Tensionor on band saw mill

[welderskelter]

 If I use rubber tires on my mill will I need a spring tensionor or just let the rubber tires take care of it. Thanks Harold

[Tom]

I would think that a combination of the both would be desirable.  Tension in a band is important to its performance. You will find yourself changing bands frequently and a tensioning device will shorten the time it takes to do it.  You could add air or deflate tires to get the proper tension, but it seems to me that it would be mighty time consuming.  The tires are more of a road for the band to travel upon.  I think I would want to find how they best did that job and leave them alone.

[welderskelter]

I guess I was wondering more of whether I needed a spring tensionor or not. Yes, I would have a way to back it off to change blades but if I am right I believe a blade changes length as it goes under power. Just checking. Thanks Harold

[Tom]

A band is under constant movement.  It responds to the tension of being on the mill, the tension of engaging the wood, the heat from sawing, the resistance from a continually dulling blade, as well as the resistance from different species of wood.  It's length is effected by a stretching, heated band as well as the members of the mill giving up their rigidity.   Bands are tensioned by hydraulics, weights, spring and I guess by the auto-tires on a mill that has them.  The fastest and most accurate of the tension devices is the spring tensioner I think. 

Yes, I would say that a tensioning device is necessary and I would lean toward a spring, first and hydraulics second.  The hydraulic tensioner might be the easiest to measure.  I would not rely totally upon the air in the tires. 

[edwardj_]

I am still in the planning process of my mill yet.  I am kinda puzzled on how a spring tensioner would work on a mill.  Dont you want it to be a constant tension?  Do you have a link to some pics of one?  The small "Jobber 200" we have at work I have been trying only has a screw tensioner to adjust the tension.  It moves the idler side pulley...

[Tom]

Hydraulic tensioners apply constant pressure (reasonably).  The oil heats from the sun and cools from the wind causing the tension to change.  But, for all intent and purpose it is steady.  That is good from one aspect, but there is also an argument against it.  You see, when the band goes from soft wood to hard wood, like encountering a knot, there is no give at all and the band is jammed into the hard wood causing it to push off and rise over the knot.

Springs are so stiff that they are pretty constant too.  But, a spring, when something catastrophic happens at the band, will give a little, kinda like a shock absorber and the band stays on line. These springs aren't your ordinary little coiled springs like you find on a ball point pen, they are very stout and it takes a lot to move one.  A screw is used to tension the spring.

With either type of tensioning you will find some who swear by one and some who swear by the other.  Either one gets the job done.

'the only problem with spring tensioners is being able to measure the tension.  You just have to depend on yours or someone else's measurement.  when the spring is worn and relaxes, you don't know what kind of tension you are applying to the band. 

With hydraulic tensioners, you have a gauge that measures the pressure being applied  by the oil to the ram that is tensioning the band.  That doesn't give you the tension of the band, only that it is tensioned properly.  You can apply that tension regardless of whether you are low on oil or in hot or cold weather by looking at the pressure gauge.

Screw tensioners make a solid bar-like connection from one wheel to the other.  The slightest heating of the band or vibration of the screw can change the tension. There is no give anywhere and that tends to abuse the band and the mill.

Some of the old resaw bandsaws and band head-rigs where the bands were up to 12 inches wide and the wheels required a three story building, were tensioned by weights, much the same as a Grandfather clock.

All of these tensioners operate by moving the idle side wheel.

[customsawyer]

I have run the hyd. type and also the air bag type I would have to say that I get by better with the air bag as I don't have to adjust the tension once the blade is on the mill.

[bandmiller2]

Hal,above is all good advice,what is ideal is something fast and repeatable.If you have compressed air and your mill is stationary I'd go with that.If your running a road show probibly spring makes the most scence.I used a heavy spring with a screw and handwheel adjust,you can have a pointer to repeat spring compression by measuring its legnth.You need something to give,of course you will have the inflated tires,for that requirement. Frank C.

[moonhill]

My mill uses a screw type adjuster, no springs or other such items involved.  A large T-handle to lock the even larger adjustable T-handle, quick and simple.  I have never had any part fail on this system, with the exception of over tightening the band in my early years.  The bearing went bad and caused the shaft to wear as well.  Bring the band tight enough to see the slack go taunt I then turn 1/4 past that. 

Tim   

[shinnlinger]

My Turner only has tralier tires and a long bolt to set tension.  Works well, but I wish it was quick relase as it is nice to be able to take the pressure off easily.  I am thinking using something from a metal cutting chop saw clamp to set a tensioner. 

[fishpharmer]

You may want to try something like this.  Not pretty but functional.  Also, releases rather quickly.  Once you figure out where you need to set the tension for cutting the threads can be marked for repeatability. 

[bandmiller2]

What about one of those load binders with the spring ,also have an adjustment eye bolt quick tension on and off. Frank C.

[punking315]

I built my own sawmill. I made a threaded tensioner on the idler side, with no springs or hydraulics.

The saw has 4.80" x 12" tires as wheels. I don't have any problems with this setup.

[welderskelter]

Thanks for the help and pics. Keep them coming. I think there are a lot of guys out there besides me that will appreciate the knowledge that is available out there. Thanks  Harold

[Fla._Deadheader]

 Check my gallery for lots of pics of our home made mill, W/ tensioner.

[solidwoods]

I'd go with a Gage that shows tension.
Inflatable wheels can change pressure with temp changes.
jim

[mikejp]

Hey everybody. My first post here. I have learned so much from this forum. I am building a mill and have a air bag. If I want to use it what air pressure should I run for proper tension. I also have a hydraulic set up off of a timberking b20. So I have options. Thanks for a great place to learn. Mike

[Magicman]

Hey everybody. My first post here.  Mike

Welcome Mike to FF....

[coastlogger]

mikejp I had this very question and John Bartley gave me the info I needed, search his post for May 19 2009. Basically you measure the stretch in your band to arrive at the right tension. Worked for me.
clgr

[mike_van]

I use a good size die spring. Toms posts about changing tension are right on the $$$

[Mr Mom]

I used a car jack.

Thanks Alot Mr Mom

[bandmiller2]

Mike, have a pressure gauge on your air bladder,keep adding air slowly until the band runs smooth without fluttering just say its 40lb add a little more say 45 and try it.In outher words use the least tension you can to cut right then remember that pressure.No one here  can give you an exact pressure too many variables.Frank C,

[bandmiller2]

Its probibly safe to say if you use tires for bandwheels you don't need a spring on your adjuster.Something quick and repeteable is a big plus something like a HD loadbinder the over center feature would make it as quick as anything and repeteable.Always good form to relieve the tension on the band when done,especially with tires as they tend to take a set if left with tension untill they run a wile.Frank C.