BS Wheel Alignment: cite your references

[Jeff Heath]

I can share my experience. I cannot give credence to my thoughts while referring to any manual. I currently have 4 bandsaws in my shop. The oldest was built in 1905, and the newest was built in 1947. The two in the middle were built in 1936, and 1939, respectively. These machines do not come with manuals, and all of the manuals available regarding vintage industrial bandsaws at the vintage machinery website, that I have read, do not discuss this issue.

I have restored quite a few bandsaws. When you do that, you get to know a machine fairly well. Here's what I have learned, based on my own experiences setting them up. BTW, I am speaking of industrial, cast iron C-frame saws.

My objective is to get them as co-planer as possible, without stressing over it once the upper and lower wheels are close. The critical factor in a bandsaw blade tracking well is the crown on the wheels. If the crown is perfectly dead center, chances are, the wheels could be perfectly co-planer and the blade will track quite well. However, it is practically impossible to manually crown a bandsaw tire and get it EXACTLY centered on a new crowning job. Because of this (and the manufacturers knew this), the tracking adjuster of the saw allows for slight variances. Each saw will have a different tracking adjustment based on the crowns on the tires.

I have owned two saws, however, where the upper and lower tires were not very co-planer. A 1942 Northfield 36" saw, and a 1939 Yates American Y20 saw. Both were out by around 1/2". They both still worked perfectly, once the new rubber tires were crowned. Without the crown, however, neither saw would keep the blade on the upper wheel. It would always fall off. Once crowned properly, the saws worked perfectly, as long as the guides were adjusted to where the blade was tracking.

The closer you get your wheels to co-planer, and the better job you do at crowning the tires, the better the saw will run true. If you put in the time and effort, you can get a good bandsaw to cut and resaw without any allowance for drift. Is it worth all the effort......depends on how anally retentive you are and wish to be.

[Chris Parks]

Jeff brings up another point, European saws do not have crowned wheels so how do they maintain tracking without the band leaving the wheels. For such a simple machine the hobbyist has a very poor understanding of it due to lack of proper information. Someone has to sit down and design these things but the thinking never seems to escape to the users. I am with Van, I hate the term coplaner and only came across it here to begin with but it seems to have escaped to the wider WW community now.

[Bill Space]

Jeff brings up another point, European saws do not have crowned wheels so how do they maintain tracking without the band leaving the wheels.....

FACTORS AFFECTING BANDSAW TRACKING BEHAVIOR AND STABILITY, a thesis
by DARRELL C. WONG, goes into great detail about bandsaw tracking theory.

He explains two modes of blade tracking. With crowned tires the crown affects blade tracking. With flat tires the blade hangs out over the edge of the tire, and the tire edge performs the same function as a crown.

Read all about it here:

https://open.library.ubc.ca/media/do...31/1.0080858/1

It has been a while since I visited this thesis. I will have to take a look and see if coplaner vs non coplaner wheel positions are addressed by the author.

[John TenEyck]

I haven't seen anyone post a reference to a manufacturer issued Owner's Manual, repair manual, engineering drawing, whatever, that shows the wheels should specifically be set to something other than coplaner. There were several references that they should be set coplanar. Seems pretty clear to me. Would I adjust mine if the saw cut fine but I found the wheels were not coplanar? Of course not, but I would and have when I had a saw that wouldn't cut straight until I did.

The teeth on a bandsaw blade result in that side riding differently on crowned tires than the back side. To compensate for that you have to tilt the upper wheel back a little. Different blade, different amount of tilt. It would completely unreasonable to expect that the wheels could be set in any particular alignment, coplanar or otherwise, and never have to adjust them.

I use my bandsaws for lots of things, one of them being cutting joinery on thick stock, think dovetails on something 4" thick for example. If the wheels are not pretty close to coplaner the blade will not sit perpendicular to the table. This presents two problems. First, the guides, including the thrust bearing, will ride closer or further from the rear of the blade as you move the assembly up and down. Second, the end of a stopped cut won't be square. Neither of these issues may be important to some folks. They are to me.

John

[Chris Parks]

FACTORS AFFECTING BANDSAW TRACKING BEHAVIOR AND STABILITY, a thesis
by DARRELL C. WONG, goes into great detail about bandsaw tracking theory.

He explains two modes of blade tracking. With crowned tires the crown affects blade tracking. With flat tires the blade hangs out over the edge of the tire, and the tire edge performs the same function as a crown.

