Meek bigbore dog clutch

[Stuart]

Phil

That's why I used what I did they hum a bit as it is

With a 3K spindle contra rotating gears in constant mesh well I will let you ponder that one

Stuart

[Jo]

With a 3K spindle contra rotating gears in constant mesh well I will let you ponder that one

  Even Mr Silky shouldn't do thread cutting above 1000rpm

Jo

[Stuart]

Jo

That's not the problem you would not want to screw cut at the speed no way

But unlike a  banjo tumbler reverse you cannot drop it out of gear as the base is locked yo the headstock with a anti rotation screw and located with the shaft that the banjo used.

It's when you use the lathe normally that the high speed is used

Stuart

I have pecked up the corn now off for a rest 

[Bjorn_B]

I hadn't heard of Tufnol before. Looked it up to see that it's some kind of laminated plastic.

But I'm wondering about a couple of other terms...

'dog gears' and 'dog clutch'

I know gear and clutch. What does it mean to qualigy with 'dog'?

Thanks

Dog clutch, a very simple mechanical form of clutch either on or off with no possibility to slip. Drive is transfered with mechanical interference rather than friction. A one tooth dog clutch (that this design will be) always indexes at the same position (a must for thread cutting work)

[Bjorn_B]

Bjorn
Have fun but do read the book carefully with regard as to the indent ball for the selector 😬😬😬😬 Gray lost his down the hole but I did not 😀

Stuart

Hehe, I noticed that, will be careful... Thanks!

[Graham Meek]

I must concur with Stuart, beware the detent ball does not escape.

For those who would like to disengage the clutch when working on hi RPM, Ken Willson did an indexer unit that bolts to the back of the clutch body. This utilises the redundant tumbler reverse quadrant holes. The Red indexing knob in the second picture of attached article can just be made out.

www.modelengineeringwebsite.com/Screw-cutting_clutch.html

Most users now go for Plastic Idler gears, the initial use of the Phos Bronze gears was a bit of belt and braces. Until the clutch had been proven to work it was not known what forces these gears may be subjected to. Neil Hemingway did his best to try and break the unit but he did not succeed, but the Phos Bronze gears were well distorted. I used Delrin on the Mini-lathe version. The one gear on this lathe has to have a 2 mm wide slot through the centre of the gear teeth to clear the encoder disc on the mandrel for the RPM counter. This lathe has since done a great deal of screwcutting and the gears look as good as new.

My best regards
Gray,

[Bjorn_B]

I must concur with Stuart, beware the detent ball does not escape.

For those who would like to disengage the clutch when working on hi RPM, Ken Willson did an indexer unit that bolts to the back of the clutch body. This utilises the redundant tumbler reverse quadrant holes. The Red indexing knob in the second picture of attached article can just be made out.

www.modelengineeringwebsite.com/Screw-cutting_clutch.html

Thanks for the heads up Gray!

I noticed the modification Ken did while pondering over making this or not and I'm quite interested in having a go at that.. but I'll make his to your design first. A 3D printer is on its way over here soon so a little bit of prototyping/tests with various body forms can be done, already made a 3D model of your design for the body so it can quite easily be modified.

Again, thanks Gray!

[KWIL80]

I have been using Oilon (Nylacast), the green stuff on mine since 2 of us set out originally to prove the Super 7 drawings in collaboration with Gray. Still going strong.

Only difference with mine is that it is not in constant engagement and can be selected in or out at will.

I would not be without the use of this Clutch although I must admit that I rarely used the auto trip.

[KWIL80]

I see Gray has saved me the job of posting the modified version

Ken

[Bjorn_B]

I see Gray has saved me the job of posting the modified version

Ken

Hello Ken! As I understand the anti rotation pin is not used and there is a plunger arrangement that indexes in the original tumbler reverse plunger holes? The whole thing rotates around the output shaft a bit like the tumber reverse? There seems to be i bit of a clearance issue regarding the quadrant "back plate casting" or whatever it could be called. I saw you trimmed away a bit on that to clear the operating lever shaft?

Regards

/Björn

[KWIL80]

Bjorn,

Yes you have to make a number of minor changes to the main "block" (machined from solid not a casting). Yes you are correct, it does rotate about the shaft as per the original tumbler reverse.

You can see from the photograph that I have made a "flat" on the operating lever shaft housing to accomodate fixing the 2mm steel plate that supports the Red knob detent set up. Top unused detent hole of tumbler reverse is plugged.

In case you are wondering what all the other gears are, this S7 has a Norton Quick Change Gearbox as standard but with an additional quadrant and clutch system for metric screwcutting through the use of the Imperial Gear Box. (As per D.A.G.Brown)

Ken

[Graham Meek]

Hi Ken,

Thanks for jumping in and helping out. I have been a little busy with trips to and from the Hospital over the past few days. Today is the first day that I have had a chance to sit down and to catch up on things. Luckily due to the quick intervention of my GP they have managed to save my eyesight, but the medication regime is taking some getting used to.

My best regards
Gray,

[KWIL80]

Gray,
I will come back "off Forum"
Ken

[Bjorn_B]

Thanks for your comments, Hope you'll get well very soon Gray.

Anyways, some progress the last few days, did some cutting of teeth on the dog gears.

I can not explain it, but this is one of the most satisfying machine operations I know, the last cut of a gear (when successful, that is)..
20160421_165902 by Bjorn Bursell, on Flickr

Coolant used, steel is EN16t...

Remained to drill holes for the dog pins.
20160422_181629 by Bjorn Bursell, on Flickr

Finished dog gears after pressing pins in (EN24t)
20160422_185622 by Bjorn Bursell, on Flickr

That is all for now..

[Stuart]

That brings back some memories 

Must have a look into using the quadrant to swing it out of mesh ,don't look like its to bad , and the silence will be golden

Stuart