- Joined
- Oct 20, 2008
- Messages
- 5,547
I wrote this last winter when I had no camera for a while- just took some pics of the saw details after using it for several months now. This may not be super entertaining for anyone not looking for bandsaw mod/repair ideas, but I hope it helps someone. Keep an eye out on Craigslist, and happy hunting! I got this machine for $45.
When I picked this saw up, the man stated that the reason they were offloading it was that it would no longer cut straight, and was slowing down production. He mentioned a few problems it had developed in use.
The Main Problems and Tuning:
When I got it home the first thing I tackled was the hydraulic feed cylinder and auto shutoff switch. As the saw drops thought the cut, the cylinder retracts at a chosen rate, controlling the feed rate. At the bottom of the cut, a switch arm contacts the top of the cylinder, being pushed closed by the weight of the saw.
The switch had developed a lot of mechanical slop, to the point where the arm would slide sideways off of the cylinder top instead of being pushed upward and turning off. They had taped a large washer to the top of the cylinder to provide a contact plate to compensate for the slop.
The cylinder itself was empty of hydraulic fluid, and the seller said that it had been leaking and did not work. I noticed that the metal line running to the top of the cylinder was bent, and pulling the fitting off center where it connected to the valve. I straightened the line, bringing the flare fitting in line again. I noticed that the nuts on the tee connection to the valve at the bottom of the cylinder were loose, so I tightened everything.
I took the top off of the cylinder to check what seals I could. They seemed to be there and intact. So, I took some auto brake fluid I had on hand and filled the cylinder, then cranked the cap on tightly. I tried dropping the saw and stopping, then controlling the descent with the hydraulic valve. It worked!
Next, the rod handle for turning the cylinder valve, connected by a u-joint and pins to the valve stem, sheared its cotter pins off due to metal fatigue at the u-joint. I installed some cotters of the correct size, which fixed it and reduced slop.
Next, I turned to the belt drive system. I saw that the variable sheave speed control was poorly adjusted. First, the nuts controlling motor slide travel were set out of the right speed range, causing the belt to be loose- the motor had been slid back until the variable sheave max pitch diameter had been exceeded. I adjusted the nuts.
I noticed there was a lot of wobble in the driven pulley on the gearbox shaft. I loosened the belt, and took the pulley off for inspection. I saw that apparently they had been having chronic problems with the pulley coming loose- the shaft was scarred in many places by the set screw, and the pulley bore was worn oversize and eccentric. The set screw was no longer sitting on the flat of the gearbox shaft.
Thankfully the shaft was not bent, so I looked around and found that I had a slightly smaller pitch pulley on hand of the correct belt size and shaft bore. I installed it on the shaft, taking care to tighten it on fully, and at the right height on the shaft- the pulley had previously been badly misaligned. I tested it over the entire range of speeds- the whole speed spectrum had been somewhat lowered, but thats fine for me. At this point, all appreciable mechanical slop and vibration had been corrected on the belt drive system.
I then turned to the blade tracking system. As per the manual instructions, I loosened the blade guides first to un-twist the blade, then used a 6 bar of mild steel flat stock for a straightedge (after sighting down it and hammering straight) to inspect the wheels for alignment. Way out!
I followed the manuals instructions, tightening set screws and turning opposing nuts, to crank the top wheel in at the top. I noticed that the top wheel had about 1/4 of endplay on the shaft. The seller had mentioned that theyd had a replacement shaft machined for the wheel. I took the wheel off of it to see what was causing the problem.
The wheel sat on a shaft integral to the tracking plate, riding on needle bearings. The shaft was bored and threaded on the end. A thick hub faced internally with a thin phenolic washer was held on by a set screw installed into the shaft end, holding the wheel on by an internal shoulder. The problem turned out to be that the set screw holding the hub down was simply too long, so that the screw bottomed out in the blind hole in the shaft end ¼ before taking all the endplay out of the wheel. I merely ground the length necessary from the end of the screw, reinstalled, and the wheel ran true.
