Related to, but slightly different from the recent post on band saw blade drift:
I, too have been wrestling with resawing. The machine is an old Walker Turner 16″ that I set up, to the best of my abilities, exactly as the recent FWW Fortune article recommended. New 1/2″ 3 TPI skip blade(s), multiple alignment/tolerance checks, the works. The project involves reducing some 60 odd pieces of low grade (lots of checking, some knots) 4×4 cherry 3-5′ long into 7/8′ boards. Flattened and squared 2 sides on jointer prior to resawing, and of course, registered those faces against fence and table.
First test run of 2 chunks with blade remaining from original Fortune recommended set up and after test cuts in small scraps of thick poplar, ash and hard maple gave respectable results, but machine squalled to beat hell, and feed pressure had to be considerably more than “two fingers”. Next run of 10 chunks, performance deteriorated rapidly, with the last several cuts burning, stalling, blowing the breaker, wavy cuts, and uneven board width.
Next day (new attitude) I changed the blade, went through set up again, and the first few cuts were quiet, although a bit wavy, as I struggled with drift. I played with the tracking on the upper wheel as I went along, got the cuts straightened out, but soon the squalling returned, the feed pressure (resistance) increased, and I was back to burning and stalling before the session was done.
Day 3: one or two cuts after running through the set up again, and it was obvious that I was going nowhere. Changed the blade again. The first few cuts were again quiet and nearly effortless, but performance deteriorated rapidly again, despite careful attention to feed rate and heat build up.
My question(s): Why are these blades (Starrett Woodpecker) dulling so quickly? Am I asking too much of the saw? Does the severe checking of the material contribute? Do the knots? (I can find no points of tooth contact with the machine…..) Incidentally, the jointer bades are dulling rapidly as well – the wood is not exactly clean, but doesn’t appear to be particularly dirty, either…. Anyone else have experience with milling out pallet wood?
Replies
How wet is this wood? If it's not dry enough, the friction will kill your blades and any chance of making good cuts. Either it needs to be dried more or blades with more aggressive teeth are needed. I think 2-3 tooth, hook may be a better choice here. You want to clear out any material cut by the teeth and the skip pattern would probably be better for dry wood. How fast are you feeding the wood into the blade and what is the RPM of the blade/motor?
Stacked and stickered for about 2 yrs, inside (but cold), so I don't think that's it... bought the blades recommended by Fortune for "handling most tasks". Is this a "most" task? I just dunno!
Do you have an effective chip evacuation/collection system? Perhaps the chips are building up after a few pieces inside your bandsaw cabinet and then the chips have no place to go, which would cause feed pressure to have to be increased as the bandsaw blade gullets would be jammed with chips and the quality of the cut would decrease. Just a SWAG...
Jeff
While I'm not happy with the chip/dust collection I'm getting, collection within the cabinet doesn"t seem to be the problem. I've got dust all over everything else, though....
I've rigged up as close to Fortune's recommendations as I can: shop vac (good one, clean filter to begin each session) under the table (reconfigured once already), brush on the lower wheel and 4", isolated by blast gates, in the base chute. The configuration of this saw's wheel covers has so far precluded me from sucking at this recommended location, but I may try a (problematic) modification here. The 4" connection seems to be essentially worthless where it is....
The dust deposition is mostly on the (adapted) base, below the table (and my shop vac rig - sigh) and on the table itself, showering down off of the upper wheel +/or the blade as it comes around.
Bottom line: I've been at this, but while it's not solved, neither am I convinced that it is the primary cause for my rapid dulling. It may be contributary, however.
Thanks for the input. Likewise to the previous respondant.
If the dust and chips are showering down from the blade as it comes over the upper wheel, this can definitely be the problem. If the gullets are already full of (or if there is any) dust, it's going to be a problem. What happens when a table saw blade needs cleaning? It burns and binds. This is no different.Also, is the squealing coming from the blade as it tries to cut or is it coming from the blade on the tires? This would be from bad tires or the blade needs more tension. "I cut this piece four times and it's still too short."
