View Full Version : Converting Clausing 8520/30 to R8 Collets?

Spin Doctor
12-27-2018, 03:50 PM
I seem to remember this being mentioned years ago that there was someone converting these Mills to R8 Collets. Any body remember or am I imagining it. If so did it involve modifying the existing spindle or did have take a replacement set of bearings. The spindle bearings are 7205's so they would only have a 25mm bore which is problamatical with a R8 Taper. The original bearings are Fafnir 7205 W's which are 15 angular contact. I'm thinking Barden 106 HRL's or any of their equivilant would work if it means a new spindle shaft. I'm very seriously considering picking up a 8530. No room for a BP. Plus the thing I don't like about the RF45 and similiar Mills is there is no way to do longer work mounted to the side of the table.

George Bulliss
12-27-2018, 03:57 PM
I have an 8525 (B&S #7) and it sure doesn't look like you could stuff an R8 into it and if you could it would be a lot of work.

I have heard of people bolting on a Bridgeport M head, which would be far less work.

12-27-2018, 05:48 PM
I have a 8520 it is number 2 m taper. I have never had a problem getting collects msc has them.. I made some tool holders to used face mills if I needed them. even made my own saw holder. I have been able to make or buy tooling to do any job I have needed to do on that mill. I had one job I did on that mill that made me a lot of money.

12-28-2018, 11:52 AM
Check with Wells-Index. I believe they can do that sort of conversion. They rework/regrind B&S 9 spindle tapers to R8. Do not know if your spindle has enough material to allow that modification.


old mart
12-28-2018, 01:29 PM
With the bearing bore at 25mm, you only have a wall thickness of 0.01725. If bearings with a larger bore were available, a special spindle could be made which would be stronger. Even a couple of millimetres would make quite a difference.

12-28-2018, 04:29 PM
I also been looking at the 8520/8530 as of recently. As well as the small Rockwell.
I also wanted the common R8 collets. The R8 collet can be reground from a B&S 9 or larger spindle. (a $450 ordeal from Wells-Index)
It's a no-go with MT2 or BS7. (unless you maybe possibly grind your own new spindle/bearings et al)
It is not feasible to do, you could just go out and buy a R8 mill, if you really need R8 tooling.
You could run straight collets with straight shank tooling, a lot of guys do that with MT2 and BS7.
I ended up buying a Select OB mill off craigslist , R8 taper, and I am all done with the shopping and fretting over collet taper.
Here is my take on it, after all my searching for the same thing you want:
You get the Clausing and deal with straight shank tooling,
You get a used Rockwell, Select OB, Enco or similar machine,
You get a table top mill/drill with R8.

12-28-2018, 04:36 PM
With a collet, could you use Tormach quickchange tooling?

12-28-2018, 08:48 PM
This is my 8520 with a Bridgeport M-head.
It is still 2 Morse taper, but it never bothered me
as to how to get tooling for it.


Spin Doctor
12-29-2018, 12:52 PM
Well this went about where I thought it would. Even given the small work envelope of the 8530 the ability to rotate the top of the collum I'd a nice feature. One could even build a slotting attachment for the oether end. If I go this route I think I'd make a new shaft and see how it turns out before replacing the original part. I think 4140 prehard should be tough enough for home use thanks for replies