And speaking of tapping, how close to an edge can I tap?

There's been a few times where I've drilled a hole close to an edge,
tapped, it, and had the threads swell the edge by the hole. Is there
some standard for how much meat should be allowed so that this doesn't
happen? Is the necessary distance different for different materials?

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

"Tim Wescott" wrote in message
...
And speaking of tapping, how close to an edge can I tap?

There's been a few times where I've drilled a hole close to an edge,
tapped, it, and had the threads swell the edge by the hole. Is there
some standard for how much meat should be allowed so that this doesn't
happen? Is the necessary distance different for different materials?

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com


I think the rule is whatever is strong enough to do the job the part is
intended to do. Seriously. I have seen some threaded holes for special
applications where the side of the hole is just plane missing.

On Sun, 22 Apr 2012 20:17:12 -0700, Bob La Londe wrote:
"Tim Wescott" wrote
And speaking of tapping, how close to an edge can I tap?

There's been a few times where I've drilled a hole close to an edge,
tapped, it, and had the threads swell the edge by the hole. Is there
some standard for how much meat should be allowed so that this doesn't
happen? Is the necessary distance different for different materials?

I think the rule is whatever is strong enough to do the job the part is
intended to do. Seriously. I have seen some threaded holes for special
applications where the side of the hole is just plane missing.

I've tapped 3/8-16 into 3/8" bar edge-on, for practice, and
the parts looked good when the holes were exactly centered.
But there was so little leeway for error that I dropped back
to 1/4-20 for the real parts used to make a metal frame.

--
jiw

On Mon, 23 Apr 2012 02:33:40 -0700, Gunner Asch
wrote:

On Sun, 22 Apr 2012 21:06:18 -0500, Tim Wescott
wrote:

And speaking of tapping, how close to an edge can I tap?

There's been a few times where I've drilled a hole close to an edge,
tapped, it, and had the threads swell the edge by the hole. Is there
some standard for how much meat should be allowed so that this doesn't
happen? Is the necessary distance different for different materials?

I use (1) diameter as the minimum distance from the edge. One supposes
that the material does make some difference. Aluminum versus cold rolled
etc etc

Gunner

That's a reasonable rule. Of course, if you produce the edge after the
tapped hole you can go closer.

"Spehro Pefhany" wrote in message
...
On Mon, 23 Apr 2012 02:33:40 -0700, Gunner Asch

wrote:
On Sun, 22 Apr 2012 21:06:18 -0500, Tim Wescott
wrote:

And speaking of tapping, how close to an edge can I tap?

I use (1) diameter as the minimum distance from the edge. One
supposes
that the material does make some difference. Aluminum versus cold
rolled
etc etc

Gunner

That's a reasonable rule. Of course, if you produce the edge after
the
tapped hole you can go closer.


IIRC I found I could get away with an 0.030" wall outside a #2 or #4
tapped hole in 6061 aluminum. There was some difference between a
cutting and forming tap, but not much.

The application was prototype RF-tight aircraft radio enclosures and
the electrical engineers didn't take notice if the threads printed
through slightly.

I probably should have left clearance for a Helicoil, but I could
drill stripped holes deeper and mark them for longer screws.

jsw

"Tim Wescott" wrote in message
...
And speaking of tapping, how close to an edge can I tap?

There's been a few times where I've drilled a hole close to an edge,
tapped, it, and had the threads swell the edge by the hole. Is there
some standard for how much meat should be allowed so that this doesn't
happen? Is the necessary distance different for different materials?


Re-cut the edge of the part after tapping.....