Metric screw cutting clutch for Myford ML7B as Graham Meek clutch

I have a Myford Super7B with QC gearbox and powered cross slide.

Lathe no SK156253
Gearbox QC155983 (in case this makes a difference)

I am wishing to make a screwcutting clutch accessory as designed by Graham Meek and to this end I have bought both Graham Meek's book "projects for your home workshop" and Brian Wood's book on "Gearing of Lathes for Screwcutting" - both of which are excellent reference books.

Graham Meek's book shows the attachment REPLACING the standard Myford cluster reversing handle and therefore leaves the reversing cluster permanently engaged when the lathe is used for non-screwcutting operations.

I see pictures of Myford Super7s with a Graham Meek style clutch unit, but with a modified cluster reversing mechanism in the position of the standard Myford design i.e. with two levers, one for operating the cluster gears and one for operating the "Meek" dog clutch. such a unit is illustrated in Brian Wood's book Fig.1.9 where he calls it "Graham Meeks reverser modification"

One thread on this site quotes Ken Willson (KWIL) as being the person to contact regarding possible drawings or details of this mod, but I have been unable to find a link to him.

Please could Graham Meek, Brian Wood, Ken Willson or anyone else give me any help as I wish to create the screwcutting dog clutch unit whilst retaining the reversing cluster gear unit to enable complete disengagement of the screwcutting gear chain. I hate running a noisy gearbox drive when it is not necessary.

Has any reader of this thread completed this mod and are there any drawings available showing this mod of Graham Meeks excellent design?

David Haythornthwaite

Hello David,

Jason's suggestion is a good one but as far as I know Ken Willson hasn't produced any drawings. I was fortunate enough to be given a bunch of photographs by him of his modification at one of the last Harrogate exhibitions.

In essence what Ken dd and I have copied is to demount Graham's clutch unit as a bolted on feature and utilize the central spigot that Myford provide for the reversing cluster lever as a pivot for Graham's unit, bringing out a new indexing fitting so that the original indexing holes for Myford's design become locators again for this device..

Now it is possible to swing Graham's unit into or out of engagement at will

I don't know where you live but I would be only too happy for you to see for yourself how I have interpreted Ken's modification, take it to pieces and refit it, take photos and measurements as you wish. I live in North Yorkshire just outside Thirsk and as my drawing skills are limited to rough ideas sketched out on fag packets, I think this might be the best way for you to absorb the detail of it

my email address is wood_y(at)btinternet(dot)com all in lower case with an underscore between the d and y

Regards Brian.

Edited By JasonB on 11/12/2019 09:30:08

A pal of mine has just completed and fitted a Meek clutch to his Warco lathe, I helped him with the design of it.

One of the main modifications was to make it so one of the idlers is on an eccentric shaft so it can pivot out of engagement with the main spindle gear when not in use.

I made one for my own Super 7, but if I were to do it again I would also try and incorporate that modification.

Phil

David,

I am easy to find on here! Look in my Album and you can see some of the photos I posted of my modification to Gray's clutch.

As Gray acknowledges, I and Tony Pratt were also involved in the final development of his clutch including me deriving the precise Myford dimensions of the Headstock, hence my insight into "how to change it"

PM me if you want further help, drawings were not produced at the time as the R&D was done on a completed unit 2011-2012! Loads of photos still on file. To my knowledge there are 2 units in addition to my own.

Ken

Ken,

David has already been in touch and plans to see what I have done in the New Year based on the photos you were kind enough to give me all those years ago.. It works very well you will be pleased to hear.

I am still to make an auto trip to complete it, but as I am sure you will know only too well, other things intervene and priorities tend to get displaced

Seasons Greeting to you

Best wishes Brian

Ken, Phil and Brian,

Thanks for answering this for me, I have been a little tardy in logging in today.

Generally,

I know quite a few people have made this attachment since publication and quite a number have added Ken's little mod.

However I feel I must draw attention to a recent malady encounter by someone fitting the device to his non screwcutting gearbox S7. Something I hasten to add I had never ever considered, but there was a reason for this person to carry out such a conversion.

