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Myford super 7

When to use clutch

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SillyOldDuffer15/01/2020 09:57:27
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Posted by Steviegtr on 15/01/2020 00:14:36:

...I have wired the e-stop to an input you can program. I have set it to cut the inverter instantly. But it only coasts to a stop. ... I asked the question as to whether it was possible to make something to stop the chuck unscrewing. ...

Not without compromising something else. Although screw on chucks are quick and convenient to change every silver lining has a cloud, in this case:

  1. The possibility of damaging the lathe (usually gears) when removing a seriously stuck chuck.
  2. Lathe not suitable for reverse working because the chuck can unscrew.
  3. Ditto harsh braking.

My view is simply cutting the power as you've done is a worthwhile improvement, perhaps the best that can be done without elaborate mechanical changes to the lathe that remove the speed advantage of screwing on. Whilst not a perfect emergency stop, cutting power will remove energy from the accident, always a good thing!

Most, maybe all, Chinese lathes favour bolt on chucks. These fix all three of the screw-on chuck's disadvantages and are totally secure. The downside is they take longer to swap and are particularly awkward for anyone with big fingers.

Both screw-on and bolt-on chucks are at the chirpy, chirpy, cheep, cheap end of the market. The grown-ups prefer camlock and other systems because these combine quick change, positive location and secure locking. The disadvantage of these is the cost, and - at least in my hobby workshop - quick change isn't important.

For what I do, being able to reverse my lathe gives it significant advantage over a Myford. For example, screw-cutting in reverse means there's no chance of a headstock crash. But I have small fingers, at least 90% of what I do is forward, and I don't think reverse is actually essential for anything - you can't tell the difference between a thread cut conventionally on a Myford and the same thread cut in reverse on a Chinese machine. I could manage without reverse.

The evidence suggests ordinary Myfords are pretty safe. With that in mind I wouldn't want to introduce a new hazard by braking one hard, though the facility might be a novel way of unsticking a jambed chuck!

Dave

Harry Wilkes15/01/2020 11:50:00
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I have never had a problem with a chuck unscrewing on my S7 suffered the opposite 😂 but I seened to remeber watching a video where someone suecured the chuck on their Myford (maybe Steve Jorden) try a youtube search

H

not done it yet15/01/2020 11:59:32
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Not sure about the ‘chirpy chirpy cheep cheap end of the market’. 70 years ago, myford were the cheaper end of the market and the Raglan was about twice the price - a far superior lathe. The Raglans still had screw-on chucks (although a L100(?) chuck option was available as an option).

I was wondering if the actual chuck run-out was 4 thou - or anything chucked in it. Neither seems that bad for a 3 jaw self-centring chuck - one just does not re-chuck items and expect concentricity. Not even with only a one thou run-out.

I don’t think I have any directional problems with thread cutting, just cutting in forward spindle direction, with tumblers and choice of front or rear cutting available. Again I might be wrong or it could be the superior quality of the lathe?

The only essential for reversing the spindle direction, as far as I can see, is when cutting metric threads with an imperial lead screw (or vice versa). And that could be done manually, if no motor reverse was available.

I remember one youtuber, who put up videos on how he made a brake for his lathe (with screw-on chuck). He never finished it, after he was informed of the possible consequences of using it!

I suspect the reason for chinese bolt-on chucks is simply cost. Nothing else.

Steviegtr15/01/2020 23:07:42
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Well as JA stated I have the same problem with the 3 jaw chuck running out. I have had the imperial dial gauge on it tonight. The chuck body & rear has 1/4 of a thou runout. Pretty perfect. Put a piece of bar or a new dormer drill bit in & it was 4 thou out, that was right up at the nose end. I found 3 sets of jaws in boxes that I got with the lathe. One set was new. So I set about fitting them. They were very tight but in they went. Dial gauge back on & I now have about 2 1/2 thou runout. Not acceptable. I have a 4 jaw with the wrong backplate so will set about trying to fit it to one of the plates I have. My problem is I am no engineer & will probably make a booboo of it.

Paul Kemp15/01/2020 23:32:59
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When I did my apprenticeship all the lathes had 3 jaw chucks, somewhere, mostly unused. 3 jaw chucks were considered poor on holding power and little if ever fitted, even frowned on unless you were holding hex bar. 4 jaw was the order of the day. 4 jaw is so much more versatile for odd shapes, off centre work, no problem with special reverse jaws, you just turn em round, you can even have some one way and some t'other. In terms of running true, they can be bang on, every time. It's hardly a problem to dial a job in and if it takes 5 mins in a hobby setting no real problem. If you want true in a production setting collets are the answer. I can't see 2 1/2 thou runout on a 3 jaw as a problem.

