Remove Blade Tension For Overnite?

plaindriver · August 11, 2013, 10:08:33 AM

On a small manual mill, is it necessary to relieve the blade tension when thru for the day? I heard that leaving the tension tight, overnite, could cause a flat spot on the belts. And if it is a good idea to relieve the tension, should I do it just a little bit or a lot? Thanks.

tyb525 · August 11, 2013, 10:17:56 AM

I don't know how the tensioner works on your mill, but my LT10 has a handle which either totally tightens, or totally releases the tension. I release mine at the end of the day, it's too easy not to.

Jeff · August 11, 2013, 10:45:04 AM

I always release mine. I have a hydraulic tensioner on my 87 lt30. If you leave it under tension for extended periods, you have troubles.

Here is a topic on that. Included in that is a document uploaded by sparks on the procedure for refilling the tensioner

dgdrls · August 11, 2013, 12:15:15 PM

Yes, yes

http://www.suffolkmachinery.com/six-rules-of-sawing.html

"ALWAYS DETENSION YOUR BANDS

When you are done cutting for the day, take the tension off your blade. Band saw blades, when warmed up from cutting, always stretch; and upon cooling shrink by tens of thousandths of an inch each cooling period. Therefore, blades, when left on the saw over tension themselves and leave the memory of the two wheels in the steel of the band, which will cause cracking in the gullet. When you leave the band on your saw under tension, not only do you distort the crown and flatten out the tires (which makes them very hard), but you also place undue stress on your bearings and shafts. Believe it or not; you can, and will damage your wheel geometry sooner or later and considerably shorten bearing life. You are also crushing your tires or V-belts."

Magicman · August 11, 2013, 01:34:24 PM

I detention when I shut down for lunch. At the end of the day, I remove the blade and clean the bandwheels.

scully · August 11, 2013, 09:13:04 PM

dered thNow here's a topic I should learn more about ! never considered how important this can be ..........

fat olde elf · August 11, 2013, 09:29:35 PM

Always release at the end of the day,,,,

Chuck White · August 11, 2013, 10:12:57 PM

I never leave a band on overnight!

I even loosen the tension (completely) when we take a break!

nk14zp · August 11, 2013, 10:56:08 PM

What about circle mill blades?

Brucer · August 12, 2013, 02:38:19 AM

I doubt that a blade that's "warm" from sawing will shrink enough to seriously increase the tension. Never seen it happen. I also doubt that the band will "remember" the pressure from the two wheels. It certainly doesn't "remember" being coiled.

However ... with a hydraulic tensioner, the sun shining on the black body can raise the temperature of the hydraulic fluid enough to force the blade tension right off the scale. If you leave the mill sit like this for several days you'll be alternately loading and unloading the bearings and the bandwheel belts in exactly the same spot. This could give you some issues.

If you're going to travel with a blade on the mill, you should keep a little tension on it so it doesn't vibrate off the mill (someone once brought me a blade that they found beside the highway -- wasn't my brand of blade, though).

If the weather is dry and the blade is still sharp at the end of the day, I'll leave it on the mill and drop the tension down to around 20% of normal.

bandmiller2 · August 12, 2013, 07:42:16 AM

I don't know if leaving a band tensioned will harm it and/or the mill, never have on my bandmill.Its good form to release most of the tension.I have operated outhers bandmills that were left tensioned,they would thump for a wile then smooth out with no apparent harm done.Its a moot point for me as I usally remove the band for sharpening at the end of the day.Shop bandsaws are left tensioned as are band hacksaws.If the mill is where someone might flip a switch or start the engine I would leave just enough tension so it won't flip the band off damaging the teeth. Frank C.

Chuck White · August 12, 2013, 07:52:49 AM

In the past, I've learned that leaving a band on the mill for an extended period time, even a 2-hour lunch break will result in rust where the band was in contact with the band wheel belts! ;)

Jeff · August 12, 2013, 08:11:08 AM

Quote from: nk14zp on August 11, 2013, 10:56:08 PM
What about circle mill blades?

Circle mill blades have no reason to be dismounted from the mill until you are changing them out for some reason.

LeeB · August 12, 2013, 09:16:02 AM

Quote from: Brucer on August 12, 2013, 02:38:19 AM
I doubt that a blade that's "warm" from sawing will shrink enough to seriously increase the tension. Never seen it happen. I also doubt that the band will "remember" the pressure from the two wheels. It certainly doesn't "remember" being coiled.

