I have a bunch of holes to tap in a fixture plate. Due to a programming
mistake I broke my last gun tap of the correct size the other day. I
don't want to tap 80 holes by hand. Yes, I have more taps arriving
tomorrow (I hope), but I'd like to get this plate done and off the
machine today. I need the machine for roughing a bunch of blanks.

Anyway, my wild idea was to chuck up a hand plug tap in the T&C grinder
and make a slash cut in each flute to mimick the nose shape of a regular
gun tap (spiral point tap).

I also need the fixture plate finished to go on one of the other
machines so I can get three parts out of the shop.

It won't kill me to have to wait, but I can get fair quality hand taps
locally. (Just a couple miles from my shop)

I expect it would work, but I was wondering any of you guys had done it
and how it worked for you.

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"Bob La Londe" wrote in message ...

I have a bunch of holes to tap in a fixture plate. Due to a programming
mistake I broke my last gun tap of the correct size the other day. I
don't want to tap 80 holes by hand. Yes, I have more taps arriving
tomorrow (I hope), but I'd like to get this plate done and off the
machine today. I need the machine for roughing a bunch of blanks.

Anyway, my wild idea was to chuck up a hand plug tap in the T&C grinder
and make a slash cut in each flute to mimick the nose shape of a regular
gun tap (spiral point tap).

I also need the fixture plate finished to go on one of the other
machines so I can get three parts out of the shop.

It won't kill me to have to wait, but I can get fair quality hand taps
locally. (Just a couple miles from my shop)

I expect it would work, but I was wondering any of you guys had done it
and how it worked for you.

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---------------------------------

I've never done exactly that but I did successfully grind the grooves and OD
taper of a dull and rusty 3/4-10 tap on my surface grinder. The indexing
spring finger was the broken-off end of a dull hacksaw blade. I don't
remember how I set up the angles but your equipment is probably different.

I think I hogged out the grooves with a hand held die grinder and only
lightly evened them up on the surface grinder. A coarse cutoff wheel on an
air grinder might quickly rough out the spiral without overheating the tap.
You could practice on a bolt. I use a hand held angle grinder to shape lathe
internal threading bits quite close to final shape.

On 12/8/2020 10:55 AM, Jim Wilkins wrote:
"Bob La Londe"Â* wrote in message ...

I have a bunch of holes to tap in a fixture plate.Â* Due to a programming
mistake I broke my last gun tap of the correct size the other day.Â* I
don't want to tap 80 holes by hand.Â* Yes, I have more taps arriving
tomorrow (I hope), but I'd like to get this plate done and off the
machine today.Â* I need the machine for roughing a bunch of blanks.

Anyway, my wild idea was to chuck up a hand plug tap in the T&C grinder
and make a slash cut in each flute to mimick the nose shape of a regular
gun tap (spiral point tap).

I also need the fixture plate finished to go on one of the other
machines so I can get three parts out of the shop.

It won't kill me to have to wait, but I can get fair quality hand taps
locally.Â* (Just a couple miles from my shop)

I expect it would work, but I was wondering any of you guys had done it
and how it worked for you.


I said screw it and thread milled them with a single form. It was
slower than TC tapping, but its done, and I was able to spend my time
working on other CAD/CAM work.

Next time I'll have taps on hand again.

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