South Bend 11, gap bed, silent chain lathe identification

I can't find this in any of the catalogs I've been looking at.

It's an 11" South Bend lathe, with a gap bed and the overhead-mount silent chain drive.

Serial number is 33817, which Steve Wells new SN database has as 1927.

Model number appears to be 3684-A or 3634-A.

How do the apron controls work? Does it use the leadscrew for traversing and cross-feed like a Model C, or does it work like a Model A?

What spindle taper does it have and what collets does it take? What is the spindle nose thread?

What are the pros and cons of this lathe?

I've been hunting for a heavy 10, but I have the opportunity to get this one for a great price. I'd miss having the 5C collets and large bore spindle, but it's probably bigger than my Atlas, and the overall machine is certainly a lot heavier duty.

Steve

Just sold a '22 5'bed version of that. The small knob left of the star clutch controls sliding/cross feed,loosen and move up/down to select slid/cross feed,tighten knob. Spindle is 1-5/8 x8 thread,believe MT3 taper. definitely a step up from a Atlas,I bought the I had to resell but was pretty nice to use.

I haven't seen a gap bed 11" but my 11" (and all the others I'm aware of) use a MT2 in both the spindle (with adapter) and tailstock. Through spindle is 7/8" spindle thread is 1 5/8", and it takes 2S collets.

Hope that helps,

-Ron

MetalCarnage said:

I haven't seen a gap bed 11" but my 11" (and all the others I'm aware of) use a MT2 in both the spindle (with adapter) and tailstock. Through spindle is 7/8" spindle thread is 1 5/8", and it takes 2S collets.

Click to expand...

When you say "with adapter", what is the spindle hole taper without the adapter?

If the thru hole is 7/8 (0.875") and MT2 at the large end is 0.700", while MT3 is 0.938", it seems that it COULD be MT3.

Oh, and while I didn't find a catalog with that exact lathe in it, I found a later model that showed the gap as 5" wide and can hold up to 16" diameter.

Steve

How do the apron controls work? Does it use the leadscrew for traversing and cross-feed like a Model C, or does it work like a Model A?

Click to expand...

Like a Model A, the apron clutch is for feeding and the half nut lever is for threading

Great version of HTRAL from those Series O days

http://vintagemachinery.org/pubs/1617/5795.pdf

SteveM said:

When you say "with adapter", what is the spindle hole taper without the adapter?

If the thru hole is 7/8 (0.875") and MT2 at the large end is 0.700", while MT3 is 0.938", it seems that it COULD be MT3.

Oh, and while I didn't find a catalog with that exact lathe in it, I found a later model that showed the gap as 5" wide and can hold up to 16" diameter.

Steve

Click to expand...

Here us how the 11" is listed in the SB catalog (granted, this is for just one year but I haven't seen any major variations from these specs for machines from previous or later years)...
















I also haven't been able to source an actual adapter specifically for an 11" so can't speak to it's dimensions. The catalog lists it as a MT2 so that's what I have to go on.

-Ron

Yes, I saw some of those in the catalogs, but not the gap bed model. I've need some of the gap bed models, but not with the model number of this one (probably because I don't have a catalog from the exact year).

A 2S collet has a body diameter of 0.750":
Collets

MT2 has a large end diameter of 0.700":
Dimensions of Standard Tapers - LittleMachineShop.com

As that is the largest diameter of a MT2 arbor, which would likely protrude slightly from the spindle, and MT2 spindle would have to have a max opening of 0.700"

Unless there is a negative spindle adapter that would put a 0.750" collet into a 0.700" hole (and I want the 5C version of that!), there is something wrong in all this.

And then there's the idea that the hole thru the spindle is 0.875" but the end is 0.700". You simply can't pass 0.875" stock thru a MT2 spindle.

In fact, the smallest MT taper that can pass 7/8" is MT4, but that can pass 1" stock, so I doubt it would be MT4 or they would just say it could pass 1".

My Atlas has a MT3 spindle with a thru bore of 25/32" (0.78125"), and that seems to correlate to the max/min diameter of MT3 0.938"/0.778".

What is the diameter of the opening at the end of your spindle?

When you and South Bend say that it is MT2, is that with an adapter or just the bare spindle? I think you said adapter, so there is some other taper in the spindle. What is that taper?

Steve

Spindle info on this page of this link to Steve Wells’ great web site:

http://www.wswells.com/data/fte/headstock/spindle/spindle-images/chart-1.jpg

Ted

SBLatheman said:

Spindle info on this page of this link to Steve Wells’ great web site:

http://www.wswells.com/data/fte/headstock/spindle/spindle-images/chart-1.jpg

Ted

Click to expand...

OK, that's making sense. Up to 1919, it was MT2 (0.700", shown as 0.602tpf although MT2 is 0.599tpf), then up to 1921, MT3 (0.938, 0.602tpf), then 1.013 with 0.602tpf, which is probably some proprietary taper.

