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Myford ML7 Chucks - Which one?

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KWIL22/01/2021 14:15:24
3447 forum posts
66 photos

I have found that TOS brand (Czech) chucks have been reasonable in price and within their stated specifications.

Dr_GMJN22/01/2021 14:20:36
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1225 forum posts
Posted by Nigel McBurney 1 on 22/01/2021 13:52:19:

The comment on a the cost of a Myford 3 jaw 100 mm chuck sold by Rotagrip is classed as eye watering,for a start if decent work is expected from your lathe then it should be fitted with a good condition r new chuck,the Myford Burnerd 3 jaw with threaded body set the body of the chuck closer to the spindle to reduce overhang, the cost is £321 is this really expensive for a good 3 jaw,back in 1967 when I was looking to buy a ML7 the cost of the direct mounted chuck was £14 and 2 shillings now in those days a skilled engineering worker was earning around or or a couple of pounds above this figure per week Nowadays according to my info a skilled man now earns around twice the amount so could possibly buy two 3 jaw chucks for a weeks wage instead of one in 1967, Its not really eye watering prices its just that we have got used to with cheap fsuspect quality far eastern imports.

I think the £321 is for a "super precision" chuck, there is another standard looking item for much less. However, they both still require a back plate - I just spoke to Rotagrip.

So in terms of geometry they would still appear to be the same as the rest of the backplate type chucks.

From what I can gather, the last internal thread/register Myford chucks were made 25 years ago, and have never been made since.

Apparently there is a method of modding a certain make of chuck to have more of an internal register and thread, but I am waiting for some more info on that.

noel shelley22/01/2021 14:27:34
873 forum posts
19 photos

Cheap chucks ! As has been said, we loose sight of quality and what it costs. Me, £17 a week, a nearly new Myford S7, well equipped £202 in 1970. Still have it ! Noel.

Dave Halford22/01/2021 15:08:00
1820 forum posts
19 photos
Posted by noel shelley on 22/01/2021 14:27:34:

Cheap chucks ! As has been said, we loose sight of quality and what it costs. Me, £17 a week, a nearly new Myford S7, well equipped £202 in 1970. Still have it ! Noel.

Me,

£30 for a 100mm Solidarnosk era 80's polish chuck, came with a leaflet bearing a little bison on it.

Dr_GMJN26/01/2021 17:27:42
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1225 forum posts

Thanks very much all - I know this thread has gone round the houses a bit, but having re-visited my lathe checks last week, my existing chuck is indeed knackered - I can see daylight between the jaws and the workpiece at the ends (the jaws are indeed bell-mouthed). This is what caused the issues with surface finish when machining the unsupported test bar (I re-did the test in my 4-jaw chuck and it was sorted).

Accepting that the 'slim body' chucks are unavailable, it pretty much boils down to:

Pratt Burnerd plus a backplate from RDG, total cost £179.12

HBM including backplate (pre-fitted) from RDG, £124.50

Arc "Chinese Origin" plus a backplate, total cost £68.64

Is it better to go for a separate backplate and machine in-situ, or is the pre-assembled HBM version OK?

Which should I get? The price differences are a bit concerning.

 

Edited By Dr_GMJN on 26/01/2021 17:27:57

Edited By Dr_GMJN on 26/01/2021 17:28:08

Andrew Tinsley26/01/2021 18:39:05
1499 forum posts

I purchased a 4 jaw independent, slim, Myford threaded chuck from Rotagrip, maybe 5 years ago, so they may not yet be extinct.

I don't know of any current 3 jaw chuck with a Myford thread. I have an Arc 3 jaw Chinese chuck. I believe they are made by Sanou but marked Arc. My Arc /  Sanou chuck was quite a revelation. The quality and finish were far better than anyone could expect from its modest price. Maybe not up to Burnerd  standards, but not far off.

Andrew.

Edited By Andrew Tinsley on 26/01/2021 18:47:24

Dr_GMJN26/01/2021 19:02:09
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1225 forum posts
Posted by Andrew Tinsley on 26/01/2021 18:39:05:

I purchased a 4 jaw independent, slim, Myford threaded chuck from Rotagrip, maybe 5 years ago, so they may not yet be extinct.

