# SB 9A Cabinet underdrive lathe



## ottrunner (Feb 7, 2021)

I have come by this old beauty, an underdrive 9A, 1946ish I am guessing.


Yes, it doesn't look like much and is well worn but I intend to polish it up to the best of my ability.  (which may not be much)
It came with another complete headstock which appears to be in great shape, photos to follow.
3 and 4 jaw chucks, steady rest, taper attachment and collets.
It also has a coolant system powered by a hoover motor so it is period correct I think if not original to the machine, I'm not sure and plan on removing it.

The price paid was $350 Canadian pesos.

"restoration" under way.


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## DavidR8 (Feb 7, 2021)

Welcome back to the forum! 
Looks like a worthwhile project!


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## ottrunner (Feb 7, 2021)

I'm not sure how worthy it is but I am certain to enjoy the process.

It's all there and hopefully the wear offers a reasonable working envelope when I'm finished.


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## brandon428 (Feb 7, 2021)

Curious. What is an underdrive lathe?


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## Mini Cooper S (Feb 7, 2021)

brandon428 said:


> Curious. What is an underdrive lathe?


That is one that has the drive motor underneath instead of behind the lathe like the small lathe on the left. The larger lathe is configured like an under drive.


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## ottrunner (Feb 7, 2021)

It's footprint is actually smaller.  The cabinet in only 48 x 22 inches.

I do like that about this little 9".  If I can pull it off it might find a nice place in the garage.  

I almost have it clean, first step.  The thing was filthy when I picked it up, you'd get dirty just looking at it.


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## finsruskw (Feb 7, 2021)

!!Did you have to show the seller your gun when you went to pick it up??!!
Helluva deal!!!


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## ottrunner (Feb 7, 2021)

I picked up a 7x10 mini lathe in the deal and sold it less the qctp and tooling that came with it, the lathe actually owes me nothing, I made money on the trip after all expenses.

I really like the lathe, it is well worn though.

It actually came with an example of what it was used to build and the tooling to do it, will take pictures later as those here may find it as interesting as I do.

edited:spelling


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## ottrunner (Feb 7, 2021)

This can came with the lathe and inside are this collection of tools and an example of the finished part I believe the lathe was used to create.







Not in 1946 but it's most recent undertaking.


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## ottrunner (Feb 8, 2021)

A little work on the labels.  Not my best work but the old eyesight needs help too.


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## ottrunner (Feb 8, 2021)

Tonight I thought I might have a go at the chucks.  Before and after of the 3 jaw which appears to be a cushman and the 4 jaw which I'm not finished with, a skinner.
Also, the headstock I received with the lathe.

I hope you don't mind me sharing my experience in this image-heavy thread.  It's a pleasure for me to do the work and while I search for information I find myself reading other threads and hope mine might someday offer some assistance.


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## DavidR8 (Feb 8, 2021)

Great work, keep it coming!


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## ottrunner (Feb 11, 2021)

Next up I thought I would have a go at the threading dial.  You can't even look at this lathe without getting dirty.  The thing is filthy.  How anyone spent time at a job working this thing is beyond me.
With this done I'm on to the tailstock, the leadscrew is very worn, at some point I will make a new one with an extenstion.


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## brino (Feb 11, 2021)

@ottrunner

Hi Neighbour!

I just found this thread and am catching up......



ottrunner said:


> The price paid was $350 Canadian pesos.



I paid $600 for my well-worn Southbend 9A, with no chucks!




ottrunner said:


> I picked up a 7x10 mini lathe in the deal and sold it less the qctp and tooling that came with it, the lathe actually owes me nothing, I made money on the trip after all expenses.



Okay, that deserves a:


However, around here that is a badge of honor! 
It really means that you got a great deal that I'm jealous of.



ottrunner said:


> I hope you don't mind me sharing my experience in this image-heavy thread.


That is exactly what we want!

Thanks for posting.
You are making tremendous progress.....there actually were two chucks under all that mess!

-brino


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## ottrunner (Feb 11, 2021)

brino said:


> there actually were two chucks under all that mess!


