Wobbly spindle, what's causing it please?

[ImanCarrot]

I have an XYZ 1500 mill (looks like a Bridgeport) with Protrak AGE 2 CNC and the finish is crap.

I know it's slightly out of tram in X, but more worrying is the fact that the bit wobbles at it's end (like the bit is bent).

So I got a bit of bar stock and stuck it in the spindle and at six inches length from the collet the runnout is about 1mm(!). Next I stuck another R8 collet in and still got a wobble- a bit less, but definately there.

*scratches head* what would cause this please?

Oh, I've cleaned both collets scrupulously and the collets too.

Many thanks in advance!

[holbieone]

are you getting any free play in the spindle bearings

if not it sounds like your spindle is bent

you can regrind the spindle if it is not out to much

write a program that ramps in "X" and "Z" that matches the taper for a R8

use a die grinder placed at the center of the spindle in "Y"

run the spindle at 500 rpm and slowly work the grinder to the spindle taper

check the contact of the taper with a solid R8 holder with some bluing on it

continue grinding until you have full contact

if you have contact at the top or the bottom of the solid holder adjust the program until the tapper matches

i did this to my spindle that was bent with .01 inch run out ,took about 4 hours

[ImanCarrot]

Nope, no play on the spindle- I pulled and pushed it in four directions stationary and when running in neutral (in case the brake was holding it).

I stuck a drill chuck in there and clocked the bar stock and found no runnout, so I stuck the first ER collet chuck in with the bar stock and marked the max runnout. I then rotated the Collet chuck and noted that the max runnout was in the same position. The same was true for the second collet chuck. I clocked the inside of the collet chuck- runnout. I then clocked the inside of the spindle with nothing in it- slight runnout but negligable.

I'm truely confused now. Maybe there's some dirt or something stopping a good surface mating- the guy who had this machine before me left it in a right 2 & 8 (state)- the head is so far out of tram in X that if you stick a bit of bar stock in there and offer up an engineer's square to it and the mill table you can plainy see a gap of about 2mm across 300mm *sheesh*

Thanks for the grinding info- wouldn't have thought of that *rummages about in his toolbox for that horrible blue stuff that gets everywhere*

[PrecisionSpindl]

Does the machine manufacturer offer an exchange spindle? How much?

Tool wobbles stems from any combination of the following: the tool, the spindle shaft, the spindle interface (collet and tapers) or spindle bearing seats.

We can offer spindle repair. If you need a ballpark spindle repair cost, send a copy of the spindle diagram and parts list to:

Precision Spindle & Accessories Inc.

www.precisionspindleinc.com tel. 519 671 3911
haviland@precisionspindleinc.com fax. 519 652 5994

[Pandinus]

Just an idea,

Could you tilt the spindle to the correct angle and mount a die grinder to the mill??? You might be able to surface the inner taper perfectly true. Just be sure not to take off any more than necessary, or anything important lol.

[gridley51]

Have you checked that the drive pin has not sheared,leaving a bit sticking up in the bore of the taper?
Can you swing the head over so you can look right up the taper to visually check it?
Mark.

[ImanCarrot]

Thanks everyone for the input. I'm gonna get a professional in to look at it, I'm not confident enough.

Thanks again.