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Author Topic: bit size vs actual bit measurement  (Read 3259 times)

Offline Mudsport96

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bit size vs actual bit measurement
« on: August 18, 2016, 03:31:46 PM »
So something I've come across is the supposed drill bit sizes. Like the 50 gage bit is supposed to be .070 but my micrometer measures it out at .0696. But it doesn't slide through the 70 jet.. So are the bits a close enough measure. Or do I need a new set of bits?
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Offline Ethan1

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Re: bit size vs actual bit measurement
« Reply #1 on: August 18, 2016, 07:40:01 PM »
Quote from: Mudsport96 on August 18, 2016, 03:31:46 PM
So something I've come across is the supposed drill bit sizes. Like the 50 gage bit is supposed to be .070 but my micrometer measures it out at .0696. But it doesn't slide through the 70 jet.. So are the bits a close enough measure. Or do I need a new set of bits?

 What part of bit are you measuring? What brand? What .0001 micrometer did you use? Electric or mechanical? It is also possible your micrometer needs recalibrated. Try remeasuring and report back.
« Last Edit: August 18, 2016, 07:44:08 PM by Ethan1 »
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Ethan

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Offline Mudsport96

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Re: bit size vs actual bit measurement
« Reply #2 on: August 19, 2016, 06:40:22 AM »
Well I put my glasses on and recalibrated my mic, it was off a fuzz and I didn't notice it(guess I need to realize I don't have the vision like I'm  20 anymore.) Its not an expensive set but I've used it for years doing crank journals and pistons, wrist pins etc.. With the larger mics in the set and had no problems.

But after recalibration its within .0001 good enough for me.

Here it is.
« Last Edit: August 19, 2016, 06:51:42 AM by Mudsport96 »
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Offline Ethan1

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Re: bit size vs actual bit measurement
« Reply #3 on: August 19, 2016, 10:22:40 AM »
Quote from: Mudsport96 on August 19, 2016, 06:40:22 AM
Well I put my glasses on and recalibrated my mic, it was off a fuzz and I didn't notice it(guess I need to realize I don't have the vision like I'm  20 anymore.) Its not an expensive set but I've used it for years doing crank journals and pistons, wrist pins etc.. With the larger mics in the set and had no problems.

But after recalibration its within .0001 good enough for me.

Here it is.

Nice mic. Almost looks like a Mititutoyo. What are the measurements now?
« Last Edit: August 19, 2016, 10:26:45 AM by Ethan1 »
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Ethan

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Offline Mudsport96

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Re: bit size vs actual bit measurement
« Reply #4 on: August 19, 2016, 12:18:21 PM »
The .070 bit comes in at .0701
So I figure a ten thousandth is within margin of error.
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Offline Ethan1

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Re: bit size vs actual bit measurement
« Reply #5 on: August 20, 2016, 04:32:08 AM »
Quote from: Mudsport96 on August 19, 2016, 12:18:21 PM
The .070 bit comes in at .0701
So I figure a ten thousandth is within margin of error.

 You would be surprised what just .0001" of tolerance will effect. I have heard people having that much LESS main bearing clearance and causing a catastrophic failure. I know this isn't an engine, so please forgive me.

 On to the drill bit. Could you have a deformation on the end of that drill bit? Are you measuring the very TIP of the drill bill or a little further up?
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Ethan

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Offline Mudsport96

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Re: bit size vs actual bit measurement
« Reply #6 on: August 20, 2016, 05:50:04 AM »
No not the very tip, just behind the tip of it. Was thinking the end might be cut different or may be bevelled for cutting. They are Bowman gold oxide drill bits. 135 degree split point...
I'm just going to cross my fingers and hope for the best. I think it will be ok
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