As you can see from the photos, the chucks were both a mess, the 4 jaw had a quarter-inch of crud on it.
Investigating paint, considering just using tremclad.  I'd like to 2 tone in a grey with the cabinet darker than the lathe.


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## ottrunner (Feb 12, 2021)

Had a quick go at the steady rest.  Filthy.
The day I can touch any bit of this lathe without gloves will be a treat.

Still needs another hour of scrub.  Seeing as stores will be back open for in-store visits next week I have put off purchasing paint and might have a look at the tintable enable available at Lowes or Home Depot.  I should have a range of colors to choose from and will mix in a hardener.


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## finsruskw (Feb 12, 2021)

An ultrasonic cleaner would speed this job up considerably and make it a whole lot less messy.
Shure was a big help when I did my project last year.


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## ottrunner (Feb 12, 2021)

finsruskw said:


> An ultrasonic cleaner would speed this job up considerably and make it a whole lot less messy.
> Shure was a big help when I did my project last year.


I'm certain it would help.  If it weren't minus 30 Celsius I could do some of this work outside.  My garage is suffering.


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## finsruskw (Feb 12, 2021)

I purchased the larger size that would hold the complete QCGB casting in total submersion. Worked like a charm.
Also made removal of 6 layers of various color paint from the headstock cover as well.
Peeled right off like it was an orange!


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## ottrunner (Feb 12, 2021)

finsruskw said:


> I purchased the larger size that would hold the complete QCGB casting in total submersion. Worked like a charm.
> Also made removal of 6 layers of various color paint from the headstock cover as well.
> Peeled right off like it was an orange!


I'm going to shop it right now.  Sadly I've scrubbed most of it already.


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## ottrunner (Feb 19, 2021)

More scrubbing.  I had already worked the cross slide and the taper attachment but went at them and a few gears the other day.  I long for the day I can touch any of this without gloves.

I also ordered a gallon of Rust-Oleum V7400 high gloss in Navy Grey.  I had considered doing the cabinet and lathe in different shades of grey but may do both in this.  I plan on adding a hardener also.

The lathe has seen a coat of paint along the way, it seems like it was originally a medium to dark grey and somewhere along the link someone opted for a lighter grey with a blue/green tint.

Jury is still out on the 2 tone vs single at the moment...viewing these photos has left me undecided.

Some photos:


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## ottrunner (Feb 20, 2021)

I had a go at the gearbox yesterday.  At some point I need to remove and clean up the underdrive system, a task I'm not looking forward to.
Also here are a few photos of the coolant system, I was thinking of deleting it but now I'm thinking of giving it a scrub and keeping it.


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## ottrunner (Feb 20, 2021)

And a bit of polishing before the kids wake up on a Saturday morning


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## ottrunner (Feb 20, 2021)

The Saturday night special.  Apron.

A bit of a nightmare.  I had to watch 4 youtube videos to find clear instructions, every one is missing something.
A lot to clean, polish and paint.  The handwheel would be best served bored and sleeved.  I may attempt that in the future.

For now, I will take care of the easy stuff, the scrub, and reassemble.


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## finsruskw (Feb 20, 2021)

*A wire wheel on a bench grinder will do wonders for those items.
So that you may want to forgo paint on some of the pieces.*


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## ottrunner (Feb 21, 2021)

finsruskw said:


> *A wire wheel on a bench grinder will do wonders for those items.
> So that you may want to forgo paint on some of the pieces.*


I'll finish a few of the parts to somewhat of a polish, I just sand them down to 3000.  Will do the knob on the carriage/cross slide handle, the face of the clutch, and possibly all of the half nut handle although that doesn't seem to be the norm.


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## ottrunner (Feb 22, 2021)

I have the apron cleaned to the point I can touch it without hating myself.  I'm going to reassemble it for now and clean the saddle.

I seem to be missing a part from the worm gear assembly and it is quite worn so I ordered another from ebay, see photos.


