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What size drill bit for a ¼”-28 tap?

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Old

Jul 22, 2002 | 02:11 PM

#1

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Joined: Nov 2001

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From: Cleveland, OH

Car: '87 Camaro LT

Engine: 355 L98

Transmission: T56

What size drill bit for a ¼”-28 tap?

it's not written on the tap itself.

Old

Jul 22, 2002 | 02:34 PM

#2

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From: Jackson County

1/4-20 is #7 if you stick with number drill set i'd guess a 9 or 10. for fractions i'd guess 3/16

Old

Jul 22, 2002 | 02:48 PM

#3

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From: Cleveland, OH

Car: '87 Camaro LT

Engine: 355 L98

Transmission: T56

thanks ede

if i measure the minor diameter of a 1/4-28 bolt, the drill bit diameter should be just a hair bigger right?

Old

Jul 22, 2002 | 03:02 PM

#4

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From: Savannah, GA

Car: 1997 Jeep Wrangler

Engine: 4.0L

Transmission: 5 speed

Axle/Gears: 8.8 rear, 4.56 gears, 4:1 transfer

1/4-28 tap is a number 3 drill bit (7/32" is very close). Remember the threads are smaller on fine then course so the hole needs to be bigger to allow for less threads. Here's a handy chart to see for yourself.

http://www.widell.com/drillsiz.html

Last edited by John Millican; Jul 22, 2002 at 03:04 PM.

Old

Jul 22, 2002 | 03:10 PM

#5

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From: Jackson County

damnit guess the dumbass in me was coming out agian. i went the wrong way. oh well i got to add 2 to my post count

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