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How to fix Bandsaw Blade drift.

cwhuffman

Aluminum
Joined
Nov 26, 2021
This could be a bit of a long shot but I would like to pick everyone's brains, especially those who had experience with correcting blade drift on a bandsaw. To give some context, I started my shop earlier this year and picked up a used WF Wells W-10-2 semi auto dual post bandsaw from a shop that was closing up shop. It is an old saw, but is still pretty solid. I got to see the saw cut in person but the owner told me I would need to replace the guide rollers and realign them if I wanted to do any amount of close or accurate cutting. Up until recently, I haven't really needed to do any accurate cutting as I have been able to feed bars on my CNC lathe and I can put the sloppy cut on the side with the remnant. However, I have a job coming up that will be machined from 3" steel bar and I cannot bar feed this material as it is a little too large for my spindle bore, so I will need to bandsaw cut them and chuck the blanks.
I set about tearing down and cleaning up the guides on the saw, replaced the rollers with new ones and did my initial adjustments checking the squareness of the blade to the table. The only thing I did not replace were the carbides on the guides as they appeared to be fine. The first few cuts I took with the saw seemed promising with only a small amount of noticeable taper in the blade feed direction, left and right were pretty square as well. I did these cuts with some scrap 1" round bar to give myself a baseline. As with any bandsaw, there is going to be a little blade drift due to the cutting forces involved, but on one properly set up it should be a consistent drift and shouldn't be very extreme. I decided since it was cutting well with the 1" bar, I would go up to a piece of 3" and test that out as well....This is where the problems start. When cutting the 3" bar, the cut starts out good until it gets about half way into the cut, at that point the blade starts to curve into the bar towards the clamp. The amount the blade drifts can be anywhere from .060" up to .200" at times and is not consistent from cut to cut. I tried to shim the guides to see if I could compensate for the drift, but all that ended up doing was creating a cut that was curved instead of just tapered. I should also mention that I was using a brand new Lenox blade for these tests and had the guides as close to the material to eliminate as much deflection as possible. I also played with the feed rate of the blade in the material and found that feeding it faster would make the blade taper more, but even slowing the feed down to almost nothing, it will still drift by an unpredictable amount. I went back to my 1 inch round bar to see if anything had changed, and it cut very consistently to the first test cuts with little to no taper at all. I also tried some square steel bar I had, and ended up with very little taper just like the smaller round bar.

I plan to contact WF Wells within the next week to see if I can solve this issue, but would anyone have any suggestions on something to try before I can get in touch with them? The part that has thrown me for a loop is the saw drifts very little, if at all when cutting small round bar or square/rectangular stock, but when I move up to the larger diameter stuff, it starts tapering off in a big way. This is a huge problem as I cannot set up a reliable machining process on the lathe if all of my slugs have tapered faces that need to be faced off. If I leave the saw as is and try to do this job, I will have to give myself at least an extra 1/4 of an inch more than I had planned for each slug to ensure that it gets cleaned up in the facing operations.

Thanks to anyone who can provide some advice.
 
A few months ago I stated having blade wandering issues with a saw that has cut perfectly straight for the last 12 years I've owned it. I replaced all the guides and set everything up dead straight. Still did the same thing- Too terrible to even use.

I finally bought some different blades and figured out it was the Lennox blades that were 100% of the problem. The blades measure perfect, but the very tips of the teeth are formed the wrong way. The three bad Lennox blades I got were all dull on the outboard side and sharp on the vise side causing it to curve towards the vise.

I tried sawblades.com blades and they're OK, but nowhere near worth the price (same as Lennox for a cheaper blade). I have some Sigmund blades currently that are working great.

One other thing- What size is your blade? blades under 1" tall just don't really work in steel. They do cut, but the pressure of gravity making them cut is enough to deflect the blade at the 25K psi stretch required to make a bandsaw blade work. Atleast that's how Sandvik engineers explained it awhile back.
 
My two bandsaws mostly use 1/2" blades, but they both cut straight unless the blade is dull. I can't recall ever using a Lenox blade and I only buy flexback carbon steel blade stock..

Larry
 
Have you checked the blade tension? Bigger stock might make low tension more apparrent. You say half way through the 3" is ok. The forces on the blade increase to max at halfway through the round, so maybe the under tensioned blade starts to drift then and gets progressively worse.
 
