Bandsaw drift and straight cuts- The table is adjustable, fellas. - Page 1
Forum section: electronics / general

author: KL27x
author_rank: Super Contributor
timestamp: March 21, 2020, 11:19:40 pm
content: Roughly 7 years of learning to use a 14" bandsaw and learning from the internet, and I finally figured this out. The internet is stupid as fuck.First off, there's a difference between getting a bandsaw to cut straight vs getting it to cut straight to the miter slot/fence. And the first part is more important. You can't really get it to cut straight to the miter slot if you can't get it to make straight cuts in the first place.Most of the info on YT gives you pointers on how to get the saw to cut straight to your miterslots/fence by tweaking the tracking. This is bad info, off the bat, because you want the saw to cut straight, first and foremost. Adjusting the tracking to get it to cut straight to the fence might work for thin material. But when you cut thicker stock, the cut will most likely not be straight up/down and will wander badly. You also have to adjust your blade guides whenever you adjust the tracking, so this is just shit and it will only work if you won the lottery and your saw and blade and tension and even where you put the saw on your shop floor just happens to be perfect.After a year or so of trying to get the saw to cut straight to the fence by watching YT idiots, I gave up and just got my saw to cut straight.So to get the saw to cut straight, you may have to adjust both the tracking and the bottom wheel. There are 4 set screws to adjust the angle of the bottom wheel. The goal is to get the blade to track roughly center on both top and bottom wheels when under working tension, but that depends on your saw. I guess truly, you want to adjust until the blade doesn't have any twist on the cutting side, from the top to bottom wheel; if your wheels ARE indeed coplanar under the tension of the current blade, then the blade will, indeed, track on the same spot on both wheels when the blade is straight. You may need to adjust both the tracking AND the bottom wheel (and everything will most likely change with a different blade thicknesses/tension.) To do this, I use only the rear guide; the side guides are not touching. In fact I don't use the side guides on my saw, at all. Well they are there, but they're a full 1/16" away from the blade and only touch if I am screwing up a cut, already. I think of it that the guides are there to keep the blade on the rear guide/bearing and to prevent the table insert from getting messed up, and to reduce flutter/vibration at the stock, not to keep the cut straight.So after you get the saw to run and cut straight? You adjust the table/slots to match the blade. At first I considered widening the bolt holes in the top of the trunnion, so I could twist the table to match the cut. But then I thought maybe put a wedge/shim between the trunnion and the frame... which I did on a 10" bandsaw in the past. But as I'm looking, I see something. Worm screws. There are 4 worm screws next to the 4 bolts which hold the trunion on the frame of the saw. It's already fully adjustable. With these set screws, you can adjust the horizontal twist of the table to match your cut, and you can adjust the cant of the blade to the table, too, to make your cuts perfectly square up/down the cut line7 years and I finally learn this. Thanks internet, for never mentioning this, anywhere.There are other reasons a saw won't cut straight. And this leads to another gripe. Wood-cutting bandsaw blades mostly run a 3 tooth pattern on the set. Left, right, center. Or right, left, center. In the former pattern, the right set teeth wear down faster than the left. On the latter, the left set teeth wear down faster. So on a worn blade, it will start to drift if your feed rate gets too high for the material. Can we fix that already, blade manufacturers? How bout a symmetrical set blade?