I don't know about the coil, but a warm blade that has been adjusted while sawing will most definitely cool and increase tension considerably. Seen it with my own eyes. Increased by 400psi.

grweldon · August 12, 2013, 09:18:21 AM

Well, since I no longer have the same memory as I used to, can anyone tell me a good way to REMEMBER to detension the blade every time? I know, get in to a routine, but I don't much so I don't yet have a routine. I'm thinking something like a "Don't forget to detension the blade" label on the mill, but then I'll just forget to read it!

LeeB · August 12, 2013, 09:21:28 AM

Remind me what it was we were talking about.

dboyt · August 12, 2013, 10:14:41 AM

Quote from: grweldon on August 12, 2013, 09:18:21 AM
Well, since I no longer have the same memory as I used to, can anyone tell me a good way to REMEMBER to detension the blade every time?

Opposite problem here. I'll forget to re-tension the blade before starting up and throw it off the bandwheels. Maybe some sort of switch that won't let me throttle up the engine unless the blade is under tension. There are limits on how idiot-proof you can make something, but the ways I find to mess things up seem to know no bounds.

thecfarm · August 12, 2013, 10:28:27 AM

Magicman hungs his apron on the lever. I wonder if a piece of string/rope from the switch to the lever would do it?

grweldon · August 12, 2013, 11:11:57 AM

Quote from: dboyt on August 12, 2013, 10:14:41 AM
Quote from: grweldon on August 12, 2013, 09:18:21 AM
Well, since I no longer have the same memory as I used to, can anyone tell me a good way to REMEMBER to detension the blade every time?

Opposite problem here. I'll forget to re-tension the blade before starting up and throw it off the bandwheels. Maybe some sort of switch that won't let me throttle up the engine unless the blade is under tension. There are limits on how idiot-proof you can make something, but the ways I find to mess things up seem to know no bounds.

Oh, yeah, I forgot that I have that problem too!

Jim_Rogers · August 12, 2013, 11:47:52 AM

Quote from: bandmiller2 on August 12, 2013, 07:42:16 AMShop bandsaws are left tensioned as are band hacksaws.

In the furniture factory I worked in back in the 80's we never left band saws tensioned up over night, that I can remember.
I don't leave my bench top bandsaw tensioned up.
To remember to tension up before starting a shop bandsaw we place a piece of cardboard with a slot cut in it around the blade on top of the table that says: "Tension blade before using" on it.
So you have to move the cardboard sign before you can cut anything, so you should be able to see and read the sign when you have to move it.
I tension down my mill every night and at lunch times.

Jim Rogers

redprospector · August 12, 2013, 04:51:10 PM

I may be way off base here, but I take the tension off my blades if I'm going to stop for any length of time. Not for the sake of the band, but for the sake of the tires and band wheel's.
That thump, thump, thump you may hear when you leave the tension on over a few days isn't necessarily the blade (but it could be), it's more likely a flat spot squashed into the band wheel tires. Some times it goes away...some times it doesn't.

Andy

trapper · August 12, 2013, 04:56:46 PM

I hold a piece of paper over the key switch that says tighten band with a magnet.

Ga Mtn Man · August 12, 2013, 05:14:44 PM

I make a "test cut" to see if I remembered to tighten the band. It's 100 percent accurate and I never forget to do it ;D

Brucer · August 13, 2013, 01:26:59 AM

Let me clarify one of my comments. If a band starts to lose tension when I'm sawing, due to heat buildup, I immediately increase the flow of blade lube to cool down the blade. If that doesn't do the trick, then it's probably time to change the blade.

The odd time the cooling trick doesn't work (when I run out of blade lube in the middle of a cut) I will screw down the tension handle to maintain tension; and as soon as the blade begins to cool down I'll back off the tension handle.

So I'll never finish the day with a hot blade, or even a warm blade) on the mill.

But, how to remember to back off the tension? I follow a routine at the end of every cutting day.
Retract all the cylinders.
- Sweep down the mill.
- Back off the blade tension.
- Read the hour meter.
- Park the head.
- Put the tools away.
Doing the same thing every day makes it a habit. At least for me.

bandmiller2 · August 13, 2013, 08:00:43 AM

Any band should be relaxed when your done sawing.I've found the minimum tension will give you the longest life.It just seems so right to tighten the band when it starts to wonder but almost always its the set or keenness of the teeth causing the problem.Releasing tension is one of those habbits that should be second nature.My homebuilt mill uses springs and a handwheel with a handle.I like the WM hydraulic system with the gauge.Whatever you use make it easy so you won't be tempted to put it off. Frank C.