Bandsaw Wheel Crossection

[trg-s338]

If one where to machine say an 18 inch bandsaw wheel for a horizontal metal cutting bandsaw blade an inch wide, would you machine a ridge on the backedge for the blade to not slip off the wheel and a relief for the teeth on the cutting edge? This is looking at the wheel crossection of course. I've not been around a large bandsaw to have examined this aspect of the wheel and my small Wells bandsaw, a poor performer, has the relief for the teeth but not the ridge for the backedge of the blade. The blade frequently slips off the wheel unless I have the tension really high. I presume that in this wheel design I'm exploring, there would be no crown, and it would be metal blade to metal wheel contact, is that right? No rubber tire? Just some random thoughts about it but would appreciate input on the design, I may build a bigger bandsaw sometime much later. Thanks.

 

[GK1918]

beleive me Im no expert on bandsaws, I just keep mine running. I do know both of mine, the wheel is
flat and my bigest in the 1940s with a well worn tire I wrap the wheel with friction tape that works, and
you must have a way on your machine to track it? I think I wouldnt make a relief especially if you have
a lot of tension It may do something crazy. I just think you have a tracking problem and I run with just
"enough" tension. Im sure the bandsaw pro's will come along.

 

[Tony Wells]

There is a narrow shoulder for the back of the blade to bear against. The width of the wheel is just narrow enough to avoid having the saw teeth ride on it. If you let the teeth bear against the wheel, you will flatten out the set of the teeth and the saw will not cut straight.

 

[CharlieW]

There is a narrow shoulder for the back of the blade to bear against. The width of the wheel is just narrow enough to avoid having the saw teeth ride on it. If you let the teeth bear against the wheel, you will flatten out the set of the teeth and the saw will not cut straight.

trg-s338,
I am a little unclear what you are trying to determine so I'll try and give a general explanation of the 2 different saws. There are 2 different technologies going on here.

Horizontal saws typically use 1 blade thickness and 1 blade width. Tony described that technology. In addition to those aspects, the blade is also twisted so the trailing side of the band clears long stock.

Vertical saw technology uses, basically, flat belt principals. They can also use different widths and thickness blades/bands. As Tony mentioned, the teeth would not only be adversely effected by running on a wheel's metal surface but they would also chew up the wheel. Bands/belts tend to run to the uphill or tighter side of a pulley. The crown of the wheel causes both sides of the band to want to move to the high point which is the center of the crown. The tire on the wheel protects the blade and wheel from adverse effects. Though the crown tends to make the the blade want to ride the high spot or crown, it has very little resistance to side forces. The side forces are supported by the guides which minimize the side forces on the band at the wheel and helps it track on the top of the crown.

Charlie W.

 

[trg-s338]

So on a horizontal metal cutting bandsaw, the wheel is configured so the teeth of the blade "overhang" and don't make contact with the wheel surface, the back edge of the blade bears slightly on a small shoulder machined into the wheel, a slight crown aids in keeping the blade centered on the wheel surface, wheel alignment/tracking system keeps the blade on the wheel. Rubber tire is optional, and guides twist the blade between the wheels to present the teeth to the work for a straight cut. Would that about summarize elements of a successful wheel design ( as in the blade has the least chance of sliding off the wheel under moderate tension and feed )?

 

[CharlieW]

There is no crown on the wheel of a horizontal saw. I am not sure what geometery keeps the blade on the wheel and against the shoulder. I suspect that one or both of the wheels have a very slight tilt which makes the band want to hug the shoulder. Possibly the twist in the blade may have an effect that causes the band to move toward the wheel's shoulder.
That may require further investigation.

Charlie W.

 

[trg-s338]

A slight tilt on the contact surface towards the shoulder would seem to help keep the blade on but I don't know for sure.

 

[bjmh46]

Actually, most manufacturers taper the wheel slightly, and provide a shoulder or flange. DoAlls manual says that a properly tracked blade should ride just shy of, or lightly against the shoulder. Having built several horizontals, I can tell you that guide positioning must define the twist point of the blade on the back edge of the blade (not the centerline). This point wants to line up with the intersection of the wheel and flange surfaces. Taper will cause the blade to want to run to the high side of the taper, thus against the flange. having the teeth hang off the edge is sound advice. I keep the distance from the flange to the wheel edge the same as the blade width and provide a chamfer to accomodate the blade set. I'll see if I can add an image:







IIRC, I used 3 degrees (per side) on these wheels.

Regards

Bob

BTW, my first post here, 'scuse my not introducing myself in the proper forum!

 

[bjmh46]

mnmh,

Yes I built the saw in 1997. I have a layout drawing in both autocad 2000 &/or r14 format. I also have some few selected details and an electrical dwg. I'd share, but bear in mind users would have to open the layout in autocad (or in the free for personal use Progecad) to get dimensions. As with everything I build in my home shop, design is conjured up based on hardware and materials either on hand or readily obtainable. Users would have to modify to suit. Best done by someone familiar with autocad, and fairly well versed in design. I've built 5 horizontals and 4 or 5 verticals--gettin' old and can't remember now!

Best regards
Bob

 

[Tony Wells]

Bob, that is a nice saw. I have a shop built saw myself. It was a project from a high school industrial arts class. It sold as a fund raiser. It's not bad, but they borrowed a few components from a factory built saw. I'm about to trade it off on another saw.

I'd be very glad to get a copy of your CAD files. I have I believe up to 2005 AutoCAD, and SolidWorks also 2005. PM me for an official email address if you're interested in sharing those files.