Myford super 7

[Mike BrettParticipant @mikebrett89695]

Hi all

When I use my myford lathe I always disengage the clutch then turn on the motor then engage the clutch to start machining. I do the reverse of this when I stop. Its just a habit I have got into. My simple question is , is this doing any harm to the machine or is it bad practise, and causing excessive wear on the clutch.

Cheers Mike

[Mike BrettParticipant @mikebrett89695]

When to use clutch

[SteviegtrParticipant @steviegtr]

If it's the Bronze cone clutch it will not harm. It just says give it a few drops of oil regularly. The old cast iron clutches can break very easily .

[JAParticipant @ja]

When I bought my lathe the factory warned against using the clutch if you were running a largish chuck at high speed. In such cases the chuck should be run up to speed with the clutch engaged.

I have not used such a configuration (and I do not intend to) but I think we are talking about 2000+rpm and a large four jaw chuck.

JA

[Mike BrettParticipant @mikebrett89695]

How can I tell which I have.

Mike

[SteviegtrParticipant @steviegtr]

I read somewhere that Myford do not encourage the use of chucks larger than 5". Not sure why. I can see your point of putting the clutch under undue loads though. I know the early clutch was a cast iron ring affair & they snap. It's one part that Myford do not sell any more.

[Mike BrettParticipant @mikebrett89695]

Funny you should say that Ja.

The very reason I asked this question in the first place was because this afternoon I was running my lathe at its highest speed . When I disengaged the motor the spindle stopped but the chuck did not. It unscrewed itself and then started to jump all over the place. I was lucky with just a few chips on the lathe paint. Not an experience I want to repeat.

Mike

[SteviegtrParticipant @steviegtr]

Posted by Mike Brett on 13/01/2020 17:47:05:

How can I tell which I have.

Mike

The older type was at the side of the pulleys under the facing case. The newer type is behind the left hand belt cover & is in the centre of the top pulley. It is brass looking with an adjusting screw in the centre. You should know as it needs oiling every few days if you use the machine a lot. This type is silent. The older cast iron one can get noisy.

[SteviegtrParticipant @steviegtr]

Posted by Mike Brett on 13/01/2020 17:54:13:

Funny you should say that Ja.

The very reason I asked this question in the first place was because this afternoon I was running my lathe at its highest speed . When I disengaged the motor the spindle stopped but the chuck did not. It unscrewed itself and then started to jump all over the place. I was lucky with just a few chips on the lathe paint. Not an experience I want to repeat.

Mike

This is one worry I have. I asked if there was any way of locking the chuck so this can not happen. Could be very dangerous.

[Mike BrettParticipant @mikebrett89695]

Thanks for all the replies people. I have just checked my machine and thankfully I have the newer brassy looking clutch. Perhaps if I had released the lever more gently it would not have happened. I have never used top speed before, I just wondered what it would run like. At least there was no work in the chuck, or worst still a milling cutter.

Mike

[JAParticipant @ja]

Myford, the original firm, supplied a 160mm four jaw chuck with the lathe when I bought it in late 2010. The chuck back plate is locked to the spindle by a grub screw mating with a annular grove. This was not the case with my earlier Super 7 which had an unlocked chuck. I have never had a chuck come loose but I have been very aware that it could happen.

I see that the present firm only supply 100 & 125mm three jaw chucks according to their web site. I find the omission of an independent four jaw chuck surprising. I not longer have a useable three jaw chuck – for various reasons it has lost its back plate. Other than collets the big four jaw chuck is the chuck of choice.

JA

[Neil LickfoldParticipant @neillickfold44316]

I always use the clutch, unless screw cutting a thread. I use the motor switch and leave the 1/2 nut engaged. Now that I have a programmable VFD, the start is softer and the stop is softer as well. Another advantage of the VFD is the ability to slow down the spindle before turning off, very helpful with the odd large work piece. With the clutch, you can also slowly engage or disengage on large work pieces.

[Howard LewisParticipant @howardlewis46836]

A, The three jaw chuck without a backplate can easily be made useable again. Just buy a new backplate, and face it before turning the OD to suit your chuck.

"Simples" Or is there some reason, that I've missed, why it is no longer available?

Howard

[SteviegtrParticipant @steviegtr]

I have just refitted the pulleys & shafts today re, fitting a new 3 phase motor & inverter. I oiled the clutch as in the Myford manual. It has been stood sometime so it must have been dry. Before & after is an amazing difference. So I could see you having problems that you had. Being that you must have never oiled it. A presumption from you not knowing where it was. It says disengage the clutch with lever & drip a few drops of oil in the gap & let it run round. Not verbatim Just roughly what it says. I found I put a bit too much oil on it & it started running down the pulley towards the belt. So maybe only a little bit to apply. As others have said with an inverter you can fully program soft start time up to about 10 seconds & same with stop. Also a nice feature is the jog for turning the spindle a little. at a time & you can give that a set point frequency. I have done the whole conversion for a little over £240 & that was using a Omron quality inverter , although it was 2nd hand so was taking a risk on that. Note the missing speed pot. Broke it while soldering wires on to it. Too much heat. 

Edited By Steviegtr on 14/01/2020 23:01:33

[JAParticipant @ja]

To be posted in the morning. Never post anything late at night!

JA

 

 

 

Edited By JA on 14/01/2020 23:45:36

Edited By JA on 14/01/2020 23:46:53

[peak4Participant @peak4]

Depending on the inverter, it's possible to wire up an emergency stop as well as the switch that cuts the input power.
I'd investigate how it works for use on a lathe with a screw on chuck.

I've both a Myford and a Warco 1330, the latter having a D1-4 camlock, so it's safe to run in either direction.
The Warco also has a foot brake, which as well as tripping the motor, also stops the spindle dead.