This, in addition to the upward re-adjustment of the top wheel tracking, brought the top wheel pretty straight. It had been like an inch out at the top.
The bottom wheel needed adjustment as well. A similar tracking adjustment served to bring the bottom wheel into line. I got it to the point that with moderate tension on the blade, the wheels were still cupped in toward each other by about ¼ total. This was a huge improvement, and was about as far as I could get it without tearing apart the tracking plates and re-conditioning them to increase the adjustment range. Its working fine for now.
I re-installed the roller guides, top first then bottom, twisting the blade back to perpendicular to the vise, checking with a square against the bed before tightening. After tightening the bottom, I rechecked at the top and adjusted a bit more until fully square.
While adjusting the bottom wheel tracking, I had noticed that the chain drive had a LOT of slack in it, causing the chain to pile up a bit on the slack side of the driven cog. The gearbox is installed with bolts over slots, giving a range of adjustment to control chain slack. I loosened the bolts and slid the gearbox until I had the chain slack out, but not particularly tight. I tightened the bolts and tried running the saw.
The blade tracked true until it fell off. I saw that I had not sufficiently bottomed the blade against the back rollers in the guides when installing them, so I re-adjusted and squared them, taking care that the blade ran against the back rollers lightly in no-load operation.
I had broken the old tension spring in the feed mechanism when fiddling with the cylinder. Its a stout spring, like 3/16 wire, and I can only conjecture it had built fatigue at the break point. I bought a new $10 spring at ACE and installed it. It was the right width and gauge, but longer than the original- I just adjusted the eye-bolt it hooked to shorter in length. This took some residual issues out of the feed system and brought operation completely in line.
The Vertical Mod:
With the saw all tuned up and repaired for horizontal chopping, I looked it over to see what it would take to convert to alternate vertical use with a cutting table.
First, the cylinder would need to be unbolted for vertical use, and the tension spring unhooked. No problem there. Then, the saw would have to be set on risers above the coolant pan to prevent the lower wheel case and motor from contacting the pan. A small part of the motor mount plate would have to be cut out to give clearance for the end of the saw bed. A cutting table would have to made and installed somehow to the lower blade guide support. The saw would have to run without the belt drive shroud in vertical mode.
I cut the risers first (with the saw), out of 4x2x3/16 wall tube from my scrap pile. After installing, I saw that the back foot flange would need to be cut off to give clearance for the driven pulley to run with the saw head vertical. The rectangle tube riser would need to be replaced with an angle iron riser to facilitate clearance for the belt driven pulley. I used an angle grinder and cutoff wheel to cut the foot flange off of the saw, and then drilled the horizontal bolt holes to mount it to the angle iron. This was measured to be at the same height achieved by the rectangle riser at the other saw foot.
The saw swung up a lot further now, but still far from vertical. I cut reliefs out of the coolant pan for the motor and heel of the saw head, cutting first less than necessary, swinging the saw up to check progress, then adjusting the relief cuts. I cut the small corner necessary for saw-bed clearance out of the motor mount plate with the angle grinder, estimating it to be well on the side of caution.
As I ground and checked, then ground more, I switched to a 120 grit flap wheel on the grinder for a nice smooth shape to the reliefs. With the saw head finally vertical, it rests almost simultaneously on the bottoms of both the motor and lower shroud reliefs, with most of the weight of the saw being taken by the thicker metal at the motor mount plate relief notch where it contacts the end of the saw bed. The coolant pan still has plenty of capacity, with the reliefs terminating 1.5 above the pan floor.
With the saw modified to include vertical position, and tested to run well when vertical, the only remaining step was to build and attach a cutting table.
I did not have a suitable piece of plate in my scrap pile, so in town I bought a piece from my steel guy. It was just an offcut, 10x1/4 flat bar and 15 long. Good enough for $10.
I determined where I wanted the blade in the table, then blocked the plate up on the saw bed and used the saw to swing-cut to the center. I brought the cut plate to the drill press, and drilled 3/16 holes an inch apart at the end of the kerf in the middle of the plate. On the mill, I milled a 3/16 slot between the holes most of the way through, flipped the plate, and aligned with the drilled holes to finish milling the slot floor.
