Myford change wheels

[Nick HulmeParticipant @nickhulme30114]

Posted by John Stevenson on 31/12/2016 08:55:06:

True a 127 will give the perfect metric thread on an imperial machine give that the machine is capable but

John,

Are then you saying it would be cynical in the extreme to manufacture and sell 127T gears for the Myfords?

😀

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Stevenson on 31/12/2016 08:55:06:

Myfords when they brought the ML series lathe out worked out a set of gear suitable for imperial and metric screw cutting and from 1947 onward's – pre internet forums and over stuffed armchairs -tens of thousands of uses from all walks of life managed to cut near perfect threads with this combination.

It's only since the advent of internet forums … < etc. >

.

Some very valid points made, John

But where would you place Martin Cleeve in the story ?

… A man before his time, or a nutter ?

MichaelG.

[Neil WyattModerator @neilwyatt]

Posted by Michael Gilligan on 31/12/2016 10:52:26:

Posted by John Stevenson on 31/12/2016 08:55:06:

Myfords when they brought the ML series lathe out worked out a set of gear suitable for imperial and metric screw cutting and from 1947 onward's – pre internet forums and over stuffed armchairs -tens of thousands of uses from all walks of life managed to cut near perfect threads with this combination.

It's only since the advent of internet forums … < etc. >

.

Some very valid points made, John

But where would you place Martin Cleeve in the story ?

… A man before his time, or a nutter ?

MichaelG.

Perhaps they hadn't invented the 'error budget' in his time

History is littered with people who work to spurious levels of accuracy (the maker of the Antikythera mechanism is one – some of its very clever functions are swamped by the limitations of the gear train).

Neil

[bodgeParticipant @bodge]

Myford did offer an improved accuracy pitch screw for one lathe they made in the early forties

Stated as 0.0005 in 1 inch, 0.0008 in 3 inch, 0.0015 in 12 inches……………b

according to www lathes ,co

Edited By bodge on 31/12/2016 11:32:31

[Neil WyattModerator @neilwyatt]

Posted by Sandgrounder on 30/12/2016 09:07:10:

Posted by Georgineer on 30/12/2016 01:04:54:

Posted by Brian Oldford on 29/12/2016 11:36:42:

I'm pretty certain others are available too e.g. 28, 63 etc.

Yes, but I don't know why, since the standard set covers all usual requirements. Can anybody suggest a reason?

George

Isn't the 63T gear used for metric screw cutting as as it's almost half of a 127T or a quarter of 254? It's less than a 1% error.

John

Edited By Sandgrounder on 30/12/2016 09:07:36

As Michael has prodded me it's my 'specialist subject'.

16 TPI is a pitch of 1.5875mm exactly. To cut a 1mm pitch thread on a machine with a 16TPI leadscrew you need to divide the pitch by 1/1.5875 which is the same as multiplying it by 0.6299212…

Now the ratio 63/100 = 0.63 is very close to 0.6299212.

So with a 16 TPI leadscrew introduce the ratio 63/100 and you can cut very accurate threads.

With 8tpi, use 63/200.

Naturally with a four-gear train you can (a) get more convenient ratios and (b) easily vary the gears to get other metric pitches.

With some lathes 21 tooth (63/3) gears are more appropriate.

The 63-toot gear gives an error of only 1 part in 10,000. That's almost certainly less than the pitch error of the leadscrew, as JS points out, so any more elaborate solution is pointless.

Neil

[Neil WyattModerator @neilwyatt]

Posted by bodge on 31/12/2016 11:30:07:

Myford did offer an improved accuracy pitch screw for one lathe they made in the early forties

Stated as 0.0005 in 1 inch, 0.0008 in 3 inch, 0.0015 in 12 inches……………b

according to www lathes ,co

Edited By bodge on 31/12/2016 11:32:31

Interesting, 0.0005 over 1" is 1 part in 2,000 and 0.0015 over 12" is 1 part in 8,000, both worse than the 63-tooth metric solution, confirming it is perfectly good for 'normal' lathes.

Neil

[bodgeParticipant @bodge]

Posted by Neil Wyatt on 31/12/2016 12:42:59:

Interesting, 0.0005 over 1" is 1 part in 2,000 and 0.0015 over 12" is 1 part in 8,000, both worse than the 63-tooth metric solution, confirming it is perfectly good for 'normal' lathes.

