Wooden Band Saw Blade Tension

[Andrew More]

I've been debating whether or not to buy a larger bandsaw. I've already got a 14" Delta, and it's been great for a number of things, but even with a riser block it seems to struggle with resawing and veneering. I was thinking maybe one of the Grizzly 17" or 20" steel bandsaws.

However, I've noticed that Matthias Wandel is at it again with a new wooden bandsaw build. As usual looks like a fun project, and relatively cheap in terms of materials (at least compared to a 1K-2K commercial model). As with previous models, like his 20" I haven't seen him use the bandsaw for this purpose.

Since I know from experience with my 14" bandsaw that applying tension to a 1" resaw blade is challenging, I'm wondering if it's possible for his wood frame models to be able to achieve the necessary tension to be able to support a 1" blade.

Anybody have experience with his 20" or other bandsaws, and know how well it tensions a resaw blade? Or any other experiences in the rigidity of a 2x4 laminant which is what he's using for his frame.

[Lee Schierer]

Since I know from experience with my 14" bandsaw that applying tension to a 1" resaw blade is challenging.

Your 14" saw was never designed for nor is it capable of properly tensioning a 1" blade. Any blade over 1/2" is pushing the limits, even with beefed up tensioning springs. Before investing time and money on a new saw that you try the following:

1. Buy a good 1/2" blade with 3 TPI.
2. Align your saw table and fence to the blade. This video is the best I know of on how to align your saw.
3. Insure your belt is properly tensioned so you get full power from your motor.

Once you do these things, I think you will have a much improved bandsaw.

[John TenEyck]

A 14" Delta can barely apply 12K psi to a 1/2" blade. As Lee said, that's enough to get the job done, even resawing and slicing veneer, with perfect setup and a sharp blade.

With respect to Mr. Wandel's shop made BS I'll give you a couple of pieces of data. The Young's modulus of wood is no more than 2 x 10^6 psi; it's 30 x 10^6 for steel. At equal cross section and span wood will deflect 15X that of steel. To apply the same amount of stress to a blade a wood frame bandsaw would have a much beefier frame than one made of steel. I don't see that in the frame I saw him making. The saw may be just fine for his purposes, but a quick assessment suggests it's not going to be able to apply anything close to the 20K+ psi many steel frame saws are capable of on their max. rated blade.

John

[Andrew More]

@Lee I've got a good blade, no so sure about the belt tension on the motor. I have noticed it slowing down, but only if I try to feed too quickly, at which point I can effectively stall the motor.

With respect to Mr. Wandel's shop made BS I'll give you a couple of pieces of data. The Young's modulus of wood is no more than 2 x 10^6 psi; it's 30 x 10^6 for steel. At equal cross section and span wood will deflect 15X that of steel. To apply the same amount of stress to a blade a wood frame bandsaw would have a much beefier frame than one made of steel. I don't see that in the frame I saw him making.

Interesting. I did a quick check on the latest video. His frame appears to be 6" wide, which is probably a few inches wider than a comparable steel bandsaw (hard to guess from pictures). From what you're saying it would probably need to be like 20" thick or so? Does it matter that most steel bandsaws are hollow inside, while his wooden one is not? From what I can tell the tension is on the outside of the frame.

FWIW, I ask the man himself, and he was kind enough to reply. His claim was "At some point I compared my 16” bandsaw to my cast iron 14” saw, and the wooden one was considerably stiffer."

Obviously cast iron is not steel, so there's going to be a bit of a difference there.

[Lee Schierer]

@Lee I've got a good blade, no so sure about the belt tension on the motor. I have noticed it slowing down, but only if I try to feed too quickly, at which point I can effectively stall the motor.

When I first got my 14" Delta band saw set up, it seemed to be lacking power. I was contemplating changing to a larger HP motor. I had a friend over and we needed to make some cuts on the saw. He noticed that when the blade was stalling, the motor was still turning. After tensioning the belt, it was nearly impossible to stall the motor. My resawing improved significantly when I aligned the table to be parallel to the blade following the instructions in the video I linked. I can not resaw and make rip cuts that don't push the wood into or way from the fence. I recently sliced off some 5/4 slabs from some green black walnut that was the max height of my blade guides on my saw which does not have a riser block with no problems.

What is the Hp of your motor?

[lowell holmes]

I adjust the tension on my 14" Jet with a riser block to a tension that eliminates flutter plus 1/2 turn.
If drift still exists I might add a bit more.