I don't know of any current 3 jaw chuck with a Myford thread. I have an Arc 3 jaw Chinese chuck. I believe they are made by Sanou but marked Arc. My Arc / Sanou chuck was quite a revelation. The quality and finish were far better than anyone could expect from its modest price. Maybe not up to Burnerd standards, but not far off.

Andrew.

Edited By Andrew Tinsley on 26/01/2021 18:47:24

Yes, the Arc chuck does look nice. I have no idea whether inexpensive = less accuracy or less durability. If it was clear-cut then I'd go for the P-B chuck.

The RDG HBM chuck under their Myford page comes with a fitted Myford register/threaded backplate - it's not integral with the chuck.

Dr_GMJN05/02/2021 15:06:43
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1225 forum posts

I got this one in the end:



The old one was dead. Should be much nicer to use now:



Once I've turned the backplate spigot, does anyone have any tips for marking and drilling the three threaded holes?

Would a transfer punch be ok, then drill and tap in the mill, or does it need to be more accurate? I'm assuming the spigot will fully locate it, and the screws will be in clearance holes to give some wiggle room, and are there just stop it from falling off.

Thanks.

DiogenesII05/02/2021 15:39:31
371 forum posts
169 photos

Transfer one, once that's drilled & threaded you can bolt it up and do the others using the clearance holes as a guide. Mill accuracy will be perfectly adequate, as you say location is provided by the register.

Once mounted, use a known-good object (shank of a fat, unused end mill?) and DTI to check run-out at the jaws. I have one of those chucks, the original 'set-up' pinion wasn't marked, you will probably find that you get wildly differing results depending which pinion you use to tighten down the work. Mark the one that gives best results.

Once you have done that, rotate the chuck about the mounting holes on the backplate, you may find a particular position will give an improved result.

I think it's a good choice, I wasn't that impressed with the 'feel' when I first had mine, but a bit of 'a wire-brush' deburr & some use, and it's improved markedly, repeatable run-out in the less-than-half-thou to one thou range depending on how fussy one wants to be setting the work.

Occasionally EK10 soft jaws turn up on sale at decent prices - well worth getting a set.

Edited By DiogenesII on 05/02/2021 15:41:57

Dr_GMJN05/02/2021 16:00:31
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1225 forum posts

OK great - some good advice.

I was surprised the jaws weren’t stamped 1, 2 & 3; I understood it was good practice to replace in the same position if they’re ever removed?

So when you say check which pinion you turn for tightening - do you mean the one you use for initial tightening? I usually nip all three up one after the other. So mark the one that gives the best initial clamp?

Thanks.

Peter Spink05/02/2021 16:23:21
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119 forum posts
41 photos

That looks nice!

I was in a similar position a few years ago - inside jaws very worn and belmouthed but outside jaws as new, so now have the luxury of a new (TOS) 3 jaw and an old dedicated chuck with just the outside jaws - saves a lot of faff changing the jaws over!

Dr_GMJN05/02/2021 16:36:43
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1225 forum posts
Posted by Peter Spink on 05/02/2021 16:23:21:

That looks nice!

I was in a similar position a few years ago - inside jaws very worn and belmouthed but outside jaws as new, so now have the luxury of a new (TOS) 3 jaw and an old dedicated chuck with just the outside jaws - saves a lot of faff changing the jaws over!

Must admit I'm quite chuffed with it - at least how it looks and how nice the movement of the jaws feels with the key. Shame its going to be more of an overhang than the old one, but there appears to be no way around this these days. Overall it should be way better than the old one though.

Mike Poole05/02/2021 17:00:27
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Moderator
3099 forum posts
72 photos
Posted by Dr_GMJN on 05/02/2021 16:00:31:

OK great - some good advice.

I was surprised the jaws weren’t stamped 1, 2 & 3; I understood it was good practice to replace in the same position if they’re ever removed?

So when you say check which pinion you turn for tightening - do you mean the one you use for initial tightening? I usually nip all three up one after the other. So mark the one that gives the best initial clamp?

Thanks.

The jaws are all different so they must be in the correct order when loaded into the slots. It is common to label the slots and jaws so they are in their own slots. The order of assembly is important but if you get it wrong it is very obvious. If the jaws are definitely not labelled then it would be useful to mark them. They are likely to be very hard and will ruin a number punch or centre punch if dot marking. A discreet grind mark or electric etch pencil mark will identify them. I would suspect that the jaws are given a final grind of the reference faces after the chuck is assembled so they are matched to the slots.