Neil

I expect myford thought that was pretty good for a cut square thread at the time , what with the war going on an all, i would hope rolled acme thread would fare better these days

I think its down to operator ability as much as anything, which ever way one goes about it ( 63 or 127 ) for a one off its pretty much a bespoke item…………b

[Neil WyattModerator @neilwyatt]

> I expect myford thought that was pretty good for a cut square thread at the time , what with the war going on an all, i would hope rolled acme thread would fare better these days

I wondered if that was true..

I found 0.004 over 12" for precision ballscrews and 0.0005 over 12" (one in 24,000) for "precision plus" so 63T may fall down for the highest precision uses (the data was from Thompson Illinois – interesting that the Myford leadscrew of the 40s is better than a 'precision rolled ballscrew' of the 2010s!)

Neil

[MWParticipant @mw27036]

I would say the main perception of things being made better in the past is probably down to the fact they might've spent more money on them than they remembered they did. So when they compare a cheap product today, they aren't actually giving a fair comparison.

A contemporary account is far better to look at for a depiction of what the quality was like, and a guide I read written in the 20's complained of poor quality castings and lathes without leadscrews at all on the cheaper end of the market, and that there were a lot of smaller manufacturers whose names have dwindled.

But I think myfords were actually quite cheap when they first appeared on the scene? Maybe they should be before the auction boom in their prices sent them to loonyville.

Michael W

[bodgeParticipant @bodge]

Posted by Neil Wyatt on 31/12/2016 16:34:43:

I found 0.004 over 12" for precision ballscrews and 0.0005 over 12" (one in 24,000) for "precision plus" so 63T may fall down for the highest precision uses (the data was from Thompson Illinois – interesting that the Myford leadscrew of the 40s is better than a 'precision rolled ballscrew' of the 2010s!)

Neil

Well that is a bit of a surprise !

A quick scan of the book case i found a piece on Drummonds circa 1919 quote pitch error for commercial lead screws…. " now never exceed an error of 0.001 inch in any inch of pitch , or 0.003 inch in any foot of length, either in progressive pitch or periodic error " the periodic error, it should be explained, is departure from theoretical helical form and occurs at each revolution of the screw; progressive error, invariably minus in character ,is the variation from true pitch length……….info from " Machine Tool Adjustment " —ISBN 1-55918-218-0

The myford lathe referred to was the 4 inch precision , which i suspect myford got from Drummond on a plate along with every thing else that Drummond were ask to hand over to myford

The 4 inch looks like a Drummond than a myford , even more so when you see one with a full 11 inch cross with the tee slots running the length of the slide  rather than across the width,………….b

Tried posting a pic but its not having it …bloody computers!!!

Edited By bodge on 31/12/2016 18:56:03

[Michael GilliganParticipant @michaelgilligan61133]

Now we're getting beyond the ordinary

Take a look at this Bryant Symons: **LINK**

http://lathes.co.uk/bryantsymons/

The correcting principle is broadly similar to that on my Gaertner microscope.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Here, for anyone 'with nothing better to do' is is Symons' patent for the leadscrew corrector:

**LINK**

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=111693A&KC=A&FT=D&ND=3&date=19171127&DB=EPODOC&locale=en_EP

MichaelG.

[HopperParticipant @hopper]

Posted by Michael Gilligan on 31/12/2016 10:52:26:

… But where would you place Martin Cleeve in the story ?

… A man before his time, or a nutter ?

MichaelG.

Definitely a nutter. The 7tpi two-start, left-hand, square thread variety.

My kinda nutter.

[John Stevenson 1Participant @johnstevenson1]

Martin Cleeve ?

I'd say if the story I have is correct then he was an amateur in more ways than one.

The story I had is was made redundant and then went self employed making special nuts and bolts hence the modifications to his Myford.

In which case he could only see far enough forward to use what he had at the expense of countless hours of work and modifying the the said Myford [ all unpaid when he was self employed ] to finish up with a lesser machine that could have been had.

Any commercially astute person would have started off with the Myford in whatever guise to earn a few bob and then invest in a specialised machine such as a Brittain to make these bolts and studs far quicker which would earn more money to then get a second machine for second op work.

