Question for those that do

J

JDS

Guest
Why do you still use the old setup (Compound set @ 29.5) method for threading? Since the advent of HSS and Carbide inserts there is no reason to use this method. I was taught to use the straight plunge method back in 89 and it has worked flawlessly and is much easier to setup. I currently us a carbide full profile threading insert and it is almost idiot proof (One reason I use it).
 
cause it works ??? its how i was taught..and was glad to see people still use it...not everyone..but some.....
hss works well at low speed....carbide does not..i thread slow.....one cutting edge at a time is fine with me.

mike in co
 
I've never used a full profile tool. I've talked to a couple people that do use them, and they say they turn the tenon a little big and just keep feeding straight in until the reach the OD they're looking for. I guess it works.

Seems like it would kinda take the fun out of the old way. I'll keep doing it that way...
 
I have never had a problem threading the 'old way' and I don't understand what is difficult about the set up. I don't plan on buying tooling to do it any differently.
 
JDS said:
Why do you still use the old setup (Compound set @ 29.5) method for threading? Since the advent of HSS and Carbide inserts there is no reason to use this method. I was taught to use the straight plunge method back in 89 and it has worked flawlessly and is much easier to setup. I currently us a carbide full profile threading insert and it is almost idiot proof (One reason I use it).
Click to expand...
The main reason I till use 29.5 degrees is that this causes the major part of the cut to come off the left edge of the 60 degree insert. This creates a back pressure on the carriage and keeps the half-nut loaded to one side. Otherwise, cutting straight in can cause a variation in leade as the half-nut is allowed to play back and forth.

Edit-
The other reason is that the trailing edge of the tool tends to burnish that side of the thread and that edge is what is loaded when the barrel is tightened.
 
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While I do not use full profile inserts, I do thread straight in. The reason I do not use full profile is we do not use them in our shop. I thread straight in because that is the way I like to do it........jackie
 
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JD, I use full profile inserts and I set my compound at 29 1/2 degrees. If I set my compound to 0 (or straight in) the handle is in an interference position with the cross feed handle and I tend to rap my knuckles. If I leave the compound alone and just feed straight in with the cross feed, I have to remember where I was on the last cut and I sometimes forget and end up making extra "free passes".
Even CNC lathe programs do not always feed the threading tool straight in. Some use a compromise angle somewhere between 0 and 29 and some even alternate feeding one pass straight in and the next pass at some angle. I saw this discussed in a book provided by one of the tooling companies, I think it was either Kennametal or Sandvik.
I spent some time running a19" LeBlond that had the compound feed locked up solid so I could only use the cross feed. It worked quite well with full and partial profile inserts. We ran a lot of metric threads and it took all my concentration to keep from breaking inserts or worse, but after doing it all day for weeks you get real good at it.

Scott Roeder
 
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Scott beat me to it. I didn't know this until yesterday when I recountoured a barrel from HV to Light Palma. I set the compound to straight in so the math would be easier (I'm mathstupid) and hated it.

I'd noticed before that when cutting 11 degree or thereabouts cones and muzzles that it was 'clumsy' but really didn't put a handle on it until I cranked it clear over to zero.

What a pita! knucklestucker city.

I can do 45* math so I'll probably shift to this in future before going clear to zero :)

al

al
 
I sure like the ability of being able to cut variety of threads with the partial profile insert. Cheaper is good for me..
 
I set the compound to 29.5 and use a CARMEX partial profile insert threading tool. It works great at low speeds. I thread at ~50 rpm while flooding with high sulphur cutting oil. I do it the same way with an HSS tool.

I use a cross slide stop so that when I back off at the end of the cut I can go back to exactly where I was. I do the infeed with the compound. Works great. Been doing it this way since I cut my first thread back in 1950 or '51.

Fitch
 
In my limited life's experiences I would have to say that what ever works for you is OK. I always use the 29.5 deg setting when threading. Here is one thing to consider; I have heard so many times, and it is evident here, "why, because that is the way I was taught". Easy to go with that system and tough to change; if your instructor said to thread straight in, do it that way but at least try a different method just for your own satisfaction.
 
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