Now I needed to mount the plate/cutting table to the lower blade guide, without obstructing the rollers and working around the alignment bolts.
My first idea (which I still consider bright) was to use this cheap drill press vise lying around- bolting the vise to the underside of the table, then clamping onto the blade guide bracket with it. After doing all the measuring and drilling/c-sinking, I re-discovered why that vise lies around not getting used. Its a warped casting for one, and for two the stupid sliding jaw is intractably sloppy. I couldnt get it to clamp tight to the blade guide bracket, even with fiddly shims.
Plan B: I used the rectangular riser block I had first cut, then discarded for the front saw foot. I torch cut, then ground a clearance notch out of it for the blade back and roller alignment bolts. I bought and installed ¾ longer roller alignment bolts, and installed them tightly and separately to keep my alignment. I drilled oversize holes in the bottom of my rectangle tube riser/table mount, and then installed it up onto the bottom of the roller alignment bolts, with large washers and nuts for an adjustment range with the oversize holes, similar to the alignment style of the rollers themselves.
After using said adjustment to correctly orient the blade in the table center slot, I fired the saw up and cut some scrap metal. It works well as a vertical saw!
The total steps necessary to switch to vertical mode from horizontal now: unbolt the feed cylinder and unhook the spring. Remove belt drive shroud with single wingnut. Swing saw up. Slip table mount holes over roller guide bolt ends, adjust and tighten table on with washer and two nuts. Cut!
Blade Notes:
The saw takes a discontinued ½ to 5/8 wide by 95-1/2 long blade, but the previous owners could not source the correct blades, so they used a stock ¾ wide by 96 long blade, and had the top tracking plate slot elongated by ½ to slightly lengthen the wheelbase. It actually works OK, but I expect tracking (already good) will only further improve with a slightly narrower blade running through the guides. MSC, for one, carries flex back and hard back blades in 96x5/8, and Lenox Diemaster II bi-metal blades in 96 x ½. Respectively, they cost at time of this writing, about $20, $17, and $42 ea., but I imagine MSC is higher in price than some other places.
When I picked this saw up, the man stated that the reason they were offloading it was that it would no longer cut straight, and was slowing down production. He mentioned a few problems it had developed in use.
The Main Problems and Tuning:
When I got it home the first thing I tackled was the hydraulic feed cylinder and auto shutoff switch. As the saw drops thought the cut, the cylinder retracts at a chosen rate, controlling the feed rate. At the bottom of the cut, a switch arm contacts the top of the cylinder, being pushed closed by the weight of the saw.
The switch had developed a lot of mechanical slop, to the point where the arm would slide sideways off of the cylinder top instead of being pushed upward and turning off. They had taped a large washer to the top of the cylinder to provide a contact plate to compensate for the slop.
The cylinder itself was empty of hydraulic fluid, and the seller said that it had been leaking and did not work. I noticed that the metal line running to the top of the cylinder was bent, and pulling the fitting off center where it connected to the valve. I straightened the line, bringing the flare fitting in line again. I noticed that the nuts on the tee connection to the valve at the bottom of the cylinder were loose, so I tightened everything.
I took the top off of the cylinder to check what seals I could. They seemed to be there and intact. So, I took some auto brake fluid I had on hand and filled the cylinder, then cranked the cap on tightly. I tried dropping the saw and stopping, then controlling the descent with the hydraulic valve. It worked!
Next, the rod handle for turning the cylinder valve, connected by a u-joint and pins to the valve stem, sheared its cotter pins off due to metal fatigue at the u-joint. I installed some cotters of the correct size, which fixed it and reduced slop.
Next, I turned to the belt drive system. I saw that the variable sheave speed control was poorly adjusted. First, the nuts controlling motor slide travel were set out of the right speed range, causing the belt to be loose- the motor had been slid back until the variable sheave max pitch diameter had been exceeded. I adjusted the nuts.
