cdn.com/v4/letter/w/a88e4f/32.png) [@Warrior1035](https://forum.onefinitycnc.com/u/Warrior1035)\
**Post date:** [April 27, 2025, 10:03pm UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749/3 "2025-04-27T22:03:48Z")

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Thanks for the reply. When you set the XYZ it lets you pick the size of the bit your using like the 1/4. After completing y at tool path and you want to switch to a 1/8 bit do you have to recalibrate it since your now using a smaller bit size 1/8 in the menu

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**Author:** ![umbert](https://avatars.discourse-cdn.com/v4/letter/u/6f9a4e/32.png) [@umbert](https://forum.onefinitycnc.com/u/umbert)\
**Post date:** [April 27, 2025, 10:49pm UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749/4 "2025-04-27T22:49:22Z")

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nope, no calibration needed, except Z. Probe for Z, that’s it.

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**Author:** ![BuckeyeDennis](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@BuckeyeDennis](https://forum.onefinitycnc.com/u/BuckeyeDennis)\
**Post date:** [April 27, 2025, 11:24pm UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749/5 "2025-04-27T23:24:24Z")

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Elaborating a little on the othe responses, when you calibrate X & Y, you are actually calibrating the position of the spindle _ **centerline** _. Changing to a different bit diameter doesn’t change the centerline, hence no recalibration of X &Y is needed. Or even wanted, for that matter, as it could introduce small relative-offset errors in features machined with the different bits.

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**Author:** ![Warrior1035](https://avatars.discourse-cdn.com/v4/letter/w/a88e4f/32.png) [@Warrior1035](https://forum.onefinitycnc.com/u/Warrior1035)\
**Post date:** [April 27, 2025, 11:34pm UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749/6 "2025-04-27T23:34:52Z")

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Thank’s everyone, I really appreciate the response!!!

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**Author:** ![mrkrag](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.onefinitycnc.com/mrkrag/32/30927_2.png) [@mrkrag](https://forum.onefinitycnc.com/u/mrkrag)\
**Post date:** [April 28, 2025, 12:30am UTC](https://forum.onefinitycnc.com/t/changing-bit-size/32749/7 "2025-04-28T00:30:34Z")

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Your toolpaths account for the diameter of the tool. Everything is based on the center line. You only re zero Z because once you change tools it is not impossible but highly unlikely it is at the same depth as the previous one.