I suppose you could get a spindle shop to bore out the proprietary taper to something more useful (MT4 or B&S9) if you can't find the spindle adapter for collets. Otherwise, an ER collet chuck will likely be the best bet.

Steve

SteveM said:

OK, that's making sense. Up to 1919, it was MT2 (0.700", shown as 0.602tpf although MT2 is 0.599tpf), then up to 1921, MT3 (0.938, 0.602tpf), then 1.013 with 0.602tpf, which is probably some proprietary taper.

I suppose you could get a spindle shop to bore out the proprietary taper to something more useful (MT4 or B&S9) if you can't find the spindle adapter for collets. Otherwise, an ER collet chuck will likely be the best bet.

Steve

Click to expand...

Steve,

I don't think you are looking at those numbers correctly. The last value for the taper diameter (1.013) goes with the spindle nose at 1 5/8" - 8 which are the same values found on my 11 SB from '39. The same one where it is stated that the spindle nose is a 2MT. I believe the confusion comes from the missing collet adapter. While SB refers to it as a 2MT surmise that they are referring to the angle of the taper being the same but the spindle nose opening is larger than the one found on the tailstock. I've looked at the spindle taper on the Heavy 10s and that seems to be the case with it's spindle. It has a TPF of .602" which is the same as a 3MT but the hole is larger.

Also, the collets do not sit in the 7/8" through the spindle, they sit in the adapter which sits in the spindle nose and butts up to the spindle.


JMHO,

-Ron

MetalCarnage said:

I don't think you are looking at those numbers correctly. The last value for the taper diameter (1.013) goes with the spindle nose at 1 5/8" - 8 which are the same values found on my 11 SB from '39. The same one where it is stated that the spindle nose is a 2MT. I believe the confusion comes from the missing collet adapter. While SB refers to it as a 2MT surmise that they are referring to the angle of the taper being the same but the spindle nose opening is larger than the one found on the tailstock. I've looked at the spindle taper on the Heavy 10s and that seems to be the case with it's spindle. It has a TPF of .602" which is the same as a 3MT but the hole is larger.

Click to expand...

I think I am reading it correctly. The three sizes are:

Same diameter as 2mt but with a 3MT taper
Same diameter and taper as 3MT
Some bastard diameter with a 3MT taper

This lathe would be the latter.

It's interesting that all the spindles are shown as 3MT taper, except the 1.231", which is a 4MT diameter and taper. Even the bastard size of 1.6295" for the heavy 10 is shown as 0.602tpf (that's actually closer to a Jarno #13 than a Morse taper 5).

The chart shows the 9" lathes with 1-1/2" spindle noses as 0.938 " with 0.602tpf, which is a 3MT.

All of my questions have been about the taper of the spindle, not the taper of some adapter (which we do not have an example of). The adapter would not be 2MT anyway as it SHOULD be 2S (if that's what it takes for collets, because you would not be able to put a 2S collet into a 2MT adapter unless you had the magic spindle enlarging adapter (see prior post).

Ted's chart directly contradicts the catalog, but the catalog contradicts itself when it says it is 2MT with a 7/8" thru hole (although, the catalog doesn't actually SAY that the spindle TAPER is 2MT, only that it takes a 2MT center, but why would you have a 2MT adapter AND then need a 2S adapter?).

I think Ted's chart is the correct spindle dimensions.

Steve

I see I may have added to the confusion. The adapter has two tapers, an exterior and an interior. I am suggesting that the exterior of the "adapters" body has the same TPF as a 2MT just as the exterior of the adapter for a heavy 10 has the same TPF as a 3MT. The "interior" taper of the adapter for an 11" SB is cut for a 2S collet.

Ted's chart is probably correct but as I've tried to say before (in my own clumsy way), the collet does not go in to the spindle without an adapter be it an 11", 9", 10", etc.

You would have a heck of a time making an adapter for anything other than the 2S collets as you only have 7/8" through the spindle (I say this from first hand experience). With any collets that are larger you wouldn't be able to get a draw tube through there to close them.

Hope that clears it up a bit.

-Ron

MetalCarnage said:

You would have a heck of a time making an adapter for anything other than the 2S collets as you only have 7/8" through the spindle (I say this from first hand experience). With any collets that are larger you wouldn't be able to get a draw tube through there to close them.

Click to expand...

The only alternate collet I would look at is 4C. It's a bit smaller than 2S, but at least you can find them. If you have to make an adapter, you might as well make it for something you can find.

The best alternative might be a 5C collet chuck, which would give you up to 7/8" holding with thru-the-spindle capacity and 1-1/8" for short work.

Steve

SteveM said:

The only alternate collet I would look at is 4C. It's a bit smaller than 2S, but at least you can find them. If you have to make an adapter, you might as well make it for something you can find. The best alternative might be a 5C collet chuck, which would give you up to 7/8" holding with thru-the-spindle capacity and 1-1/8" for short work. Steve

Click to expand...

Yep, I've got a casting kit for a 5C collet chuck COLLET CHUCK (MLA-21) but haven't found the time to finish it. Best regards, -Ron