Does bandsaw blade tension matter?

[Carl Beckett]

This has probably been discussed/debated here before, my apologies if so.

https://www.youtube.com/watch?v=4k-r5utmU2Q

This video suggest bandsaw blade tension is not the primariy influencer of drift.

I just did a bunch of resaw in white oak yesterday, and my saw worked great. This included a 10.5" wide split of a 65" plank that I simply pushed through. I use a Laguna LT18 with an extra thin RK carbide blade. I have the tension maxed out on this saw.

But I do get an occasional burn mark. Can see the guides working (the ceramic guides throw some sparks from time to time. And every now and then experience drift. So am all for learning contributing factors.

This video has me thinking I should try a resaw guide at a minimum. (not sure I am ready to invest in a sliding table but every now and then something comes along on CL that could be fitted)

[Van Huskey]

The physics of cutting on a bandsaw is more complex than any other tool found in a woodworking hobby shop. The reason is simple, you are trying to get flexible tooling to act like rigid tooling. That always has to be at the forefront of your mind when you try to understand what is going on with a bandsaw. The only things you really have to produce a straight cut from a flexible bandsaw blade is tension and the feed speed. The higher the speed the more tension you need to keep the blade straight but if you reduce the speed enough you can get a straighter cut since the forces trying to push the blade offline are lower.

One of the other issues that you face with a bandsaw is harmonic vibration. All blades will vibrate and one of the ways to lower vibration is with variable spaced teeth, like you see on high quality resaw blades especially ones designed with veneer cutting in mind. Think of the blade as a string on a stringed instrument. At low tension, the string will vibrate at a low frequency but a high amplitude. This causes saw marks in the cut that are farther apart but deeper. With higher tension the band vibrates faster and at a lower amplitude. The saw marks become closer together but more shallow. So higher tension leaves a better finish meaning less sanding and saves wood, more important when cutting veneer.

The next place proper tension helps is reducing the propensity of the blade to barrel in the cut.

As for burning carbide tipped blades are more likely to produce burning simply due to the faces that touch the wood more in the cut than a blade with set teeth that only touch the one at one smaller point on each side. The carbide tipped blade produces a more polished finish but like any tooling the higher the polish the higher chance for burning. Hand feeding produces more burning than power feeding because of the inconsistent feed rate and the stop and go action that produces hesitation marks.

When the feedrate and tension are balanced you will never use the blade guides however you have to have a pretty serious saw to never touch the (properly set) thrust bearing with any depth of cut or reasonable feedrate. You can resaw without the guides but it really limits your cut and speed. Did Ethan in the video have the bottom guides backed off or was he actually sawing with half the guides, keep in mind that was a limited depth of cut with a very slow feedrate.

So yes, tension is important but it doesn't mean you can't work around a saw with limited tension otherwise there would never have been any decent veneer cut on a 14" cast iron Delta saw.

The key to all this (and the video) is that if you know what you are doing you can compensate for a poor setup. Give a MLB player a S shaped bat and they will still be able to hit the ball, give a top ranked tennis player a racquet strung with very low tension and they are still going to run me around the court and make a fool of me. Those "handicaps" would not be their choice though.

The other issue is whether the blade actually gets bound in the cut against a fence. My gut reaction is the kerf is wide enough and the backer is thin enough that there is not enough distance from the back of the teeth to the back corner of the back to cause this, I would have to take some measurements and do some geometry to determine if it is possible. If this turns out to be a significant potential issue using a half fence or cutting with the offcut away from the fence (as with a Driftmaster Fence) would alleviate this issue. There are certainly proponents of both of those options and when hand feeding I use the latter.

If I continued to address all the stream of consciousness thoughts running through my head I would likely still be typing 6 hours from now. In the end, set the tension correctly nothing positive comes from low tension. You do not need a Little Ripper to do good resaws. I would like to have one of the much larger but OOP Laguna milling stations they sold years ago for about $2k but that is a whole different kettle of fish. That said I am sure there are people that find utility in the Little Ripper for their workflow, it is simply too Little for me to consider.

[Robert Engel]

I totally disagree with that. You did it right IMO.

Without adequate tension, the blade tends to bow with feed pressure. It also has more tendency to follow the grain.

The best way, IMO to address drift, is to adjust the table, not run a blade on the gullets as Snodgrass and others advocate because it simply does not work with every brand of saw. Michael Fortune has a video out on FineWoodworking about this.


Or, do it like we've been doing it for generations: do a test cut to determine the blade path, and adjust the fence accordingly.

[Patrick McCarthy]

VAN, thank you for the insight, i never thought of it that way. Much appreciated. Patrick

[Randall J Cox]

I have read a lot of stuff on bandsawing, totally rebuilt an old Delta 14" used it for a couple of years and sold it. Bought an older MiniMax S45 18" and have been using it last 3 years (love it). And have read lots of stuff by Van Huskey and others on using the bandsaw, all good stuff. The part that spooked me from the original post was sparks coming off the ceramic guides. I have the traditional european rollers up top but installed ceramic guides underneath. And the thought of sparks being pulled into my dust collection system scares me. Never knew that could happen... Maybe if they are not set up behind the teeth sufficiently? Can't imagine why it would create sparks with just the smooth metal blade against the ceramic guides.... Is this common? Randy PS Not trying to hijack the post, but an insight on what I consider a safety issue needs to be addressed along with the blade tension issue. I'm a little paranoid as my son has been a fireman for many years and the stories I hear would make your hair stand on end.....

[Frederick Skelly]

Van, if you are so inclined, you could add-to and polish the "stream of conciousness" words above into a good article for one of the WW magazines. It was certainly interesting and informative.

