Todays Project - What did you do today?

[PixMan]

Thanks given to all!

It was quite a chore, probably 40 passes to get it done right. The carriage was flying. With rpm at 120 and threading feed at .200" per rev, that means 24 inches per minute rate. A little puckering every time the tool got close enough to the chuck to clear the threaded section and land in the 1/2" wide groove I made. If I had a CNC lathe like Russ, I would have run at about 500 rpm. At 120, that's only 39 surface feet per minute, far too slow for carbide inserts in most cases. Fortunately for me the threading inserts are made with a high cobalt content binder to give the insert higher toughness, a little more shear strength.

I needed that shear strength because I had smashed one corner of the insert when I engaged the half nut haphazardly and it plowed into the first thread, shearing off the insert and part of the supporting anvil. The anvil under the insert had to be changed from the standard 1.5º to a 3.5º one because of the high 2.915º lead angle of the thread.

Here's what the insert edge looked like after the first couple dozen passes, at .080" deep on the compound slide infeed:



Indexed to a new edge, this is after finishing the thread, about .132" deep on the compound slide infeed:



And a shot of the Vardex threading insert holder in it's 250-401 QCTP tool holder block: