How to cut 1 inch thick steel in a timely fasion?

[Craig_J]

Guys, I'm sorry about the link to the pictures. Here are the relevant images:

This is the finished chuck. The nut is off of a commercial fixture (it's geometry is quite complex and it is hardened).



I looked at ER40 dimensions on the internet and at my commercially made MT4 - ER40 holder carefully
before starting, and indicated off the MT4 holder to set the compound for the internal taper.


The hardest part was cutting the internal threads. First I made a dummy model of the spindle.
I also wound up making a LH internal threading tool, so I could cut the threads from the inside
out. The spindle end was turned in the 4 jaw chuck before any cutting on the collet end.
Then when the spindle end fit acceptably on the spindle, I left it there to cut the collet taper
and external threads. I don't have a tool post grinder, so the finish is by file and emery cloth.


It was a tough project with many firsts for me, but very satisfying. Here is the drawing:

 

[Rick Leslie]

That's nice work, Craig. But your lathe is much too clean. Thanks for the pics. They're going in project folder. (For one day when I get caught up...)

 

[Craig_J]

Hah! not only did I spend hours finishing the part, I also spent about an hour just cleaning up before taking the picture. I'm not very good about cleaning up every time I use the shop, but I do try to do so at the end of a project. Thanks for the props, though.

I would like to add a comment about cutting the female threads to fit the spindle. You will notice from the drawing that I designed in a 0.250" landing zone at the interior end of the threads. Even so, cutting them from the outside in was just plain scary. This was before I added the VFD and 3-ph motor, so I was limited to working at 150 rpm, which is 2.5 rps, and with 8 tpi, that means the cutter is moving 0.312" per second! It is much less nerve-wracking to cut from the inside out. So I actually took the time to make a single point LH threading tool out of some 3/4" drill rod. It looks a little bit like a boring bar. My local alloy steel distributor was kind enough to heat treat it for me.

Since then I have found a much better tool for inside threading at Mesa tools. This is a fine tool, works in both directions by inverting the insert, and is a real bargain at just $37. Mesa tools is a good outfit and I highly recommend them (and they are all made here in Oregon!).

 

[raross61]

Hah! not only did I spend hours finishing the part, I also spent about an hour just cleaning up before taking the picture. I'm not very good about cleaning up every time I use the shop, but I do try to do so at the end of a project. Thanks for the props, though.

I would like to add a comment about cutting the female threads to fit the spindle. You will notice from the drawing that I designed in a 0.250" landing zone at the interior end of the threads. Even so, cutting them from the outside in was just plain scary. This was before I added the VFD and 3-ph motor, so I was limited to working at 150 rpm, which is 2.5 rps, and with 8 tpi, that means the cutter is moving 0.312" per second! It is much less nerve-wracking to cut from the inside out. So I actually took the time to make a single point LH threading tool out of some 3/4" drill rod. It looks a little bit like a boring bar. My local alloy steel distributor was kind enough to heat treat it for me.

Since then I have found a much better tool for inside threading at Mesa tools. This is a fine tool, works in both directions by inverting the insert, and is a real bargain at just $37. Mesa tools is a good outfit and I highly recommend them (and they are all made here in Oregon!).

Hi I just wanted to say I second that, Jim at Mesa tools is a great guy and he has a quality product on everything he makes! I also have another great made in USA company, here is ther website: www.breakhearttool.com I cant say enough on there products all USA made, 5c Collet stops , and Expanding mandrels, at very reasonable cost's, and great quality!

Bob in Oregon

 

[martik777]

I just made one of these too and found that setting up a carriage stop. to indicate the end of the threads, and WATCHING the stop instead of the tool made it much easier. IIRC, I was in backgear, under 100rpm though. Making the nut, is not so bad, if you skip that eccentric snap ring - seems to work fine without it.

I would like to add a comment about cutting the female threads to fit the spindle. You will notice from the drawing that I designed in a 0.250" landing zone at the interior end of the threads. Even so, cutting them from the outside in was just plain scary. This was before I added the VFD and 3-ph motor, so I was limited to working at 150 rpm, which is 2.5 rps, and with 8 tpi, that means the cutter is moving 0.312" per second! It is much less nerve-wracking to cut from the inside out. So I actually took the time to make a single point LH threading tool out of some 3/4" drill rod. It looks a little bit like a boring bar. My local alloy steel distributor was kind enough to heat treat it for me.

Since then I have found a much better tool for inside threading at Mesa tools. This is a fine tool, works in both directions by inverting the insert, and is a real bargain at just $37. Mesa tools is a good outfit and I highly recommend them (and they are all made here in Oregon!).

 

[Craig_J]

I just made one of these too and found that setting up a carriage stop. to indicate the end of the threads, and WATCHING the stop instead of the tool made it much easier. IIRC, I was in backgear, under 100rpm though. Making the nut, is not so bad, if you skip that eccentric snap ring - seems to work fine without it.

One reason I didn't try to make the nut was that I don't have a heat treatment oven to harden it. The other was laziness since I had the nut on hand!

The stock gearing produces a lowest speed of 150 rpm. With the VFD, I limit the lowest output frequency to 5 Hz and that produces a fairly ridiculous 12 rpm, which has some utility for slow jogging or unscrewing a tap. I find something like 50 rpm to be much easier to use when threading these coarse threads. If I run the threads from the inside out with reverse rotation, then I go faster because there is no possibility of a collision. I'm sure that if I were a crusty ol' machinist I would work much faster.

One thing about the G0602, I have found it possible to miss the correct mark on the thread dial when re-engaging the half-nut. There seems to be 4 engagement points per mark on the thread dial, so caution is required to hit the same thread. I don't have enough experience on other lathes to know if this is typical, but I got freaked a little after all of the work I had already put in on this part, so I left the half-nut engaged (as is necessary on metric threads anyway) and stopped the motor at the end of each pass, backed out the cross-feed, reversed the motor, then reset the cross-feed and advanced the compound for the next cut. With the VFD, it is easy to jog out quickly but cut slowly. My VFD will tolerate a stop time ramp of about 1.5 seconds, which is not instantaneous by any means but seems to work ok.

I am really just learning to use the lathe well, and don't have the pressure of a shop foreman to get me to work faster!

 

[martik777]

I think my 9A has 4 engagement points between lines as well. I find if you engage the 1/2nut just BEFORE the line it's easier, also move the carriage further from the work so if you miss, you can stop in time.

I usually do a few practice runs to get the timing down. Before I fixed my back gear, my lowest speed was 230rpm, you get good real fast!