Metric lead screw on a Myford Super 7

[Arnljot SeemParticipant @arnljotseem72268]

I have just acquired an old Myford Super 7, and I am investigating the current configuration of this. The serial number indicates that it was made in the 1955-58 time frame. It does not have a quick change gear box. As Norway has been for a long time in the metric territory, I was hoping that this Myford had a metric set up.

According to the Myford web site, a metric lathe can be identified by the micrometer scales on the slides' hand wheels reading 0-40 (as opposed to 0-100 on the imperial lathes), and the feed screw (on the slides) having a 2mm pitch. This confirms my hopes that this indeed is a metric Super 7. No mention of a metric lead screw can be found. Also, in all the information I have found on the Internet, it is indicated that even the metric Super 7 lathes had a 8 tpi imperial lead screw.

However, when I measure the pitch on my lead screw to the best of my ability, I come to a conclusion that my lathe has a 3mm pitch on the lead screw.

Did Myford or other companies ever make a metric lead screw for the Super 7?

Thank you.

[Arnljot SeemParticipant @arnljotseem72268]

[Ian ParkinParticipant @ianparkin39383]

Do you have a dial gauge? clamp that to the bed ways and turn the lead screw one turn with the half nuts engaged and see how far the carriage moves…. similary with the cross slide

this will confirm that you have metric threads

[Roderick JenkinsParticipant @roderickjenkins93242]

My understanding is that Myford never made a metric lead screw even though they made lathes with metric screws for the cross and top slides. I would measure how far the tool travels with 8 turns of the leadscrew. If the travel is 25.4mm then the leadscrew is 1/8" pitch, if 24mm then the leadscrew is 3mm pitch.

HTH,

Rod

[John HaineParticipant @johnhaine32865]

As far as I know, having bought a new metric S7, even the metric version has a 1/8 inch pitch leadscrew. As the topslide has a 2mm pitch feed screw you can use that as a micrometer to test the leadscrew pitch. Use the topslide to bring the toolpost firmly against the chuck and zero the collar (or take a note of the reading), with the leadscrew engaged and having taken up the backlash in it. Now withdraw the topslide by 2 turns, move the leadscrew through one turn, and check how much the carriage has moved by again using the topslide. You will probably find it has moved 3.175 mm which is 1/8 inch. You could also look at the dial on the leadscrew hand wheel if there is one, mine is calibrated in mm but the calibrations run to just under 3.2 mm where there's a gap. If the leadscrew is 3mm pitch the scale will be continuous. Also look at the threading tables.

[SandgrounderParticipant @sandgrounder]

My first post but I have been looking in most days for a while now.

I don't know if they ever made a complete metric lathe but until my retirement I worked at a large R & D Lab' and they had the bottom half of an ML7, the bed, carriage & lead screw and cross slide, this was purchased directly from Myford probably about 25 years ago, this was used as an optical bench and when it was no longer required I bought it from them and on closer inspection found that it has a 3mm pitch lead screw and the lead screw handwheel is calibrated 0 – 3 with a total of 15 divisions each sub divided into 10. Our own machine shop could have easily fitted a metric lead screw and split nut but from the quality of the handwheel engraving and the fact that a keyway has been cut for non existent change wheels convinces me that it was a Myford special.

The bed has no serial number, I have since added all the parts required to make it a complete lathe.

John

[John HaineParticipant @johnhaine32865]

Here's a picture of the leadscrew handwheel off my lathe (it has been converted to CNC so the wheel is replaced by a timing pulley). You can see that the calibration runs from 0 round to 3.0 x 0.2mm, then there are 5 x 0.2 mm divisions to 3.1; then 4 divisions back to zero, the last one being slightly bigger. So you can accurately feed the carriage along using the l/s handwheel by up to 3.16 mm but after than it's a guess! I believe the calibrated handwheel is standard on the S7, so if yours looks the same you will know it's an 8 tpi thread, whereas if it is truly metric it would count a whole number of mm in one revolution. (Though 3 mm wouldn't make for the easiest threading etc – 2.5 mm would be better IMHO).

When I first started using the lathe I didn't realise the screw was 8 tpi until I tried to use the leadscrew to set a dimension greater than 3 mm accurately!