[Van Huskey]

sparks coming off the ceramic guides.

All ceramic guides will spark on occasion. The majority of them seem to come from the weld area, even if it is fairly clean. It has been discussed reasonably extensively over the years. In my opinion, it is at the level of static electricity causing an explosion in a hobby shop DC system. I once pointed out that not all sparks are created equal, which if you view these ceramic guide sparks I think you will understand what I mean. They have a very short life and even in high volume air extraction don't go very far at all before burning out. They are nothing like the shower of sparks from grinding metal on a grinder or belt sander where you often see sparks hit the floor bounce and burn out after they come to rest after a couple of bounces.

Obviously, no one can say there is a zero chance of ignition (there is O2, heat and fuel after all) but IMO it is so insignificant it is not worth worrying about. YMMV

[Carl Beckett]

Thank you Van, very insightful.

Randall, search on laguna ceramic guides. It is considered ‘normal’ for OccAssional spark. Yes I do have a DC on mine. Food for thought.

[Bill Carey]

..... but an insight on what I consider a safety issue needs to be addressed along with the blade tension issue.

I've wondered the same thing when my Laguna throws a spark or 2. Just emailed Laguna and asked. I'll post the reply when I get it.

[Patrick Walsh]

Sparks are one of the reasons I git rid of my 14/12. Only one but it contributed.

Things happen fast with fire. I’m not playing that game. I don’t care what anyone saiz about them burning out or this or that is more likely to cause a fire. If I see sparks I stop.

[Van Huskey]

Van, if you are so inclined, you could add-to and polish the "stream of conciousness" words above into a good article for one of the WW magazines. It was certainly interesting and informative.

I am flattered anyone would think my drivel even when properly edited would be worthy of publication. That said the bandsaw is so controversial I would rather write about whether God exists. Before writing an article I would feel compelled to gather empirical data on every hypothesis and then have to deal with questions about the scientific method of each test. I much prefer the real time of an open forum where people are able to weigh in and agree or disagree as they see fit. I am comfortable in a situation that gets "peer reviewed" early and often, I feel better being more definitive as there will be a counter position with equal weight shortly thereafter. Even in PMs I am much less definitive. I respond to a bandsaw related PM pretty much daily and in that vacuum, I feel compelled to offer most of the counter-arguments. This is often time-consuming since I have to cover the Duginske, Iturra, Fortune, Snodgrass et al opinions including my own.

In the end a magazine couldn't pay me enough to weigh in on such a topic, I would much rather banter about it here among friends.

[Nick Lazz]

Here is an older video that has been posted before but it has great information on how to set up your saw. This helped me a lot.

https://www.youtube.com/watch?v=wGbZqWac0jU

[Van Huskey]

Sparks are one of the reasons I git rid of my 14/12. Only one but it contributed.

Things happen fast with fire. I’m not playing that game. I don’t care what anyone saiz about them burning out or this or that is more likely to cause a fire. If I see sparks I stop.

This was what I was talking about in my last post, immediate peer review. Someone reading this thread gets both sides of the ceramic spark debate and is thus forced to make their own cost-benefit analysis. It prevents taking opinion as gospel.

The workshop is an inherently dangerous place and we all should consider each risk and make our own decision so if something goes wrong the place to look for blame is in the mirror first.

BTW if someone loves the guides but has a significant fear of fire from them it is easy enough to build/buy a spark arrestor, we had some discussions about it in the turners forum prompted by the increased concern of metal dust from grinding. For DIY solutions you can search "spark bong".

[Van Huskey]

Here is an older video that has been posted before but it has great information on how to set up your saw. This helped me a lot.

https://www.youtube.com/watch?v=wGbZqWac0jU

How did I know it would be Alex Snodgrass even before clicking on it.

Alex makes a lot of good points, within the scope of the OP he is rather laissez-faire with tension. IMO his method is more useful for small crowned saws and as the saw gets larger and/or has no crown the method becomes less effective or downright wrong depending on which variable we are discussing.

[Randy Heinemann]

This has probably been discussed/debated here before, my apologies if so.

https://www.youtube.com/watch?v=4k-r5utmU2Q

This video suggest bandsaw blade tension is not the primariy influencer of drift.

I just did a bunch of resaw in white oak yesterday, and my saw worked great. This included a 10.5" wide split of a 65" plank that I simply pushed through. I use a Laguna LT18 with an extra thin RK carbide blade. I have the tension maxed out on this saw.

But I do get an occasional burn mark. Can see the guides working (the ceramic guides throw some sparks from time to time. And every now and then experience drift. So am all for learning contributing factors.

This video has me thinking I should try a resaw guide at a minimum. (not sure I am ready to invest in a sliding table but every now and then something comes along on CL that could be fitted)

Addressing the point of your original post . . . While I don't have any experience with 18" bandsaws, in the past several years I have used Alex Snodgrass's method and follow it to the letter. Since then, my resewing quality has increased significantly. I don't know about very large bandsaws, but I would think that an 18" bandsaw certainly could be set up successfully with the same method. I have a friend who has a 20" Laguna with ceramic guides. They do spark occasionally and he has found out that this is normal. Guides are there for a purpose; namely to keep the blades from straying too far from its intended path. Therefore, the blade will sometimes touch the guides. If the blade touches the guides constantly, then I would say some adjustments need to be made. Because you said that the tension is maxed out, it makes me wonder if it might not be cranked up a little too high - just a suggestion. Since you stated that you get good results, I'm not sure there is anything wrong with your setup.