Myford Single Tooth Screw-cutting Dog Clutch

[pgp001]

OK This is a bit more information about the screw-cutting clutch as requested from another thread.



To cut a long story short, around two years ago I discovered among some of my late fathers papers a design for a screw cutting clutch that works on the principle that it can only engage the leadscrew in one (and only one !!) position. I decided to have a crack at making it and a little while later accidentally found it mentioned on another model engineering forum.

http://www.model-engineer.co.uk/forums/postings.asp?th=49358

I managed to make contact with a very nice chap in the UK called graham Meek, who had years earlier designed and built one of these clutches.

Graham (or Gray as he is usually called) has also written a very good book which some people might be interested in.
http://modelengineeringwebsite.com/Workshop_projects.html

So having swapped a few ideas and drawings with Gray, I set to and made my own version based very much on his design but with a few modifications.
Grahams design used bronze gears running on hardened shafts, but I wanted to retain the tufnol material for the gears so they would still act as a crash protection device.

http://www.modelengineeringwebsite.com/Screw-cutting_clutch.html

The clutch has also been described in one of the UK model engineering magazines fairly recently.

The idea of the clutch is that you can set up the lathe to cut "ANY" thread you care to choose, and by setting stops on a rod at the back of the bed, it will disengage the leadscrew at the end of the cut.
Normally if cutting a metric pitch on an imperial leadscrew this is not possible and the half nuts should never be disengaged until the thread is completely finished. With this design, you still keep the half nuts engaged but disengage the drive to the actual leadscrew.

The key issue is that when you re-engage the clutch it can only ever be in exactly the same position as it was before, so you always pick up the thread perfectly every time, the clutch works in reverse as well.
So when cutting a thread, you start as normal, the cut automatically trips the clutch when it reaches the stop and goes into "Neutral"
Then it a simple matter of flicking the lever the opposite way and  the leadscrew reverses the carriage until it trips the stop in the other direction. A new cut is applied and the lever flicked back the other way again.
It takes longer to describe it than to cut a thread its that simple.

I will post a few build photo's soon.

Phil

[pgp001]

Here are a few photo's of the main body being machined.









Phil

[pgp001]

And a selection of the parts that fit the body.

This is the ring that does all the work, it catches a peg (dog) in the gear on either side depending which direction of travel is selected.







This is on of the gears with a peg (dog)



And the selector drum



The main shaft



The input sleeve



An Idler



Another Idler



A selection loose on the bench



And partially assembled



And ready to install on the lathe







And finally fitted and tested







Go on you know you want to 

Phil

[steamer]

Phil

That is very interesting!   I would love to understand more about how it works!

I met "Gray" on the other site, briefly...and I posted some pictures for him.   I hope he is well

Let him know about our little forum.

Dave

[tel]

Very interesting - what's involved with adapting it for the ML7? Drawings are at ... ?

[Jo]

Phil,

It looks to be a really useful little gadget. I must be honest though other than my small stuff (studs 14BA to 5BA) I don't do a lot of thread turning I think the last thing I made using the was an insert to repair the spring on my garage  .

Now if only that Coventry die head turns up no one will ever have to hear about me and my pleasures of doing studs ever again .

Jo

[Jasonb]

Nicely made, I have seen Kwil's one of these which has an extra gearwheel but can't remember what he said the additional feature allowed it to do.

http://www.model-engineer.co.uk/albums/member_photo.asp?a=10743&p=389628

[steamer]

OK...based on the parts I can understand how it works now....very clever....the cross shaft missing in the photo's ...gives it away...

I have no choice but to wonder if it could be adapted to a SB9..... .....like I need another project!

Dave

[BillTodd]

It looks to be a really useful little gadget.

That is a beautifully executed mod. I am surprised there aren't more around for other machines.

Add a retracting top-slide and you have Hardinge style threading .  Once you've used an HLV-H, you wont ever want to go back to 'threading dial doubt' and 'half-nut panic'.

Bill

[steamer]

YUP gotta agree there Bill!   
I have used the threading system before....SWEEEEET!

The HLV is a wonderful machine.....my wallet is allergic to all the zero's though

Dave

[pgp001]

Gray has actually designed a few variants of this device to fit some other common lathes, notably the ML7 for which I hobbed the gears for him last year.
So do not be surprised to see future magazine articles appearing with further details.

