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Myford ML7 tailstock bore, and threading the barrel to fit a chuck

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Bandersnatch15/07/2019 18:27:19
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Posted by Mike Donnerstag on 15/07/2019 10:48:06:

Bandersnatch: I can't say I'm seriously rich, though the £100-odd ML7 headstocks seem to be going for on eBay looks reasonable if it's a solution to the stick-drilling problem.

.... "tailstocks" I assume....

If £100 is what they are going for these days then I'd agree it's not a bad price. When I was looking about 10 years ago I couldn't find anything better than 3-5 times that price.

Mike Donnerstag15/07/2019 18:46:16
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MichaelG/DC31k: I really like the idea of the clamp-on mounting that can be removed. Even if a register is loctited on and a thread cut into the barrel, it would still function as a tailstock, albeit with a limited movement.

Howard Lewis: I think you mean the one Harold Hall published. It's on his website: http://www.homews.co.uk/page75.html - certainly a possibility, though I'd still need that thread and register at the tailstock.

Can anyone tell me the overall length of the ML7 tailstock barrel? I'm asking because even though the butt end of a violin bow is straight, it is only straight for a certain length before the curve starts (known as the camber). It could be that the tailstock barrel might foul the bow stick due to its length. (Nothing is ever easy is it!)

 

Edited By Mike Donnerstag on 15/07/2019 18:48:26

Mike Donnerstag15/07/2019 19:19:04
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Also, can anyone tell me the maximum travel of the ML7 barrel?

DC31k15/07/2019 20:56:14
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Posted by Mike Donnerstag on 15/07/2019 19:19:04:

Also, can anyone tell me the maximum travel of the ML7 barrel?

9 1/2" long.

Overall travel is 3 1/2" but that starts 1/4" inside the casting. So 3 1/4" starting with barrel flush with casting.

You will lose some of this depending on how much you use gluing on the chuck.

duncan webster15/07/2019 23:00:29
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Posted by peak4 on 14/07/2019 20:17:50:

As an alternative and maybe cheaper/simpler method, how about a metal block bolted to the slots on the cross slide, and machined to hold the bow.
Either the block could be made to hold a chuck, or could just have a simple V at centre height with an appropriate clamp, a bit like a normal V block?

Bill

How about a chuck bolted to an angle plate which sits on the saddle. The angle plate has a hole in it to allow the bow to poke through. To align it put a bit of bar with a centre in the chuck and move the cross slide till a centre in the tailstock goes in, then lock the cross slide. First time you have to fiddle about to get the height right, but once bolted up that is fixed. Sounds a lot easier than modifying a tailstock, and will accommodate bigger bows

JasonB17/07/2019 06:58:25
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Bumping this one up as it's a sad day when not one of all those Myford owners can provide a couple of measurements.

Must all be too busy talking about electric cars and navigation at sea!

Michael Gilligan17/07/2019 07:22:51
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Posted by JasonB on 17/07/2019 06:58:25:

Bumping this one up as it's a sad day when not one of all those Myford owners can provide a couple of measurements.

Must all be too busy talking about electric cars and navigation at sea!

.

Noting, of course, that those with direct knowledge will be amongst the ML7 subset.

MichaelG.

Diogenes17/07/2019 08:04:45
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..I can see that I'm going to have to break my vow of non-participation, made on the basis that someone else always comes through in the end..

I have the information required, but do have to go to work first..

more anon..

Bandersnatch17/07/2019 15:36:40
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Didn't DC31k answer it?

Mike Donnerstag17/07/2019 15:44:57
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Yep - Thanks DC31k. That is all the information I should need to see if this is practical.

Many thanks all,

Mike

mark smith 2018/07/2019 16:29:47
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Mike i assume your making bows in the Hill way??? Much easier by handsmiley

Mike Donnerstag23/08/2019 14:08:54
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What do people think about boring the back of a small four-jaw chuck to fit onto the tailstock barrel, and fitting grub screws to lock it, and possibly adjust the concentricity? That would save some length otherwise taken by a backplate. Keeping the assembly as short as possible reduces the amount of bend in the violin bow that the barrel would need to accommodate.

To this end, would it be possible to machine the jaws of a chuck to reduce the protrusion? How hard are chuck jaws? The chuck I was thinking about is the 60mm Indian chuck supplied by Arc Euro:

https://www.arceurotrade.co.uk/Catalogue/Chucks/Lathe-Chucks/4-Jaw-Self-Centring-Cast-Iron-Lathe-Chucks-Indian-Origin-by-Zither

Does anyone know of an alternative, ideally shorter, self-centring 4-jaw chuck?

Once again, any help gratefully received!

Mike

Cornish Jack23/08/2019 16:24:35
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Only just come across this thread but it leaves me puzzled (not uncommon, these days!) . I must be misunderstanding the problem, 'cos I would have used my 2MT insert with an ML7 nose thread in the tailstock and then screwed on the 4 jaw. Obviously missed something but can't see what. This insert has been most useful over the years, allowing chucks at nose and tail 3s, 4s or one of each. If nothing else, it makes centring stock in the 4jaw easy-peasy. What am I missing/misreading, please?

rgds

Bill

Mike Donnerstag23/08/2019 18:31:12
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Many thanks for your message Cornish Jack, but yes I'm afraid you missed something, or more likely I didn't explain very well. I'm using an ML7 tailstock as I need to pass the bow stick all the way through. Using a morse taper chuck carrier as you suggested means that the benefit of the hollow tailstock is lost. It's not an easy problem to solve but I think I'm slowly getting somewhere...

I've purchased an ML7 tailstock (£74 for a Mk2 from eBay) and a tailstock lever (cheapest was £92 from eBay) that will be needed instead of the normal rotating handle. I've worked out, based on the worst case, a cello bow, that the maximum length of the fixture from chuck jaw to the end of the barrel is 250mm. To make this work I think I'll need to do the following:

  1. Shorten the front of the barrel
  2. Shorten the nose of the tailstock
  3. Buy a short chuck and turn a backplate that will be secured (probably loctited) onto the tailstock barrel
  4. Cut a notch out of the back of the barrel to accommodate the bent instrument (violin/viola/cello) bow stick

The objective is to result in a fixture that I can easily and accurately remove and reattach to the bed whenever necessary, without any wasted settting-up time. I will need a minimum of 20mm of travel on the barrel, which is significantly less than the original (approx.) 80mm.

 

Edited By Mike Donnerstag on 23/08/2019 18:46:23

peak423/08/2019 20:09:30
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Mike, perhaps, rather than looking at a metal turning lathe self centring 4 jaw chuck, you might consider one from a wood turning lathe. It may well be of lighter construction, as well as being shorter.
Also , they often have interchangeable jaws; i.e. you keep the moving jaw nuts in the body, but attach different jaws to the front.

I'm thinking something along the lines of THIS, though there are many other makes and designs available elsewhere; some using a conventional chuck key, which may increase the length of the chuck's body.

Regarding the metal turning Zither chuck you linked to earlier, I would have thought that the jaws included would be too hard to easily modify, but Ketan does sell soft jaws for it.

Bill

Mike Donnerstag23/08/2019 20:21:55
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Bill: That's a good idea, though most woodturning chucks don't tend to come with jaws that are able to grip an octagon (bow sticks are octagonal - another problem to overcome!). I've actually been woodturning for many years and have a similar chuck (the old Multistar Titan), but the accuracy is questionable. They also tend to be large (mine is smaller than most, at 3".

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