Bandsaw lore

[PeteM]

I'm hoping someone can let me know the approximate range of down forces typically required to cut various thicknesses of low to medium carbon steel. Might be in an owner's manual for a horizontal saw? You might have your own rule of thumb? Maybe there's a spring scale sitting handy by your own saw?

Reason is, I'm adding a simple feed to my vertical (metal cutting) band saw and want to know the range I'll need to plan for. Saw goes down to 40 sfm; I'll usually have it around 80 sfm.

Thickest I'll cut is 6". Most common will be 1/2 - 3" thicknesses, with reasonably sharp blades, and minimum of 3 teeth in the cut.

Would much appreciate any help. Not much luck after a couple days on the other boards and a good guesstimate can probably save me a bunch of trial and error to get started.

[beckley23]

You're going to have to let the saw tell how much pressure it can take. Check with the blade manufacturer for the SFM, 80 SFM for mild steel seems low, I generally run my 1/2" bimetal bands at 225+ for mild steel. The 1" thick plate in the picture started out as a 10-1/2" X 9-1/2" plate and took about 30-45 minutes to cut out, manually pushing it through the saw.



Harry

[lynnl]

I don't have any quantitative inputs, but I don't think those asian 5 X 6" H/V saws provide enough force. It may not be a good practice, but when I'm cutting pretty thick stuff (say > 1"), I hang a plastic bag containing several lbs of steel onto the blade tensioning knob to provide more force. Seems to help a LOT! Probably stressing the drive worm & gear some, but doesn't seem to bother the blades, that I can tell. I'd think they'd wear as much or more just rubbing idly thru the kerf, than when doing productive work/metal removal.

Maybe someone will tell me why I shouldn't do this.

[Forrest Addy]

Work it out theoretically. 1/2 HP = 16,500 lb ft/min. 150 Ft/ min = typical carbon steel saw speed. 16500/150 = 110 lb - theoretically. Practically speaking it will be somewhat less maybe as much as 1/2 or 3/2 less. Much depends on saw and material parameters.

Bi-metal bands are a good deal. You pay twice as much for double the cutting speed (productiviety) and get 4 times the band life.

[wierdscience]

Go to your blades mfg and look for the "beam strength" figure for the blade type and set you are using,it will be based on a certain tension and guide spacing.

You can in theory approach this beam strength in the recomended material and tooth count before the blade begins to deflect between the guides producing a cut that leads off center.This figure will be the absolute maximum feed pressure allowable and in reality it will be something less due to blade/set wear.

I general terms the wider the blade the greater the beam strength.

[Mcostello]

I have just rounded over the back edge of a 1/2" blade on a new 4 x 6 saw. Cut about 30 peices of 3" o.d. x 1/8" wall steel tubing. Naturally will try to save blade but it jammed in cut and came off saw. Never in 10 years has this happened. Back edge of blade is wider than set.