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Myford Super 7 apron seized??

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Phil H110/05/2021 21:31:31
383 forum posts
47 photos

I have a 1975ish Myford Super 7 with quick change gearbox and cross feed. The lathe has not been used very much - probably 3 or 400 hours since it was bought brand new back in the 70s.

I had to remove the apron today because the bevel gears that drive the cross feed were jammed??

I took everything apart, cleaned the bits and no damage anywhere but the bevel gears refuse to turn when I refit the bronze thrust washer which puts an end load onto the bevel gears.

Has anybody else experienced a similar snag?

Steviegtr10/05/2021 21:42:59
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2075 forum posts
287 photos

Not had that happen Phil , mine is a similar age. One of your gib screws has not self tightened has it . Also can the gear be turned by hand through the large hole where the compound fits.

Steve.

Phil H111/05/2021 09:11:12
383 forum posts
47 photos

Steve,

The carriage and cross slides still slide very smoothly and there don't appear to be any screws that could over tighten in the apron area.

The gear that I think you are referring to could not be turned when the cross slide plunger is pulled out. Push the cross slide plunger back in and it can be turned (there is a ball clutch that couples two spur gears together to engage the cross feed).

It does appear to be the bevel gears that are giving the trouble.

KWIL11/05/2021 10:05:44
3395 forum posts
66 photos

When I stripped my own apron many moons ago I did not have this problem upon reassembly.

The so called thrust washers (parts LA50 and LA 28) are there as spacers and should not apply end thrust to the bevels.

When the cross slide is off the carriage, or if you withdraw the cross slide leadscrew, can you drive the bevels (plunger engaged) by means of the main leadscrew?

John Haine11/05/2021 10:14:16
3872 forum posts
224 photos

I had a similar problem some years back. I described it to Mr Moore of Myford at an exhibition and he explained the following method which might work for you (if it's the same problem and I recall it correctly.

  • Move the saddle to the extreme right of the bed (I think I may have slid the t/s off)
  • Slightly loosen the s/h capscrews that clamp the apron to the top of the carriage.
  • Push down HARD on the feed engagement lever and keep it pressed with one hand while you nip up the bolts.
  • Then fully tighten all the bolts.

I think that's the process. It worked for me and I haven't had the problem again. He clearly wasn't surprised at the question and had a ready answer so I guess there is a design flaw leading to some misalignment.

Martin Kyte11/05/2021 10:36:27
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2407 forum posts
40 photos
Posted by John Haine on 11/05/2021 10:14:16:He clearly wasn't surprised at the question and had a ready answer so I guess there is a design flaw leading to some misalignment.

I don't think it's a design fault, moving the saddle to the fixed end of the leadscrew ensures that the leadscrew is central to the bearings and reasonably rigid so that the saddle will self centre on the half nuts. If you do it in the middle the leadscrew is more flexible and the nuts may move the leadscrew rather than the leadscrew moving the saddle assembly. It's no different really from the technique for bolting the cross slide end plate back on. Screw right in so that the end plate is close to the nut and nip the bolts up.

regards Martin

KWIL11/05/2021 11:13:28
3395 forum posts
66 photos

The leadscrew nuts are eccentrically mounted so the Eccentric Sleeve LA57 must also be set up to ensure the correct location.

Martin Kyte11/05/2021 11:48:12
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2407 forum posts
40 photos

You are correct (KWIL) that he half nuts cam is in an eccentric mount but as this has not been touched it is reasonable to assume that it is where it should be.

regards Martin

KWIL11/05/2021 11:57:59
3395 forum posts
66 photos

Martin, OP did say he took everything apart and cleaned it, so it may have been disturbed.

K

Martin Kyte11/05/2021 12:56:11
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2407 forum posts
40 photos

fair enough.

regards Martin

Phil H111/05/2021 17:01:17
383 forum posts
47 photos

KWIL.

Thanks, yes you have identified one of the right parts on my machine. The offending part at this stage seems to be LA28, it appears to be bronze, it has obviously been rotating but both the front and back of the washer are nice, smooth and shiny. I am not clear what you mean by 'spacer' but my LA28 is definitely a thrust washer.

My list ends at LA49 but the circlip spacer for the leadscrew half of the mating bevel gear is not listed. That part appears to be a fairly hard steel.

Perhaps the machine has been modified and the thrust washer LA28 is now listed as a spacer and maybe even a different material?

Please can you describe what your LA28 and LA50 look like. Perhaps yours is a slightly later machine with a 'fix' to prevent the jam?? Also, you have got up to LA57!!! You have got at least 8 more parts than me - I'm jealous.

With the cross slide off, no I couldn't turn the bevels via the leadscrew. The bevel gears were jammed and only freed up when I started removing parts. I had to strip down the bevel stud assembly with its herd of circlips before they freed up.

