seeking specialized lathe centers

Have tou checked the usuall sources, Enoc, McMaster Carr, MSC to name a few?

Regards, Bernd

Yes. Actually, Royal and Riten offer HSS half-centers but I'm looking for something about an order of magnitude cheaper. I have never seen a soft Morse taper center offered anywhere. I know I can chuck up a bar and turn a 60° point and leave it in place, and I figure I can probably get an old

2MT drill bit which is soft enough at the base to turn a point on it, but I'm looking for an actual source. I could also probably buy an inexpensive unhardened 2MT threaded drill chuck arbor and turn a point on it.

Grant

Enco has a carbon steel MT2 dead center for $2.45. Will that do?

If the link doesn't work they're on page 330 of their current catalog.

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"I'm not grown up enough to be so old!"

That is a stock-standard hardened lathe center. Quoting directly from that catalog page: "Precision hardened & ground to closest tolerances" ..

I'm looking for a *soft* one. But thanks anyway!

GWE

Buy an asian import, which has poor heat treat, and turn the center yourself with carbide tooling?

Jim

Knowing that you're not naive, how about telling us why you want a soft-center. Are you planning on machining jello? Curious.

Boris

How many do you need? Ive got about 20 lbs of them. Half centers mostly. A large number of them carbide tipped. Most are a bit ragged, and you will have to clean em up a bit. They came out of a grinding shop.

Email me your snail mail addy and Ill dig you out some.

Gunner

"As physicists now know, there is some nonzero probability that any object will, through quantum effects, tunnel from the workbench in your shop to Floyds Knobs, Indiana (unless your shop is already in Indiana, in which case the object will tunnel to Trotters, North Dakota). The smaller mass of the object, the higher the probability. Therefore, disassembled parts, particularly small ones, of machines disappear much faster than assembled machines." Greg Dermer: rec.crafts.metalworking

A soft center can be trued in place with a lathe tool; i.e. by turning. After that it will run dead true. I'm wanting to do some fairly precise turning between centers in which I'm going to be trying to hold .0002" over 4" which isn't easy on a 1949 lathe. Nor do I own a TP grinder, although a buddy of mine does. It really needs to be done right at the time of use, though, to be most accurate, and so a borrowed grinder won't really be as good. I suppose I should take Harold's advice and just learn to turn a 2MT center out of annealed tool steel.

Grant

Grant Try Motor Tool, They mainly do live centers but do custom work and may be able to help you if you are looking for several, or quantities. I had a couple of special centers made by them that come out really nice.

Grant, imagine what happens if you took a center that was deliberatly "out" by, say, 0.005 inch. A real disaster, so to speak.

Put that in your spindle, clamp a lathe dog on the part, and install your workpiece that has perfect centers in the spindle of the machine.

Sure, the first cut you take will be 0.005 off of one side of the part. If you're not trying to line up to an existing feature, that is, if you are trying to make a brand new part from stock, this should not be an issue.

Once you clean up the outside of the part, you will wind up turning a perfect cylinder (well, if the tailstock center is in the right spot, side to side) that is aligned with the machine's axis. Obviously if the tailstock is out, you will be generating a cone.

I guess what I'm saying is that the old timers were pretty smart - they knew that as long as the dog isn't moved in relation to spindle itself during the operation, you will turn a true cylinder. I would think

0.0002 over four inches would not be limited by a thou or two of runout in the headstock or tailstock center - but rather more by the accuracy you can fix the tailstock setover.

I'd go ahead and try this if I were you - as long as you're not trying to modify an existing part that you need to line up to.

Jim

OK. Now remove the part to do another op on it, and then put it back. Oops. Up to five thou runout.

One of the good things about turning between centers is its repeatability.

Grant

Yep! Exactly right, Grant. In fact, good grinders tend to have stationary headstock centers so the minimal runout that can accompany a revolving center is eliminated.

