Drill for a 6-32 tap?

[johninct]

What is the correct drill size for a 6-32 tap? Thanks!

 

[Mr onetwo]

7/64" or a #35

 

[larry_g]

http://www.guhring.com/documents/Tech/Charts/CutTapDrill.pdf

one of the better charts.

lg
no neat sig line

 

[pancho400cid]

My handy dandy Starret chart says #36 (.1065" dia) for 6-32 UNC.

My handy dandy "Alvin Screw Data Selector" slide rule thingy says the same thing.

 

[LumpyMusic]

My Champion brand tap is imprinted with "Use drill #36 .107"


Sgt Lumpy

 

[bobadame]

It depends on what you are drilling into. The charts give drill sizes for 75% thread engagement. 6-32 is a tough one to tap because it is a coarse pitch with a very small diameter, therefore the taps break easily. For this reason when tapping 6-32s in tough materials I usually use a drill which will give me 60 to 65% engagement, especially in tough materials like stainless steel or copper. If you need a stronger fastener use an 8-32 at 75%.

 

[nehog]

My handy dandy Starret chart says #36 (.1065" dia) for 6-32 UNC.

My handy dandy "Alvin Screw Data Selector" slide rule thingy says the same thing.

#36 is the correct size, we often have used a #35 which makes the tapping a bit easier (in aluminum).

 

[larry_g]

If you look at the link I posted above and then pay attention to Bobadame's post you can make an informed decision on what diameter to make your hole. Material and ultimate strength of the joint play into what sized hole you use. Not all is black and white nor even what it seems to be.

lg
no neat sig line

 

[Ign]

Just used a #36 for 8 holes in Nylatron (nylon) today.

 

[bmxdad]

Unless it's a critical thread, save some hassle and go for the oversize drill.

 

[johninct]

Thanks!!! I am drilling into GM side post battery bolts to install a BatteryMINDer harness. I do know that there are brass stud things I could use but I want to keep it looking original. I will try to solider the screw in and use a wing nut so I can remove it easily.

 

[Jagmandave]

You know, having the information on the application and material up front would get you better answers from the gitgo.

I see this in threads every day - what's the best xxxxxx?

The answer is always the same - Depends on what you're doing with it.....

 

[larry_g]

Thanks!!! I am drilling into GM side post battery bolts to install a BatteryMINDer harness. I do know that there are brass stud things I could use but I want to keep it looking original. I will try to solider the screw in and use a wing nut so I can remove it easily.

There are many places to tap into the 12v system. Have you considered and eliminated all the other connection points? What vintage of rig are you working on? Maybe an under hood picture?

lg
no neat sig line

 

[johninct]

I am working on 1977, 1979 and a 1981 GM's.

 

[larry_g]

Most of those rigs will have a 12v junction point on the firewall that you should tap into. Follow the big red wire leaving the alternator.

lg
no neat sig line