Meek style dog-clutch for a Colchester

[Graham MeekParticipant @grahammeek88282]

Hello Taris,

The position of the trip rod depends on the easiest route to the cross slide. Ideally for ease of use it would be best on the front of the machine as in the Hardinge. Jim Schroder in the USA did a very nice adaptation of my design for a Grizzly lathe. His stops are to the rear and he has a neat stop design which flips out of the way. This makes repetition a lot easier as the screw cutting stops can remain set for the next part. This was written up in Home Shop Machinist. Graham Howe did another version for the Warco BH 600 which is similar I believe to the Grizzly. That appeared here https://www.gwhengineering.co.uk/  I think I still have the drawings for this and I will forward them to you later today.

The trip rod does not have to be round a rectangular rod will often pass through a gap where a round one of similar proportions can’t.

As regards writing up the account of your design I would have a chat with our Editor Neil. He may want an article for the magazine or he may want it to appear on here.

Regards

Gray,

[Clive FosterParticipant @clivefoster55965]

Further to Grahams comments about putting the trip rod on the back of the bed I’d also seriously investigate whether some sort of electric actuation would be practical.

In my original, unfruitful, investigations into fitting Grahams system to my Smart & Brown 1024 VSL I looked into a behind the bed position for the trip rod. I concluded it was sort of possible to do so with the taper turning attachment in place but the engineering wasn’t, ahem, inspiring. Add a DRO scale and it was impossible.

An electric actuator whether hefty solenoid or, probably more practical, motor and cam driving a short trip rod gives you much greater freedom of position and needs only some sort of micro-switch device to operate. I’d go for a clamp on the bed base to hold the switch with some sort of slider to carry either a micrometer stop or a multi-position rod carrier. Although my micrometer stop lives on the 1024 bed as part of the normal set-up replacing it with my “dumb” 6 rod multi-position stop when making several parts is extremely useful. Best way to operate the microswitch is via a sliding cone rather than direct on the button or lever.

I’m spoilt when it comes to single tooth clutches because my big lathe, a Pratt & Whitney model B 12 x 30, is built around a superb factory fitted system controlling both feed and screw cutting. Wonderful when you get used to it but if used to a normal industrial lathe it needs concentration initially.

If you plan to use the device for accurate feed stop control as well as screw cutting be careful with spindle speed. Messrs Pratt & Whitney advise that the single tooth clutches on mine should not be engaged at over 300 rpm as high speeds will damage it. So when running fast you have to engage the dog lunch and then bring the machine up to speed via the main clutch. At screw cutting speeds I can leave the spindle turning and just use the dog clutch system. Even at low speeds it’s quite loud when taking up the drive.

Clive

[Graham MeekParticipant @grahammeek88282]

I have at last found the Jim Schroeder screw cutting clutch video.

Regards

Gray,

https://canadianhobbymetalworkers.com/threads/lathe-screw-cutting-clutch.1208/

[dave.ellisParticipant @dave-ellis]

I have built a dog clutch for a Raglan Little John Mk2, the gearing from the headstock to the first stud is not 1:1 but 1:2 a 38 t gear drives a 76 t gear this works well as it slows to gearing to the clutch to half the spindle speed making it easy to engage the clutch at about 90rpm. Cleeve’s book clearly indicates that other combinations apart from 1: 1 will work and my work has proved he was right!

Dave Ellis

[Author]

Posts