"Mike" wrote in message
. com...
I need help is there a standard size hole in tap guide blocks?

I found a couple on ebay but would like to make my own. I've been
looking for plans with little luck I found a 4 hole version.

Should be hea treated ?
The ones I've fund on ebay were Aluminum or 1018

Flexbar makes one out of 4010 that is het treated. Seems like this
would be better, but is it necessary ?

If so I probably would skip making one since I don't have the means of
heat treating at my disposal.

Mixed emotions on one that is heat treated. If you get careless with a
hard one, you can do minor damage to the major diameter of a tap, so it
might be better to sacrifice the hole size from several repetitions of use,
slowly enlarging the hole as you turn your tap. Unless you're involved in
some serious tapping, using it daily, I dare say that will never be an
issue.

Hole size? The smartest thing you can do is mic the taps you'd like to
use and size the holes accordingly. The major diameter of taps is greater
than nominal, so you'll find them slightly oversized. Measure the body, or
shank of the tap. Make your hole such that the guide can be slipped off
with the tap still in the hole if necessary. You may find you need a
******* size, but the closest size you have at your disposal will work,
providing a little extra clearance, or you could bore the holes if you're
not in a hurry. With the number series, you shouldn't have much trouble
selecting a drill that will provide the proper clearance, but larger taps
can be a problem. If you drill only, double drill to insure hole size and
roundness.

Taps in the number series, below a #6, have a body diameter greater than the
major thread diameter, so the tapping block won't be able to be lifted off
without removing the tap from the hole. You might decide to make the pilot
size the body size in that instance.

Harold