Unimat 3 idler shaft bearing material

This topic has 7 replies, 4 voices, and was last updated 25 January 2018 at 22:03 by Michael Gilligan.

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25 January 2018 at 16:54 #338221
Billy Bean
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@billybean67480
Original cast iron bearing 12mm o/d by 25mm long by 6mm bore wore down so replaced with Bronze

Lasted three weeks so made a new one in cast iron as was originally.

Three weeks later that needs replacing.

Shaft is mild steel 6mm o/d and smooth and concentric.

Holes in bearings were reamed 6mm and pulley spun nicely but for some reason bearings just do not last.

Lathe gets about 2 hours use per week.

Going wrong somewhere – advice please.

Thanks

BB
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25 January 2018 at 16:54 #25773
Billy Bean
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@billybean67480
25 January 2018 at 17:01 #338222
John Haine
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@johnhaine32865
Have you thought of replacing with rolling bearings? Arc have some nice low-profile needle roller bearings that are quite easy to fit.
25 January 2018 at 17:02 #338223
Michael Gilligan
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@michaelgilligan61133
Billy,

At 12mm o/d and 6mm bore, it should be practical to replace the plain bushes with ball bearings. [use two pairs]

MichaelG.

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Edit: crossed in the post with John.

Have a look at these: https://www.ebay.co.uk/itm/ZZMR126-Deep-Groove-Ball-Bearing-12mm-OD-6mm-Bore-Diameter-10pcs/302019248019

Edited By Michael Gilligan on 25/01/2018 17:04:41

Edited By Michael Gilligan on 25/01/2018 17:06:06
25 January 2018 at 17:09 #338224
JasonB
Moderator
@jasonb
Strange, My one is still on its original bearings and shows no wear and I can't say I ever remember lubricating it there. Does not get used much now but got heavily used when it was my only lathe.

Have you got the right length belts on it as too small a belt may be putting undue loads onto the shaft

Edited By JasonB on 25/01/2018 17:09:52
25 January 2018 at 17:20 #338225
Billy Bean
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@billybean67480
Jason

Using the orange poly belts as sold on ebay for the unimat 3

They do not seem over tight – that was my first thought.

As suggested I will go with the bearing suggestions.

Michael – many thanks for the link – will get ordered.
25 January 2018 at 17:28 #338229
JasonB
Moderator
@jasonb
Just whipped my pulley off (original Austrian machine) and the bearings are Oilite ones so may be worth getting a couple of those and hope the other metals have not worn your shaft.

EDIT, these are 10mm OD and there are two of them probably about 8mm wide so either your far eastern one had a different spec or aprevious owner has been "improving" it

Edited By JasonB on 25/01/2018 17:31:07
25 January 2018 at 22:03 #338294
Michael Gilligan
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@michaelgilligan61133
Posted by Billy Bean on 25/01/2018 17:20:22:

Michael – many thanks for the link – will get ordered.

.

Billy,

This supplier gives a little more information about ZZMR126 : **LINK**

https://www.kugellager-express.de/miniature-deep-groove-ball-bearing-mr126-zz-6x12x4-mm

MichaelG.

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Note: I was a little concerned to see that the ebay listing I mentioned; although listing ZZMR126, also describes ZZMR149 [a larger size] in the 'item specifics'.
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