Paul.

Howard Lewis16/01/2020 11:42:05
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If you have 2 1/2 thou run out on a 3 jaw chuck, you have a good 'un! many will will give 5 thou when new..

If you want absolute concentricity from the start, you use a 4 jaw and clock the work until the run out is acceptable, to you.

If you want diameters to be concentric in a 3 jaw, you turn the two , or more, diameters without disturbing the work.

Work to limits that are realistic, Working to tight limits for the sake of it may not make the item function any better, just more costly in time, effort and possibly tooling. That's why a Rolls Royce costs so much more than a mass produced car.

But do you put a price on satisfaction?

Howard

Howard Lewis16/01/2020 12:01:06
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When you come to fit the backplate to the 4 jaw chuck, I would suggest;

Fit the backplate to the Mandrel (Make sure that both are clean and free of swarf; otherwise you are wasting your time )

If the backplate screws onto the mandrel it needs to be a snug fit on the register..

The accuracy with which you do these jobs, determines the accuracy of the work that you do in the future..

Skim the front face of the backplate, just enough to clean it up.

Turn the OD to be snug fit in the chuck.

If the chuck is bolted to the mandrel, drill the holes for the fixing bolts / setscrews / studs.

Once the 4 jaw is operable, in conjunction with your clock, you can obtain as little run out as you wish, produce what ever eccentricity that you need, or turn irregular shaped material.

H T H

Howard

JA16/01/2020 13:34:03
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Posted by Howard Lewis on 16/01/2020 12:01:06:

Once the 4 jaw is operable, in conjunction with your clock, you can obtain as little run out as you wish, produce what ever eccentricity that you need, or turn irregular shaped material.

H T H

Howard

And even hold hexagonal bar.

JA

SillyOldDuffer16/01/2020 13:45:04
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Posted by not done it yet on 15/01/2020 11:59:32:

Not sure about the ‘chirpy chirpy cheep cheap end of the market’. 70 years ago, myford were the cheaper end of the market and the Raglan was about twice the price - a far superior lathe. The Raglans still had screw-on chucks (although a L100(?) chuck option was available as an option).

...

I suspect the reason for chinese bolt-on chucks is simply cost. Nothing else.

It's all relative: I agree a Raglan is a better lathe than a Myford (apart from the 254s), but it's not what I would call an expensive machine either. Dean, Smith and Grace come to mind!

But so much depends on what the lathe is bought for. For many purposes it doesn't matter how long it takes to swap a chuck, in other cases time is money and a camlock will soon pay for itself.

I wonder which costs more to make, a screw mount or bolt-on? The screw-thread type requires one hole and a threading operation which industry can do in the blink of an eye. Bolt-on chucks need 3 threaded holes, arguably more work, and the bolt-on needs a more elaborate lathe spindle too. Not much in it, but both systems are 'easy' compared with a camlock.

Can't find the reference but I believe bolt-on chucks hail originally from the USA.

Dave

Edited By SillyOldDuffer on 16/01/2020 13:46:34

Mike Poole16/01/2020 13:49:51
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I have said before, does the runout of a three jaw chuck really matter? It is a useful device for turning a job at one setting. There are too many variables if you replace the work in the chuck, the job position in the jaws and how you tighten the chuck can all affect concentricity if concentricity matters then you need to indicate the job and with a three jaw what are you going to do if it is out? I have no idea of the runout of my three jaw because it doesn’t matter. If a job needs to be concentric then it’s going in a collet or the 4 jaw independent.

Mike

Howard Lewis16/01/2020 14:34:18
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The concentricity provided by a three jaw chuck will, be influenced by a number of factors.

The concentricty of the scroll plate, within the chuck, relative to the lathe axis

The concentricity of the scroll relative to that mounting register

The consistency of the teeth of each jaw relative to the other jaws.

The position of the jaw locations within the chuck body.

The relationship between the gripping face of each chuck jaw and the jaw location faces..

If you allow a tolerance of + / - 0.001" on each of these parameters, a new really good chuck will be within 0.005", A bad one could be 0.020" and still be within individual manufacturing tolerances.

