Blade Tension

[Brewzur]

I bought an old Norwood MX90(?) and rebuilt it, it just has a acme screw for the blade tensioner without any kind of gauge and I have been tightening it to about 1/16", 1/8" blade deflection, does this sound about right? Also should I relieve the tension when the mill is not in use, overnight etc?

[tcsmpsi]

There will likely be more scientific answers.  I have a similar set up.  It came provided with nominal torque on a torque wrench to gauge by.  That didn't work too well, but was a place to start.  Different blades work better at different tensions.  Setting up a new manufacturers blade, I watch the flutter of the top of the blade (run the tension until there's no flutter), stop it, then check its tone (like plucking a guitar string).  For manufactured blades I have already used and tested, I just go by the tone.  As a general 'rule', I run the blades with as much tension as they will hold up to.  On the bandmill and the bandsaws, I always relieve the tension at the end of the day.

[bandmiller2]

I really can't add much but my mill has a large spring.I tighten until the coils bind then back off some.I think most folks use too much tension,a even set, sharp band dosen't have to be fiddle string tight. Frank C.

[thecfarm]

Brewzur,welcome to the forum. Is this the first mill for you? What's all the lumber going to be used for?

[Brewzur]

Hi cfarm, yes this is my first mill and it has been a lot of work to get it up and running, I'll get a picture up soon.

The lumber I cut up first will be for fencing, loafing sheds etc. mainly to get practice milling, my "convincer' for the wife to get the mill will be cutting up old growth s/p/f from an old barn into flooring

[sgschwend]

The flutter test is one recommended even by saw manufactures.  Your Acme screw likely pushed against a spring?  If not I would guess you may/are missing a part.

Not using a sharp saw can cause all kinds of milling problems.  So my recommendation is to keep track of your saw run time and change the saw while it is still sharp.  The run amount varies with machine but 500 bf is a good starting point.

[redbeard]

There should be a common measurement from the manufacturer of where the spring is compressed too! if not measure it yourself when you are trying different tensions and remember that one that works best. There are gauges that work between two washers if you are looking for accuracy, most of the name brand mills have them available. I run my bands at 1000-1200 psi my best results are at 1000 just my 2 cents!

[Log-ic]

I had similar problems with bands that would't perform too well, so I suspected blade tension to play a role.  After reading an interesting report on www.valuetowood.ca I bought a tension meter from Lenox. This confirmed one of the statements in the report: The reading on the manometre of your mill does not necesseraly reflects the true tension in the band. Worse: the recomended manomater pressure in your mill's manual is often a wrong value to start with.  Once you know how much pressure the manometer must indicate in order to have the right strain on the system for geting the right saw stiffness things will go much smoother.  It's alike with many things: you need to measure in order to know...