Bridgeport Clone Spindle Bearings

Allan,

The spindle nose piece is as tight as you can make it using a BOA rubber strap wrench, there is nothing to get hold of with which to measure a torque. How it was done in the factory I have no idea.It certainly does not run warm done that way but has no measure movement.

JS may well tell us how did it.

Edited By KWIL on 29/06/2017 19:06:21

I've been looking at my spindle bearings and considering replacing them. I know its a sensitive job and good bearings are pricey. It's also pretty hard to learn enough about the bearings and find the proper specs for them to be able to find good prices (I'm in the UK). So I've written this doc to summarise all my findings and make it available to others who are looking at this.

https://docs.google.com/document/d/1B4wOqKddGJdzot_bYVlP38qmOxRBZChokvMLOQmkK0Q/edit?usp=sharing

Please let me know what I may have missed / not considered and so on. I realise there are large debates about clean rooms, cheaper bearing alternatives, but I have focused on equivalent specification replacements that can be achieved in the careful home shop.

Modern top brands like SKF, Timken and Toyo are so good that specially hand selected mega expensive bearings are hardly any better. I used a top Timken and bottom SKF ordinary grade bearings in the Tom Senior MT2 to R8 conversion and the spindle taper has 0.0001" tir or better which is plenty good enough for me, actually, I was delighted.

I have noticed complete spindles with bearings for Bridgeports available for under £200, does anybody know what they are like?

Edited By old mart on 28/08/2022 15:23:56

Looking at the prices of those matched pairs of bearings vs regular Timken, SKF etc single bearings I would need some convincing that they were worth 10 times as much. What difference does a "matched pair" make?

And how accurate do you want the spindle on a home hobby ancient old Bridgeport to be? If it is within one thou TIR it will work just fine. So what if the chip loading is one thou more on one side of the cutter than the other, if you are taking a 10 thou cut? Or even a two thou cut? Agonising over a tenth of a thou might be a bit of overkill. Your cutters, their collets and their holders will have more runout than that in most cases. But even regular bearings of good name brand should give accuracy somewhere down towards one tenth as Mart says above.

And regrinding the spindle after new bearings would also be overkill on a home hobby mill. Maybe appropriate for a super high precision grinder, not a flexible old Bilgeport mill. They are a good machine but not super hyper-precision.

Edited By Hopper on 29/08/2022 02:56:00

With bearings it pays to shop about, i found Buck and Hickman Newcastle to be the best price on NSK metric and googled for the best price on RHP imperial for a Denford lathe rebuild. For the savings on using unknown quality Chinese, is it really worth the effort it? The bearings look the same but manufacturing quality checks may well not be the same.

Even grinding spindles do not require a regrind when changing bearings.