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Michael G
1st Sep 2017, 11:53 PM
One of the things I'd like for the J&S is the universal head (first picture). A couple of other owners have photographed the internals without disturbing them, and I'm trying to work out what is happening in there. I'm open to other's interpretations -
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The second photo just shows some lubrication holes at the rear of the unit and the third photo shows some wicks, so there is a supply of oil going to the phos. bronze bushes. The clear cover at the rear I'm guessing is the oil reservoir feeding the wicks. Obviously you don't want end play in a grinding spindle, so I'm thinking that the two saddles (painted white in photos 2 and 3) are clamping the bushes into the housing and (starting to really guess here) the bushes have a tapered bore which mating sleeves on the shaft run in. The tapered sleeves can be moved apart using a nut and locking washer? (just seen in photo 3)

Another way of getting preload on the bushes is possibly that the thick flange on the RH end conceals a flange on the bush, and the thing in the middle is snugging up to the other end of that bush (that is, the bush is a cotton reel shape). This would mean that the bush on the LH end is just for rotation.

There seem to be two different pulley attachment treatments here too - the first photo shows a pair of lock nuts but the second and third show a grubscrew. (The knurled knob on the far left of the first photo is a tightening method for the collets that can be used - I think the bore is all of 1/2"!) Maybe the locknuts pre tension some how?

Anyway I'd appreciate other's thoughts on how this works (or could work). I did have one owner say that he would strip his down for me and get more detail but that was some time ago and I think it has been forgotten. For reference it is about 3" between the flanges either end of the casting, so not big...

Michael

snapatap
3rd Sep 2017, 10:03 AM
[QUOTE=Michael G;1926330

Another way of getting preload on the bushes is possibly that the thick flange on the RH end conceals a flange on the bush, and the thing in the middle is snugging up to the other end of that bush (that is, the bush is a cotton reel shape). This would mean that the bush on the LH end is just for rotation.

Michael[/QUOTE]

I think that the thing in the middle has a spring in it and the spring provides the preload to take out the end float. The grinding spindle in my Myford grinder has a similar setup. That's my best guess.

Michael G
3rd Sep 2017, 10:45 AM
Something like this then?
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Excuse the crudeness of the sketch, but that principle would certainly do the job. I must admit that I'm so used to assemblies that are shimmed or otherwise adjusted, the idea of springs that dynamically take out end float is something that I still don't consider first up.

I'll do some better drawings and see what I can work out. As a semi random thought, once upon a time people used to have scale calipers (also called proportional dividers too - see pic below). These were basically a cross shaped device that had an adjustable pivot so that when scaling from a picture/ drawing one side would be set on a feature and the other side would scale to give true length. I have thought that it would be handy to have a set of scalable digital calipers, so that the screen would read out a factored dimension when the tips were on a printed feature. Anyone seen anything like that?
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Michael

snapatap
3rd Sep 2017, 02:28 PM
Yep that is exactly what i was thinking. I'm pretty sure i have seen that setup on something before but i cant remember what.

Those dividers are a good idea. I have never seen digital calipers with a scaling feature, if they were available i think they would horrendously expensive (like a digital indicator with bluetooth $1100).

caskwarrior
3rd Sep 2017, 09:33 PM
I think some scaling digital calipers would be a good advanced electronics project, quite a lot of the cheap calipers have an output port and i would think the signal would be readily interpretable be a good arduino or esp32 project.

Michael G
4th Sep 2017, 04:56 PM
This is the tidied up CAD version, partly based on scaled photos. The J&S original has a proprietary collet system in the spindle (J&S 5 taper) but as I don't know what shape they are and are unlikely to get my hands on them, I thought to incorporate an ER16 collet taper and thread. It will allow me to go up to 10mm in diameter (rather than the original's 6.5mm) - not that I envisage using the collets often but it's always the size that you can't quite get to fit...
It also means that I can touch up the MT0 centres that the machine uses on the grinder itself.
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On the drawing I have 'truncate?' on the LH end. Originally this was where the draw bar knob for the collets was operated from but with ER I'm not sure that the extra length is necessary, so may shorten the shaft and possibly the base by 20mm to avoid redundant material (the drive pulley still has to go on there and is around 17mm wide). As shown the spindle is a bit over 150mm. The running surface of the spindle should be ground and I was wondering how to bodge that until I remembered I had a cylindrical grinder (a thought worthy of both :U and :doh: at the same time)

Another decision required is the chuck mount - the manual refers to a 2 1/2" chuck on a J&S 5 taper arbor. Having a chuck that grips is the bit that I'm really looking forward (no tailstock necessarily required). I could make the chuck mount to go on an arbour that matches the ER16 taper and make up a separate draw bar but the nose will have a M22x1.5 thread on it for the collet nut, in which case should I just make up backplates to suit that thread? (M22 hollow thread vs maximum thickness of 16mm for an arbor)

Michael

Theberylbloke
4th Sep 2017, 07:00 PM
Hi Michael,

Sherline produce ER16 headstocks for use on their lathes and mills. They have a range of 3 and 4 jaw chucks with native threading to suit ER16 spindles. The ones I found are 3.1" dia. They have some 2.5" dia chucks but they don't seem to suit a ER16 thread??

1042 ER-16 3-Jaw Self-Centering Chuck (3.1") — Sherline Products (http://sherline.com/product/1042-er-16-3-jaw-self-centering-chuck-3-1/)

They are fairly customer centric and happily answer emails.

There are links on that page to the other two ER16 chucks.

Cheers

The Beryl Bloke