Milling Myford Shears

Hi All,
After my previous posts regarding the scraping of the shears on m
Super 7 I have another question :rolleyes: .
The bed thickness seems fine but it's just the sides of the shears a
mentioned before that are worn(closer to headstock).
I think I know somebody that may let me use their bridgeport millin
machine.
So i was considering this. Set the bed up on the table. Dial gauge use
to true up the bed against the unused shear upright. Run endmill alon
the inside and outside edge of the front shear(this is where the saddl
runs).
This should be parallel with the rear shear due to setup.
Next up the saddle is worn on the small guide that runs on rear o
front shear.
Again true up in mill against unused edge and mill off to get squar
parallel edge back.
I hope this will leave me with a good running lathe again :)
Any comments gladly received.
Colin heat
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colinheath
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Can't see a problem with that. In fact I'm sure that's all Myfords do as the side marks look like milling marks as opposed to grinding. -- Regards,
John Stevenson Nottingham, England.
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Reply to
John Stevenson
They are... They specifically state that they mill the shears rather than grinding them. So long as the bridgie has enough travel to do the cut in one go it ought to be easy. If not, it'll be a bit more work. It may be worth doing what Myford do and turning the bed upside-down to take a cleaning cut off the feet to ensure that the bed sits flat on the table when it's the right way up.
Mark Rand RTFM
Reply to
Mark Rand
Hmm interesting. There was an article in MEW (ISTR) that gave details of Myford's regrinding service. I could have sworn that they used a ganged grinding wheel arrangement to do the sides of the shears. I'll dig out the article. The shears on my Super 7 have the remnants of a nice cross-hatch pattern on them - goodness only knows how this was done but it was presumably there for oil retention purposes, they didn't give the appearance of being milled but it is a 1965 machine so things have probably changed.
When I ground my shears (by hand) I found that it was necessary to work within one or two tenths of a thou' to get both the tailstock (inside shear faces) and the saddle (front shear faces) to run smoothly. I'm really not sure but I suspect that it may be hard to achieve the required degree of accuracy doing 3 or 4 shear faces on a milling machine. I guess it will get you close enough to hand finish though.
Mark
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Mark_Howard
They mill the shears. Gang milled on a new machine apparantly, but individually milled on a rebuild. The article from MEW is here:
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(5.4MB)
Scanned in from the Myford handout they send with a price list.
Peter
Reply to
Peter Neill
FWIW there is one solution which has yet to be mentioned. As some of you will recall, the top of my ML7 was Blancharded locally. It left the shears to do. There are two methods and the first is to scrape them which is not a particularly ardous task if the rest is able to be used as a reference to make a straight edge. I outlined this in a Postbag in MEW some years ago. I am still talking of a cost of something like =A335!
The second is possible and that is to use the no4 or rear shear as the datum. In earlier Myfords this shear was actually a non bearing surface or if you want to use the expression, was a fresh air fit. The late Kenneth C Hart, under "Martin Cleeve" and the author of the respected Screwcutting in the Lathe encountered the problem. Again, Jack Radford hit the same problem and published it. Since the Martin Cleeve modification which utilises the No4 shear, I understand that Myford now uses it. In essence, it simply means putting a gib and adjusting screws onto the rear of the saddle and adjusting in exactly the same way as any other gib.
Maybe, there is the simple answer as given and I hope that this will be tested to see what happens.
Norman
Reply to
ravensworth2674
(snip)
Peter
Very interesting, I'd like to read the 'paper' article itself...do you happen to know the MEW edition number by any chance? If not, don't worry, I'll hunt down the MEW index which I know is somewhere on the 'net. --
Chris Edwards (in deepest Dorset) ..."there *must* be an easier way!"
