6in 1/2-13 in 304 SS Need help

[Shotout]

I need advice on how to thread a TGP 303 SS rod, D.500 12in OAL with 1/2-13 threads 6in in length. Class is 2B. I tried to set it up with the tailstock in the Mazak but the threading tool (Valenite VLSR 163D) is interfering with the center even with changing the tool path data values. The Fab Shop foreman said it would be fine to use a die and do it on the manual lathe but with a brand new HSS die and lots of rich coolant (suitable for stainless) I can't get a good thread. Tried a series of adjustable dies, one looser to form the thread and a second tight to chase and finish and that didn't work well either. Manually cutting the threads is out, same reason as with the Mazak plus time involved, just can't get any tool we have in the shop in deep enough to cut a full depth thread.

In the shop we have a Summit manual lathe and a Mazak QT250. No follow rest, and no other centers that would help. Can anyone suggest a method with that equipment? A brand and style of toolholder maybe for the Mazak?

Thanks
Scott

[rusticr6]

we do lots of 1/2" diameter threading. we use a 1" shank Iscar threading tool that uses a indexable insert. then we have a 1/2" diameter center that we use in our QT 30. we had to grind some relief in the tool to get more clearance. we also use a #3 centerdrill to put a small taper for our center.

is there a chance that you could make a center to allow your tool to get in there?

another thing is maybe you could turn the shaft to a diameter of about .410 maybe an 1/8 from the face to allow the threading tool to start in the part, but still have enough room to start the thread. then you could face off that 1/8" after you are done.

[DareBee]

With long threads (especially on SS parts) we very often thread on the CNC down to about .005 stock and then finish thread with a die in the Rigid threader.

[Shotout]

rusticr6

Do you have a number on that tool holder so I can look it up? I've never had occasion to remove the center from the mazak so I'm not sure if I can make one for it, for the manual lathe no problem, I can set the taper attachment on the manual but this is a big order of parts so it would be a last resort just because of time constrains. I might have to neck it down like you suggested, but they cut the stock on their cold cut saw before hand and it is only .0625 past finished length.

Darebee thanks

Scott

[rusticr6]

im sorry, it is a sandvik holder. # is R1664FG-163D.

sounds like it will not work with your setup tho.

what about a v84 holder?

[cdlenterprises]

How many parts? Can you send it to someone with a threadroller?

[davereagan]

I was able to make M14 x 1.25 male threads in my CNC mill by spinning a die down on 13.94mm round. The material was 4140 HT and I went very slowly, maybe 50 rpm. I got about 15 parts per HSS die, but it was only $11.00 per die and the customer loved me for getting him out of hot water with his customer by getting him these bolts before they could be flown in from Japan. The thing that really made the difference was Tap Magic Xtra thick. It is recommended for Inconel and hardened steels, but I'm sure it would help on stainless. 303 is the most friendly of the 300 series stainless steels. Quite a bit easier than 304 because it is resulphurized and makes nice chips. I would think even some good old fashioned dark cutting oil with sulphur and chlorine would work fine. There is all the difference in the world between coolant and oil when cutting threads on a challenging material.

[Shotout]

Rustic thanks, I was able to grind a .125R dogbone grooving insert to get it done. Good threads so I'm going to try and find some factory ground threading inserts that will fit for future applications.

CDL it just 80, but I was suppling them for our fab shop so outsourcing wasn't feasible.

Dave I'll keep the dark oil in mind. We have a couple gallons left in a 5gal pail. I tried tap magic first before the coolant, but the heat began to be a problem about 4ins down the thread at 56RPM so I switched to the coolant since I frequently use it to tap on the VMC in 303, 304 and 316 SS with good results. Didn't think about the dark cutting oil though. Will try it next time I do something similar just to see how it does.
Thanks all