Sundstrand lathe and taper ID help needed

Hello. I am in need of some help identifying an old lathe. More specifically, I am trying to figure out what type of taper is used on the headstock.

It almost seems like a Morse taper #3 although it doesn’t seem quite right to me. I have a dead center that came with the lathe which fits correctly. I also have a reamer with a Morse taper #3 that seems to fit slightly different. When I try to release the reamer with the Morse taper by reversing the wheel on the headstock, the reamer with the Morse taper never bottoms out and it gets pushed out of the headstock like the dead center does. I noticed that the dead center sits deeper into the taper than the reamer does. See the pictures. I am marked the tools with white paint where they sit in the taper.

Help me out if you can please! I’d like to get a drill chuck that I can use in the headstock.

bkobernik said:

Hello. I am in need of some help identifying an old lathe. More specifically, I am trying to figure out what type of taper is used on the headstock.

It almost seems like a Morse taper #3 although it doesn’t seem quite right to me. I have a dead center that came with the lathe which fits correctly. I also have a reamer with a Morse taper #3 that seems to fit slightly different. When I try to release the reamer with the Morse taper by reversing the wheel on the headstock, the reamer with the Morse taper never bottoms out and it gets pushed out of the headstock like the dead center does. I noticed that the dead center sits deeper into the taper than the reamer does. See the pictures. I am marked the tools with white paint where they sit in the taper.

Help me out if you can please! I’d like to get a drill chuck that I can use in the headstock.

Click to expand...

"Headstock" is the creature on the LEFT, the one with a chuck on it. The creature to your RIGHT is the tailstock. HS "may" have a standard taper that is truncated. Some are Brown & Sharpe's "jarno" taper.

Your situation, it sounds as if you simply haven't yet gotten dings and burrs cleaned-up. Until that is done, you are somewhat in the dark as to taper fit.

A reamer is not your first nor best tool for that. More better to blue-up a known-good centre, find and hand-stone them off first.

Even cheap imported centers or sleeves are usually accurately ground. Their alloy or heat-treating may be marginal, but they will at least be undamaged. Comparing junk to junk will just have you chasing your tail. Get better goods into the zone.

If reamer is actually MT3, the big end is about .938

Since it stops well before big end. possibly the lathe has a 7 Jarno, which is 7/8 or .875 big end

What is big end of center that fits right?

All info needed is in Machinery's Handbook

If it turns out to be a jarno, they do show up NOS "now and then". I have some #12 from Grand Tool that appear to have been put into cosmoline and (the remains of) waxed paper around WWII.

Both Riten and Stark make new ones. Really nice ones, too.

johnoder said:

If reamer is actually MT3, the big end is about .938

Since it stops well before big end. possibly the lathe has a 7 Jarno, which is 7/8 or .875 big end

What is big end of center that fits right?

All info needed is in Machinery's Handbook

Click to expand...

Thanks gentlemen, please excuse my very rudimentary understanding of lathe terms.

Yes, the reamer has a measurement of .938” or so.

The measurement of the center at the paint mark in the photo (toward the big end) is .875”.

Would a 7 Jarno make sense for this old lathe?

bkobernik said:

Thanks gentlemen, please excuse my very rudimentary understanding of lathe terms.

Yes, the reamer has a measurement of .938” or so.

The measurement of the center at the paint mark in the photo (toward the big end) is .875”.

Would a 7 Jarno make sense for this old lathe?

Click to expand...

I've not known John to EVER make a suggestion that did NOT "make sense".



It simply isn't yet a certainty.

You've got metal to "clean up" - and carefully, please. It is still hiding its true nature.

jarno is a probability for lathe HS even though it never got much traction anywhere else.

If you place the tables for Morse taper, B&S taper, and Jarno side-by-side, what should leap right into your face is that jarno is ALWAYS the same taper, regardless of size or number, and the other two are NOT.

They change between sizes, sometimes each size, sometimes after two or more NOT changing. They may have been "hand optimized" for modestly better grip, each range. Otherwise, there is no obvious reason for it, nor gain from it.

Brown & Sharpes' resident genius, Chief Technologist, and Works Manager, Oscar Beale designed jarno to resolve all that.

As a byproduct of the way one calculates a jarno taper, it is "open ended". It can scale to any size, up or down.

Lathe makers need a spindle BORE. Jarno's constant angle, ANY size, made it easier to use partial-length tapers, allowed starting or ending at any point for a "gage line".

When trying to determine if a shortened taper was one size or another of MT, you have to ask if you are looking at only the small end of a large "number" taper, only the center of a medium "number" taper, only the large end of a smaller "number" taper, all of which MAY have dfferent angles, or a"half-size" MT that the maker decided for themselves.

Jarno has no such confusion. The "number" is not only a convenience - it also embeds "the math" in itself. What's more important is that the taper angle doesn't change.

My 95 year old 20" heavy GK has an 18 Jarno for a spindle taper - makes for a big end of 2 1/4". The "little" end per Jarno is 1.8" - satisfyingly close to the thru hole of 1 13/16"

johnoder said:

My 95 year old 20" heavy GK has an 18 Jarno for a spindle taper - makes for a big end of 2 1/4". The "little" end per Jarno is 1.8" - satisfyingly close to the thru hole of 1 13/16"

Click to expand...

FWIW-not-much.. the 10EE #12 jarno is MEANT to use a short adapter (to #3 MT).

I trialed a #11 jarno to see if I could reduce hang-out of the long-nosed full #12.

No joy. A "full" #12 jarno socket, it would have simple set very deep. In the truncated one of a 10EE, the smaller end isn't "there". The #11 went all the way back into the bore.

It seems likely that the tailstock has a Jarno 7 taper. I would rather have a Morse Taper 3 since it seems much easier to find tools that fit that taper. I read about a guy who used a straight shank MT3 finish reamer to convert his tailstock taper from Jarno to Morse Taper. Any thoughts on doing that?

bkobernik said:

It seems likely that the tailstock has a Jarno 7 taper. I would rather have a Morse Taper 3 since it seems much easier to find tools that fit that taper. I read about a guy who used a straight shank MT3 finish reamer to convert his tailstock taper from Jarno to Morse Taper. Any thoughts on doing that?

Click to expand...

Depends entirely on whether the TS quill/ram/barrel is hardened or not. Then there is the usual fact of roughing and finishing reamers for such tapers. In any case, reaming out that much stock is not what such a reamer does well

Bore near net and then ream would be far less of an issue - assuming a machinable condition of course