A few months ago I stated having blade wandering issues with a saw that has cut perfectly straight for the last 12 years I've owned it. I replaced all the guides and set everything up dead straight. Still did the same thing- Too terrible to even use.

I finally bought some different blades and figured out it was the Lennox blades that were 100% of the problem. The blades measure perfect, but the very tips of the teeth are formed the wrong way. The three bad Lennox blades I got were all dull on the outboard side and sharp on the vise side causing it to curve towards the vise.

I tried sawblades.com blades and they're OK, but nowhere near worth the price (same as Lennox for a cheaper blade). I have some Sigmund blades currently that are working great.

One other thing- What size is your blade? blades under 1" tall just don't really work in steel. They do cut, but the pressure of gravity making them cut is enough to deflect the blade at the 25K psi stretch required to make a bandsaw blade work. Atleast that's how Sandvik engineers explained it awhile back.
Interesting...I will have to look at the blades I bought and see if they are the same way. The places I have worked before always used Lenox blades and they were always good but it has been a few years since I have been in a shop that used Lenox. The blades are 1" tall x .035 wide, a pretty common size for a saw of this nature.
 
Have you checked the blade tension? Bigger stock might make low tension more apparrent. You say half way through the 3" is ok. The forces on the blade increase to max at halfway through the round, so maybe the under tensioned blade starts to drift then and gets progressively worse.
I am not entirely sure there is a way to adjust tension on this saw, but the pressure gauge reads north of 300 PSI when I checked that today. I do not know what the proper tension is supposed to be for this saw, which is something I would have to ask WF Wells. However, the gauge could be giving faulty readings as when the blade is released from tension the gauge still reads some amount of pressure.
 
What blade? TPI, width? Agree with Garwood, try a different brand blade.
Lenox Classic (If I remember right) 1 x .035 x 138", 10/14 TPI variable tooth. Something that just occurred to me that could also be a point of reason with this is when cutting the 3" material I have almost 30-42 teeth engaged in the cut at the longest cut point on the stock. If the blade is in fact pushing away around the center of the 3" bar, it could be because of that. I may have to pick up a blade with a coarse pitch (6/8 TPI for say) and see if that makes a difference too.
 
New blade? Feed rate, sfm? Tooth count? Coolant before and after stock? After is more important in many cases to blast chips outta gullets.
There is a fixed carbide on each guide block, check that these are dead on level to saw. The bearings are pre- guides on that saw I think, let them ride a little loose (1/16 ish total gap). The carbides are your guides.
There is the third carbide in each block that is always neglected- the backing chicolet(s). These get the most wear, and if run to long with improper mains get a groove that is impossible to adjust out.
After blade is installed it should check level at the front and back guide.

Are the columns level and parrellel? Check the bearings on the columns with the monkey test at different heights.

Even if your blade tension is off (300 psi to a cylinder or 300 lbs?) you should get straight cuts in the .01” inch range. 300 lbs is not nearly enough. Check your blade for recommended tension (you will be shocked at how high it is).

I like Morse blades.
 
4-6 blade for 3 inch is a good starting point for 1 to 4 inch stock. You can run finer or coarser blades if you adjust speed and feed rate to match blade speed. Finer blades can cut faster if you have enough gullet and chip blasting coolant on the exit. The wire brushes knock the debri off, they are secondary to backside coolant.
 
New blade? Feed rate, sfm? Tooth count? Coolant before and after stock? After is more important in many cases to blast chips outta gullets.
There is a fixed carbide on each guide block, check that these are dead on level to saw. The bearings are pre- guides on that saw I think, let them ride a little loose (1/16 ish total gap). The carbides are your guides.
There is the third carbide in each block that is always neglected- the backing chicolet(s). These get the most wear, and if run to long with improper mains get a groove that is impossible to adjust out.
After blade is installed it should check level at the front and back guide.

Are the columns level and parrellel? Check the bearings on the columns with the monkey test at different heights.

Even if your blade tension is off (300 psi to a cylinder or 300 lbs?) you should get straight cuts in the .01” inch range. 300 lbs is not nearly enough. Check your blade for recommended tension (you will be shocked at how high it is).

