Expected runout from an ER32 collet chuck

[buckie555]

I'm looking for some advice/opinions from anyone who uses ER32 collets in a production environment. I'm running a newcomer ER32 collet chuck on a bridgeport spindle and am seeing what I believe is excessive runout. I've clocked the spindle and it's spot on with no indicated runout at all. I then clocked the internal taper of the collet chuck in the spindle and measured 0.03mm runout. With a 12-13mm collet installed gripping a 1/2" endmill the runout measured just below where the collet grips the tool is 0.1mm! It's a long series endmill so the runout at the tip will obviously be considerably worse. I've tried several different collet sizes from two different manufacturers with similar results. I'm thinking I've got a duff chuck?

What do you guys think? Duff collet chuck, duff collet? I'd welcome any opinions/suggestions. Can anyone recommend an alternative good quality supplier based on experience. This is my first experience of using the ER system. Up until now I've been using clarkson autolock but switched to the ER system for what I hoped would be increased versatility.

Any help would be much appreciated.

Neil

[HuFlungDung]

Just check that you 'tip' the collet into the retaining clip in the nut before you screw the nut onto the chuck. ER collets are designed to be self-extracting via this clip, and if you do not seat the collet correctly, the pressure on the collet is very uneven, and you risk damaging or even cracking the collet body.

[MarkT]

I agree with Hu, I believe your issues are "upstream". Er32 collets normally will run less than .001 , at the tool in a sound set up. Not only does not seating the collet properly in the nut run the risk of damage to the collet body, but the human body as well! You can get tools running so out of balance that attempting to cut with them is almost futile, not to mention dangerous! Also verify your seat of the tool in the spindle.
Best of Luck!
MarkT.

[buckie555]

Thanks guys.

The collet is definitely correctly seated into the nut. You've got me wondering now whether the chuck taper is not correctly engaging with the spindle taper. Having said that when I extracted the chuck to check the runout of the spindle taper there were wide even marks on the chuck suggesting a good concentric fit. I think I'll have to spin the chuck up in the lathe to confirm it's runout and eliminate the possibility of the fault lying with the milling spindle's taper.

[DareBee]

ER 32 manufacturing specs are normally a TIR of less than .0002"

[RICHARD ZASTROW]

buckie555 According to my catalog, a .472/.511 range 1/2" "import" ER collet 1.5" from the end of the collet, "concentricity" .0006" For Parlec equivelant .0004""runout accuracy". Import $17.10 Parlec $23.00 Sounds like you could be accumulating runout from collet on back.

[buckie555]

Thanks for all your replies guys. On further inspection last night I've determined that the internal taper of the bridgeport spindle is pretty beaten up and hence the taper of the collet chuck is not engaging as well as it should. It's been well used over the years so I can't have too may complaints. My options now are either get it reground, buy a replacement part or buy a whole new spindle assembly. Can anyone point me in the direction of companies that sell replacement bridgeport spindles, either genuine or copy. Has anyone got a ballpark figure for how much a replacement part is likely to cost. I'm talking about just the spindle shaft itself and not the whole assembly.

Thanks

Neil

[titchener]

Its generally not a good idea to just replace the spindle without having it reground in the quill, so if your current spindle isn't too dinged up the cheapest way to go is to have it reground, I had this done to mine and it came out great.

You need to find a centerless grinding company that is set up to grind the spindle right in your quill assembly, which you will remove and take to them. While you're at it you might as well replace the spindle bearings. There are companies that will do this entire "spindle assembly rebuild" for you. If its a real Bridgeport I believe Hardingne offers this service.

Good luck-

Paul T.

[dertsap]

lyndex makes excellent toolholders , you get what you payed for with them

[dertsap]

company i worked at before had a new cnc that crashed so bad it chewed the spindle taper , they were busy needed a quick fix so the service guy took an old toolholder mounted it in the vise put some paste on it and brought the spindle down on it at a high rpm and reseated the taper , it came out dead nuts , from what i understand its still in use , if your spindle is screwed and you need it running now might be worth trying

[HuFlungDung]

Dertsap,
While I don't think I'd use that aggressive of a technique, I did tune up my spindle taper in that fashion, using lapping compound paste to discover the high spots in my spindle. I took an old toolholder, and turned the flange off of it to get rid of the drive key slots. Did I mention that these flanges are hardened?

I then took that toolholder and ground some lengthwise flat zones along the length of the taper in 3 or 4 places. This is necessary to get some kind of even distribution of the lapping compound, as an excess of compound will simply prevent proper contact. Successful lapping requires that the lap have distribution channels.

Anyway, I ran the spindle slowly and held the toolholder (minus the pullstud of course) by hand and ran it up in the spindle. This quickly shined up the bad spots in the spindle, which happened to be a small bump near the drive key area of the taper. I took a small flap wheel and worked that spot by itself a wee bit, then tested again with the lapping tool.

It worked out pretty well, I was able to get the runout of the tool tip in my spindle speeder down to half a thousandth, instead of three.