27/64 bit too big

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buster

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Jan 2, 2008
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Brookeville, PA
I am trying to make some executive fp's from csusa and they call for 27/64 bits but it seems too big for the tube. I've measured the tube and it measures 13/32 should I try that size bit or will it be too tight. I have drilled three blanks already thinking I'm crazy and don't wan't to ruin anymore. Thanks for the help.
 
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its_virgil

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Jan 1, 2004
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I always use a caliper and measure the tubes myself and pick the bit I think is the best fit.
Do a good turn daily!
Don
Originally posted by buster

I am trying to make some executive fp's from csusa and they call for 27/64 bits but it seems too big for the tube. I've measured the tube and it measures 13/32 should I try that size bit or will it be too tight. I have drilled three blanks already thinking I'm crazy and don't wan't to ruin anymore. Thanks for the help.
 

Rifleman1776

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Dec 18, 2004
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Mountain Home, Arkansas, USA.
CS does seem to have problems getting specs right. Can be a puzzlement, at times, as to how they come up with recommended drill sizes. Do try a smaller size. What works, works.
BTW, if you want to get real finicky, measure the tubes on every new order you receive. Yep, they can vary.
 

leehljp

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Feb 6, 2005
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Tunica, Mississippi,
27/64 is 10.7156 mm. The next smallest common size in 10.5 mm. If you want inches: 27/64 is .421865 inch. 10.5mm is .4134 inch. This is to give you a perspective of size differences in the original and next smaller commonly available size.

13/32nds is 10.3188 mm or .40625".

It looks like a 10.5 might do well and being a half mm should be able to be reasonably priced if you can find a place that sells metrics.

Here I can get 10.7 and 10.6 mm at one store but they are HIGH priced - in the $30 range each.
 

randyrls

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Harrisburg, PA 17112
Originally posted by buster

I am trying to make some executive fp's from csusa and they call for 27/64 bits but it seems too big for the tube. I've measured the tube and it measures 13/32 should I try that size bit or will it be too tight. I have drilled three blanks already thinking I'm crazy and don't wan't to ruin anymore. Thanks for the help.
Paul has a good point. I sometimes use a "Z" bit for some tubes. I have found the drill bit on the instructions isn't the best one. I like my tubes to fit closely without any play.

The best technique is to pick a smaller drill size. Drill the hole and before you move the blank, try the tube. If the hole is too small, step upwards in bit size until you find the correct one. I write the drill bit size(s) on the instructions. Sometimes it is the same one recommended, sometimes not.
 

Don_Hart

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Aug 4, 2007
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Ledyard, Connecticut.
I keep a drill bit chart that lists drill bits by number, letter, fraction, decimal and metric in the shop so I can easily find the next lower drill size.
 
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Originally posted by leehljp

27/64 is 10.7156 mm. The next smallest common size in 10.5 mm. If you want inches: 27/64 is .421865 inch. 10.5mm is .4134 inch. This is to give you a perspective of size differences in the original and next smaller commonly available size.

13/32nds is 10.3188 mm or .40625".

It looks like a 10.5 might do well and being a half mm should be able to be reasonably priced if you can find a place that sells metrics.

10.5mm drill bit won't work, the hole will be too small. I've tried it [B)]
 
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