Edited 3/19/2006 9:32 am by highfigh
Since you noticed the jointer blades also dulled quickly, I'd consider whether the wood itself is dulling the band saw blades. It's less expensive than a couple dozen band saw blades, so I'd suggest buying a similar piece of cherry from a reputable mill or lumber yard and making the same number of cuts with a new blade. Pallet wood has been who knows where and in who knows what, so your wood may be covered with grit and who knows what.
Yep, been considering this. What I am trying to mill out was/is free, however, and there's enough quality wood in the stash so that even if it costs some blades, it's worth it (I think!) to complete the project. Besides, the pile's getting in the way...
As I said, I made several test cuts on short, thick pieces of hardwood when "dialing in" the set up prior to attacking the cherry, and the blade squall was evident in this clean yard stock.
Anyone out there with actual experience milling out quantities of pallet grade stock?
I didn't catch the pallet wood aspect. Pallets get grit and grime embedded into the wood, it's proabably one of the worst things to cut. Similar to chainsawing logs that have been yarded, they get grit ground into the bark as well. When I'm cutting logs with my chainsaw, if I see a spark, game over. One spark, or one tick, it's all it takes. I sharpen my own chains and I'm good at it (lots of practice...;-)) and I can get a chain as good if not better than new, but all it takes is one tick on a rock and it's done, I've got to stop and resharpen the chain or else the whole chain will go to pot in a hurry. I'm guessing you're hitting embedded grit in the wood dulling a few teeth which throws the geometry of the blade off and compromises the whole thing, then just like my chainsaw chain, it does a self destruct. I'd bet money that's what's happening. Cut some clean wood. I'll bet you'll have a different outcome.
Also, like you, I was using my shop vac for chip collection. I've got a good one too, but it doesn't compare in any way to what a dedicated chip collector can do. A shop vac just doesn't pull the volume of air it needs to, to be effective. If you're using your shop vac on the 4" chip duct for you saw, then that's why it's not very effective. Get a dedicated chip collector and you'll be amazed at the difference. My chip collector is not a big one either, but it kicks butt over my shop vac..No comparison.
Jeff
Thanks, Jeff. I'm thinking you're at least partly right. Next session (whenever), I'm going to try getting all 4 sides milled on the jointer and table saw before approaching the band saw. Guess I'm more willing to beat up jointer and circular blades than band saw blades. At this shop (it's at work), they're routinely abused by neanderthals anyways.....and they can be resharpened!
Regarding the shop vac issue: The 4" is indeed connected to a cyclone unit, the problem here is location. If you could see this old Walker Turner and the base it's been adapted to, you'd understand more fully. I will think about how to get that line to the under table location where I've rigged up the shop vac connection, though I will probably have to neck it down quite a ways.
I've been using a shop vac in the shop I'm setting up at home to suck from 4" chutes, and you are absolutely right. In this application shop vacs, even good ones, suck (or don't, rather!) A dedicated collector is high on my GAS list (Gear Aquisition Syndrome) :-)
You might try increasing the tension on your blade and decreasing the speed of the saw. Also, the feed speed is very critical. Feed too fast and they will squall. The blade gullets are too full. Once a blade starts to dull, it starts to self destruct as has already pointed out. Another thought. You stated that the saw was old. Is your belt in good condition and is it slipping?
Right or wrong, I'm trying to follow Fortune's recommendations as regards blade tension. I am concerned with grooving the rubber tires and the resultant hassle of having to re-tire a machine of this vintage.
How does one decrease the speed of the saw, except for changing the pulley(s)?
