Myford Super 7 bed

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Hi,

I am restoring a super seven and at this point am starting the "geometry work" (having dealt with the painting). Bed wasn't particularly worn, just a 0.02-0.03 mm where it had been mostly used. I have blued it up on the granite table and proved that the far ends are touching, and after tocuhing up the feet (mounting pads) the tailstock end seem to measure the same as the headstock (virgin), which means I can assume this can be used as reference to measure against when scraping. I know the tailstock end will have to be scraped down, but am trying to think of a reason why not to leave the headstock end "as is". If I had ground it of course this would have been different, but as this was never an alternative, I am inclined to leave the headstock as reference also for later The tailstock can be shimmed (and would possibly need that anyway) to line up with the spindle. Does anyone think of a reason why not to leave this area "untocuched"?

Kind rgds
Jan Sverre

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

scraping under headstock..

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Of course, all accessories mounted to the bed would also have to be shimmed..

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Hmm.. that alone might be a showstopper..

[HopperParticipant @hopper]

It is the vertical surface of the front way that is the most critical. The flat surfaces on the top should be fine for home workshop use at .02-3mm wear. All that wear will do is allow the toolbit to drop .02-3mm below centre height, which will affect the turned diameter by less than you can probably measure at home. It is worth very carefully reading the book Machine Tool Reconditioning by Edward Connelly before diving in with the scraper.

Have you done some turning tests on the lathe to see if in fact it turns to size and true, parallel etc? If the end result is within the parameters you require for your workshop,no scraping at all might be necessary. (Assuming of course that all bearings and gibs etc are all correctly set up and adjusted first. Scraping is the last resort after first setting up all these other things. Even then, it is often the vertical surface of the carriage that needs scraping, not the bed ways.)

Edited By Hopper on 01/08/2016 14:04:57

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Thanks for the feedback!

​I am aware of the rather small significance of this kind of wear on the final result (depending on the diameter).

I am also quite OK on the scraping (yes, Connoly is one of teh books you have to go through..), so this is not a problem. I was just curious if any had thought like I do, namely to just scrape the "right-hand sdie of the bed" and leave the headstock area pristine.. I reckon it is not good practise, but assuming most restorers now would send the bed off to a grinding shop, they would not consider this at all I can and may do the whole length, but just seems liek a waste of time and also "loosing" this for future reference. As far as I can think of myself, the only accessory needing adjustment would be a fixed steady, and this is doesn't seem like too much of a sacrifce to adjust later

No, haven't done any turning on this lathe yet.. it Wasa "basket case" (rust) so had to strip ut all down and begin to breathe life into the machine again. I have my bigger lathe to use, but thought this smaller one ccould be OK for smaller/hi rev turning jobs, and it looks like it is pretty much in OK shape (apart from having been left to die outside..)

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Sorry for all the typos.. I swear it is the keyboard..

[Martin KyteParticipant @martinkyte99762]

Hi Jan

As far as I can remember (from from an article on Myford regrind) the proceedure was to apply a downward force in the middle of the bed when setting up on the slideway grinder to give a deflection of half a thou in the middle. The bed was then ground flat so that when unbolted the bed had a 'hump' of half a thou. This allowed for wear to flat and then the same again hollow to total one thou. You are not much past that even at this stage assuming that half a thou was perfectly acceptable from new.

I would agree with the other posts which suggest that the vertical ways are far more important.

It may be worth finding out the geometry of your Myford. On the early machines I think the front shear was used to guide the saddle and I believe there was /is a mod you can do to transfer the load on the saddle from the front to the rear shear which should be unworn. Maybe others will know where to find the details.

regards Martin

[KWILParticipant @kwil]

If the S7 is an early example, ie one with the "narrow" guide on the saddle, then the rear vertical face of the rear shear is unused and will be the unworn original reference face for setting out the shears.

You may well have to restore the underside of the saddle as well. Grinding this and the shears will lower the center line of the saddle to leadscrew so remember the apron has to be adjusted for this as well.

Edited By KWIL on 01/08/2016 14:27:01

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Thanks again for the replies!

​Yes, this is old enough to be the narrow (front shear) guided. I have read the other posts and article (Radford) on the topic of modifying it to so called wide guide. I might do just that as there seem to be good reasons for this.. even though as it is now, the saddle is not worn appreciably, so it is not a MUST.

I also read up on the way Myford did the grinding setup. This was however to compensate for wear, ie. making it concave, so it would take longer for wear to be a factor. Mine a little convex now, so I will scrape that in.anyway, despite understandably it doesn't do that much of a difference.. just want to get it right at this point. Haven't measured the verticals properly yet, but will do soon and then know how much it needs of a refurbish.

I will of course not leave the saddle "unblemished", and will give it a proper 20 ppi finish (try my best at least)

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

A short update. The vertical guides are not much worn, as is the rest of the bed. In the neighborhood of 1/1000 of an inch. I also took the headstock area down a well. For those wanting to follow the progress, I am doing a video series on this.

[AjohnwParticipant @ajohnw51620]

Usually the narrow guide bed has little wear on the width but a thou is a thou and it would be better with out it.

The usual problem is that the rear face of the saddle guide that runs on it will have worn to a curved shape, The gib strip will probably show the same sort of wear and may be bent. Both are pretty critical.

You'll probably find that the flat area of the saddle that sits on the rails is still pretty flat. So much so that very little if any correction will be needed. I'd doubt if correcting that would mess up heights. In fact in any lathe that uses this sort of set up and others a couple of thou wont stop things fitting together. The problems come when regrinders want to remove 0.030 or more to save setting up. Some will clock things up and just remove what needs to be removed. Rare though.

The gibs that run on the underside of both rails wear. One can be turned over but the other needs regrinding.

Shimming the saddle up to the bed is great fun. This is where a thou out can show problems 'cause the ideal running clearance on all parts is probably less than that.

Chris Heapy used to have some comments on myfords. His pages are archived on the web by some one so can be found.

John

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[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Thanks for the information! This was very good and I will check the areas closely.

Yes, a thou must be "treated" while I am at it here..

I remmeber the pages from Mr.Heapy now.. great, will look them up too

[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

Hi.. me again,

btw.. anyone knows what the factory specs were for flatness/parallelism/alignment on these lathes.

2/10.000 inch over 1 foot?

[AjohnwParticipant @ajohnw51620]

I certainly don't know and would suspect to some extent was a matter of luck. Take 10 lathes and there will be some variation in them. Some may be perfect in all respects.

I decided to sell my Myford and told the person who bought it to send it back to Myford for a bed regrind and saddle refit. The prices were very reasonable. He left it too long and the factory closed.

I've only seen one machine scraper at work. The moving part needs to be correct and the rest was done by feel by moving it around making sure that the right area is corrected aiming for perfection. He was making heavy drop forge dies on a Bridgeport and had to do it periodically because the machine wasn't really built for that sort of thing. I haven't any real experience in this area so can't really comment. I have scraped ML7 plain bearings back in. That's fun. The spindle has to be kept aligned to the bed in a vertical sense in particular. A wee bit of stressing is possible horizontally.

John

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[Jan Sverre HaugjordParticipant @jansverrehaugjord87863]

OK.

Yes, it was a sad fact that it was needed to close down the Myford works..

I have a friend (one of your countrymen) who says that some of the personell at Myfords started up again with their own grinding (maybe also restoration) service. maybe this can be an option for some that is need of having a Myford bed done professionally

Jan Sverre

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