Mike

Edited By Mike Poole on 05/02/2021 17:03:27

Dr_GMJN05/02/2021 17:11:19
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1225 forum posts

Thanks all.

mgnbuk05/02/2021 17:13:02
1057 forum posts
70 photos

I was surprised the jaws weren’t stamped 1, 2 & 3;

In your top photo of the new chuck showing the outside jaws, I can see 1,2 & 3 stamped in the bottom of the darker grey un-ground slot at the LH end of the jaws.

Nice looking chuck, but probably beyond the depth on my pocket. I have a £38 (delivered) Sanou K11 100mm 3 jaw sat waiting for the lathe to get a replacement inverter fitted & I thought that was pushing the boat out !

Nigel B.

Mike Poole05/02/2021 17:28:41
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3099 forum posts
72 photos

There is a school of thought that says leave the register undersize and then the chuck can be centralised with a bit of judicious tapping and then finally tightened, the late Commander Barker who advocated this said he never had a chuck move after adjusting. Of course a heavy interrupted cut could test this and if it did move it may spoil a job. I have said a few times that I was taught to expect a 3 jaw scroll chuck to not be accurate or repeatable, if it is necessary to replace the job in the chuck and concentricity is important then use the 4 jaw independent and indicate the job true.

Mike

Dr_GMJN05/02/2021 17:50:55
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1225 forum posts
Posted by mgnbuk on 05/02/2021 17:13:02:

I was surprised the jaws weren’t stamped 1, 2 & 3;

In your top photo of the new chuck showing the outside jaws, I can see 1,2 & 3 stamped in the bottom of the darker grey un-ground slot at the LH end of the jaws.

Nice looking chuck, but probably beyond the depth on my pocket. I have a £38 (delivered) Sanou K11 100mm 3 jaw sat waiting for the lathe to get a replacement inverter fitted & I thought that was pushing the boat out !

Nigel B.

I was just about to post this when I read your post there:

I take it all back, they are marked, just not very clearly:



well spotted!

Dr_GMJN05/02/2021 17:52:21
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1225 forum posts
Posted by Mike Poole on 05/02/2021 17:28:41:

There is a school of thought that says leave the register undersize and then the chuck can be centralised with a bit of judicious tapping and then finally tightened, the late Commander Barker who advocated this said he never had a chuck move after adjusting. Of course a heavy interrupted cut could test this and if it did move it may spoil a job. I have said a few times that I was taught to expect a 3 jaw scroll chuck to not be accurate or repeatable, if it is necessary to replace the job in the chuck and concentricity is important then use the 4 jaw independent and indicate the job true.

Mike

Thanks Mike, yes I understood that about 3 jaw chucks.

Steviegtr05/02/2021 17:58:35
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2275 forum posts
313 photos
Posted by Dr_GMJN on 05/02/2021 17:52:21:
Posted by Mike Poole on 05/02/2021 17:28:41:

There is a school of thought that says leave the register undersize and then the chuck can be centralised with a bit of judicious tapping and then finally tightened, the late Commander Barker who advocated this said he never had a chuck move after adjusting. Of course a heavy interrupted cut could test this and if it did move it may spoil a job. I have said a few times that I was taught to expect a 3 jaw scroll chuck to not be accurate or repeatable, if it is necessary to replace the job in the chuck and concentricity is important then use the 4 jaw independent and indicate the job true.

Mike

Thanks Mike, yes I understood that about 3 jaw chucks.

Unless you have a griptu 3 jaw. They are pretty good once adjusted. But not cheap to purchase. I found a new 100mm one for £550 so out of reach for most. I was lucky to have one given with the lathe when purchased.

Steve.

DiogenesII05/02/2021 19:10:13
371 forum posts
169 photos

I think the numbers are stamped in one of the jaw's slots - there should be a four-figure serial no., and the jaw number er, somewhere close by..

Apropos tightening, I guess I mean, the emphatic one - I don't find there are too many degrees of tightening down with this size chuck - I don't seem to find much movement in the second or third pinions, and I don't insist on finding some - enough pressure to hold the work, but I don't wring it 'til it cries.

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