[glenn bradley]

Like Lowell, I am in the 'flutter method' camp on setting tension. I slice 1/16" veneers without issue. If the saw is well aligned the blade really doesn't want to wander off. It is easy to run a bandsaw blade too long. Like using sandpaper beyond its useful life, this is a false economy. You waste more than you save in running a worn bandsaw blade. Change them often or go to carbide. As to running wider blades, I run a 1/2" carbide blade on my 17" saw for sawing veneer with good result.

While I agree that a 14" saw is best left un-risen (is that a word?) I would do as Lee suggests before throwing money at something. If resawing is your goal, look to a larger saw. If your heart is set on making a wooden bandsaw, go ahead and have some fun. If it doesn't work out you can always use your next new saw to cut it into stock for re-use.

[John TenEyck]

@Lee I've got a good blade, no so sure about the belt tension on the motor. I have noticed it slowing down, but only if I try to feed too quickly, at which point I can effectively stall the motor.



Interesting. I did a quick check on the latest video. His frame appears to be 6" wide, which is probably a few inches wider than a comparable steel bandsaw (hard to guess from pictures). From what you're saying it would probably need to be like 20" thick or so? Does it matter that most steel bandsaws are hollow inside, while his wooden one is not? From what I can tell the tension is on the outside of the frame.

FWIW, I ask the man himself, and he was kind enough to reply. His claim was "At some point I compared my 16” bandsaw to my cast iron 14” saw, and the wooden one was considerably stiffer."

Obviously cast iron is not steel, so there's going to be a bit of a difference there.

Here is the formula for the deflection of simple beam:

d = FL^3/48EI

F = force - spring tension
L = span - pick any value you like
E = Young's Modulus which we discussed above
I = Moment of Inertia for the cross section of the frame

Ok, if F and L are the same the deflection of the frame is controlled by E and I. E is 15X higher for steel than wood so for the deflection to be the same in a wood frame BS I needs to be 15X higher than for a steel one. The formula for I is:

bd^3/12 for a solid rectangular cross section. So if we had a wood frame that was 6" wide and 4" thick I would = 72. For a hollow steel frame of the same cross section using 1/4" thick steel it would be 23.5.

I for the wooden frame is 3X greater than the steel one, but Young's modulus is 15X lower, so the deflection will be 5X more than the steel frame for any combination of F and L.

A wooden frame bandsaw would need to have a massive frame to have the same deflection as a steel framed one. Does that mean a wooden frame BS won't work? No, it just means that there's going to be a lot of deflection in the frame to tension a blade and that will make guide alignment difficult unless they stay at the same height all the time.

John

[Jim Becker]

Even if you used engineered wood products, such as those from LP, you're not going to approach the stiffness of a heavy steel framed (or massive old-iron) band saw including tensioning ability. Cast iron bends which is why the big old machines were so massive...it helps counteract that. Steel can be formulated to be stiffer for a given application. If you intend to do a lot of "bigger work" investing in a big machine is not a horrible idea. But as was also already mentioned, a good tune-up and a quality blade combined with patience for slower cutting can do the job for a reasonable level of activity with the 14" saw. I have zero regrets about getting my MM16 years ago, but sometimes wish I would have gone larger. And I'm not even a heavy bandsaw user!

[Andrew More]

Thanks for the replies guys.

I've currently got a Delta 14" from the 80s with a 3/4 HP motor. I installed a modified Grizzly riser block kit to get it to 12" because the kit was cheap ($50) and figure it was worth the chance of it not working well.

I've been experimenting primarily with a brand new 1/2" 3 TPI Timberwolf resaw blade in the saw, which seems to work okay, other than the stalling when doing large resawing through some eastern pine I was using to make doors. I'll need to take a look at the tensioning on the motor. Right how it's mostly using the weight of the motor + a spring installed by the previous owner.

I'm mostly just a hobbyist having fun and trying to fix up an old house, so it's harder to justify the $1,500 for a Grizzly, vs $500 or so for Matthias's version, if they're comparable, since I'm willing to trade a week or so's worth of effort for $1K. Unfortunately Craigslist hasn't really turned up any winners in a year or so of looking off and on.

[Alex Zeller]

I had a Harbor Freight Bandsaw given to me. Since it was free I figured I could throw a few bucks at it and it worked ok. I put a riser block and a beefier spring on it. The 3/4 hp motor wasn't really up to the task so I upgraded to a 2hp 3450 rpm motor I had. I matched up the pin locations for the riser block and it worked the same as before.

