Metal bandsaw tracking

snipped-for-privacy@gmail.com fired this volley in news: snipped-for-privacy@4ax.com:

Mike, the only thing that can be affecting the tracking is (by your experiments) the tracking of the drive or driven wheels. I would assume that one or the other is canted slightly off-track -- perhaps by bearing wear.

As far as the chips go; have you tried a coarser blade? There's a limit to what an 18-tooth band can do!

Increasing the weight on the blade can make the chips longer, too, but can't do anything about the teeth-per-inch issue.

LLoyd

Are the wheels coplanar? I remember one guy had to turn up a spacer for one of the wheels before they were in the same plane. Sounds like that may be what it is, because if one was tilted, the blade would run off. Get a straight edge and check it out.

Hopefully, you've found a source for better blades than the banding iron ones that are packed with 4x6s. I like Lenox, there are others(none Chinese). You need at least three pitches, one of the variable pitch jobbies is handy if you chop irregular cross-section stuff.

As far as tension, you can crank down all you want, it'll barely get the blade into the recommended tension area. Just remember to back it off when done or the frame may take a set.

Might be worth a look into the gearbox, on some of the 4x6s, there's been core sand and swarf left. Doesn't do bearings any good. Mine didn't have a lot of crap, but I changed the gear lube out for some good name-brand hypoid stuff anyway. Stuck a magnetron magnet on the lid for particle accumulation plus a wrench holder.

There are several sites out there with fixes and upgrades for the 4x6, I've not done a lot with mine except to dump the cheapy chink soft hardware and get some decent fasteners into it.

Stan

What about blade tension? It sounds as if the tension is way too high, bowing the frame, and causing the blade to slip off. Have you set your guides properly? (With the manuals, you probably have.) Is the driven wheel axle nut tight? Those are the only things I can think of which could cause that. Check that the wheels are coplanar and and parallel, then go from there. It sounds like a twist (backwards reseats the blade) or bend (blade slips off.)

I've always taken that as an indication that the blade is dull.

-- The ultimate result of shielding men from folly is to fill the world with fools. -- Herbert Spencer

The only *correct* tension on these machines is as hard as you can twist the knob by hand -- and perhaps a little more. The tension knob is too small for the task. :-)

I'll bet that the third ball bearing in the guides (the one which presses against the back edge of the blade) is set too far against the back of the blade, forcing it forward. The bearing should be mounted on an eccentric, and thus fairly easy to adjust. (Note that there are two flavors of the guides. The ones which came with mine (bought new from MSC over a decade ago) has the bearings mounted to a chuck of forged steel -- nice and rigid. Others that I have seen often have the guide assembly bent up from mild steel about 1/8" thick or a little thinner, and those tend to loosen over time as the mounts for the side bearings bend.

I would suggest that you start by adjusting both back bearings as far back as you can get them. Then start by adjusting the one closest to the wheel until it moves the back of the blade just barely clear of the flange on the wheel. Then adjust the other so it is just barely touching the back of the blade while it is running free. When you start to cut, it will move that part of the blade into firm contact with the bearing, too.

But it *could* be a worn bearing in the bottom wheel's axle. Did you buy this *new*, or was it from someone else who had bought it from Busy Bee some time ago?

And, BTW, it is a good idea to open the gearbox, clean it out, and refill with proper gear oil. They frequently have casting sand in there, and grind the gears to death over time.

What metal are you cutting with it? I suspect that the Grizzley manual is assuming mild steel. (It might help if I downloaded it and read what they say, but it is too late tonight. :-)

Good Luck, DoN.

One of the classic failures on these is the lower wheel walks off the shaft. This misaligns the worm wheel in the gearbox, so it can wreck the gears, too. I eventually bored out and re-threaded the setscrew in the lower wheel, and it has not slipped since. When the lower wheel has walked out on the shaft a bit, the blade tracking starts to get unstable. The check is to take the blade off and see if the lower wheel can move axially. Any more than a few thousandths of an inch is wrong, and an eighth of an inch is a sure sign this has happened.