[Nick HughesParticipant @nickhughes97026]

Myford 7 series lathes all have Leadscrews that are 8 tpi (1/8" pitch), that's why the imperial handwheel reads 0 to125 and the metric handwheel reads 0 to 3.18mm (1/8" = 3.175mm)

Nick.

 

Edited By Nick Hughes on 24/01/2016 16:37:53

[Arnljot SeemParticipant @arnljotseem72268]

Thank you all, for the overweliming support. I did set up a dial indicator, but since my indicator only have 10 mm travel, I measured only one turn. I got really varying readings, from 3.05 per hand wheel turn, but when I measured closer to the tail stock I could see that the readings were in the 3.17-3.18 region. Not the best accuracy, and I made sure to take out the back lash when changing directions. Also the hand wheel is exactly as pictured above. (isn't it really reading 3.19 for a full turn from zero to zero?)

Could this variations in readings depending on the location be due to a worn lead screw or half nut?

So most certainly, this is a standard 8 tpi imperial lead screw, with a metric hand wheel. Was it so hard, when everything else was made metric (even the slide feed screws), to make a metric lead screw?

In any case, it seem straight forward to make metric threads with the 8 tpi lead scree, although as I understand, using the 21T gear is an approximation that works for shorter threads. I also understand that a 127T gear would be more correct. This being my first lathe experience, doing very simple things, I think this will work just fine. As a bonus I get to learn everything from scratch, instead of just twisting a few knows and not having a clue what is actually going on.

 

Since this is my first post, here is a little background: I am a computer engineer living in Norway, but educated in the US. I have been in the computer business for a good 25 years now, and work mostly with network security these days. I'm in the second half of my 50's now, and doing some soul searching regarding my professional life i miss the fact that I have never made anything. I'm only utilizing equipment that other people develop and produce, and thinking back on all the great stuff my fathers shop designed and manufactured, this feels some what of a void. Everything is made in China these days, and Europe is unfortunately just "cutting each others hair" as we say in Norway. So for the last few years, I have been tinkering with some electronics projects (Arduino, Raspberry Pi etc) and have built myself a small and simple lab. For the last few years, I've had a growing interest in machining. After reading a lot, and having watched countless hours of very good and interesting Youtube videos, I'm finally taking the leap into my machining adventure.

I have been looking for a lathe (and a mill) for a while, but remembered that there was an old lathe in my late fathers estate. He started is own business in the 50's, manufacturing professional electronics such as power supplies for military systems and later for minicomputers (he actually made the power supply for some of the very first computers developed in Norway), large audio mixers for broadcasting etc. Very many interesting things, and I used to work there every summer from the age of 12. They also had a very well equipped machine shop, with som very talented craftsmen. I remember this little tired lathe from my younger years, sitting in a corner of the machine shop. They used it for simpler things and the shop was full of very advanced machinery. This little lathe was the very first machine my father purchased for his newly started business. So taking this lathe into my own shop, restoring and taking it into my personal use feels very special.

I quickly found that the Myford Super 7 was a very popular machine, with many users and great help on the forums. There is also easy to get spare parts, and other options both from the Myford company (is it the original Myford company?) and other suppliers.

Thank you for all your help.

Edited By Arnljot Seem on 24/01/2016 17:46:50

[John HaineParticipant @johnhaine32865]

Hi Arnljot, welcome to the forum, I'm sure you will have lots of fun with the lathe. Why Myford didn't make a "proper" metric lathe is one of those mysteries of British engineering (like why did they never properly update it to take cost out so they could properly compete?) The "new Myford is not the "old" Myford, they bought the name, lots of spares, and much of the assets I think, and I believe (though I'm not sure) they have started making limited numbers again. (Though no sign of an update!). You can buy spares, it sounds like your leadscrew may be worn near the chuck end, so you may be able to replace it (and the half-nuts which will also be worn).

The exact metric feed per turn will be 3.175 mm (25.400/8), and the unworn leadscrew will be pretty accurate. So if you look carefully at the scale on the handwheel it has 5 small subdivisions between the tenth-millimeter markings most of the way round but only 4 on the last one and somehow they swallow the remaining .005 mm.

You are right you don't need a 127 tooth wheel to make perfectly good metric size fastening threads of reasonable length, there are several threads here including, or linking to, tables of approximate gear ratios for metric. Of course for metric threading you can't use the thread dial indicator but have to keep the feed engaged and rewind the carriage after each pass, but I think you have to do that on a "proper" metric lathe anyway.

