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Backplate for ER32 chuck

Recommendations for material and installation

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ChrisB03/12/2020 09:13:03
575 forum posts
192 photos

I have ordered a 125mm ER32 collet chuck from ARC **LINK** for my WM280 lathe. I did not get a backplate as I could not find one which fits on the spindle nose - so I will have to make one. From what I gathered reading some of the related posts the backplate is normally made from cast iron, some make it from steel.

I have a couple of weight plates I rarely used for their intended purpose which I was contemplating using for a backplate. They are cast iron and about the right dimensions I think. Is this a good idea?

Another question is about machining the backplate register. Some say tight tolerance for the fit of the chuck on the backplate, others say loose. For a collet chuck I would prefer to have minimal runout.

Chris

Tony Pratt 103/12/2020 09:46:08
1346 forum posts
5 photos

Cast iron or mild steel will be fine. Make your registers to a tight tolerance but if you get trouble with excessive run out on the collets you can reduce the register [back plate to collet chuck] to allow for adjustments to achieve work concentricity.

Tony

IanT03/12/2020 09:50:41
1749 forum posts
164 photos

Hi Chris,

In principle, yes the cast iron weights should be OK, although the quality of the CI may not be top notch and you may encounter cold spots and blow holes. But in general it's well worth a try - I've used old CI weights (from weighing scales - and they were perfect) and old-style flat irons (quite a few blow holes). But small holes you can fill with JB Weld and sand over if the part isn't critical. For a back-plate, it's worth trying.

There are two camps with regards close registers (or not) and maybe that depends on how confident you are on the chuck (no disrespect to Arc). I made my two ER chucks (for different lathes) just a little loose and then clocked them true. I still check them from time to time and they haven't moved but then I'm not hammering them. I know others here prefer a close register fit.

As a thought, why not try for a close fit on the first attempt and check it for truth. If you are not happy with the run-out you could then take another cut for a looser fit and clock it in? That way you can decide what is best for your chuck. If your backplate has some meat on it, you can always machine the first register off and try again.

Regards,

IanT

Georgineer03/12/2020 11:28:29
451 forum posts
25 photos

Posted by IanT on 03/12/2020 09:50:41:

... As a thought, why not try for a close fit on the first attempt and check it for truth. If you are not happy with the run-out you could then take another cut for a looser fit and clock it in? That way you can decide what is best for your chuck. If your backplate has some meat on it, you can always machine the first register off and try again.

I like your thinking, Ian, especially as I have the same job to do.

George B.

ChrisB03/12/2020 11:50:43
575 forum posts
192 photos

Sounds like a good plan Ian. The collet chuck will take a couple of weeks to be delivered, so in the meantime I'll try transforming the weight plate into a backplate and see how it machines.

Nicholas Wheeler 103/12/2020 12:06:02
447 forum posts
25 photos

Have Warco stopped selling suitable backplates?

I kept the collet chuck when I upgraded to a WM250 from a mini-lathe at an ME show. Part of the discussion with the salesman was what I wanted the lathe for, and what I already had. Two backplates were included as part of the deal.

ChrisB03/12/2020 12:23:55
575 forum posts
192 photos
Posted by Nicholas Wheeler 1 on 03/12/2020 12:06:02:

Have Warco stopped selling suitable backplates?

I kept the collet chuck when I upgraded to a WM250 from a mini-lathe at an ME show. Part of the discussion with the salesman was what I wanted the lathe for, and what I already had. Two backplates were included as part of the deal.

I guess they still sell them, but I placed my order elsewhere. Besides that I can use my money better, I'm better off machining a backplate myself rather than buying one and having it delivered.

peak403/12/2020 13:22:04
avatar
1325 forum posts
147 photos

If it's of interest to others in a similar situation, Warco do supply backplates for £36.75

Bill

Martin Dowing03/12/2020 13:48:37
avatar
292 forum posts
4 photos

As long as your lathe has MT socket the best solution is to buy on ebay ER32 collet chuck on MT shank.

They cost 10 queeds or so.

