George Thomas retractable slide for the myford.

[Brian AbbottParticipant @brianabbott67793]

Hello all.

Looking to maybe make a George Thomas retractable slide,

Anyone know were i will find the drawings to purchase?

Thanks

[Brian AbbottParticipant @brianabbott67793]

[Dave WoottonParticipant @davewootton]

Hi Brian

There are drawings and instructions in G.H.T's Model engineers workshop manual which is still in print and full of information and drawings for much else besides.

I think Hemingway do a kit for it.

There's an easier to make one in Graham Meek's book Projects for your workshop.

 

Dave

Edited By Dave Wootton on 17/06/2021 16:50:34

[DC31kParticipant @dc31k]

See third post of this thread:

https://www.model-engineer.co.uk/forums/postings.asp?th=108552

[Ady1Participant @ady1]

These gadgets are quite useful for the easiest type of screwcutting, external threads

There is also a lifting type which can be used with a motor that reverses and no retraction is required between cuts, clever stuff

If you are looking to speed up screwcutting a reversing motor switch should be your number one priority

[KWILParticipant @kwil]

Posted by Ady1 on 18/06/2021 07:47:25:

There is also a lifting type which can be used with a motor that reverses and no retraction is required between cuts, clever stuff

If you are looking to speed up screwcutting a reversing motor switch should be your number one priority

Or alternatively you could make a Graham Meek style leadscrew reversing clutch and have the motor continue to run in a forwards direction.

GHT style retractable slide is, I find, very useful indeed.

[egaParticipant @ega]

I'm not clear whether the retractable top slide or retractable screw cutting tool holder is intended.

[Graham MeekParticipant @grahammeek88282]

There is one omission in the GHT plans with regards to the Retracting Topslide. An Erratum appeared some time during the articles publication in ME, but it never was included in his book. At least not the First Edition.

Myford provide a cast recess in the topslide casting to clear their adjustment collar. On some castings this recess is not long enough to allow the fully designed retraction. I do not know if Myford altered this when they remodelled the topslide. This may have been accommodated by Myford's, as there were very close links between George and Chris Moore.

Regards

Gray,

[Martin KyteParticipant @martinkyte99762]

I made one from the Hemmingway kit although I have the book as well. The Hemmingway kit suppies the bearings, gears and left hand lead screw and nut. Very pleased with mine. It doesn't get used for screwcutting much but the advantages of the smooth operation and large micrometer dial which is free settable with a clamp screw is very usefull. It's not hard to make and worth it just for the better micrometer dial.

Hemmingway kit

regards Martin

[GreensandsParticipant @greensands]

Could I request someone to post some photos of the Graham Meek retracting top slide tool holder on this thread. Thanking you in advance.

[Nigel Graham 2Participant @nigelgraham2]

I am not sure using a reversing-switch as Kwil suggests, entirely a good idea.

There is a temptation to switch back and forth with the motor and lathe still moving, which would worry me. By the time you’ve waited for the machine to come to rest you have lost any time advantage anyway.

I would go as far as to say the reversing-switch has only function in screw-cutting. That is when cutting threads, typically metric ones on inch-based lathes, that need the clasp-nut keeping closed on the lead-screw throughout.

It is much better to use a thread-dial indicator, which with adroit manual clasp-nut operation or indeed automatic feed-stopping or tool-retraction, will allow threading even to a shoulder with care, at reasonable speed without stopping the motor. We are not on piece-work!

 

There was once published a simple design for a clasp-nut trigger based on an over-centre tension-spring action, for Myford lathes. I forget by whom and where but it was probably in ME or MEW. It does not retract the slide or tool, simply stops the saddle movement by opening the clasp-nut.

I start screw-cutting by grooving to thread depth at the end of the intended thread, before dropping the speed and engaging the lead-screw. This gives an aiming-point and a definite run-out.

