ECN Forum Forums General Topics of the Trade General Discussion Area A Lesson In Screws

I keep breaking tritap tools so I use the cordless drill. If you need to tap holes or enlarge them use your cordless with the clutch set way down. This is also great for tapping those old black enameled boxes for ground screws.
7/64 bit for 6-32; 9/64 bit for 8-32; 5/32 bit for 10-32

If you are useing fractional drill bits to drill for 6-32,8-32,10-32 you are useing the wrong drill bit it should be a number drill, I do not have the sizes handy right now,and some dirtbag stole my Snap-On tap and die set.

Correct drill sizes are:
6-32 No. 36
8-32 No. 29
10-32 No. 21

You're right ... but most guys don't have the numbered bits. The fractionals I listed are the closest to the proper number and work just fine. On the Dayton sheet they are the actual sizes listed to be used.

I just bought a set of these
I like them even better for those old black boxes.

electricman2 are those the sizes for self tapping machine screws too? I noticed the insructions for square D grounding bar kits say to use a #26 bit for the #10 screws that are included. I bought some #26 bits and I have been using them to drill and tap for green grounding screws, they work just fine. Maybe the 26 is not much smaller than the 21? Very confusing how screws get bigger as the number goes up but drills get smaller. Just like AWG I guess.

The BA (British Association) threads that PaulUK refers to above get smaller as their number gets bigger. The only thread of this type that might be familiar to Americans is the 2BA thread on the points and fins of darts - bigger than the old UK electrical standard of 4BA.

Check here for more information on BA threads and here for other threading trivia including those famous Whitworth threads.

[This message has been edited by Hutch (edited 11-24-2004).]

Hutch,
The old Whitworth thread is still alive and well over here!.
It became common over here because of a lot of bicycles being imported here from England in the years after WWII, I think every thread on the bike was the same profile.
There is still a bicycle factory just south of here that uses the Whitworth thread on it's cycles, I have no idea why they never changed over to metric threading.

{Sorry, that's WWII, not WWIII!, Oops }

[This message has been edited by Trumpy (edited 11-25-2004).]

I always thought when WWIII happened we would all be gone!!!!

If WWIII doesn't kill us all off, then WWIV will be fought with sticks and rocks....