tap drill size

=A0 =A0 ...Jim Thompson

must be some hard steel you have there, normally I put the tap in the cordless drill and it is never a problem even with a hole that is sligthly too small

-Lasse

Jim Thompson wrote in news: snipped-for-privacy@4ax.com:

...Jim Thompson

I have a small Craftsman tap/die set and the 1/4-20 tap calls for a #7 drill;IOW,a 0.201 or 13/64. those are pretty deep threads,a lot of material being cut away.

I'd probably select a #6/0.204 or even a #5/0.205 would work OK. shallower threads,but should hold well. (but not "max load",whatever that is...)

the guide on my Drildex drill set also calls for the 13/64 drill for a 1/4-

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Measure the core diameter of the tap and go down a bit for eccentricity and general wobbles. Alternately, try your larger drill on a scrap piece, tap the hole and then inspect it with a magnifier - if the threads are flat-topped you've gone too far.

Chris

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Do you have time to fight a broken tap out of the steel? Been there, done that, don't like it! Does the connection need all the strength of full threads? If not, drill the hole larger. If you don't drill the hole larger, at least use a good quality, sharp tap, there is a big difference. Either way, do use a proper lubricant. I'll be away, and won't bother you while your doing this, tell your wife to go away too! Mike

PS. Most of my experience is with 4-40, 6-32, and 8-32 in aluminum. I phased out the 4-40 without any regrets.

I would say that your tap is dull or you have soft steel. Chinese taps are horrible. If you don't need strength, you can go down to a 60% thread which I do in titanium, actually, 55% for some fasteners that hold a decorative plate.

.. Mark

qrk wrote in news: snipped-for-privacy@4ax.com:

You also don't state if you are using any lubricant. It makes a huge difference.

Doug White

The 0.201 (13/64") is for softer materials. You want to go to a 7/32" drill for harder materials. Also, you have to decide if you want 75% or 50% threads.

I was in manufacturing for 25+ years.

Bill

You can't beat PTFE lubricants - slick50 or Finish line grease from a bicycle shop.

--- IME it's not normal.

As someone else suggested, make sure your tap is sharp and use lube.

If you haven't done any tapping in a while, it may be that the tap isn't being held normal to the panel when it starts biting into the metal, which can cause it to bind up.

In order to make that go away, get or make a "tapping block" which is nothing more than a block with a 1/4" hole drilled through it perpendicular to the face being drilled, hold it against the panel, insert the tap into the hole and start the tap into the panel that way.

Works great!

JF

...Jim Thompson

Are you using lube ? Soap is Ok.

Are you using cutting oil?

Cheers

Phil Hobbs

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

You need some cutting oil, Kerosene or plain oil will do.

Cheers

If you want the tap to rust rapidly!

This is side-loaded, so I'm not worried about upsizing drill size.

Thanks! ...Jim Thompson

Good idea! When I went out to get a larger bit, I bought a vanadium tap :-) ...Jim Thompson

Really good idea! When I can, I use my drill press to get a vertical start. In this case, it's free-hand, so your "tapping block" is a SUPER idea! Thanks! ...Jim Thompson

Of course not! I'm an EE :-( But I will ;-) ...Jim Thompson

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