Super accurate tapers on a manual lathe? Necessary for a turbine?

[sp1nm0nkey]

Say I wanted to turn a taper to +/- 0.0003 or so on a manual lathe. Assuming I had the ideal setup (tight machine, temperature control), is there a better way than setting the slide on a piece of scrap, measuring, and tightening and tapping the slide with a mallet to get it dead on, and trying again?

I'm curious if this is possible, but I'm also curious if this sort of accuracy is necessary for the spindle on a turbine. I know that it has to be perfectly concentric, and the parts that the compressor and bearings and other things rest on have to be within extreme tolerances, but would this sort of accuracy be necessary on something like http://www.5bears.com/gt012.htm? I wish I could contact the guy but maybe the people here could provide some insight.

[the4thseal]

what are you tapping on? Are you talking about the tail stock? Setting up for tappers is not that big of a deal, what kind of lathe are you talking about? I an ideal world your tolerance is possible if you do your part.
TC

[sp1nm0nkey]

Not tapper, taper. Cut on the compound rest. I'm going to be using a clausing which I can get down to 0.0005, but I'm curious how it could be done.

[Zumba]

It's questionable as to how good of a surface finish you'll be able to obtain using the compound. You'll probably have better luck with a taper attachment that guides your cross slide. Then at least it'll be power fed. Surface finish is very important if there are mating components, especially bearings.

With that said, cutting a taper to +/- .0003 is definitely possible on a manual lathe. My 15x50 Grizzly will do it easily, though it's about as high end as mid-sized Taiwanese machines go.

Whether or not your Clausing will do it will depend on what condition it's in. If you plan on doing a lot of precision work, you may want to look into getting a Hardinge HLV or Monarch 10EE.

[RICHARD ZASTROW]

Zumba, A man of good taste and distinction. If you have a high res. DRO on all axis you can set it up to be a very accurate taper. We had that set up on MANUAL W&S 5A SADDLE TYPE TURRET LATHE and cut damn near perfect tapers on taper-cone pulleys for paper machine web speed controls.

[sp1nm0nkey]

Well, I'm not so conerned as to if the machine is capable as I'm curious as to how I need to set up the top slide.

[One of Many]

The whole time I was reading his procedure, wondering why try and flip the part end for end and retain runout had me mouth agape. Hardinges are nice, but not that nice. Then I got to the part where he discovered his own flawed procedures.

He could have flipped the part, but at least roughed all the critical diameters and finished them in the final turning to retain concentricity.

A couple of methods to set the compound for short tapers.

If you have the turbine, you could true it up in the chuck. Rough set the compound, then indicate the taper in using the compound. Part of that trick is to make sure the indicator is running on the centerline. Otherwise a false reading can result.

Another method would be to set the compound rough, cutting the taper in a piece of scrap stock. Then using hi-spot blue to compare the trubine taper to the one just cut, to inspect if the taper is out enough to justify correction. (I.E. recutting after each slight adjustment for fine tuning the compound to a known reference angle.)

If you already know the taper angle. Standard taper blocks can be used to indicate and set the compound also.

In any method, the chances are that some hand work and/or minor compensation will be required to create a perfect match with the hi-spot blue.

Keep in mind that very minor changes to the diameters will alter the seating position rapidly. In other words, if the turbine is supposed to sit on the shaft in a critical position, you best learn how to sneak up on that too.

DC

[WA Toolman]

If you have a taper attachment, you can set up a 10" sine bar to the appropriate angle, feed across with an indicator, and set it that way. I've also used that method on OD grinders to do tapers to .00002 tolerance where QA used CMM to check it in Clean Room. (Aerospace)

[the4thseal]

just to clear it up. I know that you were not talking about a tapper, i was wondering what part of your lathe your were tapping on? you know, striking ect. The info tht you have been given by the forum is as usual right on the money.