Jon

There's a 4X6 bandsaw group on Yahoo . There's a lot of info in the archives , and if you can't find the answer there someone on the group likely has the answer to your problem .

All good advice in the previous recommendations. I shimmed both wheels with brass thrust washers to get them on the same plane (checking with a long straightedge spanning both wheels) also, the washers minimized the wobble of the free wheel.

DoN's comments wrt the back edge rollers.. definitely worthwhile to check those.

Safety first.. I removed the worm shaft pulley and installed a long tap handle to manually rotate the wheels and band slowly while adjusting the pitch of the free wheel.. an adapter for a slow running variable speed drill would serve the same purpose of running slow (with full blade tension) while making checks. Using the saw's motor to run the blade while making adjustments (or any time the blade guard is off/open) would be a safety risk worth avoiding.

The powdery swarf sounds like worn blade teeth, you should at least see fine sparklies for chips with a fine-toothed blade, and of course larger chips with a coarser tooth pitch. You'll get used to the prickly feel of sharp blade teeth on your fingertips, but a magnifier may reveal small flats on the tips of the teeth you're using now, indicating a worn blade.

Also, after correction of the wandering blade travel, it's important to avoid too light of a downward pressure (while cutting) on the blade.. rubbing without creating chips will dull the teeth quickly, so try to maintain at least moderate downward pressure.. more pressure is good when the chips are plentiful.

You may have noticed it mentioned before.. a good cutting lubricant is very cost effective and greatly enhances cutting performance. My long-time favorite has been Lenox ProTool Lube.. just scored several 6 ounce bottles on eBag at $3 each (Fastenal no longer stocks it).

Lastly, avoid cutting OBF old bed frame.. the hard spots will wipe away the tips of the blade teeth immediately. If necessary, it's better to cut OBF with a cutoff disk in an angle grinder, or use a hacksaw to avoid the need to change the bandsaw blade. HSMs would be better off avoiding it, since it also wipes out cutting edges on drills, and it doesn't weld worth a damn.. it'll look like it's welded, but the weld is likely to pull out with light to moderate force.

"Wild_Bill" wrote

What do you suggest for 1-3/4" rock drill rod? I spent over an hour making one ragged cut with an abrasive chop saw.

jsw

Annealing that spot wasn't an option, eh?

I've had good luck with the little 3" abrasive cutoff blades for die grinders. One 1" strut piston rod took about a minute and a half, including two repositionings of the thing. They're hard, too.

-- The ultimate result of shielding men from folly is to fill the world with fools. -- Herbert Spencer

[...] [...]

Thank you all.

To answer some of the points that have been raised:

1) The saw was bought new. 2) I opened, cleaned and re-filled the gear box immediately after purchase. 3) The back guide bearings do not touch the blade when not cutting. 4) I use it to cut mild steel almost exclusively 5) To get the tension they recommend (actually, the recommendations differ between manuals!) I use a pipe wrench - with three fingers only. 6) The tension adjustment and tracking adjustment are interdependent on this machine. Presumably the frame bends. This happens at quite low tensions. 7) The wheels were *not* co-planar. The driven wheel was slightly further back. This is where the fun started:

a) I thought I would remove the driven wheel , inspect and clean the shaft and reposition it. I had no difficulty removing the set-screw. b) The wheel was quite tight but with some effort and Liquid Wrench I was able to get it to move axially about 3/8". When trying to remove it completely it simply got stuck and would not budge. I tried rotating it on the shaft and it did so with major effort. I could see no evidence that a key is involved. Manuals does not show one. I looked and felt all around the hub and could not see/feel any more set screw/pins/whatever. c) I though I would just move the wheel forward as far as it would go and fix it there with the set-screw and be done but the set-screw