Problem number one,

The pocket in the rear of the attachment is designed at 8 mm deep. This is to accommodate the cast boss on the rear of the Myford headstock where the Tumbler reverse was fitted. This usually stands proud of the casting by roughly 8.5 mm. On this particular headstock the boss stood out from the surrounding surface by only 6.5 mm. The attachment with its 8 mm pocket was hitting the headstock casting before bottoming out on the machined face of the boss.

To rectify this 1.5 mm of material needs to come off the adjacent faces. Just making the pocket only 6.5 mm deep will not solve the problem. This has an adverse effect with reference to the Input gear of the attachments position relative to the Mandrel gear. The clearances are tight here so the relative position of this face in the Main body at 8 mm need to remain as drawn. The extra material removed does not weaken the Main body but it will mean the selector bush and the selector shaft will need reducing in length.

Problem number two,

The position of the output Myford gear on the attachment was not in line with the Myford gears on the standard quadrant banjo.

A packer between the banjo and the mounting bracket brought the gears into line but now the leadscrew gear could not be fitted as the leadscrew was not projecting through far enough. A needle roller thrust fitted at the tailstock leadscrew bearing bracket allows the leadscrew to come forward sufficiently for the status quo to exist.

I hope these words of caution help those considering following the same route. Whether the headstock casting was a rogue, or a very early one, we shall never know. It does however go to show you cannot take anything for granted and it always pays to check first.

Regards

Gray,

Good morning Gray,

I have just found your notes above. As you say, things can't be taken for granted and I imagine this particular application of your clutch may not show itself very often.

However, in your usual thorough way you have worked out a solution covering both difficulties which I am sure was received gratefully by the individual concerned.

I will if I may copy your notes to more permanent storage in case I am asked for help, unlikely I know, but scouting taught me a number of things including preparation.

Season's Greeting to you and yours

Best wishes Brian

Problem Number Two.

It is possible to fit a needle roller thrust bearing arrangement to the leadscrew bracket without incurring the leadscrew positional shift, both my Super 7s are so fitted, one a PXF and the other standard, both with gearboxes.

Hi Brian,

I was about to source and purchase a billet of aluminium for the main body of the device. I do not have a "tame" supplier of aluminium and wanted to order it so that I am ready to go when I have seen your modified device. From Graham's book, the finished overall slab of aluminium needs to be 125mm x 62mm x 25mm.

I presume that modifying the design to incorporate your modification will not require a larger block for the body. Can you confirm this please. On the pictures that I have seen, the modified part is hidden.

I am posting this on the forum thread in case it helps others.

Kind regards and all the best for Xmas

David

Hello David,

I confirm that the dimensions you quote for Gray's device are correct. The alterations for KWIL's modification came from odds and ends out of my ever useful scrap and junk box; I'm sure you will have such things you can find

I do recommend using Tufnol for the 25 and 30 T idlers, these need to be cut at 20 degree PA to match the gearing that Myford chose either side of the normal reversing cluster. I can lend you my cutters if needed

My first ones were made in black nylon, the 25 tooth gear gradually began to deform and smear running engaged over part of it's width with a brass gear so I had to remake that. The 30 tooth idler is still fitted but being wider there is better width engagement and that has only minor deformation which doesn't seem to be troublesome, yet!

The modified bit is attached to the rear face and without braving the wind and rain to trek across to the workshop, I feel sure it is surface mounted. I seem to remember 1/8 inch plate was what I used.

All good wishes to you as well

Brian

Hi Ken,

Having never carried out this needle roller conversion I have assumed the original Hemingway conversion machined away part of the leadscrew bracket. If this is not the case then I am wrong in my resolution of the problem and an additional spacer needs to be fitted.

The S7 in question had a custom Metric leadscrew fitted, hence why it has no gearbox, and is heavily modified.

Hi Brian,

I hope all is well with you and I reciprocate the Xmas greetings. Thanks for the kind words.

Hi David,

The material does not have to be aluminium, I chose that as it was to hand and machines easily. I know of other constructors who have made their main body from Cast Iron. Mild steel could be used but it will distort due to internal stresses and would be a real problem to machine.

Regards

Gray,

Brian

I am following this thread with great interest and will just mention that I have had good results from gears cut from Nylatron which I understand to be nylon loaded with "moly". My gears are rather larger and in use mesh with steel gears.

ega,

I used what I had at the time which was obviously not the best move. Since then I have a bought slab of 1 inch thick Tufnol sheet to use for gears of this kind, but the replacement for my failed 25 T was made from two offcuts bolted together and cut as one gear. That has behaved faultlessly.

