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#4598615 - 12/08/17 10:22 PM Metal Bandsaw Blade Tension
CCI Offline


Registered: 07/15/09
Posts: 132
Loc: New Mexico USA
Bought an old horizontal/vertical metal band saw of unknown make, likely pretty old, seems to run good now. It was a mess, but I took it mostly apart, cleaned and lubed, reassembled, adjusted as best as I could figure out, and it cuts real well, square to well inside of 1/32".

Only problem is on thin wall tube sometimes the blade will stop. It's a fairly fine tooth blade. I suppose it could have something to do with metal wheels on metal blade, maybe this is to be expected. On thicker material it cuts very smooth.

I tensioned the blade as much as seemed prudent with the hand wheel,it used to stop a lot, now it hangs up only on 1/16" material just as it enters the vertical component of the square tube. So now I'm wondering, how tight is tight enough and how tight is too much on that blade?

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#4598637 - 12/08/17 10:59 PM Re: Metal Bandsaw Blade Tension [Re: CCI]
92saturnsl2 Offline


Registered: 03/02/04
Posts: 1282
Loc: Flaherty, KY
Tight enough is when the blade won't stop while the saw is running under a normal load/feed. I usually don't need to turn them too tight unless something is wrong with the saw-- I do it by feel, about a good snug plus another half a turn.

All of the ones I worked on had a rubber insulator on the metal drive wheels to grip the blade better. Perhaps this is worn off? Metal on metal might be a rather poor friction combo... Is the tooth pitch/count appropriate for the material being cut-- do you know what it is?
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#4598801 - 12/09/17 08:39 AM Re: Metal Bandsaw Blade Tension [Re: CCI]
motor_oil_madman Offline


Registered: 11/29/09
Posts: 4860
Loc: Houston, Texas
There should be rubber on the wheels called tires.
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#4598951 - 12/09/17 12:10 PM Re: Metal Bandsaw Blade Tension [Re: CCI]
George Bynum Offline


Registered: 12/18/04
Posts: 283
Loc: Greenville SC
Originally Posted By: CCI
Only problem is on thin wall tube sometimes the blade will stop. It's a fairly fine tooth blade. I suppose it could have something to do with metal wheels on metal blade, maybe this is to be expected. On thicker material it cuts very smooth.

I tensioned the blade as much as seemed prudent with the hand wheel,it used to stop a lot, now it hangs up only on 1/16" material just as it enters the vertical component of the square tube.


My question is what "fairly fine tooth blade" means. I was always taught that there should be 2 teeth minimum in the material, so for 1/16 material, 32 tpi of finer. The way around that is with controlled feed where singe point tooling works.

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#4599619 - 12/10/17 08:04 AM Re: Metal Bandsaw Blade Tension [Re: 92saturnsl2]
CCI Offline


Registered: 07/15/09
Posts: 132
Loc: New Mexico USA

Tight enough is when the blade won't stop while the saw is running under a normal load/feed. I usually don't need to turn them too tight unless something is wrong with the saw-- I do it by feel, about a good snug plus another half a turn.

I got it to the point where the blade wouldn't stop, after removing the blade and cleaning everything, it seems tighter than I would have expected but I don't know anything about this anyhow.

Snug plus a little bit. The blade stretched a little after a few uses, another maybe quarter turn did it.

All of the ones I worked on had a rubber insulator on the metal drive wheels to grip the blade better. Perhaps this is worn off? Metal on metal might be a rather poor friction combo...

This is part of the reason why I think it might be really old. The wheels in their present state don't look like they are missing any rubber, they look like it was never there. The depth of the flanges that retain the blade from sliding up off of the wheels are just a little more than the blade thickness. If there was ever any rubber there, the flanges would have been ineffective. This thing also has a little gearbox that requires gear oil. It leaks, needs a new gasket, which I will have to make.

Is the tooth pitch/count appropriate for the material being cut-- do you know what it is?


I will get a count. It's pretty fine, probably OK for thinner stock. I don't know if it's fine enough for 1/16" wall square tube, but close.

I can see where this is going. Now I need to figure out where to buy blades. How are the sizes indicated? If it's by circumference, how does one actually measure that? Or center to center on the wheels?

I appreciate the help -- thank you!

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#4599628 - 12/10/17 08:13 AM Re: Metal Bandsaw Blade Tension [Re: George Bynum]
Langanobob Online   content


Registered: 04/24/09
Posts: 209
Loc: Reno, Nevada

Is there an adjustable hydraulic cylinder to control the feed rate? You might try slowing it down. Like George said you probably need a very fine tooth blade for 1/16Ē material. Coolant makes the wheels slippery and Iíve had some trouble with blades slipping when using coolant and I turn the coolant flow off when sawing difficult material. I mostly use a bandsaw for solid bar stock and it may be that a horizontal bandsaw is just not the right tool for cutting thin wall material, unless maybe that is all youíre cutting and you can keep a fine tooth blade on all the time. Otherwise itís a nuisance changing blades for the tubing.

About rubber tires, they are found on wood cutting bandsaws.

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#4599665 - 12/10/17 08:56 AM Re: Metal Bandsaw Blade Tension [Re: CCI]
92saturnsl2 Offline


Registered: 03/02/04
Posts: 1282
Loc: Flaherty, KY
Blade is measured in length, width and thickness. Something along the lines of 11' x 1" x 0.035. Most places sell common-size blades, and can create custom ones. Tooth per inch is the other variable-- this can be fixed (6 teeth per inch for example) or variable (e.g. 6-10 teeth per inch). The variable ones handle a greater range of material thicknesses with less performance loss.

I've used primarily Ellis metal-cutting saws that are only air cooled, and these have the rubber "tire" on the wheels to grip the blade. There is no flange to retain the blade-- the proper tension on the blade centers it just fine unless something is damaged on the saw (guides, bearings, etc.)

At shops I've worked in, we cut material of all sizes/thickness and do not change the blade between them, rather change the load/feed so as not to damage the blade when cutting a material size not appropriate for the tooth count.

I my own experience, a 4-6 or 6-10 TPI is acceptable cutting anything over 1/4" thickness. 8-10 and 10-14 can easily handle down to 14 gauge (~ 1/16) provided you have your feed rate set correctly. There is some tables you can look up online that suggest how many teeth should be making contact with the given material. This is not a hard and fast rule, however and you cannot get it perfect for all situations. For example angle has two legs, tube has two walls plus a flat side, so the number of teeth making contact will vary wildly depending on where the blade is in the cut.

If the tension is right and saw is configured/set up correctly, if the blade is mismatched you will either get poor cutting performance or sheared off/dull teeth-- the blade shouldn't actually stop. Too much tension and the blade can snap, and you will shorten the life of the bearings in the saw guides/wheels.

You can literally count the tooth per inch -- if it is not consistent (varies at different places of measurement) you have a variable TPI. Most blades intended for ferrous metal are raked meaning the teeth are slightly offset from center in each direction.
_________________________
1985 F-250HD 7.5L 4x4 135k- Maxlife 15w-40 HDEO [for sale]
04 Odyssey EX 180k PUP 5w-40
96 Maxima GLE 248k Castrol Edge 5w-50
07 Chrysler Pacifica Limited

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