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View Full Version : Newbie with some newb questions....



daved20319
06-09-2010, 11:51 AM
First, great site, I'm learning a lot just reading through it. Been a wood worker for years, got into air guns a few years ago, and finally convinced the wife that I NEEDED a metal lathe to work on them :-). Had planned to get a brand new Grizzly 10x22, but when I went to order, it was on back order for at least a month! Needed to strike while the iron was hot, money earmarked for one thing frequently gets used by something else. So I hit the local Craigs List for a used machine. Ended up getting an older Grizzly machine, a 12x24 belt drive, in nice shape, and for the same price as the new 10x22. A lot more features, weight, and power, I think I did okay. May not look pristine, but it runs sweet:

http://i185.photobucket.com/albums/x226/daved20319/Lathe-001.jpg

It also turns out some nice work for an amateur, here's a brake I made for one of my rifles, this is as-machined, in 6061 aluminum:

http://i185.photobucket.com/albums/x226/daved20319/Turning-004.jpg

Ignore that scratch at the muzzle end, I dropped the damn thing when I parted it off :-(! So much for the self intro, on to a question.

First, is anyone familiar with this machine, and is there anything I should be on the look out for? I'm using carbide tooling and a QCTP I got from Little Machine Shop. Maybe not the best, but the cost is such that I'm not worried about messing something up while learning. I've already got new tooling on my list :-).

Second, and most important at the moment, I'm really confused with doing metric threading. I'm going to be replacing the barrel on one of my air rifles soon, it's threaded 13x1. My lathe owners manual is no help, it says I need to move the lower 40T gear out to the 120T ring on the combo gear, but I don't know how to keep it there once I do. Am I missing a spacer? Also, how do you back up the carriage to restart the thread without disengaging the lead screw?

Thanks in advance for any help here, folks. And brace yourselves, this is probably only the beginning of the dumb questions, I'm sure I'll be back :-). Later.

Dave

Fasttrack
06-09-2010, 02:10 PM
Also, how do you back up the carriage to restart the thread without disengaging the lead screw?


I can't help on the specifics of your machine, but generally the procedure for metric threading on an imperial machine is as follows:

1) As you approach a shoulder, turn off the machine and let it coast to a stop, hopefully before crashing into the the shoulder.

2) Retract tool

3) Reverse spindle direction

4) Rinse and repeat as neccessary ;)

The half-nuts are NEVER disengaged if you have an imperial lead screw. You can pick up a thread if you accidentally disengage the half-nuts, but you don't want to make a habbit of it!!

huntinguy
06-09-2010, 09:54 PM
Usually you swap the gears around in position. The inside becomes outside and outside becomes inside. Not sure if that holds for your specific lathe, works on mine.

If you look around on some of the modeling websites, you will see a crank handle that some of the guys use for threading. In short, you disconnect the power and rotate the spindle by hand, using a crank.

http://www.homemodelenginemachinist.com/index.php?topic=7735.0