Replacing tires isn't too bad, so don't let that affect what you do.Changing tension may help a lot if part of the problem is band vibration as you make the cut. The screech could be indicating this. Note that this does not mean higher tension is always better, just that the change may result in reduced vibration. A band with a different set configuration (alternate set vs. a raker5 for example) might also calm it down. If your tires are in decent shape, I don't think you can do much harm by changing tension. That machine was built for hard work. Pete
Edited 3/23/2006 2:55 pm ET by PeteBradley
Good input, Pete. Nice to talk to someone with a machine of similar vintage.
I, too have had a hard time imagining cutting a hole in this machine. But...I have no factory dust chute. As I said, I rigged, then reconfigured a wood and plexi collection box under the table, enclosing the area as best I could. Other than rigging a deflection plate/sheet that the blade would pass through (there is something of the sort already existing as part and parcel of the lower guide assembly, but it's quite narrow - perhaps only an inch wide), I can't see what else I can do, save increase the airflow by bringing the 4" cyclone line to this location.
Regarding the tires: the upper tires were indeed grooved. Not having the immediate wherewithal to replace it (them), I (gulp!) spun the wheel by hand while applying 120 grit paper to the tire. I did improve the situation to feel, but am aware that I may have compromised the integrity of the crown. Maintaining the tracking seems better since, however.
Any opinions, should I attempt to replace them, on rubber vs. urethane?
Other difficulties I have had with this old machine: no tension indicator, so that I'm having to guess using the parameter of "1/4 inch deflection without turning the tip of my finger white" - pretty subjective, and how much blade should be showing below the upper guide when deflecting it!? Also, this machine's fence is configured to the right of the blade, with no way possible to change it. Hence when trying to figure out which way the blade needs to go to exactly center it on the upper wheel, I get all turned around, time and time again. It's like being dyslexic or something!
Did I mention http://www.owwm.com? There's a forum there that is excellent, with participants who know more about machines than we ever will.
I think your box is a good idea, you need to maximize air momentum (flow and speed) across the blade. The cut plate at the bottom further helps to catch the stream of dust. Not sure of your exact configuration, but I think you're on the right track. It will probably just take some tinkering. Tall cuts such as resaws will always throw dust around even with good dust colletion.
Nothing wrong with a little sandpaper on the tires, though if you had grooves you're probably due for new. My biases are to not listen too closely to the breathless internet recommendations for "upgrades" such as urethane, cool blocks, etc. Our machines were designed for a lifetime of accuracy and hard work without any of that stuff. There's a tire replacement "how-to" on owwm. No great skill is required, though strong fingers help.
Built-in tension indicators are notoriously inaccurate. Think of them as a guideline, or a way to get back to a previous setting quickly. You need enough tension to remove flutter (this includes flutter in the side of the blade that's going up). You can pluck the blade and it will make a clear "ring" sound instead of a "thunk". You'll find it by feel soon.
Pete
You got it. Change the pulleys or change motors. Is the motor original? When you buy a used machine, you never know what has been changed on it. I had a light duty saw on which someone had replaced the original motor with one that was too big and too fast. I changed to a smaller, slower motor,changed pulleys to increase the speed of the slower motor and got the saw to run like it should. The big motor was too much for the saw. It sounds to me like your problem is more related to a combination of tension , rare of feed and blade choice.
I hear you with regards to the dust/chips. Need to chew on this a while for a good solution. I'm currently sucking from under the tablewith 1.25" ID, at about 45 degrees directly down, out of a 3 sided plexi/wood box, 4th side being the machine, lower guides, etc. The bottom is neccessarily open, though. I can't see how to further enclose the area - do you think 2" ID would work better? I was going to try, but didn't have a 2.25" hole saw. Lots of thinking to do as to the 4", which seems to me should be the primary, but as I say, appears to be doing very little as currently located.
As to the squall: definately coming from the blade in the cut. Even changed the thrust bearing on top (another story....) thinking that was it, but no....
I'll second the folks who think your wood has a lot of grit in it. Rather than chewing up good jointer or saw blades, you might consider cleaning it up with a belt sander first.
