Back plate dimensions and tolerance

HI I am Bernard Start in Corbridge.

I am preparing to make a backplate for a EC32 collet chuck.

I have measured the spindle face with a caliper and find register 51.96mm and 65.20mm btween 3 studs or 75.20 PCD (Pitch Circle Diameter)

I would apreachiate guidance to more accurate measurments.

I would be happy to share a beer at my expense.

Hi Bernard, what sort of machine do you want the chuck to fit onto?

There may be a standard one available

Cheers Ed Dinning

Sounds like a far eastern machine. The spigot is a nominal 52mm so just make your backplate as close a fit as possible as that is what will affect how concentric the backplate is when fitted.

Stud holes have plenty of clearance for M8 studs so 75mm nominal PCD is fine.

Thats how I have done it on my 280 when making backplates.

Welcome to the party Bernard, I can't help with the question but it is good to have you here. Best wishes. Noel.

Welcome to the forum Bernard.

Agree with JasonB, sounds like a ' standard ' 52mm nose used in the majority of far eastern machines, so will be sized to within normal manufacturing tolerances at the factory that made it, so its definately going to be a ' try it for a good fit ' exercise.

Gentelmen thank you for your interest and help.

The title was FP (Face Plate) for Wiess 250 (Chinese) look-alike Warco WM250.

I am searching for a simple drawing of the spindle face (nose) showing register and stud PCB dimensions with tolerances. The UK dealers Warco and Amadeal have no stock.

This I am sure you know this is so critical to get minimum run out so I do not want to rely on my guessing stick.

Didn't you mean an ER32 not ec32? If so, surely you can get a good direct fitting one quite reasonably from many sources, so why the need for a backplate? I can appreciate you wanting high accuracy for your set up, but the sort of lathe you appear to be talking about does not appear to sound like toolroom standard., And what about the spec of the collets themselves? (See many posts on this subject elsewhere on the forum).

Apologies if I've got totally the wrong end of the stick (not unusual)

Regards

I've not seen a 52mm recess backplate ER chuck and the other sizes I have seen the recess would not be deep enough anyway.

Thank you Mike. I do indeed mean ER32. I should know I own one already. It has spent the last 10 years on my ML7 which is being replaced by a Weiss WBL250F

I just want to put it on my new 250 and need a new FP which I hope to make as good as I can.

If such a drawing does appear, what will you do if it disagrees with your measurements?

If the drawing has any tolerances on it, what do you do if your register is outside those tolerances?

The piece of metal at the front of the lathe spindle has to be the ultimate arbiter of what you make. A piece of paper with lines and numbers on it will not change that.

An option is to make the register fairly loose, then with the securing bolts snug but not tight, tap the collet taper into the best concentricity you can measure. Then drill, ream and pin both parts and finally tighten the bolts.

That won't work

It is fine to do that when positioning the chuck onto the backplate

But as the backplate will need to come on and off the spindle nose many times it wants to be as good a fit as you can on the spindle.

Jason you hit the nail!

You can do just that, and I argue results will be better! The alternative is to machine the backplate register slightly oversize, also allowing slack on the bolt holes.

The chuck is offered up to the spindle as normal, and the nuts turned finger tight or slightly more. At this point the chuck will be slightly off-axis.

Next step is to fit a large diameter test rod in a collet, and clock it with a dial indicator whilst turning the spindle by hand. If it's off centre, tap the chuck gently sideways to nudge it into centre position with a mallet. After a little practice it can be done in less than 3 taps. Then tighten the nuts with a spanner.

No need for an accurate register, or exact measurements and tolerances. The alignment will be as close as the dial indicator can detect, which is about as accurate as it gets, better than a worn or indifferently made register, and adjustable,

I suggest an accurate register is only needed if the operator in in a tearing hurry, and can't spare few minutes needed to clock it.

Dave

I am sorry I think I may have caused some confusion here.

The EC32 Collet chuck I have has a 72mm register rebate on rear and cannot be offered to mate with the spindle which has a 52mm boss register. Hence the back plate and the need for accuracy.

I will not be happy with any solution that involves drilling, reaming and pining the spindle face in situ.

Thanks SOD your solution is on hold for the worst senario even with a BP. In the meantime I try to do the best.

I have been following this thread with interest. I don't know the features of the Weiss 250 lathe, but the dimensions you quote do not tie up with the usual style of spindle nose found on the Warco and Amadeal lathes.

Is this a Camloc style spindle nose? If so, a look at lathes.co.uk spindle nose information might help.

Otherwise I am baffled!

Neil

The following might be of interest. Backplate fitting

This is downloadable pdf article from a trusted source (Arc Eurotrade) who show this on their website page that features backplates and is a article from a back issue of MEW.

Hope it helps, Mike

For those that don't know what they are talking about this is the spindle of my Warco WM280, the WM250 is the same

The spigot on the spindle marked with a green cross is 52mm nominal diameter. The hole in the chuck backplate also marked with a green cross is 52mm nominal diameter. On the other side of the backplate is a 95mm spigot that the chuck registers to.(125mm chuck)

The three hole sin the larger flange on the spindle are approx 9mm dia and easy clearance for the three M8studs sticking out the backplate and positioned on a 75mm PCD.

To change chucks the nuts behind the flange are undone, the backplate complete with chuck slid off and then another chuck slid on and the nuts replaced,

Worth pointing out that as supplied the backplate on my Warco 3-jaws chuck is a tighter fit than that on the 4-jaw and faceplate. This is because the fit of the 52mm diameters is what registers the chuck/backplate combination to the spindle each time it is changed. The fit is so close that the nuts need to be used to jack the chuck off and nipped up in turn to pull it back on. Originally this had to be done for the full length of the spigot but if you look closely at the hole in the backplate I have added a 1degree taper to 2/3rds it's length so only nee djack about 3mm before it is loose enough to pull off by hand.

A quick measure with the digital callipers shows my spigot spot on 52.00, the hole in the 3-jaw backplate also 52.00mm and the hole in the 4-jaw backplate 52.01mm allowing for the fact digital callipers are not exact on internal bores I would say there is maybe 0.01mm clearance but I machine the other backplates I have to fit by feel not measurement.

Edited By JasonB on 05/05/2023 18:49:56

Hi Niel thank you for your interest.

The lathe is a Weiss WBL250F manufactured 11/2022

The spindle is basic 3 hole and not camloc. The spindle flange is : -

15mm thick

100mm diameter

52mm diameter register boss

8mm register boss hieght

24.5mm spindle bore

3 M8 fixing studs on 75mm PCB

All with my guessing stick

I hope you are unbaffled

Your backplate needs to be a snug fit bon the 52 mm register, and the collet chuck needs to be a snug fit (virtually size and size) on the register von the backplate.

Those registers detrmine the concentricity, and therefor the accuracy, of the work held in the collet chuck.

Howard