Does anyone know if there is a standard internal taper used with the D1-6 spindle mount? I have a Sheldon R-15 lathe, and haven't been able to figure out what the internal taper is, so that I can get a dead center.
If there is a standard, I'm not aware of it. I have heard that Royal is pretty good about supplying centers to order for most any lathe.
I went to look at an R-15 a few weeks ago that was up for auction as I've been looking for something a bit bigger than my 10EE. Unfortunately, this one was in rough shape, with a longer bed than I can comfortably squeeze in my shop. Sold for less than $500, I think. It was a little lighter than what I expected, but had most of the things I'm looking for in a replacement for the EE, so I'll be keeping my eyes open for a good one.
Look in Machinery's, in the Standard Tapers section, among all the tables one is called "American National Standard Self-Holding Tapers - Basic Dimension (ANSI B5.10-1981)". The table starts out with 3 tiny B&S tapers, then has the full Morse taper series to MT #7, and then it continues into the "3/4 inch per foot series".
It's my understanding that relatively modern lathes with spindle bores too large for the MT series use the 3/4 in/ft series. A D-6 would need about a #250 taper, the # correponds to the taper diameter at the large end, e.g. 2.5" for the #250.
Actually, that used to be called a *live* center in the old books (because it rotated), and the dead center was in the tailstock. Then the ball-bearing centers came along for the tailstock, and things got confusing. :-)
One difference between the headstock and tailstock centers was that the tailstock ones were hardened, while the headstock ones were soft, and were often turned to a precise concentric 60 degree taper after insertion, so it would be as close to perfect as could be expected. No runout that way.
Jacobs? I think that Morse is more likely. But some makers used their own proprietary tapers, and some used tapers which were once standard, but which are very hard to find these days.
My Clausing, with an L-00 spindle, happens to use a Morse 4-1/2 taper. Morse never listed it, but the Morse tapers got swept into the ASA standard for part of the range, and they seem to have created a
4-1/2 to fit the larger gap between the MT-4 and MT-5 tapers.
Another part of the ASA range uses the Jarno tapers, and the other end (the small end) uses B&S tapers, I think.
You'll also find B&S tapers in some lines of dividing heads, including those made by B&S, of course. :-)
A lot of the lathes with proprietary tapers, and some with normal tapers like my Clausing, have available reducing sleeves to convert the spindle's taper to a convenient size. I've got a sleeve (home made) to convert the Clausing's MT-4-1/2 to MT-3, a match for the tailstock taper.
Maybe one of the others know just what taper your Sheldon used. Does it have a taper turning attachment? If so, you can tune it so an indicator reads a constant value as you feed into the spindle (measuring the far side) and you are just about ready to cut the outside taper for your own home-made adaptor. Once it fits, then you drill and bore it, and finish up with a Morse taper finish reamer to produce what you need.