Instead he was left with a machine that could do everything but no one job well given setup time.

As an amateur the mods he made were stunning, as a person trying to earn a living he wasted endless time, money and effort.

Many years ago I was in the same boat, or close. When lasers were in their infancy I was in on the ground floor and used to make a limited run each month of a very small but specialised component which from the manufacturer was expensive.

I use to make these ironically enough on a ML7, pretty much standard and i looked at what to do to speed this job up. I could have modified the Myford but for me time was money so I went out and bought a Myford C7 Capstan and tooled it it for this one job.

It used to run one morning a week to produce a months work. I wasn't bothered about getting extra work for it for two reasons.

It's boring running a capstan and the company who the part were for paid me very well and due to manufacturers supply issues they could keep running [ and earning ] when other were waiting for spares.

This machine in it's heyday used to earn about £400 per hour. [ No typo ]

After about 5 years things moved on, those early lasers were scrapped and the new generation didn't need these spare so the machine was sold. I never looked for other capstan work as I had other irons in the fire that weren't boring.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 01/01/2017 00:47:55:

Posted by Michael Gilligan on 31/12/2016 10:52:26:

… But where would you place Martin Cleeve in the story ?

… A man before his time, or a nutter ?

MichaelG.

Definitely a nutter. The 7tpi two-start, left-hand, square thread variety.

My kinda nutter.

.

He always struck me as being the epitome of the ingenious engineer.

If I understand correctly, that much-modified ML7 was used for some serious levels of 'War Department' production … does anyone know more detail ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Stevenson on 01/01/2017 10:09:55:

Martin Cleeve ?

I'd say if the story I have is correct then he was an amateur in more ways than one.

The story I had is was made redundant and then went self employed making special nuts and bolts hence the modifications to his Myford.

In which case he could only see far enough forward to use what he had at the expense of countless hours of work and modifying the the said Myford [ all unpaid when he was self employed ] to finish up with a lesser machine that could have been had.

Any commercially astute person would have started off with the Myford in whatever guise to earn a few bob and then invest in a specialised machine such as a Brittain to make these bolts and studs far quicker which would earn more money to then get a second machine for second op work.

Instead he was left with a machine that could do everything but no one job well given setup time.

As an amateur the mods he made were stunning, as a person trying to earn a living he wasted endless time, money and effort.

< etc. >

.

Thanks, John

… our posts crossed in the æther.

MichaelG.

[not done it yetParticipant @notdoneityet]

Question: Is there a myford lathe which does not rely on the threading lead screw for power feed?

As I see it (many will not, I suppose) lead screws wear out fast enough to fall foul of any initial claimed 'super tolerance' without continually driving the power feed mechanism full time (when in operation).

Just one aspect of the superiority of the Raglan lathes over the myfords of the day, I guess? Raglan's later gear change wheel arrangement adoption (without the 127 gear) was close enough for them, as conversion for metric thread cutting. And it is close enough , for me, now.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 01/01/2017 10:54:49:

Question: Is there a myford lathe which does not rely on the threading lead screw for power feed?

.

Answer: Not so far as I am aware … but your question does prompt an interesting thought: It might not be beyond the wit of man to devise a stepper motor drive, to work using the fast traverse rack … thereby 'saving' the leadscrew for screwcutting and such.

MichaelG.

[Mark KilgoreParticipant @markkilgore24274]

Another idea in that vein would entail using the longitudinal groove in the Myford Super 7 lead screw (for powering the cross feed) to drive the hand wheel, a la the old South Bends. A bronze miter gear would ride along the lead screw, with a key to be driven by the slot. This would mesh with another gear with axis parallel to the hand wheel axis. All else is imagination.

I discussed this idea with Ivan Law at a London show years ago and was not encouraged. His thought was that a Myford lead screw would wear so slowly as to make this adaptation unnecessary. Would surely be cool, though. In place of doing all the engineering involved, I just bought a new lead screw against the day.

[HopperParticipant @hopper]

I dunno guys. The leadscrew on my old Drummond has been doing double duty for feed and screwcutting for 80 years odd now and still has not worn out. Several brass half-nuts that engage with it have been replaced though. The most wear I can roughly measure on the leadscrew with digital vernier is one thou on the thread width at the high-wear area near the headstock end. Good enough for me.

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