author: coppercone2
author_rank: Super Contributor
timestamp: March 22, 2020, 03:02:34 am
content: I swear my band saw cuts more strait if you put candle wax on the blade (+ everything there)I also saw something on youtube about using a grinding stone on a running blade to some how improve performance and reduce drift, but I am too lazy because I have a belt sander 1 foot away and I always end up sanding anything I cut anyway (for now)He like put a dremel on some kind of jig (maybe you can mount it to a small XY table and clamp it to the base), turned the band saw on and slowly pushed the dremel into the band saw blade before getting a particular spark pattern and stopping . (not sharpening it, , more like ensuring uniform tooth deflection or something). I want to say he did it from both sides of the saw.I never cared too much, because I have two sanders (oscillating one that you can put cylinders on if you want) and traditional belt sander... I feel like I can tackle most things, and I basically need to use it to get rid of burr/chamfuer.What I want to do is make a jig that allows a XY table to be fitted on the sander, so I can feed carefullyI assume what he was trying to do with the dremel/sharpening stone is try to improve the hit accuracy of the teeth to reduce drift, I guess since the band saw is a long linear thing, its bouncing/wiggling around in the trench that it dug, and an errant tooth tends to pull it to one side?And, is it even a good idea to run the stone parallel to the blade? I thought it might make it run hotter or something if the entire edge is not sharpened properly, and it kind of sounds like something that should be done in the factory, not sure if thats a tool geometry factor that changes with use and age. IIRC he said that the performance improved, however I saw this 5 years ago or so.I assume this should be done with a sharply dressed stone to decrease burring, if its attempted? (so the material is ripped off rather then burnished?)

author: KL27x
author_rank: Super Contributor
timestamp: March 22, 2020, 09:56:29 am
content: Grinding the sides of the teeth?That is something you might do to reduce the set, to make the kerf narrower or smoother. Or it might be something you do after sharpening and hand-setting the blade, to knock down the hi-liers from your human variability. Esp if you are cutting softer materials, those outliers might stick around for awhile.I have done it once, on a fine tooth saw, to try to get clean cuts in PVC pipe. It made the kerf smaller (and the blade couldn't cut a curve, anymore), but it was a failure for my purpose; I still had to debur/chamfer, after.The part that gets me is there are scores of YT videos on how to set up a bandsaw to cut straight, to the table/fence in particular. And I have watched too many of them. And I have never heard anyone suggest adjusting the table. Imagine my surprise to find out it was fully adjustable, all along, with those four worm screws. My (cheap) 14" saw can't be the only one to have this feature, and yet I could have gone to the grave without ever knowing it was there... because I looked it up on YT.In combination with the trunnion, the table is adjustable in every possible axis. Trunnion for left/right tilt. The worms screws adjust the forward/back tilt and the rotation/twist. But there are 20 videos on YT explaining how to adjust your saw out of whack until it can just maybe cut a piece of plywood straight to w/e random position your table happens to be (on that day, that feed pressure, and that thickness of plywood, cuz the saw don't cut straight anymore, lol). The best is "just put the gullets on the crown with the tracking knob, and bob's your uncle."

author: tautech
author_rank: Super Contributor
timestamp: March 22, 2020, 10:36:18 am
content: Quote from: KL27x on March 22, 2020, 09:56:29 amStripping the high or wide flyers is a common technique to have a blade cut smoother or reduce side striping as it pulls all teeth back to the same width and height however it's generally a last resort before a full sharpen although if a tooth has too much set it will only reduce it a bit after the rest are sharpened too.

author: coppercone2
author_rank: Super Contributor
timestamp: March 23, 2020, 02:26:16 am
content: I don't think you can cut a material without the need of a debur afterwards unless you chip the edge (like cutting acrylic on a saw), if the material is cleaved off there is no bur left behind?Like, theoretically it cannot be done? Under a microscope, I would assume it would need to look like its chipped, even if the chip is tiny (which is still worse then a real debur. I thought cutting HAS to leave a bur, wheras cleaving (like breaking glass) does not leave a bur, but is ugly and does not happen unless the material is glasslike/fragil0e, but might not make a difference in strenght for a welding process like acylic weld, or inhibit flow to braze.. and not sure what a cleaved edge does to welding instead of a non deburred edge, maybe a nasty bur can inhibit heat flow but its hard to think about it since its being totally molten with high force). since cutting is deformative, wheras cleaving has stuff get knocked off. I thought it was just something non attainable given the forces at work. Maybe case hardened stuff will cut with 0 bur, since the layers near the edge become nonlinearly hard and will chip off from the force of the blade? like an oreo cookie, where the cookie part is the hardened material, and the cream in the middle is the normal material.maybe with a sufficently long saw, if the cut was conducted before some off alignment teeth come in to knock the burr off while the saw is still in position, it would benefit not to have a flat saw? it would be like a little hammer flying into the bur to knock it off made by the mainly strait saw

