I've dismantled the head of my Pinacle Excel turret Mill, which is another clone of a varispeed KRV2000 to locate the source of the steadily growing noises within.

As expected I find that the bushes in the spindle sliding pulley are wornout and there is a small "scuff" on the shaft opposite the keyway. There are two split "plastic" bushes 39mm od, 35mm bore and a plastic key. The motor sliding pulley and key seem fine

I contacted Excel in Coventry, and was pleasantly surprised to learn that new bushes and key are available for only £139.60+vat, they were very helpful and konowledgable t.b.h.

Before getting my hand that deep in my pocket I want to try my own repair…

I wonder if anyone has tried making their own from PB or Delrin or?

I've got an oilite bush with 35mm bore which could be skimmed down to fit and then stuck in with bearing retainer…

Hard to imagine I could do any real damage… but would love to hear form someone whose actually done one.

Edited By Mark Simpson 1 on 06/01/2017 13:16:00

Edited By Mark Simpson 1 on 06/01/2017 13:16:51

Thanks Clive, Chris and Muzzer – your thoughts are much appreciated.

Re: the oilite… the inner bearing surface would not be machined, only the exterior which has a step in it to aid location… I had not thought about the lube affecting bonding tho… maybe better with a bit of PB. The current "plastic" bearings are loose and rotation is stopped via the "plastic" key… The pulley is keyed to the shaft so there is no rotation; only slding whne you change speed… The key looks like Delrin and isn't very hard, I guess to act as an overload safety device.

In these machines the Spindle bearings are seperate from the drive bearings, so the only side loads are from the belt which floats between two sprung pulleys…

It seems that although these things are similar, there are a lot of differences in the materials used… apparently these were P.B. until value engineered

Edited By Mark Simpson 1 on 06/01/2017 15:24:00

I've put it all back together last night, and she runs again, much smoother and heaps quieter… I also got a maybe another 1000 rpm by fitting a new belt; the old one was worn to 34mm high as opposed to 38mm…

I bought a piece of 2" acetal from ebay, and used a very positive rake CCGT 09T304 NF25 tool to cut the acetal, it was surprisingly easy to machine and get a great finish; though as Clive said you have to wait a few seconds for it to cool down before final measuring. Made both bushes from a 6" length + one scrap one which I broke when sawing out the keyway.Keys were a couple of bits of Brass as that's what the manufacters now supply.. All glued together with loctite 638 after several de-greasings

It had the advantage that I could make the bushes and keys to the current size of the shafts,and longer to spanover the "scuff" on the pulley shaft; i was worried that fitting manufacturers bushes to the worn shafts would lead to accelerated failure of the new bushes.

I gained some experience in working with acetal and probably spent a day making/fitting bushes and keys; the rest was another day or two strip down, cleaning and lubricating the whole machine.

if (when) it fails again I will add 3 step pulleys and a simple V belt,and use my inverter for the steps in between.

Total cost less than £20 as opposed to £302.40. I did spend another £95 on a new belt but I would have had to do that anyway.

Thanks for the advice; it really helps to have this forum around.