Setting tension on band saw blade
Lonnie Bird suggest that one can learn to set proper tension on a band saw by putting moderate pressure sideways to deflect it 1/4″ sideways held between guides set 6″ apart. It would seem to me that one could be very precise by putting something like a pull fish weight scale on the blade and tugging so many pounds sideways. It seems to me it is a matter of mathematics and vectors. Not sure if it would be something like the sin or tangent of 5 degrees (based on the geometry of the deflection) times the desired pounds per force you are trying to achieve. Wait. The idea is simple if the math clouds the head.
If you want to exert a force of 200 pounds on a 3/8″ blade, how many pounds do you need to pull on it to get it to deflect 1/4″ I would think there would be charts. A tool to measure this (a fish scale) would be a lot cheaper than a strain gauge and in theory, just as accurate.
If I use my math model to get a 3/8″ blade under 20,000 psi, roughly 200 pounds of tension to deflect 1/4″ requires 16 pounds of force sideways. This seems on the surface more than “moderate pressure” but maybe I under estimate my strength. It is the method I’m interested in than the rightness of the math
Peter
Replies
I'm with Roc for most of us woodworkers. If you are in high production cutting metal, buy one of these.
http://www.grainger.com/Grainger/MORSE-Band-Saw-Blade-Tension-Gauge-2CDN9
Rat hole
The bikes with the extra wide hubs. He built bikes for guys like him. Well over six feet tall. Over two hundred pounds and usually with a motorcycle moto cross back ground who wanted to do it in the dirt with a bicycle. Shipped his bikes all over the world
Page down
http://www.retrobike.co.uk/forum/viewtopic.php?t=42004
The good one ! ! ! ! =
http://www.retrobike.co.uk/?p=241
AHHHH THE GOOD OLD DAYS ! ! ! ! !
He is in "The Hall Of Fame "
http://www.mtnbikehalloffame.com/page.cfm?pageid=6&memberid=33
Formula
http://wheelfanatyk.blogspot.com/2009/01/spoke-length.html
Ping ping rather than thug thug even thung thung is good
A well made and sharp blade is far more important than higher tension. I have found with my Laguna even if I leave the blade less tensioned that I intended she still cuts beautiful and that is with a big'O wide blade. The skinny blades for curves are easy to over tension so I just listen for some ping rather than thung thung sound and it is good. I think the blades can work just fine over quite a wide range of tension and the less the easier it is on the saw bearings. So to quote the owner of Laguna: tension the blade enough and no more. Easy to do with some experimentation with each blade one has. Usually I am all gung-ho for measuring tools but the bandsaw blades do fine without high precision tensioning.
You mentioned the bend over an anvil tension gauge. I have built super high quality bicycle wheels every year for forty years. I usually have one or two spoke tension gauges in the shops I have built wheels in. I never use them unless there is an argument to be settled. I can tell by feel where the tension should be for all types of wheels and I just build them right.
For anyone who knows or cares I built the first wheels for all of Doug Bradbury's hand made Manitou brand mountain bikes. What made his wheels unique was they had extra wide spacing between the hub flanges where the spokes connected to the hub. More likes motorcycle than a bicycle.
The frames were custom built to order for each owner. The frames were extra wide where the axles went in to run these extra wide axle spacing hubs. Since these babies were WAY off the charts for known bicycle wheel building spoke lengths I calculated spoke length using a math formula. With this formula one could measure all the components of the wheel, calculate for the slight elasticity of the stainless steel spokes and ( if one poked all the right buttons ) have the top of the spoke end wind up at the bottom of the screwdriver slot in the spoke nipple. Used sin and cos etc.
Usually about forty five minutes from beginning to measure the components and run the formula to a finished wheel that was ready to ride
Fun to do with a basic scientific calculator. I now have the formula in an Excel spread sheet on my iPhone. It is always a pleasure when I finish tensioning and truing a wheel and the end of the spoke is right at the bottom of the nipple slot. Been doing it so long I can hit it every time. I still enjoy it though. I"m easily entertained.
So you see, I am with ya but not for bandsaw blades.
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