For the dust collection to work right, you need a strong current of air pulling across the blade under the table. My machine (similar vintage, 20") has a plate on a 45 degree angle below the table as part of the factory dust chute. The blade passes through a slot in the plate, and the plate forms the bottom of the chute. This helps to separate the dust from the blade as it goes by.
You definitely need more than 1.25". Most likely the best approach is to use the same diameter as the vacuum hose.
Pete
Edited 3/22/2006 1:20 pm ET by PeteBradley
Thanks for your input, Pete. The belt sander suggestion is worth a trial run, at least.
Question: with your similar vintage machine, are you pulling from under the table only, or have you rigged up collection at the lower rear of the lower wheel cover, as per Fortune's recommendation? The configuration of the Walker Turner wheel covers (domed on the outside, reinforcing ribs on the inside) has thus far kept me from trying to rig something there....
My machine came with one 2" port from the factory. I couldn't imagine cutting any holes in it. It does get a small pile of dust inside the lower door, but it's not significant.
I have heard that the door modification helps Delta 14" machines a lot, but have no personal experience.
Pete
The fact that the saw cuts well with a new blade and then steadily deteriorates is a pretty sure sign that the blade is dulling rapidly. Knots, checking, and dirt on the wood can all cause a blade to dull rapidly, and a combination of all three can wear out a blade very quickly.
The description of the condition of the wood, combined with the fact that your jointer blades are also dulling quickly, makes a pretty good case for the wood damaging the blades and I can't think of any other explanation that would so neatly fit with the facts.
Also, you mention that this is pallet wood. Did you pull nails out of the wood you are cutting? Pallet nails will almost always leave small pieces of steel and abrasive rust particles in the wood after they are pulled out, and are another source of blade wear and damage. Wood salvaged from pallets is rarely a bargain.
John White, Shop Manager, Fine Woodworking Magazine
John: Thanks much for your input. I was waiting to see if someone would link the checking and knots to the problem.
No nails, though. I should clarify: pallet grade, but never assembled into pallets per se. These pieces were used as bunks.
I hear your warning about the bargain end of it, yet I'm-a-gonna see this through to the end....learn the lesson the hard way if you will. I can't help but think that nearly 250 BF of cherry, (before culling the junk) is worth some sweat and, apparently, some blades. Or maybe, the last 40 pieces or so will end up in the stove. We shall see. Thanks again!
Did these have a finish on them, bunks meaning bunk beds? Almost all paints and many clear finishes are as hard as glass and will also quickly dull a blade.
Knots can be extremely hard and checking can cause problems by dragging the blade to the side and also because checks can have pockets of dirt trapped in them as can some knots. If you sanded the wood for any reason that can also leave behind abrasive grit that will dull a blade faster than normal. Another thing to check is the ends of the boards. If they've been stood on end they can have grit, sand , and even small stones lodged in the end grain.
John
No, no, John, no finish! As a long time salvage wood user, I'm well aware of the dulling problems involved with power planing or jointing off a finish, either paint or clear. By bunks, I mean the timbers on which materials are stacked to either keep them off the ground or (relatedly) to allow a fork lift to get under the stack. I thought this was a universal term. Mebbe jest in these here Green Mountains....
You have confirmed what I was suspecting as to the knots and checking affecting the blade tracking within the wood itself.
I have, since beginning this discussion, indeed checked out the raw, rough sawn stock, looking for evident grit, both on the surface and within the checking. It may well be there, but it's sure hard to detect....scrubbing the surface with a wire brush and examining the resulting debris, reveals no tactile grit. But from the use they were originally put to, and the configuration of the pile that I picked them from, it is probable that there is some degree of dirt contamination.
Having determined that this may at least be causing part of the problem, let me ask you this: with a booming market in old growth lumber salvaged from old buildings and even from long term underwater submersion, what kind of tooling are these salvors using?
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