And these figures take no account of any angular misalignments, or wear during use.

Rather than complain, be pleasantly surprised at the accuracy of an item produced for relatively low cost, in high volumes for our hobby!

Howard

Steviegtr16/01/2020 23:10:58
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Well from all the comments it would seem the best I can expect is what I am getting from a 3 jaw chuck. The make is Prat & whitney. So today was the 1st day I have tried turning with my new to me lathe. Outcome on some mild bar 1 1/4" dia just cleaning the 1st 1" along the bar. Taking between 3 to 5 thou at a time. I made a proper mess with it. Tried dry & with cutting oil . Still a mess. The tool was a hss one. Not one of those triangular tipped ones of which I have none yet. The tools have Eclipe printed on them so I guess good steel,,,, crap operator. P.S it was not chattering ,just a bad job done by me. Guess it can only get better. Going onto youtube to gain some education . Also comments from you guys who know what you are doing. Regards

Steve.

Hopper16/01/2020 23:46:47
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Did you sharpen the tool bit? Got pictures of it?

What you need is LH Sparey's book "The Amateur's Lathe". Gives the full run down on how to grind your HSS toolbits for various purposes.  And just about everything else you need to know to learn to use your Myford.

YouTube is entertaining but it's a poor substitute for education.

 

Edited By Hopper on 16/01/2020 23:51:24

peak417/01/2020 00:11:14
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To help people to help you, and I'm most certainly not one of the experts, it might be useful to post photos of, the setup, the finish, and the tools.
Also tell us what RPM and feed you were running.

"Mild Steel" can come in a whole range of varieties, especially if it's come out of a scrap box, and you've no idea of its origins. Some turns beautifully, the finish on other stuff looks like it's been pebble-dashed.

1 ¼" bar is a reasonably large diameter in some ways on a Myford; does it fit up the bore of your 3 jaw, or were you just using the section of the jaws in front of the chuck body? If the latter, and without tailstock support, particularly on a worn chuck, the finish would likely be compromised.

Don't worry about setbacks for the time being, all will progress well given time. ( I hope anyway as the 8" square plate I've just faced looks appalling. )

Bill

not done it yet17/01/2020 07:05:00
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I agree a Raglan is a better lathe than a Myford (apart from the 254s), but it's not what I would call an expensive machine either. Dean, Smith and Grace come to mind!

Agreed, but we are talking hobby lathes? There were not so many working class who could afford a new Raglan back seventy years ago. New Myfords were mostly all they could afford and there were still huge numbers of adepts and similar types still in regular use doing a good job - as well as the much better Drummonds of the pre-war period.

Just remember the 254 was myfords attempt to copy the Raglan, but some 25 years after the Raglan came to the market - it should have been a better lathe by then! Apart from the lubed gearbox, I don’t think they advanced that much - even if at all.

These days every bolt hole is drilled at the same time - Howard will confirm that Perkins even fitted as many as 32(?) bolts in a single operation to fit cylinder heads. We are talking here of lathes made over half a century ago by the then current methods of manufacture - and some are still far better than the current batch of chirpy chirpy cheep cheap lathes imported from afar.

I am quite happy to work within the limitations of my older lathe. The last Raglan offering is a huge improvement on the first models. Does the myford 254 have an automatic adjustable carriage trip, for instance, that will reproducibly cut to within 0.1mm of the shoulder?

But all irrelevant. These lathes are British manufacturing history and were still improved copies of older designs or clones of American lathes, even back then.

S-gtr is very much in the minority, to have a Pratt and Witney chuck. Most have Pratt Burnerd (still a good chuck). But with only 2 1/2 thous run out, I would be happy with that. I swapped the jaw positions until I achieved minimum run-out with my old 3 jaw chucks, then marked the slot for the first jaw - and left it at that.

If without tail stock support, the lathe itself could be the source of the poor finish - as well as the other reasons offered. Wear in the slides and bearings can make getting a good finish a challenge, but all possible to overcome - as demonstrated by some superb examples of models made with such examples.

Steviegtr17/01/2020 09:19:59
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tool tipPratt chuck1st cutBy Not done it yet.

S-gtr is very much in the minority, to have a Pratt and Witney chuck. Most have Pratt Burnerd (still a good chuck). But with only 2 1/2 thous run out, I would be happy with that. I swapped the jaw positions until I achieved minimum run-out with my old 3 jaw chucks, then marked the slot for the first jaw - and left it at that.

