Yet another 4X6 question

I have a 4x6 probably 25/30 years old. It has always had a problem of
throwing the blade[the blade comes off while cutting]. The problem as
become progressively worse. If you remove the blade and spin the idler
wheel you can feel a roughness in the ball bearings. When taken apart
and the bearings rotated against a moving belt they seem fine. My
conclusion is that the bearing seats are not co-axial.
Now the questions:
Does this seem like a reasonable conclusion? If not what might be the
problem?
If so what can be done about it? I thought about turning down the shaft
so the bearings don't bind and seating them to the shaft with Locktite.
Any and all solutions will be appreciated.
Thanks in advance.
Chuck P.
Reply to
Pilgrim
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Pilgrim fired this volley in news:pilgrim- snipped-for-privacy@70-3-168-216.pools.spcsdns.net:
Locktite.
You suggested contradictory treatment vs. problem. IF the bearings are so worn that the shafts are no longer in alignment, replace the bearings. The shaft doesn't run in the bearing, it's a snug or press fit in the inner race of the bearing. The shaft does not rotate IN the inner race, it rotates the race itself, and any wear is between bearing elements.
Turning down the shaft would worsen the condition.
I have an old, well over-used 4x6. The blade jumps more now than it did when new, but seldom when the blade is sharp and the feed rate is correct. Dull blades exacerbate the problem a lot. And despite the wear on my saw, if the blade is sharp and the feed rate is correct, it cuts a straight line.
Even on the cheapest Chinalloy saws, all the wear parts are replacable, except maybe the tire on the driving wheel, and perhaps the gear-box gears.
LLoyd
Reply to
Lloyd E. Sponenburgh
Mine never cut square when it was new out of the box, then I replaced the cheap guide bearings with good ones (size 6200 2RS), and wow, this thing cuts a 2.5 inch bar so square with a sharp blade, that the out-of-square is inside the "nap" of the cut.
Reply to
Richard J Kinch
Interesting fix; it's good to know of another mode to watch for these saws to cut out of square. From the 4x6 group over on yahoo, some have noticed that this can also be caused by the pivot rod (bed to bladewheel assembly hinge) holes being improperly positioned.
Jon
Reply to
Jon Danniken
Poor cutting performance as far as cutting a straight downward cut can also be due to other reasons, Jon.
The set angle/tilt of the upper saw section, where it's supported by the strut, and a lot of end play in the hinge pivot rod can also increase the chances of unwanted blade drift from the intended/desired path.
Using washers and shaft collars can position the upper saw section in a fixed position on the hinge pivot rod.
Shims added to the strut that support the upper saw section can also improve the direction of the blade travel.
Both of these solutions are described here (with pitchers 'n stuff, too)
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Reply to
Wild_Bill
Reducing the shaft diameter would worsen the problem, Chuck, IMO. Even if the bearings aren't positioned perfectly parallel to each other, a small degree of error wouldn't matter a lot at the slow speed of the blade wheel. I can't recall from memory just how the bearings are situated, but if there is a spacer between them in a single bore, I'd check that the ends of the spacer are parallel.
If the ball bearings aren't perfectly centered axially, this would likely be more of a problem, IMO, but since the hole(s) is/was probably cut in one operation, I would expect them to be positioned relatively accurately.
My 4x6 is not so old, but I haven't had any problems with the blade walking off the wheels, and the saw has seen considerable use. Before I used the saw, I practically disassembled the entire machine, and checked the alignment of almost everything as I reassembled it. I noted that shimming the free wheel was required to bring it to the same plane as the drive wheel. I placed a tap handle (the long type not the T-handle type) on the input pulley shaft and wound the blade around by hand while watching the tensioned blade go around. Looking back now, a variable speed drill motor would've probably been easier, but it allowed me to see that the blade was tracking properly in slow motion (although not cutting any metal).
Some other details of the 4x6 bandsaw are here:
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Reply to
Wild_Bill
Indeed. Line bored out of square.
Which means you put a shim on the base plate where you lay your stock Its best to put in a .25 plate that covers the entire work area, and simply shim up one side or another and screw it down permanantly.
Gunner
"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""
Reply to
Gunner Asch
Or just make all of your projects out-of-square, then cut one leg shorter (possibly two).
Otherwise, there was one owner I read of, that sawed off the cast ears and replaced them with pillow blocks.
Reply to
Wild_Bill
"Wild_Bill" fired this volley in news:_BS6l.87434$ snipped-for-privacy@en-nntp-08.dc.easynews.com:
Wouldn't it have made more sense to plug the holes, and re-bore them?
????
LLoyd
Reply to
Lloyd E. Sponenburgh
That's probably a good solution, Lloyd. One thing that I can think of as far as adding the pillow blocks is; it starts to look more like a real machine.
Kinda like the cars sitting along the side of the interstate highways with about $3000 worth of new wheels and tires on them.
Reply to
Wild_Bill
I'm not sure about the bearing at all.
Typically, these have an Allen setscrew below the upper wheel bearing block which tilts the upper wheel to control the angle so you can minimize the chance of the blade walking off.
Aside from that -- you *do* know that the proper tension for the blades is as tight as you can possibly turn that plastic blade tensioning knob by hand? Actually -- that gets the blade to the low end of the proper tension range. You *can't* grip it hard enough to over-tighten the blade.
Try the bearing block tilt adjustment screw first -- and the belt tension knob.
Good Luck, DoN.
Reply to
DoN. Nichols
Im going to have to do that with a largish Spartan automatic saw in the not to distant future. Previous owners didnt bother to lube anything, and over a period of years, the unbushed saw frame pivot holes went not just out of round, but keyshaped.
It will be faster and easier to simply install pillow blocks with movable mounts and dial the sucker in, than busting it all down, welding the holes up, then finding someone to line bore it, then putting it all back together again
"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""
Reply to
Gunner Asch
Simple, elegant, and easy to implement. Thanks Gunner, that's an excellent solution!
Jon
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Reply to
Jon Danniken
It might if your machines are large enough. You could install pillow blocks with a hand drill.
jw
Reply to
Jim Wilkins
Thanks for the reply. The bore[s] for the bearings were done in two operations. One from each side. That is why I think the bores may not be coaxial.
Chuck
Reply to
Pilgrim
I used a strap wrench on mine, and eventually stripped the plastic handwheel off the jack screw. I made a new handle with a crank on it, and then ended up breaking the upper bearing block at the large axle hole, where the cross section is the smallest. I ended up welding it up with nickel rod and sistering a piece of 1/4" plate to it, also welded with the nickel. I've not had a lick of trouble with that part since, though I've now replaced the blade guide bearings and the main gearbox bearings and seals.
If the main gearbox (drive wheel) bearings are bad (or going) it will definitely mess with your tracking. Depending on how long they've been bad, your main gear may also be toast due to running out of position. There's guys on eBay selling the gear, shaft, and one of the two bearings as a unit.
--Glenn Lyford
Reply to
glyford

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