05-11-2015, 10:58 PM
Just read through this whole thread, I was wondering why I had missed it previously then realised it is cunningly concealed in the 'milling machines' section even though it is all about cutting acme threads on the lathe...at least the last 8 pages or so are!
I have just gone through this whole process myself, as briefly described in my other post. Made the new 1" 5tpi crossfeed screw then cut the bronze nut, plus a spare. I had all sorts of problems with the first attempt at an internal acme thread, could not keep the tool bit mounted in the boring bar- turns out I had cut the clearance angles in the opposite direction, thinking for some reason that the internal threading tool had to be ground the same as the external threading tool. It was only after taking the nut out of the chuck that I could see I had been rubbing the back side off the thread the whole time.
After grinding the tool the right way around, and loctiting the toolbit into the boring bar, cutting the internal thread was super easy. I did the whole thing with plunge cuts off the cross slide, with a dial indicator set up as a poor-man's DRO. I started off by drilling to 3/4", then used the acme threading tool on a fine feed to bore to the minor diameter- I then knew exactly where the tool was and how much further to cut when doing the actual thread.
I've been thinking about incorporating some sort of backlash adjustment into my nut, thinking about those spring-loaded arrangements someone linked to- seems to me that they would result in the tool being held against the work by a spring- either when turning or boring- which would be worse than leaving the backlash in.
Also, I wasn't game to grab anything on the dial except the number 1 while doing this thread. I'm too easily confused.
I have just gone through this whole process myself, as briefly described in my other post. Made the new 1" 5tpi crossfeed screw then cut the bronze nut, plus a spare. I had all sorts of problems with the first attempt at an internal acme thread, could not keep the tool bit mounted in the boring bar- turns out I had cut the clearance angles in the opposite direction, thinking for some reason that the internal threading tool had to be ground the same as the external threading tool. It was only after taking the nut out of the chuck that I could see I had been rubbing the back side off the thread the whole time.
After grinding the tool the right way around, and loctiting the toolbit into the boring bar, cutting the internal thread was super easy. I did the whole thing with plunge cuts off the cross slide, with a dial indicator set up as a poor-man's DRO. I started off by drilling to 3/4", then used the acme threading tool on a fine feed to bore to the minor diameter- I then knew exactly where the tool was and how much further to cut when doing the actual thread.
I've been thinking about incorporating some sort of backlash adjustment into my nut, thinking about those spring-loaded arrangements someone linked to- seems to me that they would result in the tool being held against the work by a spring- either when turning or boring- which would be worse than leaving the backlash in.
Also, I wasn't game to grab anything on the dial except the number 1 while doing this thread. I'm too easily confused.
Lathe (n); a machine tool used in the production of milling machine components.
Milling Machine (n); a machine tool used in the production of lathe components.
Milling Machine (n); a machine tool used in the production of lathe components.