If without tail stock support, the lathe itself could be the source of the poor finish - as well as the other reasons offered. Wear in the slides and bearings can make getting a good finish a challenge, but all possible to overcome - as demonstrated by some superb examples of models made with such examples.

Sorry wrong name of chuck. Some photo's. A friend says he thinks I had the tool too low. Many thanks for all the help. I did not have a tail stock centre in. Could that be the issue. Or one of them.

Length of bar

Edited By Steviegtr on 17/01/2020 09:21:33

SillyOldDuffer17/01/2020 10:21:38
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Five things jump out from Stevie's post about poor finish:

1. Using a nice Myford with a Pratt Burnerd chuck doesn't guarantee high-performance turning, especially when the driver still has 'L' Plates!

2. The cutting area is too far out from the chuck without support (a steady or tailstock). Vibration will ruin the finish. Stick a DTI on the end and see how far that rod/pipe bends when pressed with a finger. Rule of thumb, an unsupported job shouldn't project more than 2½x it's diameter from the chuck. Be extra careful cutting jobs not fully gripped by the full length of the chuck: they can lever out with painful results. (Don't ask how I know...)

3. I'm instantly suspicious of the red-painted cutting tool. It's a brazed carbide type, which have to be sharpened on a special wheel. Carbide performs best pushed hard and fast by a rigid machine, and hobby lathes are relatively slow and underpowered. Chinese hobby lathes tend to do better with because they're faster, but my 2800rpm / 1.5kW WM280 only just gets into the carbide manufacturers recommended working zone. That said, carbide does a good job at slower speeds, especially with sharper inserts, the main problem being relatively poor finish. (I use carbide inserts most of the time because it's convenient.) Owners of classic lathes, like the Myford, tend to prefer HSS tooling because it's cheap and gets a good finish without fuss. (I switch to HSS when carbide won't produce a good finish, or I need a specially shaped tool.) The disadvantage of HSS is having to buy a grinding wheel and learn how to use it. Fact I learned on this forum; brand-new brazed carbide tools may need to be sharpened before use - this probably explains many disappointments!

4. What metal is being cut? I wasted months struggling with my mini-lathe before finding that my junk box was full of scrap that didn't machine well. My advice, beginners should avoid scrap and DIY store metal like the plague! Instead buy known material with good machinability, look for words like 'free-cutting'. Ordinary mild-steel is OK rather than good in a lathe: EN1A is twice as machinable, and EN1A-Pb is better again, a joy to use. Brass is more forgiving, but it still pays to get alloys intended to be machined. Aluminium can be a pig: pure Aluminium and the alloys sold to make extrusions all machine poorly - nasty soft sticky stuff. The Alloys intended to be machined are much better, but they need to be lubricated with paraffin.

5. There's a lot to learn. Materials; lubrication; carbide vs HSS; tool-shapes; work-holding; cutting-speeds; depth-of-cut; feed-rate; the limitations of the machine; driving the dials and measurement; gap between expectations and practicalities; etc. Buy a copy of LH Sparey 'The Amateur's Lathe'; read it carefully, but remember it was written before carbide and DROs. You might like to read something more modern as well, perhaps our own Neil Wyatts 'The MIni-lathe'. Books from the 'Workshop Practice Series' are also highly recommended, and Camden Steam are always worth checking for Engineering related material - reprints of Industrial Classics, and books on Clocks, Gunsmithing, Foundry Work, DVD Training etc.

Good news - it's all excellent fun. Don't be discouraged by early failures. Very few of us take up knitting instead!

Dave

Edited By SillyOldDuffer on 17/01/2020 10:26:35

JA17/01/2020 11:35:35
961 forum posts
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I cannot improve on Dave's excellent reply.

Just a suggestion - experiment and keep notes on what you have done. That is what industry does for metals such as high temperature alloys.

JA

SillyOldDuffer17/01/2020 11:42:27
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Posted by not done it yet on 17/01/2020 07:05:00:

I agree a Raglan is a better lathe than a Myford (apart from the 254s), but it's not what I would call an expensive machine either. Dean, Smith and Grace come to mind!

Agreed, but we are talking hobby lathes? There were not so many working class who could afford a new Raglan back seventy years ago.

...

 

I think we're having a violent agreement! I see Myford's as top-end Hobby Lathes, nudging into the small development workshop, but not ideal for education, persistent busy precision work as might be done by University Technicians, or for repair work in garages and ships etc. They were always a poor choice for production work.