When you're doing fine work, you must think totally differently from the norm. Having worked in grinding for a considerable time, and also having worked with many that considered themselves machinists, I can tell you without hesitation that some people will never understand, nor be able to perform, precision machine work. It isn't what you do so much as what you are. You must become one with the machine, and not understanding the ramifications of centers that aren't true is a big part of failure.

By the way, Grant, a center that is stationary need not be made from anything particularly good in the way of material. A cold rolled piece of stock will suffice unless you are taking very heavy cuts. Just make sure that your chuck has a firm grip on the piece you turn, and it can't move in the jaws when tailstock or tool pressure is applied. My normal procedure in the rare circumstance when I turn between centers is to use a piece of stock that is short where I grip it, so the slightly sprung jaws so typical of a 3 jaw chuck still grip the piece at the end, preventing it from wallowing about. I also like a shoulder on the shank end, so the thrust of the tailstock and the cut bear against the jaws, further eliminating any possibility of the center moving in the chuck. Give that a go. Promise you, it works great and is quick to set up.

Harold

OK, right - you cannot reliably pick up the OD if you remove the piece, or remove the dog from the piece. That idea was good only if you are trying to profile the OD of the part, in the *same* setup.

Once you pull it out, of course, all bets are off.

Just out of curiosity, what other operation are you going to do on the part, in between turning it between centers?

I hope you're not going to do anything that'll remove the centerdrills! :)

Jim

Actually, I was going to take it over to the other lathe which has a taper attachment ..

GWE

Then that machine has to be dialed in, in advance as well, and has to have the same kind of center. Take harold's advice and turn them in place. *Do* put a shoulder on them to keep them from disappearing inside the spindle!

Jim

Just a suggestion, but I've taken broken taper shank drills and cut the off to make centers. The shanks are usually not hardened, and you normally have from 1/2" to 3/4" beyond the shank that is machinable as long as you didn't cut it with an abrasive wheel. A few swipes with a file will quickly show where the hardened part begins. Soft centers are ok until you remove them, but have to be recut every time they're knocked out.

I use a live center for most work, but when I've needed to make a special center, like some very small diameter half-centers, I've used one the MT/Jacobs taper arbors that I keep in stock for the purpose. The cheapest ones are best because they're not well heat treated and are easy to cut. I also use these for making up threaded arbors. I've seen them on sale for as low a $2.95 . Anyhow, the Jacobs taper end, if a small size, isn't too hard to soften with a torch. Cut them easily with the compound and finish off with a jury rigged toolpost grinder consisting of a good flex shaft machine handpiece mounted on the biggest boring bar tool holder.

====================== Ebay seller [Ajax] has #3 MT half dead centers for 16$ [buy it now]

I have had good luck turning hardened? centers with carbide tooling. I teach some manufacturing tech classes, and over time the school had accumulated a dozen or so dead centers that were worn, had been used for center punches, etc. I glass beaded the lot, and with 500 RPM, very light feed and good cutting oil was able to produce a very acceptable finish. We had to stone off a few dings on the shanks. I used a #2->#5 MT adapter to fit the center to the lathe spindle. Put a good center in first and used a test indicator to verify the compound was actually set for 30 degrees, not just reading 30 degrees. About half of these were centers that had apparently been shipped with the lathes, and the others were unknown composition (but schools generally by the economy grade). All were file hard.

I scrounged up a carbide endmill and a #2 MT to 1 inch straight shank adapter. Will let you know next week if we were able to produce a half dead center from one of the reworked centers.

Some of the older lathe texts such as Milne [see lindsay books at

] show more of a 3/4 dead center, and I think this is what we will initially try for, although I dont know how well the corners of the endmill will stand up cutting hard steel. We may wind up flat cutting.

The older machining books caution that the cut must be to the front and that you must always cut from the inside out to avoid putting any load on the cut-away section. They also caution that the only time you should use a half dead center is to face off the end of the work.

George McD

I bought some cheap centers ($1 ea) and put some of them into my wood stove to anneal them. Sure softened them, had no trouble drilling them.