One thing I have for the Warco is a spindle adaptor, so I can use Myford screw on chucks with the larger lathe.
For obvious reasons, I don't use the brake when I've got a Myford chuck on the Warco.

If need be, when using high speeds, put a wedge under the brake to stop it operating.

Bill

[SteviegtrParticipant @steviegtr]

Thanks for that. 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. No d.c injection. I asked the question as to whether it was possible to make something to stop the chuck unscrewing. Someone said that some of the chucks had a grub screw to lock it on , but not sure exactly what was meant. Pretty good electrically as it was my career but the lathe. Just a learner.

Edited By Steviegtr on 15/01/2020 00:15:16

[peak4Participant @peak4]

Posted by Steviegtr on 15/01/2020 00:14:36:

Thanks for that. 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. No d.c injection. I asked the question as to whether it was possible to make something to stop the chuck unscrewing. Someone said that some of the chucks had a grub screw to lock it on , but not sure exactly what was meant. Pretty good electrically as it was my career but the lathe. Just a learner.

Edited By Steviegtr on 15/01/2020 00:15:16

Personally I've never come across anything on a Super 7, but that doesn't mean to say no-one's done it.
A conventional grub screw doesn't seem a good move though as It would possibly throw the chuck off line with respect to the spindle register.

I do use mine for screw cutting in reverse, and have even used it for turning short tapers in reverse.
Some folks are prepared to risk it by just tightening the chuck well down on the register, but that doesn't really appeal.

I only had short workpieces to do, so I used a drawbar through the spindle with a knurled knob on the left hand end. My 4 jaw has a slightly smaller through hole in the backplate than through the throat in the chuck. I just added a washer and screwed it to the drawbar.
For the 3 jaw, there is a slight gap behind the chuck but in front of the backplate. That allowed be to use a washer with two sides guillotined off, and the edges thinned down, such that I could fit it in the gap without separating chuck from backplate; this again was screwed to a drawbar.

It worked fine for me, with no danger of the chuck rolling across the floor.

The reason for turning a taper on the back of the workpiece was thhat I'd already used a boring tool to turn an internal taper in a Quorn spindle, and wanted to make a batch of arbours with the topslide at the same setting.
Hence turn internal taper with a very small boring tool in the conventional manner, and then swap to a larger tool, and turn the external taper on the arbours with a bigger boring tool and the lathe running in reverse.

Conventionally, to turn the external tapers on the arbours, I would have had to hold the thinner end in the chuck and use normal turning tool, but doing it this way made it easier to cut the thinner diameter, turn down and thread the end of it, and also cut the taper without removing the workpiece from the chuck, hence maintaining concentricity.

Bill

Bill

Edited By peak4 on 15/01/2020 01:47:43

[Mike PooleParticipant @mikepoole82104]

The big bore 7s had a security screw but I think it worked by locating in a groove on the nose but not tightening so it avoids fighting with the register. It would not stop the chuck being loosened but would prevent the chuck completely unscrewing and getting its freedom.

Mike

[JAParticipant @ja]

Posted by Mike Poole on 15/01/2020 07:30:58:

The big bore 7s had a security screw but I think it worked by locating in a groove on the nose but not tightening so it avoids fighting with the register. It would not stop the chuck being loosened but would prevent the chuck completely unscrewing and getting its freedom.

Mike

Correct.

Whether the security screw is tightened or not makes a small but measurable difference to the true running of the chuck.

JA

Edited By JA on 15/01/2020 08:54:28

[JAParticipant @ja]

Posted by Howard Lewis on 14/01/2020 19:24:39:

A, The three jaw chuck without a backplate can easily be made useable again. Just buy a new backplate, and face it before turning the OD to suit your chuck.

"Simples" Or is there some reason, that I've missed, why it is no longer available?

Howard

My three jaw chuck never ran very true, around +/-0.004". I did not use it often and tolerated it when I did.

About 7 years ago I decided to do something about it and bought another backplate. This did not fit onto the lathe spindle. My other chucks (the existing three jaw, 2 four jaw, catch plate, big faceplate and adaptor for Myford collets) had not problems. The inside diameter of the thread in the backplate was correct but the thread crest appeared to have too much flat on it. Measurements convinced me that another 0.003" to 0.004" needed to be taken off the flank of the thread. An easy afternoon job: I accurately mount the backplate, face to face, in the big four jaw chuck, pick up the thread with an internal screw cutting tool and remove the excess metal.

One little problem, my lathe is Imperial with 1/8" lead screw while the thread is M42.5 x 2mm. To get over this little difficulty I bought a gear set from John Stephenson (late of this forum) that fitted to the quadrant in the gear train to the gearbox. I am sure that this would have given an approximate Metric thread but the assembly fouled the casing of the lathe. Therefore everything was put aside.

Sometime later I bought the Myford conversion kit for cutting Metric threads, very expensive but justified since I had, and still have, a project requiring it. Looking at all the bits I realised that the conversion is not a quick job and you only do it if you have to. Since I did not have to the kit is on the shelf waiting for its intended use.

Last year I felt a little ashamed of all this, recognising that the undersize thread was a one off and its production batch was years ago, I bought another new backplate. It did not fit.

And this is for a chuck I don't use or need. Everything a three jaw chuck can do can be done in a four jaw chuck. A three jaw chuck only wins in the ease speed of setting up.

So the unusable three jaw chuck sits on the back of the shelf, unloved.

Enough said.

JA

[SillyOldDufferModerator @sillyoldduffer]

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 WilkesParticipant @harrywilkes58467]

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 yetParticipant @notdoneityet]

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.

[SteviegtrParticipant @steviegtr]

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.

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