Mine missing key and the gear is worn thin


ebay replacement


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## ottrunner (Feb 22, 2021)

apron back together after giving the nut control lever a bit of a polish.  There are some well-used parts in here I will replace at some time.  Prior to purchasing many more parts I will complete the clean-up and paint.  I've taken the first pass at the saddle and will post photos once it is back together.


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## ottrunner (Feb 25, 2021)

A bit of cleaning on the bed.
This machine had a coolant system and the bed has modifications for that.  They may factory or have been added afterward.  There are 2 drain holes and brass "blockers" which would prevent fluid from getting into the cabinet via the belt opening.  Also, the headstock has an additional bit of flashing totally enclosing the cabinet.

Tomorrow I expect to complete this to be able to handle it without gloves.  Awaiting hardener and then I may start painting.
I still need to pull the motor and pulleys from the cabinet.


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## ShagDog (Feb 25, 2021)

Coming along nicely.


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## ottrunner (Mar 3, 2021)

Had a few warm days so took a break from scrubbing dirt.


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## SLK001 (Mar 3, 2021)

finsruskw said:


> I purchased the larger size that would hold the complete QCGB casting in total submersion. Worked like a charm.
> Also made removal of 6 layers of various color paint from the headstock cover as well.
> Peeled right off like it was an orange!



How big is and where did you get your ultrasonic cleaner?  How much did you pay?


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## ottrunner (Mar 7, 2021)

Weekend progress.  
I thought I'd have a go at the headstock.  Seeing as I have 2 of them I thought I would disassemble them both, cleaning up the original first.  
The original headstock has modifications for coolant, a shield on the back, and slots for the brass block off plates on the bed.

It shows a bit of wear but I'll clean it out, put in new felts and offer it for sale on ebay with lots of photos.  It might be a nice part for someone looking to make a bench lathe work as an underdrive.

The rear shield


The slots, factory cut or after?


Oil drain passages cleaned out.  Some marks on bearing but nothing to catch a nail on, lots of life left in it!


That's it for today.


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## ottrunner (Mar 8, 2021)

Although the new headstock appeared to be in excellent condition I thought it best to disassemble and inspect.
The bearing surface on it is perfect although it doesn't have the "high speed" grooves.
The spindle wicks were replaced with horizontal type rather than the underdrive spec ones.  The proper rebuild kit is on the way, stuck in USPS limbo.

I will complete disassembly and repaint and hopefully, the new felts will be here.  I also ordered the needle bearings to perform that upgrade.

It's also missing the surface tension breakers for the oil return, I will take them from the original headstock.


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## ottrunner (Mar 10, 2021)

I pulled out the motor today, 550 3 phase.  I don't believe I can get a vfd for that.  Guess I will shop for a new motor.


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## ottrunner (Mar 11, 2021)

16 balmy degrees here today so I wheeled the cabinet, it's on leveling castors now, they raise the lathe 3 inches and a tall man needs that extra height to prevent back pain.  Went over it with a wire wheel on the grinder.  It will need another session of that to go over what I missed.

Plan is to paint the cabinet the same color as the lathe but keep the lip and interior of the chip pan natural.  Maybe sand it to 320, or even 600 for a bit of sparkle.

Pics on that in a week when it's warm enough once again for a second round.  The garage is like a bomb went off inside an 80-year-old lathe cabinet, lathe parts everywhere.


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## ottrunner (Mar 23, 2021)

Sunny days, just trying to get things in order.  I was about to throw out the coolant system, it is a cast iron tub and weighs a ton but while dragging it out to the curb for the scrapper I noticed this:
	

		
			
		

		
	



It's an actual south bend part!  I guess that means a paint job and reinstallation.

Now that I have done away with the 550v motor that was on the lathe I'm considering using a treadmill motor, I have one, thoughts?


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## mattthemuppet2 (Mar 23, 2021)

treadmill motors are great, I'm working up a mount and drive for my SB9 right now. A 2hp (real, not TM duty) motor would be a good fit for a SB9 as that'll leave you plenty of power with the speed turned way down. Make sure you gear/ pulley the motor down - they run over twice as fast at full speed than a regular 1750rpm motor. Mine has a 4:1 reduction from motor>countershaft, then 1.5/0.8/0.5 (I'd have to check) ratios from countershaft>spindle.