The problem with Myford's in education and production is simply that they aren't robust enough for those environments. It's not that they're badly made or lack features, but they're small and delicate. Heavier lathes like the Raglan and up are a much better bet.

Myfords can of course be used for precision work, but again they're too delicate for everyday, all-day, reliable no-fuss performance in the hands of a busy technical team, as opposed to recreational work done by one careful owner! And Myford lathes are just too small for much mechanical repair work: a bigger lathe is needed in a ship's engine room.

I think Myford the company shut down because their potential customers were almost all mean-bean hobbyists. Those hobbyists wanting new were very tempted by Chinese value for money. Others spotted the enormous benefits of buying a surplus industrial machine dumped on the market when CNC took off. Previously unaffordable new, or likely to be worn out second-hand, these suddenly became available in good nick at very reasonable prices, often costing less than a second-hand Myford, and at a time when VFD's solved the 3-phase at home problem. Unfortunately as well, most Myford enthusiasts bought pre-owned equipment. Trouble is buying second-hand Myfords did nothing to support Myford the company and Myford the business went down because so few of their fans were loyal enough to buy a new lathe. What Myford needed to do was develop a new lathe, of the Chinese type, but finished to old-Myford standards, that was profitable at a selling price slightly above the competition. That's really hard to do and risky. I guess the owners chose to invest their money elsewhere.

My point about threaded and bolt-on chucks being cheap was that better is available if needed, not that all lathes fitted with them are nasty rubbish! For hobby purposes, I think quite rough machines will do satisfactory work. Chinese hobby lathes don't win beauty contests, the controls aren't silky smooth, and the owner has to keep an eye on adjustments. But - with care - they can and do cut as accurately as anything else. Much the same can be said about badly worn industrial machines: by working around the defects the operator can still do good work. The main problem with both compared with a solid well-made fully-fitted machine in good order is the time wasted fiddling with them, which might include chuck changing. In most professional settings, machines that waste time are a disaster; in most hobby workshops, it doesn't matter. For amateur purposes I think what's produced by a skilled operator is more important than the machine. Professionals play by different rules!

Dave

Edited By SillyOldDuffer on 17/01/2020 11:44:48

Howard Lewis17/01/2020 12:52:23
3536 forum posts
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Your piece of steel looks, to me, to be torn, rather than cut cleanly.

This suggests to me possible causes, whether in isolation or in combination. A tool that is not sharp; tool off centre height; or wrong cutting speed for the material.

You might do better to use a High Speed Tool, which can be ground on an average grey carborundum wheel.

Not clear from the photo that your brazed carbide tool is really sharp.

Grind the HSS to give 5 degrees clearance on all faces, front, side and top (otherwise known as "rake" ) For these purposes, The exact angle probably does not matter too much as long as it is somewhere between 5 and 10 degrees.

One thing which has not been mentioned, is one of my hobby horses, setting the cutting edge exactly on centre height. Too high and the tool rubs rather than cutting, too low and the clearance angles are wrong.

A quick check on the tool, being at centre height is that when facing, there should be no "pip" at the centre. If there is, the tool is not at centre height. Shim it until there is no "pip".

My advice would then be to make up a simple centre height gauge.

PM me with an E mail address, and I'll send a picture of the one that I made, and constantly use.

Once you have confidence that the tool is sharp and on centre height, you can begin to look at the ".What is itesium?" that you are trying to cut.

Also, what is your cutting speed? For Mild Steel, most folk would be aiming for about 100 feet / minute.

So for 1 inch diameter, the speed should not exceed 380 rpm. If in doubt, go slower.

Don't rush the feed. Difficult to estimate, but try to aim for about 0.004" / rev.

Don't be so slow that the tool rubs, rather than cutting. This generates heat which softens the tool so that it looses its edge, and becomes blunt. And so the vicious circle continues!

For this you have to learn how to turn the traverse wheel at a constant sped. This will require both hands, smoothly changing over the drive from one hand to the other.

You could use the power feed, via the Leadscrew, but that is a complication far too far for you at this stage, I suspect.

Also, putting a small radius on the cutting edge of the tool would improve the finish. But DON'T try this yet, or you might make the tool rub.

You have taken the first steps; just build on these. You need to to learn to walk before running!

These more advanced techniques can come after mastering the basics. We are all on a learning curve. None of us know everything!

HTH

Howard

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