Need help picking out a toolholder for cutting threads

I use the craftsman 2918 threading tool holder for all of my external threading. It looks like the No. 50 that BGHansen posted. It came with my lathe. I made a special tool holder for it for my Norman QCTP. I have used it from 8 tpi to 40 tpi and metric threads with no problems. Only takes a quick swipe with a hone to keep it sharp. I'll never wear it out in my lifetime and whoever ends up with it after I am gone will also probably never wear it out in their lifetime.
 
The textbook external thread has a radius equal to .289 x the pitch at the root of the thread. My threading inserts have a small radius at the tip but there is no way that they will cut textbook threads for all pitches. They will cut acceptable threads, however. The minimum pitch will be determined by the size of that radius, If the radius is .005"(guesstimate), the minimum pitch will be .017" or 58 tpi. As to maximum pitch, that is limited by the size of the 60º geometry; how deep you can plunge without interference from the insert body. On my inserts, that is about .068" I would be able to just cut a .090" pitch or 11 tpi. To cut finer or coarser pitches would require different inserts.

The case is even worse for my internal threading tool because of interference from the tool holder. The minimum internal thread diameter I can cut is 9/16". This leaves only the UNF thread of 9/16-18 and that with a 60% thread. Needless to say, it doesn't get used much.
 
RJSakowski said:
The textbook external thread has a radius equal to .289 x the pitch at the root of the thread. My threading inserts have a small radius at the tip but there is no way that they will cut textbook threads for all pitches. They will cut acceptable threads, however. The minimum pitch will be determined by the size of that radius, If the radius is .005"(guesstimate), the minimum pitch will be .017" or 58 tpi. As to maximum pitch, that is limited by the size of the 60º geometry; how deep you can plunge without interference from the insert body. On my inserts, that is about .068" I would be able to just cut a .090" pitch or 11 tpi. To cut finer or coarser pitches would require different inserts.

The case is even worse for my internal threading tool because of interference from the tool holder. The minimum internal thread diameter I can cut is 9/16". This leaves only the UNF thread of 9/16-18 and that with a 60% thread. Needless to say, it doesn't get used much.
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I made an internal threading bar out of a 1/2" rod and some HSS. So like you, I can't thread anything under about 5/8", and a fine thread at that.

To do smaller internal stuff is the territory of Micro100 solid carbide bars or grinding your own. The Micro100 carbide tools are wonderful and do a great job, but they are intolerant to newbies blundering. I snapped a Micro100 carbide boring bar due to a thoughtless moment. Expensive lesson, but they do work great, and last a long time - if you don't mess up!
 
WobblyHand said:
I made an internal threading bar out of a 1/2" rod and some HSS. So like you, I can't thread anything under about 5/8", and a fine thread at that.

To do smaller internal stuff is the territory of Micro100 solid carbide bars or grinding your own. The Micro100 carbide tools are wonderful and do a great job, but they are intolerant to newbies blundering. I snapped a Micro100 carbide boring bar due to a thoughtless moment. Expensive lesson, but they do work great, and last a long time - if you don't mess up!
Click to expand...

I grind my own. The smallest that I have done was for a 4-48 thread. I used an 1/8" HSS tool bit for that one. Drill blanks work for these; also shanks from old pulley taps and reamers.
 
mmcmdl said:
Looks like you're going to be threading barrels . :encourage: I'm going to post a pick here in a couple minutes of what I had to make as an apprentice . I'll say that carbide inserts are great with CNCs because they are easy to replace and offsets rarely change . Manual lathes like HSS unless you have a large rigid machine and are comfortable threading up to a shoulder . These threads you stated would require a very small tool . I've owned all the Aloris blades and holders over the years as well as every insert tool ever made most likely . My go to tool will always be this to make what I need .

This will grind 60 degree and Acme tools with all clearances needed on a surface grinder . Up to a 5/8 shank tool . Lot of compound angles going on and we had to figure them out years ago . I couldn't today , thats for sure . :grin:
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Yes, that is the plan.
I just bought two suppressors a couple weeks ago and all paperwork has been submitted to the ATF.
Now I have around 6 months to a year to practice and get good at it, before I actually thread any of my barrels.

So I need a tool that would be best for those smaller/finer threads.
The larger more coarse threads will be later on down the road.
 
JeepsAndGuns said:
Yes, that is the plan.
I just bought two suppressors a couple weeks ago and all paperwork has been submitted to the ATF.
Now I have around 6 months to a year to practice and get good at it, before I actually thread any of my barrels.

So I need a tool that would be best for those smaller/finer threads.
The larger more coarse threads will be later on down the road.
Click to expand...
Won't take too long to get good at it. Practice a bit at basic threading. Then try a barrel blank to get used to the material. After that, it will all be easy...
 
I ground a broken carbide tool into an internal threading tool on the tool & cutter grinder. Took a couple of tries to get it correct. I broke the first one due to careless handling. Skinny carbide = very fragile.
 
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