*would not go back *! d) The manual says this should be a M8 screw. This was clearly wrong, the screw is 5/16-18. I tried a different 5/16-18 screw to get into the hole (I thought there may be an alignment problem) and it behaved the same way - it would turn about two threads and then it would become difficult to turn. e) I cleaned the set-screw hole, blew it out with compressor, looked down with a light, poked about there with a stick to no great benefit. f) I run a bottoming tap as far as I could but still was not able to get the screw in far enough to hold the wheel securely. g) In the end I made a little 1/4" diameter plug, dropped it in the hole and screwed the set-screw after it. This did the job. h) The blade now runs much better after I re-adjusted the tracking/tension. However, the driven wheel is touching the cover.

I left it at this point. I do not pretend to understand any of this. I shall try cutting something on Thursday...

Michael Koblic, Campbell River, BC

[ ... ]

This eliminates my primary guess.

[ ... ]

You know that 5/16 is *very* close to 8mm?

0.3125" ~= 0.315" as I said, *very* close. 18 TPI calculates out as 1.411mm -- and the M8 is probably M8x1.5, so it will go in a few turns before wedging.

So -- the *screw* may be 5/8-18, but the threaded hole is probably M8x1.5. Did you try purchasing a M8 screw and trying it?

The two are close enough so I would expect my "screw chkr" to not tell the difference. You would need a proper thread pitch gauge engaging perhaps a half inch of screw length to tell for sure.

I have made that mistake, and put 5/8-18 setscrews in some Phase-II BXA sized (Series 200) tool holders. To get them to go all the way through, I had to run a proper 5/16" gun tap through the holes -- but this now means that all my tool holders use precisely the same Allen key, and the threads were close enough so there was no ill effect other than dulling that tap. :-)

That again sounds like you need a proper M8x1.5 setscrew.

Because you could not get a through hole without succeeding in pulling the wheel.

Probably a good enough fix, now that the threads are some combination between 5/16-18 and M8x1.5. :-)

O.K

Good luck with that, DoN.

So, if the bottom wheel is touching the cover, it needs to go back as does the top wheel. Of course. the guide rollers will need readjusting after that as well. I would have gotten out the pulley pullers to remove the bottom wheel, cleaned up the no doubt burred-up shaft, retapped the setscrew hole while it was off and replaced the setscrew with a decent domestic-made one. I've never seen SAE hardware on any of the asian 4x6s, it's no doubt one flavor of an 8mm hole. There are several pitches to choose from, it'll be the one that no one in town has, I speak from experience here.

Stan

"DoN. Nichols" wrote

I store my metric taps in the drawers with the screws and use them to check the pitch of unknown hardware. A screw picked at random from the drawer could be mis-sorted but the taps are marked for size.

jsw

I agree with the puller procedure to get "eyes on" the problem area.

I strongly dislike the displaced metal deformation on shafts due to the cupped or pointed set screw making removal of pulleys/gears etc, difficult or almost impossible.

One could cut away the deformation with a center-cutting endmill in a drill (use a small piece of thin wall tubing or durable tape to protect the threads), or be vewwy vewwy cahfuwl.. then after the drive accessory is removed, file a flat on the shaft (and possibly a slightly longer set screw for re-assembly).

Otherwise, forcing the pulley off the shaft won't completely destroy it, just score the bore as the pully material passes over the displaced high spots on the shaft.. definitely not as practical of a solution compared to the above method, but we've all done it when the particular situation dictated it.

-- Cheers, WB .............

So, if the bottom wheel is touching the cover, it needs to go back as does the top wheel. Of course. the guide rollers will need readjusting after that as well. I would have gotten out the pulley pullers to remove the bottom wheel, cleaned up the no doubt burred-up shaft, retapped the setscrew hole while it was off and replaced the setscrew with a decent domestic-made one. I've never seen SAE hardware on any of the asian 4x6s, it's no doubt one flavor of an 8mm hole. There are several pitches to choose from, it'll be the one that no one in town has, I speak from experience here.