author: gerts
author_rank: Newbie
timestamp: March 23, 2020, 05:18:23 pm
content: I finally got good results on my bandsaw after I gave up trying to cut parallel to the table. I have an adjustable fence that I can pivot to set the angle of the fence to the drift of the blade. For setup before cutting, draw a straight line on a scrap board and freehand cut it on the bandsaw. I then adjust the fence to the angle that the board follows as the blade cuts the marked line. Solved a lot of my problems. I can now resaw 8" boards down to 1/32" and not end up making wedges.The "grinding" of the blade I think is stoning the "back" of the blade. I think this is for better tracking and less wear on roller bearings.

author: cvanc
author_rank: Frequent Contributor
timestamp: March 23, 2020, 06:55:52 pm
content: Quote from: KL27x on March 21, 2020, 11:19:40 pmYes. Yes, it is.

author: SilverSolder
author_rank: Super Contributor
timestamp: March 23, 2020, 07:34:50 pm
content: Quote from: gerts on March 23, 2020, 05:18:23 pmThat's what I do as well... but I switched to using a circular saw most of the time, as it is less faffy!

author: KL27x
author_rank: Super Contributor
timestamp: March 23, 2020, 09:21:54 pm
content: Quote from: gerts on March 23, 2020, 05:18:23 pmYeah, I imagine an adjustable fence would be handy for frequent adjustment. But if you use the same blade for most of your sawing, you can maybe just adjust your entire table!? Then you can use your miter slots, too? Now, I just adjusted my table to the cut (and why did it take so long?), so I don't know how long it is going to stay in tune. But it's amazing even when free-handing, to be able to cut and feed the stock parallel and square to all the lines and edges of the table.I actually use a sled with my bandsaw quite a lot. In the past, I only used it for plywood and thin materials, and being careful with feed rate. It's going to be way more useful, now.QuoteBecause I adjusted the entire table rather than a fence, I got to use my sled. I put a scrap of plywood on the sled and I adjusted the table to where I could make a straight cut when force-feeding the saw with a high feed rate on the sled, just taking thin slices off the scrap. So far so good. (Of course, you have to tune the saw to cut absolute straight, first, which my saw has been good that way for years.)Just go to where the trunnion attaches to the frame. In my manual, this is called the lower trunnion. I bet you anything, if you can buy an adjustable fence for your saw, your lower trunnion has set screws, one next to each of the screw/bolts holding the trunnion to the frame. If you can level a 4 legged stool, you can adjust your table. If these set screws aren't there? You can add then in half an hour, yourself, so long as your lower trunnion plate is thick enough steel. Or just stick some shims/wedges under it.This lower trunnion mounting plate adjustment is also how you get your cut perpendicular to the table. For many people this does not matter that much. But it's the only way you're going to get there, other than dumb luck that the table is set correctly for your saw and particular blade, out of the box.

author: gerts
author_rank: Newbie
timestamp: March 24, 2020, 04:31:24 am
content: One of the things I experienced is that different blades will have different drift so a fixed setting never worked for me.

