Lathe Dogs

[jrrdw]

What are Lathe Dogs used for? I looked around and couldn't find anything. I think i may have missed it, or i'm not searching rite. I'm still feeling my way around here.

[Geof]

Driving material held between centers. Have you seen a picture of a dog? They have a hole with a setscrew one side and a vee opposite and on the side with the vee there is a 90 degree arm thing sticking out. When turning a shaft between centers; that is a center in the spindle and a center in the tailstock something is needed to drive the shaft, it will just rotate on the center in the spindle. The dog is clamped onto the end of the shafte and the arm sticking out fits in a slot in a 'driving plate' that is mounted on the spindle instead of a chuck. Sometimes to save time taking off chucks the center in the spindle will just be a piece of stock turned to a 60 degree taper and then the arm just rests against a chuck jaw.

[jrrdw]

I just got my tool kit and it has 2 of them in it. A straight and a 90 degree. So in short, you clamp it to your part and the tail stock pushs it against the face plate so the part will turn. Thats how i picture it working from your reply, thanks Geof.

[Al_The_Man]

Due to my back ground not being machining, I picked up a very usefull little book that I believe there are several copies come up on Ebay, and that is 'How to run a Lathe' by the SouthBend Lathe works.
The first printing was 1914 and mine shows the last as 1944!
But there is a multitude of information that is still pertinent today.
It would answer your question in detail and maybe many more you might have.
Al.

[Geof]

Originally Posted by jrrdw I just got my tool kit and it has 2 of them in it. A straight and a 90 degree. So in short, you clamp it to your part and the tail stock pushs it against the face plate so the part will turn. Thats how i picture it working from your reply, thanks Geof.

The 90 degree uses the driving plate with a notch the straight would be driven by a bolt fastened into the faceplate.

Take Al's advice and pick up one of those books. Finding out how things used to be done is instructive even if you never actually do them.

[jrrdw]

I just pick up The Home Machinist Handbook, by Doug Briney. It's been good so far, i'm in the plan reading chapter now. Thanks for the advice, i'll take all i can get!

[chipsinpan]

Lathe dogs are pretty much a lost tool nowadays. I have a big selection up to about 6" hanging on the wall collecting dust . Back when all I had was clunky old belt drive lathes , all the tailstock tapers wouldnt hold a drill without spinning . So a 2 jaw dog was the perfect fits all drill helper , that you could ride on the tool post with a backward tool to hook the dog on .
Also if you want to cut a moderate taper , you would offset the tailstock and let the shaft ride between centers with the dog engaged in a face plate hole .
If you need to turn diameters on a long shaft and guarantee that both ends are on the same centerline , you put a centerhole on each end of the shaft , and that way you can flip the pc end over end and still hold the same CL.
As mentioned above , we would put a soft bar in the chuck and just turn a taper that is perfectly true to the head axis