Sprunger bandsaw restoration/modification


plotlm

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I thought I would post this in case someone might find it useful.

 

I recently picked up my first bandsaw for my tiny basement shop. Its a "Sprunger",which was an American brand that disappeared in the 80's.

 

Here's the bandsaw when I got it home. Not too terrible, but the paint was pretty nasty and base had a lot of rust:

 

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Not having a bearing puller, I jerry rigged this out of a piece of plywood, clamps, and a bike bearing tool (forgot what it's called) I had from fixing an old bike a while ago. I could probably have just used a bolt instead of the bike tool. I was kind of surprised when this actually worked- The lower wheel was pretty stuck on the shaft.

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I left the body casting on the frame at first, since it made stripping paint easier. I later did take the stand apart- it's made of formed angles bolted together, rather than being welded. Not especially sturdy, but the saw overall isn't very heavy. That main body casting is aluminum.

 

I used "Citristrip" paint stripper, hoping that it would be a bit less toxic in the basement where I was working. It worked OK, but I would be hesitant to do it this way again- The stuff apparently still presents some health risks, and this was a LOT of work. There was a rather absurd amount of work scrapers and wire cup brushes to get the parts cleaned up, derusted, and ready to paint.

 

I only brushed off rust, not paint, since it's a pretty good bet the old paint was leaded. So I only scraped the paint, to keep it wet and contained.

 

If I ever do something like this again, I'm taking the parts straight to a sandblasting shop.

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Skipping a bunch of steps here- I primed the aluminum casting with rustoleum aluminum primer, and the rest with rustoleum clean metal primer. The paint is rustoleum as well. I decided that red would be cheerful.

 

I brushed the paint on- While it looks OK, I had a lot of problems with runs and drips, probably because the temperature was a bit low (and, to be fair, a lack of painting skill). Live and learn. Again, if I was going back in time, I would have just paid to have the parts stripped and painted at a better equipped shop.

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The motor was a GE 3/4 horse, 3450 RPM, single phase. It still ran, but was packed full of sawdust. I took it apart as much as I could and cleaned and vacuumed it out. (I didn't completely take it apart, as I got stuck on getting the bearings off the shaft, but I probably got 95% of the dust out).

 

I did notice the the bearings felt pretty gritty when turning the shaft by hand. Not a great sign, but I replaced the old cord with a grounded 12GA cord, and reassembled.

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As I reassembled, I bolted the base to a leftover piece of 3/4 plywood. This gave the base a wider stance horizontally, and improved the stiffness of the base quite a bit. I cut up a sheet of black rubber into washers, to try to dampen vibration between parts of the assembly.

 

I also replaced a lot of the old rusty hardware and square nuts with new.

 

The saw was now basically back together how it started.

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So after all that work, I was ready to finally use the thing! I put the blade back on (which I think is a 16 tpi blade), and I clamped my shop vacuum nozzle up under the table, turned the vacuum on, turned the saw on, and...!

 

It blew the fuse and the lights went out.

 

So, replaced the fuse, plugged the vacuum into a different circuit from the saw, and got the thing running. It shook and rattled, the wheels spun like fan blades, and generally gave the impression of an unhappy piece of machinery. Nonetheless, I took a couple of test cuts on the scraps. It did cut, and hey, this is easier than ripping by hand..

 

I realized then that I had flung fine sawdust all over the place. The vacuum had done very little if anything to catch the dust. Did a little digging on the internet, and I realized that I had a number of problems:

 

  1. The speed of the saw was too high to begin with. The pulley reduction was 2.5:5, with a 3450 RPM motor. This meant my wheels were moving at 1725 RPM- and, cast right into the frame, was a note saying "700 rpm". I realized that at some point, someone had either changed the motor or the pulleys. I was running the blade at over 6,000 FPM!
  2. The belt was pretty far out of alignment
  3. The aluminum wheels were far from perfectly balanced
  4. The motor was probably not worth messing with- it blew another fuse in short order, and those bearings did not feel right
  5. From what I read, I was unlikely to catch any sawdust at that speed with a shop vacuum. I would need a real dust collector with higher airflow. (But given the weak electrical in the basement of my rented house, how was I going to power that and the bandsaw at the same time?)
  6. The blade guides were pretty crappy to begin with, having just round pieces of steel as side guides. The face bearings were all gummed up and would need to be replaced.

 

EDIT: Also, for my purposes, the 16 TPI blade was way too fine, and was probably making the dust problem even worse..

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You should be able to get round "cool Blocks" to replace the guides, upper and lower (under the table)

Math and a bigger pulley should slow things down. Maybe find an electric motor shop, they could replace bearings and make sure if it's even worth the effort. I have gotten lots of years out of old GE motors just like that one.

Never messed w balancing wheels, how are the rubber tires ?

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So here's where things get a little bit unconventional. I had been watching "The Woodwright's Shop" and I'd recently seen "Rise of the machines" where Roy Underhill demonstrates a number of hand-powered stationary equipment. Definitely a show worth checking out, I saw it on youtube.

 

Anyway, it got me thinking- What do I really need from this saw? I really just want a way to rip and resaw boards easier than by handsawing. If I think about this machine comparing to that, rather than comparing to modern bandsaws, maybe I can solve a number of problems.