I noticed there was a lot of wobble in the driven pulley on the gearbox shaft. I loosened the belt, and took the pulley off for inspection. I saw that apparently they had been having chronic problems with the pulley coming loose- the shaft was scarred in many places by the set screw, and the pulley bore was worn oversize and eccentric. The set screw was no longer sitting on the flat of the gearbox shaft.
Thankfully the shaft was not bent, so I looked around and found that I had a slightly smaller pitch pulley on hand of the correct belt size and shaft bore. I installed it on the shaft, taking care to tighten it on fully, and at the right height on the shaft- the pulley had previously been badly misaligned. I tested it over the entire range of speeds- the whole speed spectrum had been somewhat lowered, but thats fine for me. At this point, all appreciable mechanical slop and vibration had been corrected on the belt drive system.
I then turned to the blade tracking system. As per the manual instructions, I loosened the blade guides first to un-twist the blade, then used a 6 bar of mild steel flat stock for a straightedge (after sighting down it and hammering straight) to inspect the wheels for alignment. Way out!
I followed the manuals instructions, tightening set screws and turning opposing nuts, to crank the top wheel in at the top. I noticed that the top wheel had about 1/4 of endplay on the shaft. The seller had mentioned that theyd had a replacement shaft machined for the wheel. I took the wheel off of it to see what was causing the problem.
The wheel sat on a shaft integral to the tracking plate, riding on needle bearings. The shaft was bored and threaded on the end. A thick hub faced internally with a thin phenolic washer was held on by a set screw installed into the shaft end, holding the wheel on by an internal shoulder. The problem turned out to be that the set screw holding the hub down was simply too long, so that the screw bottomed out in the blind hole in the shaft end ¼ before taking all the endplay out of the wheel. I merely ground the length necessary from the end of the screw, reinstalled, and the wheel ran true.
This, in addition to the upward re-adjustment of the top wheel tracking, brought the top wheel pretty straight. It had been like an inch out at the top.
The bottom wheel needed adjustment as well. A similar tracking adjustment served to bring the bottom wheel into line. I got it to the point that with moderate tension on the blade, the wheels were still cupped in toward each other by about ¼ total. This was a huge improvement, and was about as far as I could get it without tearing apart the tracking plates and re-conditioning them to increase the adjustment range. Its working fine for now.
I re-installed the roller guides, top first then bottom, twisting the blade back to perpendicular to the vise, checking with a square against the bed before tightening. After tightening the bottom, I rechecked at the top and adjusted a bit more until fully square.
While adjusting the bottom wheel tracking, I had noticed that the chain drive had a LOT of slack in it, causing the chain to pile up a bit on the slack side of the driven cog. The gearbox is installed with bolts over slots, giving a range of adjustment to control chain slack. I loosened the bolts and slid the gearbox until I had the chain slack out, but not particularly tight. I tightened the bolts and tried running the saw.
The blade tracked true until it fell off. I saw that I had not sufficiently bottomed the blade against the back rollers in the guides when installing them, so I re-adjusted and squared them, taking care that the blade ran against the back rollers lightly in no-load operation.
I had broken the old tension spring in the feed mechanism when fiddling with the cylinder. Its a stout spring, like 3/16 wire, and I can only conjecture it had built fatigue at the break point. I bought a new $10 spring at ACE and installed it. It was the right width and gauge, but longer than the original- I just adjusted the eye-bolt it hooked to shorter in length. This took some residual issues out of the feed system and brought operation completely in line.
The Vertical Mod:
With the saw all tuned up and repaired for horizontal chopping, I looked it over to see what it would take to convert to alternate vertical use with a cutting table.
First, the cylinder would need to be unbolted for vertical use, and the tension spring unhooked. No problem there. Then, the saw would have to be set on risers above the coolant pan to prevent the lower wheel case and motor from contacting the pan. A small part of the motor mount plate would have to be cut out to give clearance for the end of the saw bed. A cutting table would have to made and installed somehow to the lower blade guide support. The saw would have to run without the belt drive shroud in vertical mode.
