Lathe Dogs

Not always true, tubular parts may be held internally with a chuck whilst held by a plug on the tail stock end, solid parts may be held in a chuck and tail stock to great effect and may be turned closer to the head stock end without the dog being in the way.

If one is concerned about the part walking in the jaws just turn a pocket in soft jaws for the job at hand.

This is a 6 1/2" OD 64" long steel tube held internally with a chuck and a plug that I made for the tail stock end, held .003 the entire length and the finish was excellent. At this size anything closer is best done on a cylindrical grinder.

todaystube1_zpssd2itc5v.jpg
Turning soft jaws would not have made an ounce of difference in the job I was doing; If you can't hold onto it with a 24" 4 jaw chuck, a 3 jaw of any size is not going to help a bit. Using the round stock on the chuck jaws was at the suggestion of the old timers who were my bosses, some of whom would have started their trade long before WW-2, mostly in railroad shops.
As to the tube job you make an example of, this is apples and oranges --- I had to OD grind some tubes a bit smaller and shorter than that and had much trouble with the tubes walking around and grinding eccentrically; I finally filled them with coolant water and the problem disappeared, also did same later when grinding the hard chrome on them.
 
Lathe dogs work really well to single point multiple lead threads on long shafts by indexing on a face plate with equally spaced dog drivers for the number of leads desired . Most likely you will also need a steady rest because of the length of such shaft.
I have also found tham to be useful in gear hobs, if you need to remove work piece to measure pitch diameter or anything else like tooth profile and helix.
 
Luis,
Would you care to elaborate on your method of setting your dog/s, ensuring your multi lead threading is equidistant. And how you cut internal threads to suit?

Cheers Phil
 
That tom's techniques on youtube has a video showing what i'm thinking of. If the work piece is whipping to much to be safe you can start it up with the center drill in contact with the work which will suport it (i use a biger center drill if it's extended a long way) If you have a fixed steady that would be a good time to use it.

Stuart

whopps nearly forgot vid link :)

Thanks I learned something in that video that I never thought of and didn't know... great tip on center drilling with the stock extended. :)
 
Pay attention to order of operations to help guide how to


hold the part . Even for a simple part a plan doesn’t hurt and minimizes stress .
 
I'm a bit concerned about the dog 'biting' me. For smaller parts up to 20 mm diameter I hold the part in a W20 collet in the headstock and a center in the tailstock. I work on a Schaublin 102 VM lathe. Taking the part out and then returning it gives me an eccentricity of about 2-4 microns what is good enough for my purpose (building clocks).
The other day I had to put in a center on a 360 mm long shaft-assembly. I was advised to turn a short bar to the end diameter and use it to set the steady-rest. The steady-rest can then be relocated to the end of the job and a center put in. The actual turning is done between centers. It worked really wel.
 
Last edited:
Back
Top