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## ottrunner (Mar 23, 2021)

mattthemuppet2 said:


> treadmill motors are great, I'm working up a mount and drive for my SB9 right now. A 2hp (real, not TM duty) motor would be a good fit for a SB9 as that'll leave you plenty of power with the speed turned way down. Make sure you gear/ pulley the motor down - they run over twice as fast at full speed than a regular 1750rpm motor. Mine has a 4:1 reduction from motor>countershaft, then 1.5/0.8/0.5 (I'd have to check) ratios from countershaft>spindle.


Do you have a thread on the go so that I can see your progress?


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## brino (Mar 24, 2021)

ottrunner said:


> Do you have a thread on the go so that I can see your progress?



I believe this is the thread (now on its 6th page):

https://www.hobby-machinist.com/thr...-silent-drive-casting-trade.87737/post-837781

-brino


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## mattthemuppet2 (Mar 24, 2021)

thanks Brino, that's the one 

here's my DP








						Treadmill Motor Conversion On A Walker Turner Drill Press
					

alright, next project on the list - adding a variable speed treadmill motor and tach to my WT drill press which also doubles as a sort of mill. It currently has a 1/3hp motor with 5 step motor>intermediate>spindle pulleys to give 250-900rpm and 3000-5000rpm. Changing belts in the lower range...




					www.hobby-machinist.com
				




mill








						Treadmill motor conversion for a Grizzly 6x26 knee mill
					

I bought this second hand last year and it's awesome (1st proper mill!), but I've been spoilt by the variable speed treadmill motors on my lathe and drill press, so I've been waiting awhile for the opportunity to add a treadmill motor to my mill.  The 3 usual challenges are 1. how do I stop the...




					www.hobby-machinist.com
				




and current lathe








						Atlas 618 Treadmill Motor Install
					

Hi all,  this is a summary of my recent project to install a treadmill motor on my Atlas 618 (see http://www.hobby-machinist.com/threads/wiring-up-a-treadmill-motor-i-know-i-know.37159/ for the full experience!). It got a bit lost in that thread and Nels thought it would be worth posting it here...




					www.hobby-machinist.com
				




though that's been through a fair few changes since


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## ottrunner (Mar 24, 2021)

ok, 2.75 hp treadmill motor in hand, 4000 rpm.
The motor I took off was 3/4-1725 and had a 2.5 and 3 inch pulley opposite a 10 inch and 9 inch pulley

the original at max rpm would have been turning at 430 rpm on the 3/9 and 575 on the 2.5/10
The treadmill has a 1.5" pulley, on the 9 it would run 667 on the 10" 600.

Not terribly far off and I can install an rpm gauge to ensure I don't run it too fast.  I think a serpentine style belt will work just as well as the old v groove did.  The pulley on the motor was v groove but the lathe side is flat.

I believe I need a 38" serpentine belt, I'm also going to get a cheap dc controller and do away with the treadmill speed controller.


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## ottrunner (Mar 24, 2021)

Question:
I have 2 headstocks.  The original is the "high speed" model (I have read) where the bearing is grooved.  The other, no groove.

The original grooved headstock does have some marks, scoring.  Not the second one, it seems perfect.

Which would you go with?


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## mattthemuppet2 (Mar 24, 2021)

I think your numbers are crossed - should be 575rpm at the countershaft for 3/9 (3:1 step down) and 430rpm for 2.5/10 (4:1 step down). What are the ratios between your countershaft and spindle pulleys? Either way, you won't be running at full speed all the time, I typically do most of my work between 1/3 and 2/3 speed.

I'd go with the high speed headstock as long as you can get the spindle to within the correct amount of deflection and it doesn't overheat.

I would also caution against using a cheap DC controller. Some people have reported success (eg. RJSakowski), while others have not. A guy I knew used a cheap amazon PWM signal generator with his MC2100 treadmill controller and blew the controller up within a day. KB drives are good and you can get enclosed versions (Pentadrive) - UlmaDoc on here uses alot of them. Original MC drives are also very good, but the newer ones (MC2100) need a little extra work. My setups have been dead nuts reliable in the years that I've had them, other than some cheap switches (tip, buy the good switches from Amazon), and that's what I'd aim for.


