More Newbie Questions - Lathe This Time

[Bamban]

Now that the BP is set up, I am turning the attention to the Atlas lathe I picked up on a package deal with the BP. It is an ACER 12x36 Taiwan made. I read about setting the compound to 29-30 degrees, so I took some pictures for you guys to tell me where the previous owner set the compound. And maybe he has a reason for it.


Here is the first installment




I grabbed the protractor to see what readings I can get. Ran it against the 2 different angles to see which one is really the correct one and which one to adjust to as needed. It looks like one is closer in reading to the graduations against the point where the 2 angle cuts meet. Should I adjust this? I read for general purpose work, 29-30 works fine, should I move the angle following the machine markings or use a protractor? Is this critical? I am assuming for reference "zero"





The AXA tool post appears to biased to the right side, is there a reason for this? Should it be centered? Again, all these are as they came from the previous owner.





Thank you!

 

[JimDawson]

If the compound was perpendicular to the lathe center line, that would be 90* by the scale. So, 90-60=30, the compound is now set at 30*. I have seen lathes with the protractor scale numbered in either direction, most Asian lathes seem to be numbered like yours. setting the compound 29-30* is standard for threading 60* threads. On your scale there is no mark for 29* (61*) so you just have to rotate to where you think it is. This position moves the compound handle out of the way of the cross slide crank, and is a good position for general turning.

The right hand bias of the tool post is just where it wound up. Mine is not always centered because I don't watch carefully when I tighten it down. As long as the T-nut is within the T-slot, you should be fine. Normally you would not let it overhang unless absolutely required for an operation, and then take care that you don't overload the setup and break something. For some odd machining operations, I have had to move things around in what might be called ''unconventional'' positions.

 

[chuckorlando]

Yea they can be numbered either way. Just depends on if the 0 is from the x or the y. I find myself moving my angle all the time due to it being such a small machine (9x20) it helps in getting around this or that. In school they are for the most part just set at 29/61 there abouts and left there

 

[Bamban]

Jim and Chuck,

Thank you for your input. Looks like I need to leave the compound alone for now.

 

[Frank Ford]

Typically, you set the compound at 29 (or 61) for single point threading, and many of us keep it at that setting for convenience if we cut threads often. But, the reason it's adjustable is so you can change it easily. Yesterday I set mine at 1.5 degrees to turn a quick 3 degree included angle taper for a little mandrel, and I'll just leave it set there until I do another job - then I'll change it to whatever angle works for the next operation.

 

[Andre]

Just set it on 30 degrees. Don't get hung up on the 29.5 degree business. The last pass on a thread should be a full cut (moving the cross slide in, not the compound) using the threading tool as a form tool. You get a smoother and more accurate thread that way.

 

[Hawkeye]

Just to stir the pot, I normally set the compound to parallel to the bed for everything but threading and tapers. That way, if I'm facing or cutting to a shoulder, I can lock the carriage and advance the tool with the compound to sneak up on that final dimension.

Lately, I've done threading using only the crossfeed. Not too much difference in finish, so it works for me.

 

[John Hasler]

Just to stir the pot, I normally set the compound to parallel to the bed for everything but threading and tapers. That way, if I'm facing or cutting to a shoulder, I can lock the carriage and advance the tool with the compound to sneak up on that final dimension.

That's what I do too. I mostly use the compound if I'm not using the leadscrew and the length of the cut is short. The rack on my carriage is pretty sloppy (needs a couple of bushings).