[BazyleParticipant @bazyle]

I think someone posted pictures of the Myford clasp nut trip this year.
Another retracting tool holder. https://bbs.homeshopmachinist.net/forum/general/2077022-auto-retract-threading-tool-mr-whoopee-take-a-bow/page2
Although the link is to a post in Jan 24 I think his Youtube channel shows newer versions as he develops it.

[Nigel Graham 2]

On Nigel Graham 2 Said:

 

There was once published a simple design for a clasp-nut trigger based on an over-centre tension-spring action, for Myford lathes. I forget by whom and where but it was probably in ME or MEW. It does not retract the slide or tool, simply stops the saddle movement by opening the clasp-nut.

I think the design you may be thinking about was by Jack Radford in M E in the late 1970’s. It is described in his book which I believe is still available from TEE publishing.

[bernard towersParticipant @bernardtowers37738]

Ive made both the retracting slide and the Meek reversing dog clutch and as they say its the dogs. out of interest someone said its for external screw cutting but its also for internal with the adjustable slide stop fitted so more useful than a flip up toolholder.

[David George 1Participant @davidgeorge1]

I have made a version of GHT screw cutting tool holder The drawings are free to anyone that may wish to see or use. Although my one is used on an Drummond /Myford M type lathe it wouldn’t need much alteration to fit on any lathe as the operating ramp would need to fit to the lathe you have.

 

 

 

David George

 

[Michael GilliganParticipant @michaelgilligan61133]

Very impressive, David

MichaelG.

.

P.S. __ may I just take this opportunity to commend your Audio track to Mr. Duffer  … this is a glorious example of the noise-spectrum of a lathe at work.

[Greensands]

On Greensands Said:

Could I request someone to post some photos of the Graham Meek retracting top slide tool holder on this thread. Thanking you in advance.

Please find attached the photographs that you asked for,

One advantage this device has over GHT’s design, (I have made this so I know), and that is it moves the operating handle nearer the operator and away from the vicinity of the revolving Chuck.

By far the best is the Retracting Topslide. This takes standard tooling and can be used to do external and internal screwcutting without requiring another toolholder. They will of course fit any lathe,

Regards

Gray,

[Graham Meek]

On Graham Meek Said:

Please find attached the photographs that you asked for,

 

One advantage this device has over GHT’s design, (I have made this so I know), and that is it moves the operating handle nearer the operator and away from the vicinity of the revolving Chuck.

By far the best is the Retracting Topslide. This takes standard tooling and can be used to do external and internal screwcutting without requiring another toolholder. They will of course fit any lathe,

Regards

Gray,

Thank you for sharing photo of your modification!

I use metric lathe with no thread dial indicator, requiring me to keep clasp-nut permanently engaged when threading

(regardless whether imperial or metric).

This is not too much of a problem…

VFD motor drive has switchable electronic brake

(only switched ON when threading) giving almost instantaneous motor stopping ,

but, I would like to add retracting slide to my lathe – I presume it is described in detail in your lathe modification thread?

Thank you (and with apologies to OP for thread drift…)

[Graham MeekParticipant @grahammeek88282]

Hi Chris,

The modification for the Emco Compact 5 is shown in the Compact 5 modifications, but not in detail. Luckily the construction article was published in MEW in January of this year.

Regards

Gray,

 

[Graham Meek]

On Graham Meek Said:

article was published in MEW in January of this year.

Thank you – will look it up!

[Clive FosterParticipant @clivefoster55965]

Apologies for further topic drift but can someone enlighten me as to why retracting slide conversions for Model Engineer type lathes always seem to be applied to the top-slide.

Industrial lathe practice is to have retracting device, where fitted, on the cross-slide. My Pratt & Whitney B, like some other machines, has a concentric quick thread in the dial carrier assembly. Lever operated cam devices are also used. I can see no special advantage to a top-slide fitting and one or two disadvantages.

On purchasing The Model Engineers Workshop Manual I was most impressed by both the retracting tool holder and the retracting slide devices and resolved to build something to use on my SouthBend lathe a soon as a suitable “Round-tu-It” could be captured. In the interim I decided to adopt Georges “star turners” angular in-feed method of putting the cut on with the top-slide whilst using the cross slide for tool retraction and repositioning. Using the lathe dials to calculate the actual infeed needed to achieve a thread to book dimensions being an attractive piece of low cunning.