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## ottrunner (Mar 24, 2021)

The countershaft and spindle pulleys are typical south bend 9".  At this moment I have yet to measure them as I figured I'd go with the center and use variable speed to do the rest.

I have a lot to read in regards to dc speed controllers it seems.  I did rob the treadmill of it so I do have that option but the treadmill did have a 3-second delay which I would have to figure out how to work around.

My hope is to get the motor to spin as fast as possible while having the spindle turn no more than it should at max-rated speed.

I will take your advice and go with the high-speed headstock.  It does have some scoring but would likely last me 100 years as I'm not much of a machinist (although I do hope to pick up the hobby and partake at it for however long I have left...lol).  I had intended to sell one of the headstocks but I'll keep it as a replacement if needed.

Thanks for the input Matt.


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## ottrunner (Mar 24, 2021)

Just to review:  Take this over a perfect headstock that doesn't have the high-speed
	

		
			
		

		
	



	

		
			
		

		
	
 grooves?


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## ottrunner (Mar 24, 2021)

My memory...serves me late every time.  If you notice on this headstock the casting at the top of the photo is broken, looks like someone might have given it a wee tap.

that broken off bit might allow metal, dirt, what have you, enter and run down into the oil passage.  I believe that was the reason I was going against it.

Thoughts, opinions?


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## mattthemuppet2 (Mar 24, 2021)

I'd go with the other one then, just keep it well oiled and don't over speed it for very long. 

As for the spindle/ countershaft pulley ratios it's best to think of each giving you a speed range. My lathe didn't come with a countershaft, so the pulleys that I'll be making will give me ranges of 500-1500, 250-850 and 150-500, give or take. There's a large degree of overlap but you'll find that there's a sweet spot for any given operation. I'll probably spend most of my time in the middle pulley, but I know from experience that I'll be using the ones on either side fairly frequently, plus the back gears on the odd occasion.

The easiest and usually cheapest drive to go for is an MC60/65. Super easy to set up, easily modded to avoid the "return to zero speed on start" issue, but might struggle a little if you really tax the motor. That doesn't happen much on my lathe, but it does happen fairly frequently on my mill. Next is the MC2100, can provide the full juice for a 2hp motor but requires an external PWM source for controlling speed (I'll be using an Arduino). For more money but less hassle, KB DC drives are really good. Never used one myself, but they're highly recommended.

Or use the one you have (free!) and see how it goes, plus whether or not it'll p!ss you off enough to want to change it


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## ottrunner (Apr 21, 2021)

I'm still here!
I think I will attempt the high-speed headstock, if it fails I'll swap out for the other.
I have the treadmill motor installed and went with the controller attached.
My hold up right now is the rebuild kit, the first went from USPS to China, the second is expected next week.
My 3d printer isn't a workhouse at boxes.


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## mattthemuppet2 (Apr 22, 2021)

looks great to me, good looking motor and a neat enclosure for the drive. I'd recommend a reversing switch though - you won't need it often, but if you ever want to thread metric it'll be essential. Also if your controller needs you to turn the speed to zero everytime you switch it on (some do, some don't) then the reversing switch allows you to turn the motor off without turning the controller off, so the motor starts again at the same speed. I have that on my drill press, bit of a pain but less than having to reset the speed everytime I stop the motor.


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## ottrunner (Apr 22, 2021)

I've decided against the enclosure, a pain to get into if I need to in the future.  I've ordered one from the Amazon and expect it tomorrow.

I intend to use the original Forward Reverse switch.  The controller does not reset.
Which gets me thinking.  I plan on running the variable DC from the controller to the original switch.  It has F Off R.  Is there any harm in having this switch on the off position while it receives DC voltage?


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## mattthemuppet2 (Apr 22, 2021)

Nope. It won't receive voltage as the circuit is open.


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