machining ovals, and not on purpose.

Usually you can use backlash compensation and get roundness to come out pretty close, I generally will bore or ream any holes that need to be closer than a thou or so anyways.

Ballscrew bearings often will differ from your run of the mill angular contact bearings in that the contact angle is usually higher, on the order of 60 degrees, whereas generally speaking your spindle bearings will be 15 or 40 degrees; something to keep in mind if you're buying your bearings from the surplus market.

That said, you can *probably replace a 60 degree bearing with a 40 degree one and still be okay as long as you're not machining titanium and other tough to machine materials at balls to the wall removal rates.

And then there is dual-row type, which so far, I've never encounterd:

Interestingly, my Bridgeport horizontal machining center does not use the angular contact type but uses a 53205 thrust bearing with spherical ring instead:

is your cadcam software outputting X xxxx Y xxxx R xxxx TO SWING the radius

or X xx.xxxx Y xx.xxxx I delta from start point J delta from start point

I ask this cause was having a problem with a 1994 mori seiki mv 40 yasnak I-80 control CNC mill . boss's post was configured to output R x.xx to swing rads . I could not make a round hole for prayer or promises which ever axis I approached the circle became the wide point in the ellipse

I knew the r could be used to make rads in wire edms but never used this for it nor for mills .

I reconfigured the post to output I J and suddenly I'm making round holes!

Well, if it is making noise then there's a fair chance that the problem is in the thrust bearing, motor, or ballscrew...if it's the motor of course this won't affect backlash but an easy way to test your thrust bearings is to remove the servo motor and put an indicator against the end of the ballscrew and then turn the crew back and forth by hand, if the indicator reading changes each time you reverse directions then there is definitly a problem with your thrust bearing.

To test for a worn ball screw, first you must first determine and repair any problems with the thrust bearing, after which point you'll place the indicator onto the table instead, checking for backlash while turning the screw and reversing direction same as before.

I would say that it seems you have some kind of tool compensation affecting your cut;I think the i j are bypassing that compensation giving you the proper geometry for the result.

I ran into that on a wire machine. I havnt used r since.

Bearings are 60 degree type. Found the belt is shot and the pulley on the screw is all rusty. No joy finding a replacement yet.

Remove 333 to reply. Randy

New bearings installed, X-axis now quiet. Need to machine a hole to see how it gets. I don't think the bearings were that bad to cause the out-of-round, the belt was shot and the pulley all rusty.

Remove 333 to reply. Randy

I wouldn't worry too much about the rusty pulley, your new belt might wear out in ten years instead of twenty is all.

Not sure what went on in there, pulley is rusty, several teeth were packed full of old belt material and belt is serverly worn, grooves are very wide teeth are thin. I'm sure the filled in pulley grooves were causing most of my machining errors.

I think a nice smooth tooth face would most definately help belt life.

Remove 333 to reply. Randy

encounterd:

I think I'd still probably put it back together after thoroghly cleaning it with a wire wheel and get it running again while researching other options. Mori Seiki may well have the part in stock but I'll bet it's not cheap. Also, several ebay sellers appear to have parts for these; you might want to email or phone some of them and ask if they might have a spare pulley kicking around.

Otherwise, you can either make your own or buy one with a straight bore that has the proper tooth configuration, and then bore the center of it out to a fairly large diameter, leaving a flange at the bottom....then you take the old pulley and turn off the teeth so that the taper center portion can be lightly press fit into your new pulley, after which point you'll want to drill and tap 3 places through the flange at the press fitted bores' interface for set screws, so as to positively lock both articles together.

Machine is back together and running. It's a YCI Supermax Rebel 1. OEM does have the pulley for $268 I have the local bearing/power tranmission place looking for options. Salesman at the bearing jooint suggests I switch the whole setup over to a newer style belt. Motor pulley is the tough one if I swicth to another belt style, Fanuc motor has a tapered shaft.

Remove 333 to reply. Randy

Ahh, for some reason I thought you had a Mori Junior

I would probably go back to an older style...

I found the specs on that taper a while back but don't have it handy, you should be able to find it if you look.

Belt is a Gates HTD 550-5M-30

In this size all I can find is 25mm wide pulleys, not 30. Weird cause the 30mm belt is easy to find.

Remove 333 to reply. Randy