Read all about it here:

https://open.library.ubc.ca/media/do...31/1.0080858/1

It has been a while since I visited this thesis. I will have to take a look and see if coplaner vs non coplaner wheel positions are addressed by the author.

Bill, interesting but flat wheels get a few pars and that is it with no real attempt to explain them. It is pretty obvious how a flat wheel works and I suspect that the flat wheel pre-dated the crown wheel but I might be wrong. I haven't read the entire thing but I will. The bibliography might be useful as well. Thanks.

[Pat Barry]

With flat wheels the blade teeth should overhang the wheels? Never heard of this before. Is that right?

[Chris Parks]

With flat wheels the blade teeth should overhang the wheels? Never heard of this before. Is that right?

That is the recommendation of the manufacturers of the saws that I have used and owned. What must happen is by tensioning the blade the overhang acts like a clawed hand and starts to fold or clench over the edge of the wheel and this action defines the tracking on the top wheel. Other theories or knowledge welcome as that is only my take on it.

[Bill Space]

....The teeth on a bandsaw blade result in that side riding differently on crowned tires than the back side. To compensate for that you have to tilt the upper wheel back a little. Different blade, different amount of tilt....

John, are you sure about this?

For example, when calculating blade tension the teeth material that extends beyond the gullet is ignored.

I do not know, but it seems to me a blade that had the teeth removed would track on the bandsaw the same as an identical blade which had the original teeth. At least for the most part, since the with the teeth missing the weight and balance of the blade would change somewhat.

Bill

[Chris Parks]

My thoughts on this is we are getting into an area of engineering that no one has facts to prove and anything said is speculation. Assumptions never made anything a fact unfortunately. Bill's statement that teeth affect weight and balance do not ring true to me but I can't disprove it so I won't comment and leave it at that.

[Alan Schwabacher]

My thoughts on this is we are getting into an area of engineering that no one has facts to prove and anything said is speculation.

I disagree.

Take a look at the Masters thesis in mechanical engineering provided earlier in this thread. There are specific facts listed, sources for those facts, and theoretical treatments that allow behaviors to be understood. There are careful checks that the predictions of the theoretical model well match the behavior of actual machines. The things you are claiming to be speculation are mostly summary statements from that work.

[Chris Parks]

We agree to disagree, I have looked at the thesis and I could drive a truck through the holes it leaves, as I mentioned above flat wheels get about two pars.

[Bill Space]

We agree to disagree, I have looked at the thesis and I could drive a truck through the holes it leaves, as I mentioned above flat wheels get about two pars.

Could you list some of those "holes" in that thesis?

Appreciate specifics as I am doing my best to understand the intricacies of bandsaws, and have a lot to learn.

Thanks... Bill

[Chris Parks]

Bill, I still haven't read the whole thing and I don't know if I will because the whole point of the document in the author's words was that it was a reference to the workings of bandsaw mills and not bandsaws per se that a hobbyist such as you and I would operate. You may say and I certainly can't contradict you because I simply don't know that the two machines are in essence the same animal but what very little I think I know about bandsaws tells me that they most probably aren't, two wheels and a band being the only common thing between them but operating and setting them up being worlds apart. If anyone has direct knowledge of the two machines I would defer to them. The reference to cutting logs makes me back away from any comparisons.

[Van Huskey]

Mr. Wong references both the tern bandsaw and bandmill in his thesis. Most current scientific papers will be bandmill facing since the bandsaw (vertical woodcutting) is essentially dead in industry. The highspeed bandmill use is actually growing though since the preferred residential flooring has shifted back to wood in the US over the last 20 years. A bandmill is essentially nothing but a horizontal bandsaw on steroids. It does not produce a paradigm shift on the level of Newtonian to quantum physics, most everything that applies to one applies to the other in a general way.

I just made it a few pages into the paper last night, partly because making sure I completely understood all the terms in the nomenclature section took a little more time than most of the scientific papers I have read on bandsaws/bandmills.

Since I have just started digesting the information I can't say for sure but nothing I have seen so far suggests to me that it would not be applicable to bandsaws that we use. The last thesis I read in this arena was one on the causes of band breakage (again industry facing) and pretty much confirmed with data my opinions as well as conventional wisdom. This paper does list an expansive number of variables that impact tracking, my guess is most of them will have very limited impact on the hobbyist sized saws.