Made even more alluring when I realised it made derivation of feed changes needed to rectify any errors should the fit prove inadequate almost trivially easy. That the SouthBend (and Boxford) style cross-slide stop set up is pretty much ideal for this employment of the cross-slide was a significant contribution to this decision.

It all worked well enough that making specific retraction device seemed a rather a waste of time. As with most folk my list of jobs outpaced the time available to do them more years ago than I care to admit so any pruning was welcome.

When a Smart & Brown 1024 replaced the last (of 3) SouthBends I stuck with the method but, as the 1024 both lacks a cross slide stop and any sensible way of fitting one, I had to adjust things slightly. My practice now is to make the cuts with cross-slide dial on zero and arrange the initial setting of the top-slide dial such that it will also read zero for the final cut. Muscle memory handles the half turn (ish) needed for slide retraction just fine. Reading the dial for re-setting isn’t quite as quick as returning to a stop but there isn’t much in it. The 1024 has nice big dials.

Indeed I’m so used to the simple read the dial at zero variant that I rarely bother to employ either the built in slide retraction device or bi-directional cross slide stops built into the P&W.

Clive

[bernard towersParticipant @bernardtowers37738]

Maybe its because of the practice of setting over the topside to lessen the load on a not so heavily built lathe

[Clive FosterParticipant @clivefoster55965]

Bernard

Setting over the topside for angular indeed so one side of the threading tool does most of the work certainly reduces the loads on a lightly built machine. But I don’t see that it makes any difference whether retraction is along the line of feed using a device built into the top-slide or perpendicular to the work when the device is on teh cross-slide. Either arrangement would seem to work equally well in practice.

That said I’m unconvinced as to the appropriateness of the “standard” angular in-feed method for Home Workshop and Model Engineer types. Having to accurately set the top-slide angle to half the thread angle and convert the book values for thread depth into feed distance along the angle seems an undesirable multiplication of complexity. Not to mention more things to go wrong. Some American sources advocate an in-feed angle slightly less than half the thread angle to generate a shaving cut on the trailing flank to improve finish. Which just makes the numbers harder. At least sine 30° for 60° threads is easy to deal with. 27.5° for Whitworth not so much.

Georges “star turners” method sidesteps all this nonsense requiring only that the indeed angle be no greater than half the thread angle, preferably a bit less to get that shaving cut on the trailing flank. Touch the tool to the work, set both dials to zero, move along past the end of the job and feed the cross-slide forward by the depth of thread to be cut then reset the dial to zero. Pull the topside back for starting clearance and move the top-slide to make your cuts with the cross-slide on zero.

Finish with both dials on zero so what you cut is what you set.

Which may not be what you want.

I’ve never cut an overly deep thread first time through so easy enough to tweek the cross side forward from zero to get it right. I guess my threading tool grinds tend to be bit too pointy. My favourite SKF/Dormer/Johannesson chasers give results dead on the money.

So easy. Never understood why that method didn’t become standard.

Clive

[Tony Pratt 1Participant @tonypratt1]

The superb Hardinge HLV lathe I worked on featured a retracting top slide, although definitely an industrial machine it is on the smaller end of such things and the GHT slide I fitted to my Myford super 7 I’m sure was ‘inspired’ by the Hardinge.

Tony

[Graham MeekParticipant @grahammeek88282]

Hi Tony,

Having known GHT very well I can vouch for your assumption.

Regards

Gray,

Also it is far more convenient to add this feature to the topslide than the cross slide. Especially on the S7. Having said that one design for a retracting cross-slide has been published by Jim Schroeder for a Grizzly G0602 lathe. This lathe does have a different cross-slide arrangement to the S7. It is interesting to note that Jim also added a retracting topslide afterwards.

Regards

Gray,

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