Unwanted Taper

[bill stupak]

My lathe is cutting an unwanted taper. A little backround first, it's a Craftsman/Atlas 12x36 I just bought. It has 1/2" thick flat ways that have .002" wear on the outboar way for about the first 8" from the head stock, everywhere else measures spot on. I don't have a machinists level, so I got it close with a regular one and used "Rollies Dads Method" to align the lathe. Please advise me if I did this correctly, I chucked up a steel bar 16" long with the same dimension through out, mounted a dial indicator in the tool post, made sure it was on center and found the high and low spots next to the chuck. I then zeroed the DI on the average. I moved the carriage to the end of the bar and found the average of the high and low and compared that to zero. The difference was .007, I then shimmed under the rear of the HS till the two averages met. I then repeated the whole process and found a difference of .001, I shimmed again until they matched. Now it is still cutting a taper of about .003 in just 2". My test piece is aluminum 2" in diameter, I am taking .005 cuts and it measures smaller next to the chuck. There is no provision to adjust the headstock as it fits snugly between the ways. Any advice?

Stu

 

[Karl_T]

You didn't do Rollies the way I did a long time ago.

I put a large diameter piece in the lathe, made a skin cut. Adjusted on lathe. Repeat.

IIRC, you need to raise the back leg in front


My story, We bought a 16,000 lb. Mazak M4 and was told level is CRITICAL so we got the best Starret level and spent a whole day leveling the machine. Well, it cut a taper. So, I started twisting the lathe by raising/lowering the front leg at the tailstock. After about ten skin cuts and adjustments it was turning perfect.

 

[wa5cab]

Stu,

I assume that "HS" means "Headstock". When you say that you "shimmed under the rear of the HS", do you mean that literally (between HS and bed) or do you mean that you shimmed under the rear of the HS leg?

 

[bill stupak]

You didn't do Rollies the way I did a long time ago.

I put a large diameter piece in the lathe, made a skin cut. Adjusted on lathe. Repeat.

IIRC, you need to raise the back leg in front


My story, We bought a 16,000 lb. Mazak M4 and was told level is CRITICAL so we got the best Starret level and spent a whole day leveling the machine. Well, it cut a taper. So, I started twisting the lathe by raising/lowering the front leg at the tailstock. After about ten skin cuts and adjustments it was turning perfect.

Your way is how I started to make adjustments and then got sidetracked by "Rollie". I think I will go back and try that .

Thanks, Bill

 

[bill stupak]

Stu,

I assume that "HS" means "Headstock". When you say that you "shimmed under the rear of the HS", do you mean that literally (between HS and bed) or do you mean that you shimmed under the rear of the HS leg?

Yes that was not stated correctly, I shimmed under the leg.

Bill

 

[cdhknives]

How do you tell the difference between twist and tailstock alignment? Are you hanging large stock out without supporting it on a center at the tailstock?

 

[bill stupak]

Success, I've got it to less than a thou on my test piece. I had multiple problems in my measurement and going too far in my shimming. Now onto aligning the TS.

Thanks, Bill