OXA 250-007 Parting Tool Problem, Also lead screw speed problem

[LX Kid]

I did a search for my problem but it was from some time ago. It probably still holds true today though. I have a Craftsman 6" lathe and the parting tool is problematic on the compound slide. Not able to get the blade set low enough to do any cutting. I turned the blade around, on the low side of the holder, and the tool holder has to be used on the other corner of the tool holder. This puts the compound an tool post very close to the chuck assuming your parting is a close in cut required. Cuts mediocre but not so good that I wouldn't just tget he hacksaw out and lethe the lathe assist me in cutting the part off. They "say" the solution is to buy a 250-007-T which is a level tool holder rather than a ramped as the 250-007 is. Anyone with an Atlas / Craftsman 6" lathe have any experience with this problem? Now some boring pics. Thanks

 

[WesPete66]

What kind of tool & tool holder is is the 1st photo? Is that the parting tool?
Also, what is the speed problem about?

 

[RJSakowski]

Re: the parting tool, several possible solutions come to mind. 1. The description of OXA 250-007 states that it will use 1/2" or smaller parting blades. A smaller blade will get you closer to the spindle center line. 2. You may be able to remove some of the material at the bottom ot the parting tool holder to get you closer to the spindle center line. 3. If you set your compound angle at 0º and position the QCTP to the left you will be able to drop the parting tool holder below the top of the compound.

 

[LX Kid]

I'm having a terrible time getting a good cut finish. I've tried several different types and radiuses at different chuck speeds being 730, 950 and 1120 rpm's. I was wondering if my lead screw speed is too fast? How do I slow down the lead screw with the gears that I have? I ordered a set of 3D change gears bu twon't be here till next week. Pic shows two 64T gears of which one is on the lead screw shaft. The stud gear is 32T. Amyone have any suggestions for me?

What kind of tool & tool holder is is the 1st photo? Is that the parting tool?
Also, what is the speed problem about?

It's an OXA 250-000 QCTP. The slowest chuck speed I can go is 730 rpm without using the back gear which is going to be too slow. I've tried 1/4", 3/8" and 1/2" cutting tools of different cutter profiles including various carbide cutters. I thought it might be a vibration problem so I put a glass of colored water on the ways and nothing noticeable.

 

[Nogoingback]

There are number of factors that can contribute to your problem. A 6" Atlas is a very light lathe and as a
result not very rigid. Be sure that your gibs are as snug as possible. The tool needs to be sharp and at
the correct height. For parting off, the tool needs to be exactly 90 degrees to the work. Using carbide
tools is probably not going to help at all: high speed steel is more appropriate for the speed of your lathe
and the fact that you'll need to take light cuts. Instead of using power feed, try feeding by hand: you'll
get a better feel for what's needed.

My first lathe was a 6" Atlas and I had problems with it as well, which is probably why most of what I made
on it was aluminum. In the end, I threw in the towel and bought a bigger lathe.

 

[LX Kid]

There are number of factors that can contribute to your problem. A 6" Atlas is a very light lathe and as a
result not very rigid. Be sure that your gibs are as snug as possible. The tool needs to be sharp and at
the correct height. For parting off, the tool needs to be exactly 90 degrees to the work. Using carbide
tools is probably not going to help at all: high speed steel is more appropriate for the speed of your lathe
and the fact that you'll need to take light cuts. Instead of using power feed, try feeding by hand: you'll
get a better feel for what's needed.

My first lathe was a 6" Atlas and I had problems with it as well, which is probably why most of what I made
on it was aluminum. In the end, I threw in the towel and bought a bigger lathe.

Wish I hadn't sold my South Bend 9A last month as it was very accurate with no issues. I realize the 6" was primarily made for starter and generator rebuilds but the lathe should do better than what I'm getting I did try doing slow travel by hand and pretty much the same results. I put a 6" round bar in the chuck and lifted vertically and horizontal with no play. When I did the restoration I put new bushings in. All the gibbs are tight with no slop. I'll try other round stocks and see what happens. Thanks

 

[LX Kid]

I guess I figured it out! Putting cutting tool on "dead center" didn't work for me. I dropped the tool bit down .040" and it started cutting pretty good. I may even be able to improve on this. A little emory cloth and it will shine like a new penny!

 

[RJSakowski]

To slow down your lead screw, interchange the gears front to back so that you are driving from the smaller gear on the reversing tumbler. From your photo, this should halve the feed rate or close to it.

 

[markba633csi]

I'm guessing you had a good reason to sell your South Bend? I can't imagine why you'd replace it with a 6" Atlas
Secondly, RJ is correct you should be able to utilize the tumbler gear to get an additional X2 reduction- the other gears would need to be inverted inside to out (or front to back as Atlas calls it) plus possibly make one gear change to fit everything on the banjo (harp)
Thirdly, stick with HSS tooling, it works best on Atlas machines
-Mark

 

[LX Kid]

I did more checking on dead center and was wrong about it being dead center at 3". It's actually 2.967 as best I can measure. By lowering the tool height by .040" things got a whole lot better! As far as selling he South Bend, the money paid for the restoration and I already had the Craftsman lathe that I restored in 2019 but had never put it into running condition till after I sold the South Bend. I don't need a large lathe to do my little bit of playing around with. I think I have the mental disorder of being a "tool junkie" instead of actually having a real need for a lathe. This 6" lathe was the 3rd one I have restored as well as a 1937 Craftsman drill press.