Recommendation for an internal threading tool please

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Need a tool for internal threading of 316L seamless tube. Generally about 1/2" deep into a .900 - 1.120 hole. Tried grinding out of a HSS blank & a brazed carbide bit, but didn't get good results with either. Will be making 28 tpi mostly.

Anyone recommend a good threading bar or indexable tool for it? I don't really get the LH/RH part of it when I look for tooling. I plan to cut these feeding from the right towards the headstock with the tip of the tool facing me. Not planning to run in reverse with the tool tip facing away from me cutting on the far side of the stock.
 
Have you tried using a 1/4 28 tap.. No kidding use a smaller tap as a boring bar and set up to thread as with single point. Best to use a two flute tap. well that is my suggestion anyway give it a try.
 
No. I'd have never even thought to try that.

Any kind of tap? tapered, spiral, bottoming, etc?

I have a couple 1/2x28 taps - would that work or do i need to get a 1/4? Any risk to the (hand) tap from doing this? I like the ones I have & wouldn't want to wreck one.
 
With the chuck rotating normally, that is towards you, or counterclockwise from the tailstock end of the lathe, you would want a RH (right hand) toolbit go cut threads on the front side of the hole. I always kept it straight this way. Right hand tools come from the right side or end of the work to start cutting. Left hand tools come from the left side or end of the work to start cutting. Simple.

Aloris makes excellent boring/threading bars for what you want to do, with replaceable inserts.
 
+1 on a good quality tap. Personally I prefer to use a tap for 1/2" internal threads & smaller & a die for any external threads smaller than 5/16". But I awlays try to do it on the lathe when possible for better results. Much quicker & easier for smaller sizes than single pointing.
 
I can't really use a tap. I'd need an oddball custom size & several of them. Tube ranging from 1.00 - 1.50 OD with walls ranging from .050 - .065. Would need a lot of non-standard X-28 taps to do that.

I really wouldn't know where to begin even trying to size 28 tpi tap to fit a 1.005 or 1.120 hole. If all the tubes i used were the same that would work but different projects use different materials, wall thickness, OD, etc.
 
Oops, not sure what I was thinking, for some reason I didn't realize the sizes you stated. I pretty much much use indexables for everything with the exception of a couple of brazed carbides & a few really small boring bars.

I use Carmex for threading tools (internal & external) but everyone has a favorite. Seco & Kenametal are also nice but pricey. I mostly thread 20, 24, 28, & 32 tpi with 20 being the most. I use full profile inserts for 20 & partial profile (equivelent to a sharp V) for everything else. Indexables seem expensive at first. I got them two years ago & while I don't do everyday production work, I have used them a lot (I mostly thread Ti64) & I'm still on the first insert tip.

If you do go with indexables & will cut 28tpi a lot it's best to go with a full profile insert but that insert will only be good for that one thread pitch. With the full profile insert, theoretically (I've never tried yet) you should be able to cut the thread & major diameter together. Meaning as you thread, start with a slightly oversided diameter, when the full profile insert startes turning down the major diameter to spec, you should have a perfect size thread. (Please correct me if I'm wrong)
 
sssfox said:
refinery Mike wasn't meaning that you use the tap as a tap. He meant for you to use the teeth as the cutting tool. That's why he suggested a 1/4" tap for a 1+" hole.
Click to expand...

I get that. Mike is saying use an undersized tap as a cutting bit. I'll try using the smaller tap in the way suggested.

Darkzero is saying use a tap the standard way. Using the right size tap in the way intended isn't practical because of the pre-determined hole size.
 
Mesa Tool has an interesting threading tool.

It can do internal, external, right or left hand.

Pretty inexpensive also for $32 or $36 depending on size.

Check them out HERE.

He also sells inserts for grooving either square or radius bottomed grooves.

Gary

58threadinggroovingtool.jpg

58threadinggroovingtool.jpg
 
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a 1/2 by 28 thread tap would be even better, more ridged. and you already probably have a boreing bar holder that would fit a half inch tap. The natural taper of the tap allows each tooth to take a little and reduce the chip load per tooth. You do have to drive it in at 90 degrees not at the usual 29.5 degrees as usual. Because a tap has very little relief on the threads. but with such a shallow thread i doubt that will pose much of a problem.
 
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