Henry Brown03/12/2020 14:01:32
avatar
398 forum posts
91 photos
Posted by ChrisB on 03/12/2020 09:13:03:

Another question is about machining the backplate register. Some say tight tolerance for the fit of the chuck on the backplate, others say loose. For a collet chuck I would prefer to have minimal runout.

If you do have go for a relaxed register you can clock it all on your lathe and lock it up, stamp the adaptor so you will know where to put it back and drill and ream between the bolt holes for a couple of silver steel dowels to ensure it stays where you want it.

I've got the backplate but not the chuck assy yet, that's how I'll be doing it if the tight register option doesn't work to my satisfaction.

Emgee03/12/2020 14:04:54
1828 forum posts
240 photos
Posted by Martin Dowing on 03/12/2020 13:48:37:

As long as your lathe has MT socket the best solution is to buy on ebay ER32 collet chuck on MT shank.

They cost 10 queeds or so.

The problem with that method is you lose the ability to pass long rod through the chuck.

Emgee

ChrisB03/12/2020 14:08:33
575 forum posts
192 photos
Posted by Martin Dowing on 03/12/2020 13:48:37:

As long as your lathe has MT socket the best solution is to buy on ebay ER32 collet chuck on MT shank.

They cost 10 queeds or so.

The lathe has an mt4 taper on the spindle so I could go with an ER32 MT4 collet chuck. My concern of going that way is ''precision tooling" at cheap ebay prices. The probability is there will be some degree of runout in the collet chuck, there might be some in the spindle taper as well (have not checked it) and there will be no way of correcting that. With a backplate mounted chuck I will be able to do some slight adjustment.

ChrisB03/12/2020 14:12:40
575 forum posts
192 photos
Posted by Emgee on 03/12/2020 14:04:54:
Posted by Martin Dowing on 03/12/2020 13:48:37:

As long as your lathe has MT socket the best solution is to buy on ebay ER32 collet chuck on MT shank.

They cost 10 queeds or so.

The problem with that method is you lose the ability to pass long rod through the chuck.

Emgee

And that as well.

Good point there Henry. Glad I asked before I started on my own!

Martin Dowing03/12/2020 16:16:04
avatar
292 forum posts
4 photos
Posted by Emgee on 03/12/2020 14:04:54:
Posted by Martin Dowing on 03/12/2020 13:48:37:

As long as your lathe has MT socket the best solution is to buy on ebay ER32 collet chuck on MT shank.

They cost 10 queeds or so.

The problem with that method is you lose the ability to pass long rod through the chuck.

Emgee

Apparently he has MT4 in his spindle.

There is a good chance that a pipe-drawbar allowing to pass through 20mm bar (limit of ER32) can be designed to cater for that. and MT collet chuck drilled and threaded accordingly.

Though yes, otherwise your concerns are of course legitimate.

ega03/12/2020 17:28:50
1937 forum posts
159 photos

If the MT mounted chuck plus drawbar method is used then the tail end of the draw bar could usefully incorporate some means of stabilising protruding material.

John Haine03/12/2020 18:10:47
3531 forum posts
194 photos

Check that the mt4 taper in the headstock is full length first! In the myford big bore S7 it's shortened.

Edited By John Haine on 03/12/2020 18:11:25

ChrisB04/12/2020 06:18:52
575 forum posts
192 photos

I found this video on youtube **LINK** where the collet chuck is made adjustable through 4 screws. Another way to do it.

Henry Brown04/12/2020 09:48:32
avatar
398 forum posts
91 photos

Seems a lot of trouble to go to when a few taps of a soft mallet will do the same thing, unless you are designing offset in for later use but he seems to just be correcting his spindle runout. Unfortunately the sound has packed up on my laptop so I could only watch selected bits of the video!

Howard Lewis04/12/2020 10:09:57
4143 forum posts
3 photos

When I mounted an ER32 chuck onto my lathe, it HAD to be mounted on a backplate, (Which I fabricated )

before tightening the bolts securing the chuck to backplate the surfaces were coated with Loctite, and the internal taper was then clocked, and gently tapped until it ran true.and the bolts tightened.

Some years later, having machined a cast backplate, the chuck and fabricated backplate would not part company, so that the original assembly remains!

HTH

Howard

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