I cut the risers first (with the saw), out of 4x2x3/16 wall tube from my scrap pile. After installing, I saw that the back foot flange would need to be cut off to give clearance for the driven pulley to run with the saw head vertical. The rectangle tube riser would need to be replaced with an angle iron riser to facilitate clearance for the belt driven pulley. I used an angle grinder and cutoff wheel to cut the foot flange off of the saw, and then drilled the horizontal bolt holes to mount it to the angle iron. This was measured to be at the same height achieved by the rectangle riser at the other saw foot.
The saw swung up a lot further now, but still far from vertical. I cut reliefs out of the coolant pan for the motor and heel of the saw head, cutting first less than necessary, swinging the saw up to check progress, then adjusting the relief cuts. I cut the small corner necessary for saw-bed clearance out of the motor mount plate with the angle grinder, estimating it to be well on the side of caution.
As I ground and checked, then ground more, I switched to a 120 grit flap wheel on the grinder for a nice smooth shape to the reliefs. With the saw head finally vertical, it rests almost simultaneously on the bottoms of both the motor and lower shroud reliefs, with most of the weight of the saw being taken by the thicker metal at the motor mount plate relief notch where it contacts the end of the saw bed. The coolant pan still has plenty of capacity, with the reliefs terminating 1.5 above the pan floor.
With the saw modified to include vertical position, and tested to run well when vertical, the only remaining step was to build and attach a cutting table.
I did not have a suitable piece of plate in my scrap pile, so in town I bought a piece from my steel guy. It was just an offcut, 10x1/4 flat bar and 15 long. Good enough for $10.
I determined where I wanted the blade in the table, then blocked the plate up on the saw bed and used the saw to swing-cut to the center. I brought the cut plate to the drill press, and drilled 3/16 holes an inch apart at the end of the kerf in the middle of the plate. On the mill, I milled a 3/16 slot between the holes most of the way through, flipped the plate, and aligned with the drilled holes to finish milling the slot floor.
Now I needed to mount the plate/cutting table to the lower blade guide, without obstructing the rollers and working around the alignment bolts.
My first idea (which I still consider bright) was to use this cheap drill press vise lying around- bolting the vise to the underside of the table, then clamping onto the blade guide bracket with it. After doing all the measuring and drilling/c-sinking, I re-discovered why that vise lies around not getting used. Its a warped casting for one, and for two the stupid sliding jaw is intractably sloppy. I couldnt get it to clamp tight to the blade guide bracket, even with fiddly shims.
Plan B: I used the rectangular riser block I had first cut, then discarded for the front saw foot. I torch cut, then ground a clearance notch out of it for the blade back and roller alignment bolts. I bought and installed ¾ longer roller alignment bolts, and installed them tightly and separately to keep my alignment. I drilled oversize holes in the bottom of my rectangle tube riser/table mount, and then installed it up onto the bottom of the roller alignment bolts, with large washers and nuts for an adjustment range with the oversize holes, similar to the alignment style of the rollers themselves.
After using said adjustment to correctly orient the blade in the table center slot, I fired the saw up and cut some scrap metal. It works well as a vertical saw!
The total steps necessary to switch to vertical mode from horizontal now: unbolt the feed cylinder and unhook the spring. Remove belt drive shroud with single wingnut. Swing saw up. Slip table mount holes over roller guide bolt ends, adjust and tighten table on with washer and two nuts. Cut!
Blade Notes:
The saw takes a discontinued ½ to 5/8 wide by 95-1/2 long blade, but the previous owners could not source the correct blades, so they used a stock ¾ wide by 96 long blade, and had the top tracking plate slot elongated by ½ to slightly lengthen the wheelbase. It actually works OK, but I expect tracking (already good) will only further improve with a slightly narrower blade running through the guides. MSC, for one, carries flex back and hard back blades in 96x5/8, and Lenox Diemaster II bi-metal blades in 96 x ½. Respectively, they cost at time of this writing, about $20, $17, and $42 ea., but I imagine MSC is higher in price than some other places.