John,

Thanks for describing that procedure. At least know that there s a common issue out there.but there is no way that a loosening and retightening of the cap screws would shift this particular jam. It really was as tight as a weld until I stripped it down.

KWIL/ Martin,

I didn't take the half nuts off or the rack and pinion assembly gears - perhaps I should have called it a partial strip down. I stripped the parts associated with the bevel gears and kept removing parts until the gears unlocked. That included the cross slide off, the leadscrew removed off the machine, the apron off the saddle and both bevel gear assemblies removed.

Phil H

Steviegtr11/05/2021 22:09:20
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2075 forum posts
287 photos

Phil do you have the manual parts book for the S7. I have one in pdf format if you need one.

Steve.

Phil H112/05/2021 09:14:21
383 forum posts
47 photos

Steve,

Yes thanks, I have the manual for my machine but it looks like there is a difference between my manual ending in LA49 for the apron assembly and the version that KWIL appears to have. I am wondering which version is later and whether Myford knew about this fault and carried out a modification.

Can I ask whether the manual you have on pdf ends at LA49 or is it like KWILs going as high as LA57?

It might also be a good idea to contact Myford maybe. I at least need to contact them or do an online search for some new parts because some of the small circlips look like they have seen better days and I need a new felt pad for the front of the carriage - oh and new drive belts maybe.

I think my machine is suffering from old age and poor storage rather than excessive use.

KWIL12/05/2021 09:55:17
3395 forum posts
66 photos

Phil H.

Yes of course the proper name is "thrust washer" and they are just plain "thick" washers that take up the gap between the gear and the circlip, for instance.

You say they apply "end load" onto the bevel gears, they should merely position the gears so that they can turn freely when assembled correctly, any axial load on them comes from the bevel gears trying to move apart. They should be bronze, not shown as available spares, neither are the circlips, but they will be standard sizes of course, perhaps Myford could identify them for you if asked.

Manual is S723W, (actually there is an error on the Myford site, there are two manuals with and without power cross feed. S723W and S723R, Myford manage to miss number the first as S273W !!). Highes LA number is LA61.

Lastly, you public profile does not show a location, a general area would be helpful as one of us may be nearby.smiley

Phil H112/05/2021 10:51:12
383 forum posts
47 photos

KWIL,

Thanks for getting back and yes that is interesting because my manual is S723R and the apron parts list ends on page 45 with LA49!!

I think that was the snag regarding the thrust washer/ spacer - whatever. My washer was definitely applying excessive thrust and might explain why it has always been relatively hard (not excessive just a bit stiff) to operate the leadscrew handwheel.

I am in Cheshire between Ellesmere Port and Chester by the way.

I now have the bevel gears operating smoothly again and the leadscrew will turn everything quite smoothly without the cross slide fitted.

My plan?

I will test whether the cross slide operating mechanism works properly with the cross slide fitted but without a couple of the circlips that I need to hold the operating knob in position.

I will then remove the spur gear assembly from the apron and reassemble without the power cross feed so I can use the lathe.

I will search and get hold of the spare parts (circlips and three countersunk 2BA screws plus other bits and pieces) so I can reassemble the thing properly when I have everything.

In parallel, I will contact Myford and see if they know what has happened and why since about 1975ish. I have the lathe receipt somewhere.

Thanks so far everyone.

Phil H

Steviegtr12/05/2021 11:18:59
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2075 forum posts
287 photos

Sorry for being late getting back to you. The part Numbers go to LA61.

Steve.

Phil H112/05/2021 16:14:36
383 forum posts
47 photos

Steve,

No problem and thanks for getting back to me. The pdf version would be greatly appreciated please. I have sent my e-mail address via a PM. It will be very interesting to see how they managed to cram another 12 parts into such a small apron.

The clutch mechanism for engaging the cross feed works perfectly fine now but I have stuck to my plan and removed the apron spur gears for now and reassembled the whole machine. I will look for new circlips etc online and rebuild after I have done the research etc.

I don't want to start another debate on Chinese versus old British machines but I have to say that I was very impressed at how well some of the parts fit together. Perhaps too well and too complex and obviously too expensive. Impressive though.

Phil H

Martin Kyte12/05/2021 16:51:07
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2407 forum posts
40 photos

Posted by Phil H1 on 12/05/2021 16:14:36:

I was very impressed at how well some of the parts fit together. Perhaps too well and too complex and obviously too expensive. Impressive though.

Phil H

It tends to be what happens when a long lived design is evolved over time, you don't get so much of 'that will do for now we will make a different one soon' Ford amongst others do it with the Fiesta and did it with the Cavalier. It's not country specific more buissness model.

As you say the downside is the machine cost relatively speaking.

regards Martin

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