I was still kind of new to woodworking so I didn't want to be too far out of my comfort zone. When I got around to trying to make the wheels coplaner I found the pins were so far out of alignment that I was surprised the blade would even stay on the saw. I pulled the roll pins and just used the bolt. Once properly set up it was day and night difference better. The motor was a different story, too fast and too my HP. The belt was always slipping no matter how tight I got it.

I eventually sold it (with the 3/4 hp motor) for $50 and stepped up to the 19" Grizzly. A giant leap forward. But I use my BS quite often and for me, a hobbyist, it'll most likely be the last BS I buy. If you haven't set up your BS correctly. The 3/4hp motor is going to really limit any resawing. If you have to buy a replacement motor you're better off selling what you have and getting a better saw. Personally I think a wooden BS is just going to be endless fiddling and in the end more frustration than it's worth. I think for what you want one of the lower end 17" Grizzly saws might work just fine for around $1000. Rikon and Laguna may have a 14" saw for about the same money.

[Thomas McCurnin]

Ditto on the limitations of a Delta 14" band saw, but you can do an amazing amount of work if you know what you are doing and tune the saw right. No need to upgrade.

I like this guy, "Bandsaw Tuning For The Anally Retentive" https://www.youtube.com/watch?v=9DzbJYIPPNE&t=638s

[Andrew More]

Alex, you raise some good points that I'm trying to weigh in my own mind. You could be correct that a DIY bandsaw is going to be a lot of extra work and fussy for potentially not much payback, it's definitely a risk you take with DIY. OTOH, I've also been able to do a number of things over the years that have saved me big time. Just this morning I was able to replace the control board on our fridge rather than paying a tech and saved the food from spoiling.

In the case of the bandsaws, it seems like a simple enough machine, and I've watch enough of Matthias's videos to know that they work pretty well for him. He's got an interesting video of him milling a 24-36" ash log with the 20" bandsaw with a massive blade. I've also seem him do a lot of smaller detail work as well. What I have not seen him do is much veneering or resawing, because he's much more a tinkerer or hobbyist, and high-end furniture doesn't seem to appeal to him. Buying plans reduces the amount of fiddling and aggravation to a very manageable level, IMHO, but who knows? It's all a gamble on some level.

I'm using $1,500 as the number since the BS Matthias is currently making is a 26" monster, which might be closer to $2K from Grizzly. He's also got plans for a 16", but I don't think the trade offs make as much sense at that point.

[Alan Schwabacher]

When you look at Matthias Wandel's latest large bandsaw, note that he points out that it has large wheels to allow clearance, not for use with wide blades. It is designed for use with narrow blades, so does not need to be as beefy as a saw designed for resawing.

[Jim Dwight]

For what it's worth, many years ago I got a degree in mechanical engineering and I see no problem with the mathmatical approach applied above to addressing strength of a wooden bandsaw. The beam between the two wheels would have to be very large to overcome the much lower stiffness of wood.

I once had a wooden frame bandsaw. It was not of Matthias's design, he wasn't very old when I built it. It used a metal parts kit. It was mostly 3/4 plywood but the frame was a box frame of 3/4 plywood but it still would not tension a 1/2 inch blade. I added a 2x6 and it was better but still did not work great. I threw it away in 2013 in the process of moving into the current house. I later bought a Jet steel frame 14 inch saw with about 13 inch thickness capacity. It has as large a motor as can be used on 120V and has cut everything I've tried easily. But I have not resawn hardwood thicker than 6 or 7 inches thick so far. I also haven't tried the 1 inch blade I bought for it. I have a low tooth 1/2 inch blade and that's all I've used so far. My Jet was on sale for $1,000 when I bought it.

I like Matthias's videos (both of them, there is one in Germany too and he also has a wooden frame bandsaw). He seems to be technically trained or at least inclined and I am confident his bandsaws work. But I do not believe they will do the work of a steel frame bandsaw. I wouldn't try a blade bigger than 1/2 inch and they may not tension that. But you can do a lot of work with a 1/2 inch blade.

I saw the video where he makes boards out of a tree by fastening the trunk to saw horses and rolling the saw to make the cuts. I plan to make a base for my Jet to raise it some and to give me some storage drawers. It will have locking casters so I might even try that idea some day. I'll need really high sawhorses, however.

If you want to mess with it some more, I would get the moment of intertia (I in the equations) for hollow rectangular tubes and for solid beams. You can google up the equations and they can be easily put into a spreadsheet. Material in the center does count. If you could make a wooden beam 15 times higher in moment of intertia, to overcome the 15 times lower youngs modulus, you would have the same deflection.