[chris stephensParticipant @chrisstephens63393]

Hi Guys, I suspect that they kept the Imp lead screw because they could not afford to update the TPI gearbox to Metric. Towards the end of the real Myford times were increasingly hard, sadly true but inevitable.

A point of interest on the difference between Imp and Metric lathes, the Imp cross feed is in direct movement and the Metric one reads in diameter reduction. According to Mr Moore, the Myford boss at the time, this was the convention, so they followed it.

chriStephens

[Brian WoodParticipant @brianwood45127]

John Caines,

Welcome to the forum, I hope you will find it interesting and useful.

A good number of years ago on a visit to the Myford works Open day, they had a bed in the rear test and assembly workshop equipped with an imperial 1/8 inch pitch leadscrew in the normal position along the front and a 3mm pitch metric leadscrew running down the back of the machine. I can't now remember what it was used for, but your works could easily have picked up another special of the same kind.

I do remember that both could be coupled to the saddle.

Regards

Brian

[Arnljot SeemParticipant @arnljotseem72268]

Thank you all for the valuable information. If I determine that the probable worn lead screw and half nut needs to be replaced. Would there be any benefit of having a metric screw and half nut made instead of buying a new imperial one? One of my fathers previous employees is running a rather nice machine shop, and I could ask for a price. Probably a lot more expensive than buying an 8tpi, but if the benefits are great…..

Regards

Arnljot

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian Wood on 24/01/2016 19:23:21:

A good number of years ago on a visit to the Myford works Open day, they had a bed in the rear test and assembly workshop equipped with an imperial 1/8 inch pitch leadscrew in the normal position along the front and a 3mm pitch metric leadscrew running down the back of the machine. I can't now remember what it was used for, but your works could easily have picked up another special of the same kind.

I do remember that both could be coupled to the saddle.

.

I remember that one, Brian

… It was a custom-built linear dividing contraption, used for scribing the 'Ruler' on tailstock barrels.

Clever use of available parts.

MichaelG.

[Brian WoodParticipant @brianwood45127]

That was it Michael, well remembered! I thought at the time what a useful thing that would have been for them

Brian

[SandgrounderParticipant @sandgrounder]

Posted by Brian Wood on 24/01/2016 19:23:21:

John Caines,

Welcome to the forum, I hope you will find it interesting and useful.

Thanks Brian, I've already found it both.

This is the metric handwheel on my Myford.

John

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Caines on 25/01/2016 09:11:30:

This is the metric handwheel on my Myford.

John

.

Well … That is certainly designed for a 3mm pitch.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Before anyone objects: Yes, I know it's a '10'

This [Beeston] lathe is stated to have a 5/8" x 3mm pitch leadscrew.

MichaelG.

[AjohnwParticipant @ajohnw51620]

I thought that at some point Myford did start using a true metric lead screw – seen by not having a gap / odd divisions at the end on the hand wheel dial scale.

If true they should be able to supply lead screws and nuts for either.

John

–

Edited By Ajohnw on 25/01/2016 10:48:35

[egaParticipant @ega]

I see that Michael Gilligan's 10 has top slide and cross slide feedscrews threaded 3/8" x 2mm pitch to go with its hybrid leadscrew.

Also interesting that John Caines' handwheel has intermediate markings which omit the leading zero eg ".2". Is this normal practice for metric leadscrew handles?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ajohnw on 25/01/2016 10:47:58:

I thought that at some point Myford did start using a true metric lead screw – seen by not having a gap / odd divisions at the end on the hand wheel dial scale.

If true they should be able to supply lead screws and nuts for either.

John

.

John,

The validity of your closing remark would depend upon the definition of several terms:

1. Myford
2. they
3. should

So far as I am aware, the current Myford Ltd only makes/supports some of the product lines of Myford [Beeston].

MichaelG.

[Arnljot SeemParticipant @arnljotseem72268]

Hello. I just want to thank you all for the help with my metric vs imperial question. Below is a picture of my well used Super 7 lathe, that I am gradually restoring. Also a picture of my first ever lathe "project"; using the answers from this forum, to cut an M8x1.25 mm thread. Since I was missing the 40T which is used in many of the metric standard threads, I found this table very useful in finding other gear combinations to cut the same thread. http://www.homews.co.uk/page30.html

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