need a 5/8-12 RH Acme tap

[metalmagpie]

Making a slide hammer adapter to fit my Proto slide hammer. I need a 5/8-12 RH Acme tap. Nobody seems to carry one.

Ideas?

metalmagpie

[10KPete]

Never heard of that size. Single point???

Pete

[lakeside53]

Is it square thread or real acme?

Acme is not normally "single pass" - there a set of taps, or a multi-stage (Tandem) tap for one pass. Even if you find one...$$$$

As a reference, here's an import 5/8-8 for $120. https://www.mscdirect.com/product/details/04794400 USA is $180. OK...halve that 'cos it's MSC.


Single point it.

[tom_d]

That's definitely an oddball size there. The standard for 5/8 is 8tpi. How did you determine the 12 thread number, and are you sure it's a 5/8? My reason for asking is I'm wondering if by measuring from thread to thread to get the 12, but you have a 6 thread that's a double start? Still an odd one, though.

Is the thread form symmetrical? Reason for asking is that there is such thing as a 5/8-12 in the Buttress thread form.

[danlb]

Might this be an instance where an Evan-nut would work? A melt in place piece of delrin can take many forms and be used for many things.

Dan

[RichR]

Googling for:

5/8-12 acme tap

returns a link to:

e-taps.com/ofertapage-20110.html

They only list an ACME 5/8-12 Finisher and it says to email or call.

[metalmagpie]

How did you determine the 12 thread number, and are you sure it's a 5/8?

Caliper OD = 0.624" ergo 5/8".
Put a 12 tpi thread gage on it and it dropped right in. Doesn't fit, of course, but you can easily tell it isn't 11 or 13.

Seems like Proto and Mac put Acme threads on their slide hammers.

Of course, they could be buttress threads or maybe square but my eyes aren't up to deciding which.

metalmagpie

[metalmagpie]

Acme is not normally "single pass" - there a set of taps, or a multi-stage (Tandem) tap for one pass.

Sadly, it's in a blind hole. :-( One of those tandem taps definitely won't work.

I have a good workaround, this is just me wondering.

metalmagpie

[MattiJ]

16mm 2mm pitch metric trapezoidal tap would be a lot more common but its 12.7 tpi..

[metalmagpie]

I got out my 10X magnifier head band and really looked at the thread. It isn't acme and it isn't 60 degree based either. It appears to be some proprietary thread with round tops and straight sides. I'm going to punt on this one.

metalmagpie

[754]

Can you work around blind hole, like make bushing or drill other end open then fill...then single point it.
Sometimes roughing with a 60 deg tool first..eases the real threading.

[redgrouse]

Hi metal magpie, try these people -- Tracy Tools in the UK http://www.tracytools.com/taps-and-dies/acme-taps
They have them listed in various sizes.
John

[danlb]

I got out my 10X magnifier head band and really looked at the thread. It isn't acme and it isn't 60 degree based either. It appears to be some proprietary thread with round tops and straight sides. I'm going to punt on this one.

metalmagpie

Ok, time to look at alternate plans? Cool!! ; I'm not sure what you are trying to tap but had some ideas.

First, if you find a tap with a matching thread ( 1/2 - 13) can you use the trick where you dill the hole to the right size, then cut a hardwood shim to pack into two of the flutes to make the effective diameter 5/8? It will then be cutting with only one (or two) edges but that might get you there.

Second, if you have a shaft that is 5/8-12 with an odd thread form, is the part you are threading soft enough to make the shaft "self tapping" by grinding some flutes into the shaft? You can make up for the damage by using locktite when you assemble it.


Just throwing those out there.

[Paul Alciatore]

Single point it? Are you serious or just kidding? The basic thread height of an acme thread is 1/2P. At 12 TPI the pitch is 1/12 = 0.0833"/2. Actually you need to cut a bit deeper than that for clearance. Since the thread is on both sides of the hole you multiply that by 2 and get a total thread height of 0.0833". Now, 5/8" = 0.625". And 0.625" - 0.0833" = 0.5417". That's about your minor diameter. So, you are going to grind a tool with a total width, shank plus the cutting tip's protrusion, is less than that figure. I calculate that the shank part of that tool will be about 0.500" wide. And then you are going to cut a 12 TPI thread with it. OK, I guess it could work if you take light cuts. Good luck.

I would recommend that you start your cut at the bottom of the hole and run the lathe backwards. And you need to be careful of clearances on all parts of that tool, not just under the cutting edge.

I think the OP will need to either change his design, if he can, or make a special set of taps starting with a taper tap that has only half height teeth and going, by stages, to a bottoming tap with full size teeth. I would think a minimum of three would be needed but more likely four or even five.

In any case this is going to be difficult. I expect the OP is working with steel and he needs a full depth thread for maximum strength. He did say it was for a slide hammer. An insert does not sound like a workable idea.

Thee are, of course, companies that will make custom sized taps. Here is the first one I found:

http://catalog.tapcotaps.com/request...-taps-and-dies

I am sure there are more. I am not recommending this one or any of the others.

Never heard of that size. Single point???

Pete

[MGREEN]

O1 tool steel rod annealed.
Turn yourself a bit of live tooling with the end profiled to match and smaller
than minor diameter.
Gash some teeth then harden and hone.

Contrive some way to rotary drive it on the tool post.
Set the lathe gear train for correct pitch and use back gear for slow feed.
Mike