If you look here:-
Towards the last few postings you will see the progress on the ML7 version.
http://www.model-engineer.co.uk/forums/postings.asp?th=49358&p=12

Jo
You don't just use the device for screwcutting, it comes into its own when using power traverse as well, so you can cut up to a blind shoulder externally or internally and it will disengage the feed at the same point each time.

Phil

[John S]

Now if only that Coventry die head turns up no one will ever have to hear about me and my pleasures of doing studs ever again .

Jo

Went in the post today -- honest..............

[Jo]

 

[arnoldb]

Thanks very much Phil 

A very handy mod indeed, and I'll be on the lookout for the ML7 version.

The main reason it immediately grabbed my attention is the reversibility while keeping the feed nuts engaged.  I really dislike switching my ML7's motor between forward and reverse continuously, and as the majority of work I do is metric, I've usually reversed things by either just turning the chuck in reverse by hand or for coarser threads using the leadscrew handwheel to crank things back.  This is easy to do as I'm fortunate enough to have the rare factory clutch on my lathe.  In fact, when threading I rarely even switch the motor off.
And that's why this solution will suit the way I work down to a T.

Unfortunately it won't work with John Bogs' simple flip-up threading tool holder, so it'll be the "normal" cross-slide or topslide infeed and retract operations, but with a retracting tool holder even this would become a breeze 

Come to think of it, this mod might even help make it easy to turn multi-start threads - though some experimentation would be needed first to test a theory in practice...

Go on you know you want to 

- I have a home-brew gear cutter for Myford gears and I'm not scared to use it.  There's the little matter of a Corliss build to finish off, but after that, as soon as I can get my grubby little paws on the ML7 version of this, I'll be off  . 

Kind regards, Arnold

[pgp001]

Gray has done a very nice design for a retracting tool holder as well.

Phil

[Jo]

The drawings for this were published in Engineering in Miniature Vol 33 (Jan -  Mar 2012) pages 218, 279, 324.

Jo

[tel]

Thank Jo - about 10 years after I stopped taking magazines in general - have to try and winkle out some back numbers.

[John S]

Gray has done a very nice design for a retracting tool holder as well.

Phil

Must dig his book out and take a better read. bought it at a time I was too busy.
I have one of Gray's clutches fitted to a C3, what a machine, doing some 19tpi tapered gas thread fittings in brass the other week 900 revs up to a shoulder and never had to change the old boxers once.

[Jasonb]

Tel drawings are on the net as is the article previously linked to those these are to fit the BH600 not myford.

http://modelengineeringwebsite.com/Meek_screwcutting_clutch.html

http://modelengineeringwebsite.com/Screw_cutting_clutch.html

J

[Goldstar31]

Like many of an older generation, I gave up taking Model Engineer, Model Engineers Workshop and Engineering in Miniature for many reasons - one of which was lack of originality.There were others but enough!
Obviously, it prompts me to buy the book( for my Myford S7B) however one point comes up and that is- are the book drawings imperial as All my cutters are such.?

Thank you

Norman

[Graham Meek]

I do not know if you have been following the Model Engineer Screwcutting simplified thread recently, however the ML7 version of the clutch is now finished.

I regret to say the drawing units in the book are in Metric, but as the Screwcutting Clutch has to mate up with an Imperial machine many of the metric dimensions are merely conversions of an Imperial measurement. Where a 10 mm reamed hole is specified this can quite easily be 3/8" reamed and so on. Nothing in my designs is carved in stone, and I welcome individuals putting their own stamp on my original design, I have never thought my designs to be the last word.

Gray,

[steamer]

Hey Graham!

Welcome!.....Let me know if I can help with anything.

Regards,

Dave

[ths]

 Hi Gray, and welcome to the forum. I have been following the screwcutting simplified thread, and feel that your ideas (and execution) are superb. Like Arnold and Tel, I'd be very interested in the ML7 version. Is it available in a book?
Cheers, Hugh

[Jo]

  Gray,

Any chance of posting an introduction. Our members are international so they may not be aware of your good work on other forums  .

Jo

[Graham Meek]

Hello Jo,

At your request I have posted an introduction to myself, I do hope I have not overdone it?

As regards my work on other forums I only regularly write on the Model Engineer site, my work does appear on other sites like the modelengineering website and Ron Chernick's Model Engine News, but that's about all. I do regularly write for Engineering in Miniature and they graciously thought my work warranted a book.

Thanks to all for the warm welcome

Gray,