Thread: What is a Lathe Dog good for?

It seems to me a lathe dog is stone age technology. I worked in several tool and die shops and I have never seen anyone use a lathe dog.

When I took machine shop class in school they made us use a lathe dog just so we knew what it was. That is the only time I ever used one.

If you have work that is supported by its centers and need to flip / remove / test fit often. This is the way to go for accuracy and repeatability.

I have seen the self driving dead centers, but dont trust em, always use a dog.

Cheap on biscuits? Never barks?

Chazz

How else to drive a part when turning a small taper with the tail stock set over?

But mostly, the lathe dog just lays on the floor near by ;-)

In the world of gunsmithing, we use them often. Have a variety to fit the job. Use the steady and follow rests, too.

But I'll agree in today's world of CNC dominance, the dog is pretty much obsolete.

Its brother is the grinding dog - use them all the time.

http://img.photobucket.com/albums/v3...Dcp_1147sm.jpg

J.O.

Originally Posted by CalG

But mostly, the lathe dog just lays on the floor near by ;-)

However it REALLY gets annoying when it jumps up and down and barks at the cat head.

IME, it's alot easier to work out unwanted tapers in a part between centers than it is working with a chuck that might or might not spring the part somewhat. It's also easier (for me) when finishing from both ends. It's old as old gets, but it does still work...just sayin'.

The Atlas, and South Bend lathe books have nearly a chapter
about using wet rawhide, and other schemes for
between center work.

Accidents waiting to happen?

I've only used a lathe dog a couple of times in a lathe.

Most of that work can (and is) held in an adjust tru chuck,
collet, soft jaws, or four jaw.

Yes, you can offset the tail stock and turn a taper,
but get fast center hole wear especially on heavy parts.

The wear changes effective shaft length altering the taper
as you machine the part.

Ok, you can use ball centers for that chore but who does.

I would guess a dog is used mostly on cylindrical grinding
of precision shafting, and process rolls these days.

Oh yea, I have one on the radial arm saw to replace the
lost height adjustment crank.

Kap

A single lathe dog is useless, but a whole family of them in different sizes is essential if you do odd work. I probably set up to work between centers 5-10 times a year, and a lathe dog of some sort figures in every time.

If it is going to be heat treated and ground between centers, it usually should be turned between centers. Used when accuracy and concentricity are important.

I have one job and I can't think of a good way to do it without the dog. The part needs to have a small ID feature turned to critical size and concentric with a taper on the part's other end. There's a mandrel for the taper with centers on both ends. The part is mounted to the mandrel (large nut) and the mandrel is mounted in the lathe to turn the ID. The only problem is, the ID can't be accurately measured with the part still mounted. A caliper will give a ballpark figure but not good enough. So, a witness surface gets turned moderately close ( caliper check), then the part has to be demounted to be measured, then remounted for a finish cut or sometimes more than one if I'm edgy.

I machine alot of my pump shafts and electric motor shafts between centers using a lathe dog. It keeps the shafts journals running absolutely concentric from end to end.




They also work great for having to remove a stub shaft from time to time. Clamping one on the end of the shaft gives you a good area to hit with the sledge, or for picking up a shaft vericaly with a sling when theres no hole tapped for an eye bolt.

I'm turning a few parts on a manual lathe that in use, will spin fast, require good balance and are in very close proximity to the housing, so concentricity is paramount.

They require holes gun drilled through them, 48:1 depth to bore ratio.

First they are gun drilled, then the centers located on the hole = ID concentricity.

Then the various shoulders/diameters and threaded end(s) are turned between centers, which adds OD concentricity.

And finally as John pointed out, they are ground over-all between centers = total concentricity on the finished part.

I don't know of a more expeditious way to consistantly achieve these results on a few parts, some of "what lathe dogs are good-(vital) for," to me.

Bob

Great way to secure large twist drill bits in tailstock taper, assuming your tailstock is as work out as some that I've worked with. Just let the dog tail sit against your compound rest and plow right in.

Seems to me like the lathe dog is a trailing piece of tooling that was better used when other tools that worked with it were more popular/available. Ex: a centering machine (kinda like a lathe that was just for putting a spot in the ends of a shaft so you could mount it between centers) and arbors. Not sure what the specific name for them is but they're a shaft with the ends machined to mate up perfectly with the dogs so you could mount collars or expanding sleeves on them to capture stuff from the inside and leave loads of workspace on the ends. We have a number of them and I've seen them in old catalogs. Can't say I've had the oportunity to use one yet. Set-up time's the killer with this stuff.

Originally Posted by El Mustachio

Great way to secure large twist drill bits in tailstock taper, assuming your tailstock is as work out as some that I've worked with. Just let the dog tail sit against your compound rest and plow right in.

Another great example for using a dog. I have to use this set-up on my big monarch when using large drills because the spindle doesnt have a notch to catch the tang.

I've used lathe dogs frequently making new motor shafts, double suction pump shafts, shafts of any kind in fact. Handier than chucking when you have a batch to machine. if you use lathe dogs much you will soon accumulate a tuna can of little pieces of copper used to pad the work from the dog V and the set screws.

I prefer straight dogs and a stiff driver. Bent tail dogs may slip right into the driver plate but they tend to make the shaft "S" shaped.

the fast way to setup in a c-c situation is for me to :

chuck a 1" round piece of prehard 4140 ... then turn a 60deg point w/ the compound(i use the
same 6" bar again and again, just true it every time i chuck it...) then, use a dog to drive the work center to center .

Keeping lathe dogs around is part of the standing army problem that is so hard to explain to managers and bankers, like the 16" rotary table that sat on a shelf for years, then a job came in that I absolutely, positively, could not do without it. You have to set the value by how much you will lose if you need it and don't have it rather than cost per square foot of shelf space or interest on the cost of the tool, especially if they are small and inexpensive. Just like the cost of maintaining an army is not a profit and loss each year proposition but judged by the cost on not having soldiers ready to go when bad guys show up on your border. I don't use dogs very often, but sometimes when I do, nothing else will work.

Bill