Stan

Never seen the stuff, as far as I'm aware, but any abrasive that doesn't cut thru metal effectively, is apparently the wrong abrasive. I'm not seeing follow-up comments, but maybe Ed or someone else knows what rock drill rod is.

Some abrasive products just don't shed dull grit, exposing fresh and sharp grit as the attempted cutting is taking place. Then what happens is the dull particles heat up and glaze in place.. basically forming a smooth glass surface with zero cutting action.

The other major drawback of some (generally softer) materials is, the cutting abrasive gets clogged easily, likely not the case with with the rock drill rod. Anyone who's attempted to grind "just a little bit" off of a copper or aluminum piece knows what happens very quickly to a grinding wheel which otherwise is very effective at grinding steel.

A thick layer of copper embedded in hard security bars will effectively stop a common abrasive cutting disk that would otherwise cut thru the security bar material relatively easily. Additionally, random odd-shaped bits of HSS, hard ball brearings and carbide shards embedded in the bars would limit the effectiveness of most saw blades.

Certain materials definitely need specific cutting products and procedures, but I could only guess that a disk with diamond grit "might'a could'a" been much more efficient at cutting the rock drill rod.

"Wild_Bill" wrote

The drill rod was run over and pretzeled by an excavator at a blasting site. The man they gave it to for scrap it let me cut off a straight end in exchange for some cast iron I didn't need. I think the reddish, non-branching sparks mean manganese steel.

The Enco chop saw was on the end of 100' of extension cord out behind his place and not at its best. Maybe it's the $3 wheels I buy, or not leaning hard enough on it, but it doesn't cut mild steel over an inch wide very well either.

Now that it's home, the rod cuts easily enough with a hacksaw and a file and isn't packed full of sand, so I'll risk a bandsaw blade on it.

jsw

[...]

The critical point is that this set screw would not go into * the hole it came out of in the first place*. It was not particularly difficult to unscrew either.

It was a perfect fit into a 5/16-18 screw gauge.

I can find no evidence that M8 with 1.5 mm pitch exists - all the references I have seen mention only 1mm and 1.25 mm pitch in this size. What are the odds that a set screw of this nature would be of so uncommon configuration?

Michael Koblic, Campbell River, BC

"I have a cheap 4x6 band saw which I bought on sale from Busy Bee and which came with a Harbor-Freight manual."

Was it in the original unopened package? If not it might have been returned as defective and the wrong screw installed to 'fix' it.

When Enco had a local retail store they let me look around the storage area where I found and adopted several such unwanted orphans with easily repaired defects. Sometimes Home Depot, Lowe's and the Harbor Freight store will make deals to get rid of their problem children too.

The trick is being able to diagnose the problem and estimate the repairs on the fly, without taking it all apart. More than half of my stuff including almost all of the computers and even this house was 'broken' when I bought it, cheap.

jsw

Which suggests that the threaded hole in the hub was metric, while the screw was not.

But how many threads did the gauge engage. Mine (a "Screw-Chckr" plate) is not much over two threads when you get that coarse -- not enough to tell the difference between 5/16-18 and M8.x1.5.

A result of a search for M8x1.5 on Google (one of many returns, BTW).

And I see hints that it was used in some automotive applications.

This one is sort of confusing:

Because it has a "code" of "M8-1.25-32CR", but down in the description I find:

Thread size / Pitch = M8mm x 1.5

Note that the Japanese have their own interpretation of metric threads, which do not always match the ISO threads, so they may have used it as well.

And the saws come from either China or Taiwan, and they tend to use sizes which are very close to fractional inch sizes, so they may use the M8x1.5 *because* it is so close to 5/16-18. And that screw may have vibrated out in transportation, and the importers screwed in the nearest inch size, because it *looked* like it fit.

Pull the hub, and re-tap *fully* for the 5/16-18 and you should be fine.

Enjoy, DoN.