Need a source for a 1 3/16 - 16 3B UNS Tap - SPIRAL POINTED

50BMG DUDE · Aug 3, 2016

Hi guys,

Anybody got a source for a spiral point 1 3/16-16 tap? It's a UN Special thread. I can find them with std plug straight flutes, but not with a spiral point. Otherwise do you know of anyone who can add a spiral point to an existing tap? Most of the cutter guys we use won't do it.

Thanks!

Chris

Bobw · Aug 3, 2016

It takes about 20 seconds to turn a large plug tap into a spiral point/gun tap... There is no magic to it, each flute does
not need to be exactly the same.. A dremel tool with a cut off wheel or a die grinder...

I found this out tapping some ali-nickel-bronze... Holy F-Hell.. That stuff EATS HSS.. Just kept sharpening the
end and sharpening the end.. Had to do it after every 2 holes... And I just kept moving at more and more
of an angle... And TaDa.. Spiral point. I still have the taps from that job, and I still use them.. 3/4-16..
1.5" thru, power tapping in the mill... and it pushes the chips right out the bottom..

Perry Harrington · Aug 3, 2016

If I'm not mistaken, that's the buffer thread tap for an AR-15 receiver. You might want to consider thread milling instead of tapping, it's much easier, produces a cleaner thread (IMHO), and is more controllable for pitch diameter. Also, the torque required to tap that hole is pretty high, which can move the part in the fixture if it is not really secure, you might end up with a little tap drift.

wesg · Aug 3, 2016

Or for a handguard. Can't remember which is which.

50BMG DUDE · Aug 3, 2016

Yup, It's an AR buffer tube thread. We threadmill now but 2 passes with a single point type tool takes 2 minutes per part. I have 1600 parts to make and figure a Rigid tap cycle would be much faster. This is for production work obviously so I'm a little shy on using a dremmel on a $140 tap. I'd like to send out for grinding to someone who can do it or find one COTS.

Chris

Bobw · Aug 3, 2016

50BMG DUDE said:
Yup, It's an AR buffer tube thread. We threadmill now but 2 passes with a single point type tool takes 2 minutes per part. I have 1600 parts to make and figure a Rigid tap cycle would be much faster. This is for production work obviously so I'm a little shy on using a dremmel on a $140 tap. I'd like to send out for grinding to someone who can do it or find one COTS.

Chris

I couldn't find the original one I messed with, but here is a sharpened spiral point.. With a cut off wheel. A non-sharpened spiral point, and
a regular old hand tap.. All you literally have to do is come in at an angle, and give it some positive rake.. Nothing to it... Of course its
best if you can find what you need, but occasionally you can't, and you have to do it yourself.. Do it a few times and its not scary anymore..
Even with a $140 tap.

Edit: I don't know how deep you are driving this, but at that diameter, you may have enough room in the gullets to run a straight flute tap.

Atomkinder · Aug 3, 2016

50BMG DUDE said:
Yup, It's an AR buffer tube thread. We threadmill now but 2 passes with a single point type tool takes 2 minutes per part. I have 1600 parts to make and figure a Rigid tap cycle would be much faster. This is for production work obviously so I'm a little shy on using a dremmel on a $140 tap. I'd like to send out for grinding to someone who can do it or find one COTS.

Chris

Why bother with using a single-point style when you can make any diameter with a form style tool in one rotation? Sure you only get one thread pitch, but that's all your making for 1600 parts. I'm betting it'll be at least as fast as tapping at that diameter and it's also adjustable to fit.

Thread Mill 5/8-16 UNF MariTool

http://www.onlinecarbide.com/9162516.html

Lakeshore's got an uncoated version, perfect for the application I'd think:
3/4-16 Carbide Thread Mill Uncoated

72bwhite · Aug 4, 2016

don't need 2 passes with a single point either
but for that many just get a 3/4 16 thread mill and be done with it

50BMG DUDE · Aug 4, 2016

72bwhite said:
don't need 2 passes with a single point either
but for that many just get a 3/4 16 thread mill and be done with it

Will try the 3/4-16 route. I've never used one of those and neither has anyone else in the shop. From what I'm guessing you drop in and make 1 rev ?

The hole is a only 1/2" deep

We are using a spring pass with the single point because there was an issue in the past with some rejected parts.

Thanks guys !

Chris R

Limy Sami · Aug 4, 2016

Just out of interest.

What were you going to drive a 1 3/16-16 tap with, ...........and as I don't know the part in, in what material?

Take care.

Sami.

Perry Harrington · Aug 4, 2016

He's tapping 7075 into a fairly thinwall section. Colt did it with a tap, but you REALLY need to hold that part securely to avoid the part deflecting due to a very large contact area and the torque it generates. I would also be concerned with concentricity and warping of the material. You'd want some soft jaws that fit the part closely so it doesn't have any unsupported features.

He's cutting this thread:

WILLEO6709 · Aug 4, 2016

get a multiple tooth threadmill specific to pitch..... 2 rev max. 1 pass and done

Ox · Aug 4, 2016

You seem pretty sure on that 7075....

I've seen those come in _ in plastic! (with way oversize threads - thousands of them IIRC)

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Need a source for a 1 3/16 - 16 3B UNS Tap - SPIRAL POINTED

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