author: KL27x
author_rank: Super Contributor
timestamp: March 24, 2020, 06:53:30 am
content: Each blade can be different due to set. This is usually when the blade is kinda wearing out. On a low TPI blade, I will just reset the side that needs it.Different blade thicknesses/tensions bend the saw frame/chassis a different amount. When the saw cuts a different line after a blade change, it's because of this. If you look at where the blade tracks on the bottom wheel, you will see this:When you go up in blade thickness/tension, your blade will run farther forward on the bottom wheel. When you go lighter, the blade will track farther back on the bottom wheel. If you want the saw to cut the best, you have to tune it for that blade tension. Period. If you set the blade so the gullets are on the crown on the top wheel, but they aren't on the crown on the bottom wheel, then your blade will have a twist. You will have to run some fancy guides nice and tight and lose 10%+ of your horsepower to cut halfway decent through any thick wood.Also you will notice, eventually, that if you tune the blade to run true after changing weights: when you go higher weight, your blade will sit farther to the right in the table insert. And that the blade will cut more to the left; e.g. you will have to push the material angled more out to the right (relative too w/e it was before, of course); if you have a fence on the left, the blade will wander more towards the fence. And as you go lighter, the opposite. This is due to the way the frame twists under blade tension. This is because, at least in most saws, the axles run into the back of the frame, only, not the front. And the back of the frame is more rigid. As you increase the weight of the blade tension, this makes the frame twist in a predictable way. On my saw, the top wheel moves more forward (towards me; top of blade ahead of the bottom of the blade) and out/right with more tension. This also alters the axis of rotation of that top wheel.The top wheel tracking only adjusts the tilt in one axis. To get the blade to run right, you have to adjust the bottom wheel, which is adjustable in both axis. You have to adjust the bottom wheel to aim at the moving target of the top wheel.All this madness makes the adjustable table fairly essential to use a miter slot.I get around that by not changing blades on my bandsaw unless it's some kinda necessary. And it's almost never that kinda necessary for me to change blade width/tension. Or TPI, even (I have only rarely changed to a finer pitch for large batch cuts, and I have always been disappointed with the very tiny difference). I'll find out soon enough how long it will continue to cut straight to the miter slots, running the same blade widths/tensions.If you have the set screws, adjusting the table is 5% more work after tuning the tracking and the blade guides.Once the saw is tuned to a blade, that's like "don't mess with it." If you already ignore your miter slots and use a rapidly adjustable fence, why not mess with the table adjustment? At least get it roughly square in a few minutes. Perhaps, like me, you forget or never knew it was there? Like the modern internet body of knowledge on the subject?

author: gerts
author_rank: Newbie
timestamp: March 26, 2020, 06:22:20 pm
content: Quote from: KL27x on March 24, 2020, 06:53:30 amHi KL27x. Thanks for the detailed info. What bandsaw do you own? Is it a Delta 14" sized machine? I've got a 14" Delta and a 24" Mini Max. Thanks.

author: KL27x
author_rank: Super Contributor
timestamp: March 26, 2020, 11:32:26 pm
content: Rikon variant. I guess that's the other common one.

author: dbctronic
author_rank: Regular Contributor
timestamp: March 27, 2020, 06:41:43 pm
content: I'm with SilverSolder, I only use a bandsaw when I want to do scroll cutting. My very old used Delta, which I use for wood and plastic, is extra faffy, and will break the blade if it is not keptconstantlycentered on the big circular thingies. The other, for metal, is just too slow for anything but thin sheet steel, and metal cutting blades need constant purging when cutting aluminum, which I do by cutting shallow slots into scrap steel.My friend and co-house owner just finished converting a little table saw we retrieved from the curb into a cutting table that has both a router and a Milwaukee reciprocating saw. Fast and accurate!!!My rules for not wasting time on YidiotTube videos:1. Only use as a last resort. People take more time and thought to write than they do to fire up a webcam and start yakking.2.Immediatelypunt any that start out with:A. "OK, so basically..."B. Lots of silenceC. Very poor sound qualityI violated my own rule a few months back, to watch a video in which a guy tried to make his own surface plate out of granite floor tiles. Five minutes of him trying to use engine valve grinding grease (), not taking any measurements before beginning (), guessing at a proper grinding technique, "discovering" what a mess he'd made (), and trying unsuccessfully to use a spot depth guage to determine whole-plate flatness ().He finally confessed he had no idea what he was doing. I wanted to shoot him, but hey... I ignored my own advice, so...