I shall be showing this new detail to David when he visits in the New Year, but to mention it here might be helpful to others. Graham warns in his build notes that the indexing on the triple grooved thimble with a small spring loaded ball in a vertical drilling runs the very real risk of the ball over-riding the outer groove and dropping into the workings of the clutch to jam it in that position.

I had exactly this trouble on early testing and took the ball out to replace it with a short hardened slug of the same diameter. That at least prevents jamming from a rogue ball in the works but began to give other troubles arising from wear in the hole supporting the slug, leading to a tendency for the slug to tilt in the soft aluminium hole and begin jamming again. I suppose a steel sleeve for the hole and a longer slug at the start of the job might delay that, but to make that alteration at the time was a lot of trouble.

The next iteration has moved to the rear of the unit where Graham shows a trip rod and here I have built on a quadrant shaped piece to grip the actuating shaft with three drilled dimples for a spring loaded ball to engage. The short stiff spring is contained in a horizontal drilling back into the body of the clutch

Thus far this modification seems to work well and the longer radius of the quadrant has also allowed a better separation of the dimples for a decent positive action of left, off and right to clutch control with much more spacing that was available on the thimble in the clutch

Maybe the problems of miniaturisation arising from a considerably larger design are beginning to show I think.

Regards Brian

An idea constructors might want to consider for the Myford 7 series selectors is the one I have used on the Emco Maximat Super 11 earlier this year.

This does away with the need to have vee grooves and the possibility of one of the ball bearings coming adrift. The holes for the Engaged positions are slightly smaller than for the Neutral setting. Despite the remote control lever on the Maximat the control is very positive. It is a pity I had not had the benefit of CAD all those years ago.

Regards

Gray,

Hello Gray,

That is a neat solution which at the same time separates the operational indents from the neutral and allows more space in cramped surroundings.

Regards Brian

I have just checked the instructions for the HK leadscrew conversion and, apart from cleaning up any scoring on the faces of the bracket, this is not altered in length; the instructions indicate that there is no need to remove the leadscrew for this modification.

Edited By ega on 13/12/2019 11:16:08

Edited By ega on 13/12/2019 11:17:05

Graham and Brian,

I obviously need to wait until Ihave seen the unit in real life when I visit Brian in the new year, as I am having great difficulty in visualising the operation fully at present from just viewing the drawings. I have sent off for an aluminium billet and was wondering how thick the tufnol should be for the two idler gears (25 Teeth and 30 teeth ?). It would appear that the answer is 1" thick.

I must be getting senile as I have had problems visualising it all in my mind and I can usually see quickly how machine parts interact. One problem is that one photo that I have been studying is on a machine that has DAG Browns metric quadrant fitted and that is even more difficult to see.

I look forward to seeing your machine Brian and thank you for your offer to loan the cutters. I shall be very careful with them.

By the way Graham, I have just completed the retractable toolpost from your book and it works well.

Kind regards and thanks to all for the help.

David

David,

I have a 'plank' of tufnol in the right [ 1 inch] thickness, plenty enough to cut a piece off as source material for your idler gears.

Regards

Brian

Hi David,

Glad to hear you are pleased with my Retracting Screwcutting toolholder. As regards the operation of the unit there are a number of YouTube postings by people who have made the clutch, including the Myford Big Bore and Wabeco lathe. "Meek screwcutting clutch", usually gets to it, but some kine Moderator might put a link to some on here.

As regards the DAG addition, you need to ask yourself do you do a lot of Metric screwcutting?. If not, then it is probably easier to live with the standard Myford Metric conversion.

Hi Brian,

Thanks for the kind comments regarding the selector detents, wish I had thought of it earlier.

Regards

Gray,

Edited By Graham Meek on 14/12/2019 11:30:51

Gray

Nice solution on the detent balls.

As for doing metric threads I now use the 33 and 34 tooth change wheels that have been discussed on here a few times, for most work they are more than adequate.

**LINK**

My own Meek clutch on the S7 is still performing faultlessly by the way.

Happy Christmas

Phil