Reply to
Chris Edwards
Hi All,
Thanks for all the helpful replys. In reply to yours norman i would b concerned putting an adjustable gib on the rear of saddle as well a front would cause major setup problems(sqaure saddle) I am going to use the rear shear on mine as it's unused on the side and make a jig that will hold a little grinding tool or scraper. thi should make it fairly accurate. If i get it done i will take pictures and write it up. Cheers Coli
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colinheath
Ah. Thanks Peter,
I remembered the picture of the ganged cutters but the dodgy grey matter recalled these as being grinding wheels.
Mark
Reply to
Mark_Howard
Colin, I am wondering if someone could dig up the appropriate bit of Martin Cleeve for you. It is in Model Engineer but whether it is in the later set of his articles, I don't know but I doubt that it is in the ones which start Vol 113. I am in the middle of a Super 7 rebuild but three things are immediately apparent on your description. The first is that your bed top is worn. This is a cheap and easy improvement to do a regrind. Remember the wear which is causing the trouble is in two planes. The dip in the bed at 6" from the headstock and 6" in from the front shear. The Saddle goes into this "narrow" Theoretically, more than the top thous of wear disappear. The next point is to square the wear of the front shear to go parallel with No 4. I am ignoring the under-wear(sorry) of the shears. To all intents and purposes, the lathe bed is then fine- or within most peoples aspirations. ( You are never going to get a new lathe- new lathe- so accept what you have)
The saddle has a tongue- no I forget the proper word- but it will be worn down at each end. Call it bowed! You can scrape it to remove the bowing- but it could be out of your present range of capabilities. You can soon check what I say by blueing up the tongue- and see what I mean.
Unless you bring the alignment of the bowed tongue to be parallel with the headstock, you might as well go home because it will never be a success.
You therefore bear onto the front and rear shear and make the tongue a fresh air fit. The rear gib was the fresh air one before- but should be nigh perfect.
Importantly, I am not talking theory, Cleeve did, Myford has done it and I have done it twice.
I am not an engineer but I do understand geometry fairly well.
The important thing in all of this is that you will not spoil anything. All that you will be doing is drilling and papping four or five holes for gib svre adjusters and adding a gib.
It can all be made to revert but there is a bonus.
The modification provides for the re- alignment of the saddle with the headstock.
I hope that these modifications are easy and acceptable.
Norman
Reply to
ravensworth2674
I didn't realize he had been buried - won't the relatives object? ;-)
Regards, Tony
Reply to
Tony Jeffree
So your Judge Jeffree- the Hanging Judge.
Seriously, Tony, this Cleeve- Kenneth C Hart man- was a bloke whose face didn't fit the GHT's and Jack Radfords, Tubal Cain's and Prof Chaddock's of this world. He had a ML7 and couldn't afford the whole lot and from his ML4 made all the extra bits to a fantastic bit of machinery. He went on to do things like making his own socket screws- got the issues, went on to divide and graduate with the simplest toys and so on. When he was made redundant, he continued to use this convered ML7 to make specialist nuts and bolts and earn a good living. All he had was the Myford and and a drilling machine. He made the rest from chunks of metal.
It was this attention to detail that I commended his workings in the lathe restoration. He actually made a lathe from and published it again in ME.
Guess who is a bit of a history nerd? My kindest regards- might see you and John at Harrogate.
Norman
Reply to
ravensworth2674

Sorry Chris, I have no idea which issue it came from and unfortunately it's not listed on the reprint.
Pter
Reply to
Peter Neill
Hi All,
Thanks for your many wonderful replies. I did in the end hand scrap the shears. I used a machine vice as in MEW last year i think. measured form the back shear as this is untouched. then carefull worked away at it. it now runs lovely up and down the bed. also milled the tongue down on the saddle back to square as it wa indeed badly bowed. Done some cuts to check and it faces parallel an turns fine too. I am very pleased and will use for a year or so. If it wears again will send away for total regrind of bed and saddle so i have a accurate machine. I have a feeling at present my skills will put the errors in not th lathe ;) i will soon find out as im attempting a froment engine. cheers coli
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