I need a dead center for my 'new to me' Le Blond Dual Drive. Looking at the choices on-line, I have:
Carbon steel, hardened and ground, import
Bearing steel, import
Carbide tipped, import
Carbide tipped, USA
I expect to use the dead center with a face plate and dog for driving, with a live center in the tail stock. In that scenario, does it really matter what I get?
Where I do use the dead center in the tail stock, is there a single center that will work with all materials? Or do I need more than one?
Ed: For the HS carbon steel is fine, TS a live center is prefered but carbide tipped is second. Lube is needed at the TS for anything other than a live center.
One of your options is to make a center for the headstock, which you'd do by chucking a piece of steel and turning the desired point. You would then drive the piece with one of the jaws, which would engage the tail of the dog you'd use. The advantage of this setup is that the center will be dead concentric with the spindle, which isn't always the case when you use the spindle taper and a commercially made center, in particular, if it's an import.
If you choose this route, it's a good idea to have a shoulder on the gripped material, which would be firmly placed against the jaws of the chuck before turning.
That way it won't be subject to shifting under a heavy cut.
Be careful of the live center you use for the tailstock. I've seen some that are not properly made, so the point isn't concentric with the center of rotation. It most likely will still yield a round part, but the center in the work piece won't be concentric with the turned diameters, so if the part isn't inserted in the same position in relation to the center, concentricity on further work will be lost. To ensure that your center doesn't fit this description, place a DTI on the point and spin it by hand to see if it runs dead true. Don't rely on eyesight alone, as the eye can't discern small deviations. What appears to be true may not be.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
I do not have a commercially made center for the headstock of my current 17x60. I did have one for my previous Rockwell 11x37. But even when I had one, I used Harold's suggested turn in place approach. I had a good size chunk of bar stock left over. Turned a small step long enough to fully engage the jaws, and just a little below to the OD to both provide repeatable finish and roundness AND to provide a positive stop so it doesn't slide when loads increase. Every time I mount it, I skim it to (relative) perfection for the spindle axis, use it, and set it aside for next time. No worries about tiny bits of trash at either bushing or center interface, no worry about quality/accuracy/repeatability of spindle taper, bushing tapers (inner and outer), or the center itself. It's always right every time, and easily replaced should it be used up or damaged, or if I need one just a bit longer/smaller/whatever. And as an added bonus, the 3 jaw chuck provides a most excellent way to drive a dog using the jaws, and no need for a dedicated dog driver (which I also don't have in D1-6).
I do exactly the same, any center used at the head stock end is done with a dedicated shop built center that get's trued each time it's used. Then it doesn't matter just how accurate or inaccurate your chuck is.
Since turning between centers is the most accurate way of turning any shaft that has to be removed and replaced or rotated 180 degree's. I look at it that's it's a place where your depending on the accuracy of your centers to give you repeatable results. For myself I don't think that's a place to pinch pennies. So I try to buy carbide tipped full and half centers that are from a good manufacturer. Then use a real good lube and keep a careful watch for any heat build up from the lube drying out, or the shaft getting tight due to expansion between the centers. But if you've got an excellent brand name live center, then it would have to be some really accurate work before the few 10ths of error that a good live center has would start to affect your work.
Thanks for all of the excellent information and suggestions. Certainly, the notion of using a turned center in the chuck is very appealing as I don't have a face plate for the lathe. If that's one less thing to buy, so much the better!
So let's talk live centers for a minute. Since I don't have one of those yet, either, I've been looking at two -- a Royal, with just the 60° included angle tip, or an Interstate, with 7 interchangeable points. The Royal has "TIR of +/1 0.00005 in. guaranteed"; the Interstate 0.0012 - 0.0039 in.
Obviously, the Royal seems vastly better, but is also less 'versatile' than the multipoint option. Being relatively new to lathe work, how often will I use something other than a standard point?
To be honest? Those multi point live centers all depend on your work and projects. Impossible to answer for sure. Usually one live center isn't going to handle everything that comes along though. But imo you do need at least one really good live center. Hard to go wrong with those Royal centers tho. Interstate is just a barely subtle way to disguise it's made in China though. And at those numbers I wouldn't give it room in my shop. .001"- almost .004" is terrible. Those should be 10ths not thousandths.
One more thing to consider. A lot of manufacturer's make what they term as an extended point, it's usually designed and meant for CNC lathes, but they work just as well or better on a manual machine. That extended point can allow your tool tip to get in just a little bit better than the more standard types. I've only used one so far, but anything I buy in the future will be that style of point.
Royal at one time made a real expensive and specialised live center years ago. It was meant to be inserted into the tail stock just like a normal center, but it had a very accurate level on it, and the tip was a live center with a hardened and ground ball tip. And the ball could be offset for taper turning instead of fooling around with the tail stock offset. They were VERY expensive but I still want at least a used one in very good condition. Google images should pull up some pictures of them. If I have to I'll even make one.
I like the interchangeable points for versatility, but like the dead center in the spindle bushing, it's just more places to accumulate errors.
For my day to day tailstock centers, I have 2. One big heavy Rohm. It's a beast, and well used, but it still runs true, and is used for heavy stuff and heavy cuts. I also have a Concentric spring loaded live center that is used for more moderate loads and when I am most concerned with accuracy. It's also nice for parts with a lot of heat generating work because the spring loaded tip can adjust for the heat expansion. I'm very happy with the pair. I've also got a Polish Skoda a bit smaller than the big Rohm that is quite good, but mostly sits in the drawer. And I've got a tiny extended point Concentric for more delicate work and to get clearance at the end of the ~4" diameter tailstock quill. And finally I have a bull nose tip for the concentric, as well as a dedicated bull nose live center (US made back in the 60s, don't recall the brand), and some shop made live centers I got from the Honeywell surplus. Horses for courses...
I've got carbide tipped dead centers for some potential hypothetical use someday, but have yet to encounter that need.
To follow up on Russ' (BadDog's) post, re drive plates, on my D1-5 spindle I use.a D1-5 pin (available individually for.a.few quid) threaded into a larger diameter piece of.bar, pop it in and wind the.bar down, tighten the cam and voila, drive pin for lathe.dogs...
To take up the slop on the pin and dog, a cable tie around 'em works well, I find!
Just my ha'pennorth
Rules are for the obedience of fools, and the guidance of Wise Men - Douglas Bader