 

So what I did was to slow the saw waaaaaaay down.

 

I got a new motor from surpluscenter.com, a Baldor, 1/4 HP, 1140 RPM unit. The new motor is about the same size as the old 3/4 HP motor, and runs at about 1/3 the speed. So I am guessing that the torque is about the same- 1/3 the speed, 1/3 the horsepower, = same torque.

 

I also replaced the pulleys, which were 5 and 2.5 inch, (4.75 and 2.25 pitch diameter) and with 10 and 1.5 inch pulleys. (9.75 and 1.25 pitch diameters)

 

This meant that my old speed, which was 3450 * (2.25 / 4.75) = 1,634 RPM, * (14*3.14159) = 71,876 inch/min, or 5989 feet per minute. With the 16 TPI blade, I was getting 19,167 teeth per second hitting the wood.

 

My new speed was 1140 * (1.25 / 9.75) = 146 RPM (less than 1/10th) = 6,428 inch/min or 536 feet per minute. I replaced the 16 TPI blade withe 1/2", 4TPI timberwolf blade. Now I would have 429 teeth per second hitting the wood.

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The other thing I did was to replace the guides entirely. I machined my own guides out of aluminum, and used some 3/4" sealed bearings I had around. I made wooden models first, to test it out.

 

I also made a dust hood to easily plug the vacuum into. I drilled and tapped a small hole in the casting to add a little piece of plywood to reduce the clearance as the blade reenters the body, to reduce clearance there too. (By the way, if you see the problem with the hood, you are ahead of me- I realized my initial method of mounting didn't allow me to change blades! I cut it up and and instead secured it with a couple of external screws to make it easier to remove.)

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Here's the bandsaw now. I replaced the flimsy motor mounting plates with 3/4" plywood, which is much, much stronger.

 

Slowing the saw down has one major disadvantage, of course- it cuts more slowly. But in my situation, it solves a lot of problems:

 

  • The saw produces dust slowly, and the dust is also moving slowly. My vacuum has no trouble keeping up with it- I get almost no dust in the saw  or floor after cutting. This has saved me the cost, space, and electrical needs of a dust extractor, (the only other major power equipment I use is a drill press and chop saw). The slow speed also means that I can feed the wood in at the optimum speed to avoid producing fine dust, which matters a lot to me since I work in my basement.
  • The slightly out or round, lightweight wheels, and the lightweight aluminum frame of the saw just don't matter much now- It's going so slowly that there's just not much vibration.
  • One bonus is the tremendous torque I get- the saw doesn't really seem to care what it's cutting, it just chugs slowly along at the same speed no matter what.
  • I also like to do a bit of machining- at this speed I think I could probably put a bimetal blade on this and cut some aluminum.

 

This kind of modification might be a bit perverse to someone trying to get the best, fastest performance from their equipment, but for me, the amount of time I actually spend making cuts is so small compared to the amount of time I spend on all the other parts of a project, I don't really mind being patient with the saw. It still rips faster (and straighter) than me with a handsaw!

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Thanks for your responses guys!

 

The previous owner did recently put new tires on, I think they are urethane. They looks alright to me- I am pretty sure that it's the wheels themselves that are a bit out of round, just watching them turn. I've never tried truing wheels either. Making it so slow has made it a bit of a nonissue, but maybe I'll give it a shot in the future.

 

The table seems smaller than it could be. I don't know why they wouldn't make it extend in to the column to give the maximum support for deep cuts. I was thinking about making a new, bigger one out of plywood. Has anyone tried that before?

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Oh, I'd go for it.  I've seen some of those Atlas presses come up on Craigslist and I've wondered about them. They're certainly more charming than any of the imported presses I've seen- I've got a Jet which I use, but can't really love.

 

As far as scaring someone off from such a project, I think my biggest mistake in the project was how I made the paint stripping harder than it should have been, but other than that it was mostly a pleasure.

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  • 2 weeks later...

Great job restoring this bandsaw.  I just picked up the exact saw today from Craigslist and am looking to do the same thing to mine.   I need to repaint, add dust collection, buy new tires and buy a new blade.

 

I have a question.  Inside the top, it says to use a 94" blade. Were you able to find one, or do you just use 93 1/2" blades?

 

I, fortunately, have the original 1725 rpm 1/2 hp motor with it and all of the bearings look fine.  Both thrust bearings turn pretty good. 

 

I probably won't strip all of the paint off of the saw.

 

The previous owner spray painted the cast iron table black.  <_<

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Hey Joshua, I can confirm that a 93-1/2" blade works fine. I'm using a timberwolf blade of this length, 1/2" wide, 4 tpi, and there is a good amount of room in the tensioning to handle this.

 

The spring on mine is pretty old, so I had to put in a ~1" spacer on the tensioning rod, to allow the tensioning knob to put enough compression into the spring to get good blade tension. The downside to this is that if I want to take the blade off, the spring is still under some tension when I run out of thread on the knob, so I need to take the knob all the way off to change blades. Right now I am just using this for fairly straight cuts so am not changing the blade, but sometime down the road I am either going to replace the spring with a new one with a higher spring constant, or replace the knob with something with a longer thread, so as to do away with the spacer.

 

I'd be interested to hear how your saw works out, since you've got it set up in more of the original condition.

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