I like Morse blades.
I will have to check out the Morse blades once I get to the route cause of my cutting issues. I do not have any form of parts manual or drawings with this saw other than the schematic for the electrical system. I knew there were some carbide guides that will wear, but when I took the guides off they appeared to be in good shape, but I did not know there was a "third" carbide guide. This is something I will have to ask WF about this coming week. The columns as far as I can tell are square to the bed, they may be a little worn but that is to be expected with the age of this saw. I will double check but the blade tension gauge gives readings in PSI, since I do not know what the surface area of the piston is I cannot calculate the force. This will be another thing I need to ask WF too.
 
I moved to Lenox blades years ago after the Starrett blades went to shit. Then when Lenox blades became problematic, I stumbled onto Wikus blades and all my bandsaw blade problems became a thing of the past. You can even hear the difference as the Wikus blades operate silently with no screeching or singing like the others always did. A 1" blade is supposed to be tensioned to 30-35,000 PSI? IIRC. There are many factors in a bandsawing system that make it productive or a nightmare if things aren't working in harmony.
 
.... A 1" blade is supposed to be tensioned to 30-35,000 PSI? IIRC. There are many factors in a bandsawing system that make it productive or a nightmare if things aren't working in harmony.
Agree.
Why do blade manufacturers give psi instead of pounds force? Expecting people to do the math is lazy. 1”x1/32 takes about a 1000 pounds, which is 32000 psi. You still need to adjust for saw frame harmonics, lower tension helps that at the cost of blade track and slip, quality of cuts and life of blade. To high and you get better cuts (chasing a few thousandths over 8 inch cut) but short blade life.
 
Agree.
Why do blade manufacturers give psi instead of pounds force? Expecting people to do the math is lazy. 1”x1/32 takes about a 1000 pounds, which is 32000 psi. You still need to adjust for saw frame harmonics, lower tension helps that at the cost of blade track and slip, quality of cuts and life of blade. To high and you get better cuts (chasing a few thousandths over 8 inch cut) but short blade life.
There are machines that aren't stout enough to ever achieve 'required' tension, so adjust accordingly. Some incorporate a spring into the mechanism that won't allow that level of tension if used acording to the operators manual, which implies the machine designers were clueless about importance of blade tension.
 
i have always set my blades off how much they stretch at 6”. i think it’s around .004 but i would have to check. i have it written on the saw. i just set my calipers at 6” and use a set of small vise grips to lightly clamp them to the blade and then tighten it the .004. never had a problem that way.
 
Agree.
Why do blade manufacturers give psi instead of pounds force? Expecting people to do the math is lazy. 1”x1/32 takes about a 1000 pounds, which is 32000 psi. You still need to adjust for saw frame harmonics, lower tension helps that at the cost of blade track and slip, quality of cuts and life of blade. To high and you get better cuts (chasing a few thousandths over 8 inch cut) but short blade life.
Should be 2000 lbs force--you are tensioning both the working side and the return side of the band.
Bob
 
I once got a horizontal WelSaw from a contractor because it wouldn't cut straight, and he was tired of screwing around with it. I checked everything over and could find nothing obviously wrong. Then I noticed that the collar on the spring balance had moved about 1/4" by the paint mark. I put it back where the paint mark indicated and the saw then cut straight from then on. It was simply too much cutting pressure.

Have you ever used a PortaBand saw by hand? The secret to getting a straight cut is to cradle the saw and not let its weight go entirely on the blade. My boss wanted an industrial look to his new kitchen and wanted to put 6" steel channel against the ceiling, with rivet heads making look like old bridge beams. The room wasn't a rectangle so it required inside and outside cuts. I cut all the 45 miter cuts with a Portaband and everyone was blown away by how closely all the joints fit together with hardly a touch of a grinder.
 
Lots of good advice above. Typically bandsaw accuracy problems are due to 1 - blade problems, 2 - band tension problems, 3 - blade overheating. The first two have been addressed above.

One thing to keep in mind is that bandsaw coil stock is not straight. If you lay out a coil of band flat on a floor you will notice that the cutting edge side is shorter than the back side, which causes it to gently curve towards the cutting edge. This is because the cutting edge will heat up and expand in use, and unless it is tensioned higher than the back of the band it will cause wavy and inaccurate cuts. The bands are designed shorter on the tooth edge - with the working temps in mind so that they will be straight in the cut after they've heated up.

If your tension is inadequate, then the cutting edge side of the band will not be equal length to the back side once it heats up. Cut inaccuracy will result.

If you don't have access to a band tension gauge, the stretch method mentioned above is a good alternative. You just need to find out the proper stretch measurement from the band manufacturer.
 








 
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