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# 13" Lathe Large V-Belt Pulley Size

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#### dwall174

##### Aluminum
I recently picked up a 13" SB Turret lathe that has the 3-step cone pulley set-up.
The previous owner changed the v-belts & pulleys to apparently make run it faster than normal?

I want to try to get it back to as close to the original speeds as possible.
According to several manuals I've checked the motor pully should be 2-17/32", But I haven't seen anything on the original size for the large v-groove drive pulley.

Does anyone know what the size of the large V-groove drive pulley is on the 3-cone pulley set-up?
I'm pretty sure it's the same as the 4-cone pulley models, but it could be a little different because of it being a turret lathe?

Doug

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I'll guess there was a 13 turret lathe, but all I have access to is the 1952 catalog that only shows the 16" named the 2H

Its avreage speeds with the two speed motor were 600 on high speed and 300 on low speed.

There is a fair chance this relates to the lower (in cabinet leg) cone pulley's speed

If this was the actual case, you would need a ratio between motor and lower cone pulley of 2.92 to 1 if the motor on high speed was 1750 RPM

Because 1750 divided by 600 is 2.92

If you apply this to your figure of 2 17/32, you get a diameter of 7 3/8

You get to do the math and see if I am wrong as to what you have there

All that really amounts to is knowing the ratio made by the small step on the spindle and the large step on the lower cone - and provide whatever pulleys are necessary to make your motor drive the spindle at whatever speed you think it needs to run at

Not sure a 13", but on a 16" the upper, larger vee pulley is 12" OD.

Looking at the 55th edition, page 13 of pdf, the 3 cone pulley of 13" and 13" turret shows top speed at 940 rpm. I'm personally fine with adjusting any south bend to a 1000rpm, as you're not that far off anyhow.

HTRL 55th edition:
South Bend Lathe Works - Publication Reprints - How To Run A Lathe 55th Edition | VintageMachinery.org

The pdf:
http://www.vintagemachinery.org/pubs/1617/17726.pdf

Top spindle speed will be 2x the upper vee pulley speed, using small upper cone pulley for top speed.

Whether you change upper vee pulley or not, you can probably hit your mark by knowing motor speed, and just replacing motor pulley to get that upper vee pulley to half spindle top speed. Though I prefer motor pulley atleast 2.5" with 3" even better. Use this calculator to figure it out:
Pulley Calculator. RPM, Belt Length, Speed, Animated Diagrams

On the 16's I built I used 3.5" on motor, and upper was 12", which put me a hair over 1000 rpm on spindle.

We discussed pulley and belt sizes quite a bit on this page if you're interested:
Getting Another South Bend 16x6 Operational

Edit: You might confirm your 13" spindle spins 2x large vee pulley while on small cone pulley. Paint mark Large vee and spindle/chuck. If rotating large vee once, spins spindle two rotations, well there you go.

Top spindle speed will be 2x the upper vee pulley speed, using small upper cone pulley for top speed.

You might confirm your 13" spindle spins 2x large vee pulley while on small cone pulley. Paint mark Large vee and spindle/chuck. If rotating large vee once, spins spindle two rotations, well there you go.

That would be hard to do right now since I have the lathe all disassembled.

I moved most of the manageable parts inside & down into the basement where I can work on cleaning & refurbishing them during the winter. I'm currently going through the parts & figuring out which ones are worn down or damaged & I plan on replacing.

I don't have the under-drive pulley assembly totally disassembled yet, so it's hard to get an accurate measurement on the cone pulley! But it looks like the large cone pulley is 7.875" & the small spindle pulley is 3.250", that should give me a ratio of about 2.42 to 1

On the 16's I built I used 3.5" on motor, and upper was 12", which put me a hair over 1000 rpm on spindle.
Judging by that it looks like you have a 3.4 to ratio from the motor to the large pulley!
Being my ratio between the under-drive's large flat pulley & the spindle's small pulley is around 2.4 to 1, I'm figuring I'll need about a 4 to 1 ratio from the motor pulley to the large drive pulley shaft?

Doug

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I was thinking I read somewhere, and I think it was a 13", that the op had a hard time getting the vee belts on because pulley was close to the motor base. My 16" is close, but no issue to install belts. Could not possibly tell you where I read it though.

In looking I did find this thread, which could give you a rough visual of the original vee pulley, probably a 4 cone pulley, but I would guess vee pulley the same:
13 Inch 1981 With Taper Attachment

You probably saw it, but Brad Jacob had an excellent restore thread, also in the basement !

Didn't see his vee pulley though:
https://www.practicalmachinist.com/...-13-restoration-247779/?highlight=restoration

I was thinking I read somewhere, and I think it was a 13", that the op had a hard time getting the vee belts on because pulley was close to the motor base. My 16" is close, but no issue to install belts.
The other possible problem I can see with a larger pulley, is that it would interfere with removing the pulley assembly with-out removing the V-pulley first.

You probably saw it, but Brad Jacob had an excellent restore thread, also in the basement !
Yeah I saw that thread, But I don't plan to move the whole lathe downstairs! I'm only moving the manageable parts into the basement to work on them while its cold outside.
No big shop here! Just a regular two-car detached garage that I don't heat 24/7. With it going down to the single digits at night here in Michigan it would cost too much to heat 24/7

Here's a good (Large)PDF file that covers a lot of details for refurbishing a 13" SB lathe. http://www.wswells.com/ppp/r-battelle/1954-13-refurb.pdf

The above PDF file & this web site with a series of videos by George Bell South Bend 13" Restoration - Disassembly, Preparation for assembly - YouTube Pretty much follow the instructions in this rebuild kit South Bend Lathe Model 13" ● Full Rebuild Package ● Manual, Felts, Oil, Grease! | eBay

With the above information & your YouTube videos South Bend No. 2-H Turret Lathe 16"x6' circa 1942 part 1 - YouTube I'm pretty sure I can get through this rebuild.

Doug

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Last edited:
Here's an update to my lathe pulley issues!
I had to put this project on hold for most of the summer because of lower back problems. After about 8-weeks of physical-therapy, I finally realize what I can & can't do any longer.

I had the bed, base, legs, & chip-tray already in place where I plan to put the lathe.

Now that I'm slowly getting back to working on the lathe, I realized the new large pulley I got for the lathe will not fit on the upper step-pulley shaft without lowering the under-drive assembly inside the base.

I recently picked up a Powermatic 1200HD that I'm also working on rebuilding & naturally as luck would have it, I placed it in the way to easily get at the lathe with my shop crane.

The lathe base (hard to see) is under the side window in the pic. below.

So, I opted for plan "B"
I braced the bed & chip pan up & used a small scissor jack to take the weight off the base. From there I was able to pull the base out enough to get it on a hand cart & move it to an aera of the garage I can get my lift into place.

With access to the base, I just reversed the process I used to first install the under-drive assembly in the base.

It was a lot easier to work on it up on the stand, And a probably a lot better for my lower-back.

Doug

It's probably a good thing I pulled the base out & put it up on the stand to work on it.
The pulleys & belts I used are size "B" which should give me a little extra grip!

With the larger width "B" pulleys I also ran into a slight clearance problem since the pulley's & belts were originally size "A"

I had to grind down a couple of non-critical areas of the motor mount assembly.

Being that the original pulley used a taper-pin to hold it in-place, the shaft naturally didn't have any keyway to match the standard pulley. I really didn't want to disassemble the cone pulley & new bearings I already put in, so I opted to add a couple of extra setscrews to the new pulley.

Doug

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