author: KL27x
author_rank: Super Contributor
timestamp: March 27, 2020, 07:26:16 pm
content: I don't have a table saw. My shop is half a 2 car garage. So I do all my major cutting on the bandsaw. Any refinement is with the belt sander or the planes and sanding blocks. My shop motto is to "just remove the spots." I can often get by with using my router table for making smaller parts that have to be parallel and square. I use it like a jointer/planer for small parts and for making slots; I don't do crown molding or decorative edge treatments.QuoteYou are using the wrong saw for aluminum. Too many people want to use 10+ tpi for aluminum just because it is "metal." Try using your wood saw. I cut aluminum as thin as 1/8" using a 4 1/2 tpi blade at wood speeds. Hardly any rougher cut than using a fine tooth blade. Brass, ditto. Use the wood saw, dude. It will cut fast, it won't clog, and it will clean up with a file.My blade broke the other day, so I had to reinstall one. I learned some finer points, I may have misspoken.The tracking thing: You definitely don't have to adjust the bottom wheel every time you change to a different blade. As long as the blade is sitting firmly on both wheels, and not so far back from center that the teeth are cutting into the tire or whatnot, the blade should be ok. The blade automatically finds the highest spot on either wheel. So if the blade is not in the same spot on either tire, it can still be fine. Just that if you change tension enough, the blade won't be able to sit right on both tires.The direction the blade cuts will change with any change in tension. Even installing the same blade at a lower tension*, I had to rotate the table CCW to adjust for the change in cut direction. And I had to tilt the table just a hair back (front up, back down) to get the blade perpendicular, again, because it was slightly laid back. Just as stated before, these changes are consistent, once you learn them for your saw. In fact, I realize now that this is the best way for me to know my blade tension. If I am reinstalling the same blade as before, I can test the direction of the cut to know if my tension is lower, higher, or the same as before. (Well, not counting blade set issues).*so it won't break after 2 years this time, hopefully; and it didn't break anywhere near my braze joint this time, so I finally got that down.The blade lasted a resharpening/reset, and I also noticed my rear guide bearings are shot. So all told, I think it lasted pretty well.

author: KL27x
author_rank: Super Contributor
timestamp: March 27, 2020, 07:41:17 pm
content: I also found an easy way to check and adjust your table alignment.Take a scrap of plywood, and cut some slots along one edge. Say every inch or so, cut a inch deep slot. Then put it on a sled or miter attachment in your table miter slot/s, so you will take a slice off that edge, which is now interrupted by these slots. Feed the scrap through at the highest rate the saw is still cutting nicely.The slots/interruptions allow the blade to return towards normal/free. So every spot there is a slot, you will be able to feel a change in height of the edge of that plywood when the blade is not cutting straight. This is very quick, only takes a small bit of scrap, and it won't deviate the blade so much that you mess up your table insert or sled.It doesn't matter if your sled or miter attachment is perfectly square. After you get your cut to be straight, then you can adjust your fence/gauge for square.Edit: also not-so-obvious-to-me the first time: make sure to screw in your trunnion level/stop bolt so it's freefloating before you adjust the twist or the tilt of your table.

author: tautech
author_rank: Super Contributor
timestamp: March 27, 2020, 07:56:20 pm
content: Unfortunately I've lost contact with the professional saw doctors I once knew as they had a wealth of knowledge of all things sawing but I well remember the the log breakdown bandmill at the sawmill at my first job from school.Massive steel carriage that ran on rails carried the logs through the bandsaw and returned back in what seemed like an instant fro the next pass. The carriage was steam propelled and IIRC returned at peak speeds of 40 MPH.It was 2 story beast of a thing with 6ft wheels and a massive old 200HP electric motor driving it.6M long 1M dia logs were dissected into a # of flitches (slabs) in little over a minute then run through multi blade scrag saws slicing off up to 6 boards at a time.Today some decades later small horizontal bandmills are readily available for those that own or need to process timber from small woodlots.https://www.farmtrader.co.nz/reviews/1406/farm-forestry-wood-mizer-sawmillhttps://woodlandmills.co.nz/product/hm130/Who says bandsaws can't cut straight ?