What size drill bit for 3/8-16 helicoil? - Chevelle Tech
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post #1 of 4 (permalink) Old Oct 20th, 09, 1:42 PM Thread Starter
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Rich
 
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What size drill bit for 3/8-16 helicoil?

I have a helicoil kit coming in the mail to fix a stripped threaded hole in a cylinder head. I don't have the kit yet but I could buy the drill bit ahead of time if I just knew what size bit to buy! Maybe 25/64th if I'm remembering correctly?

I checked the Helicoil website and they were no help!
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post #2 of 4 (permalink) Old Oct 20th, 09, 1:48 PM
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Mike
 
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Re: What size drill bit for 3/8-16 helicoil?

Quote:
Originally Posted by Rich-L79 View Post
Maybe 25/64th if I'm remembering correctly?
Bingo!

http://www.helicoil.in/pdf/HeliCoil%...onal%20Kit.pdf

Mike
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post #3 of 4 (permalink) Old Oct 20th, 09, 1:49 PM
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Rob
 
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Re: What size drill bit for 3/8-16 helicoil?


Tap Chart - Helicoil Threads

Tap sizeDrill size
2-56
3/32
3-48
#33
4-40
#31
4-48
#30
5-40
#30
6-32
#25
6-40
#26
8-32
#17
10-24
13/64
10-32
#7
12-24
#2
1/4-20
17/64
1/4-28
G
5/16-18
Q
5/16-24
21/64
3/8-16
X
3/8-24
25/64
7/16-14
29/64
7/16-20
29/64
1/2-13
33/64
1/2-20
33/64

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post #4 of 4 (permalink) Old Oct 20th, 09, 4:36 PM
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Tom
 
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Re: What size drill bit for 3/8-16 helicoil?

Rich,
When I do Helicoil repairs, I go with the recommended drill size for steel/iron parts, and use some kind of oil for the tap, preferably cutting oil, but motor oil will work. But if the helicoil repair is to be done in an alum part, such as an alum intake manifold, then i use a drill that is 1/64 smaller than the recommended drill size. AND I USE LOTS OF LIQUID FOR CUTTING, SUCH AS WD40, to prevent galling of the tap.

Tom Parsons
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