Bandsaw tension

[rst rob]

Hi all just got a new bandsaw with no lever for tensioning the blade, record 250.
Would normally leave the blade un tensioned at work but thats a far bigger blade but seems be be a bit of a faff without a lever was wondering if anyone else has the same model and if they have had issues leaving the blade tensioned.

 

[deema]

I would highly recommend you take the tension off. The smaller bandsaws have bearings that have a very short mean time between failure under tension. There are a few tests I’d recommend that we did on a SCM S45 to determine its actual capability. I would also suggest you familiarise yourself with how the blade tensioning system works, it’s incredibly ease to destroy the tension spring. The following thread we wrote goes into a lot of detail on the setup and limitations of a bandsaw.

https://www.ukworkshop.co.uk/threads/scm-minimax-s45-bandsaw-teardown-overhaul.135069/

 

[Spectric]

I purchased a BS400 bandsaw and one of the buying decisions was because the 400 had the tensioning lever but the 300 did not, it cannot be good to leave a machine fully tensioned as the strain on the frame cannot be good and then as said the bearings which will be point contact when it is not running.

 

[yetloh]

I would highly recommend you take the tension off. The smaller bandsaws have bearings that have a very short mean time between failure under tension. There are a few tests I’d recommend that we did on a SCM S45 to determine its actual capability. I would also suggest you familiarise yourself with how the blade tensioning system works, it’s incredibly ease to destroy the tension spring. The following thread we wrote goes into a lot of detail on the setup and limitations of a bandsaw.

https://www.ukworkshop.co.uk/threads/scm-minimax-s45-bandsaw-teardown-overhaul.135069/

...and blades last onger before they break - especially the bimetal variety.

Jim

 

[sams93]

Having gone through the process of repairing a second hand bandsaw which somehow ended up with worn out bearing hubs in the wheels, unknown as to the cause but potentially something like this could have contributed, I always make sure to untension my bandsaws when they arent in use

 

[Ed Weber]

I have never released tension on either of my bandsaw's except for blade changes, no bearing issues to date.
One saw is a 14" Asian import Delta clone, 20 years, The other is a 5 year old steel frame 17" saw.
This is a vanilla, chocolate debate unless and until, someone can supply actual evidence. Not anecdotal stories.

 

[Ttrees]

Actual evidence of wheel bore wear would likely thin things down to the few machines out there with foot mounted motors, so the saw could be accurately set up in the first place.

The same could be said for the rubber I suppose, though that being highly variable.

Evidence of blade damage (on a bandsaw) I would imagine could be nearly as variable
as all the rest.
Here's an excellent thread from Van Husky regarding the differences in various types, from a pragmatic standpoint, (a very experienced users point of view)
https://sawmillcreek.org/showthread.php?149862-Lets-talk-bandsaw-blades
All that said, I detention mine, it only takes a few turns with such a hefty thread.
There's some mention of stress cracks from sharpening yer own blades on the Cook's sawmills YT channel, so that could be added to the discussion for those with machines capable of handling 1" blades.

If those things were addressed, then we'd have a much clearer picture on things.

 

[Ed Weber]

I agree, but considering the thread in your link was from 13 years ago and nothing has changed, I'm not sure we're any closer to knowing anything as fact.

 

[deema]

I agree, but considering the thread in your link was from 13 years ago and nothing has changed, I'm not sure we're any closer to knowing anything as fact.

Read the thread we wrote and I linked. I go thorough the detail of the bearing design life. MTBF is just that, average time to failure, that means some will last a lot longer and some a lot less. It’s about the design parameters that are selected. One thing that is certain, leaving static tension on a bearing will reduce its life.

 

[Sideways]

Read:
https://en.wikipedia.org/wiki/Brinelling

 

[Ed Weber]

Yes and this leads to the inevitably sarcastic comment,
"do you put your car on jack stands every night so you take the pressure off the bearings'?

If the tool is designed properly, the bearings will not need any addtional type of maintenance.
Also, there is material fatigue Fatigue (material) - Wikipedia
Cycling the pressure on and off of the machine and blades, can have it's own negative effects on all the parts under pressure.

Yes, bearings and other parts wear, but IME there has been no appreciable difference between the two approaches of relieving tension or not.
As I said in the earlier post, factual evidence is required, I have yet to see any.

 

[--Tom--]

I do so I can reduce the price per use of my fancy schmancy Starrett blade tension gauge. If I left the tension on I hate to think how much that thing would cost me per use

(And I got it “cheap” on eBay)

 

[deema]

Yes and this leads to the inevitably sarcastic comment,
"do you put your car on jack stands every night so you take the pressure off the bearings'?

If the tool is designed properly, the bearings will not need any addtional type of maintenance.
Also, there is material fatigue Fatigue (material) - Wikipedia
Cycling the pressure on and off of the machine and blades, can have it's own negative effects on all the parts under pressure.

Yes, bearings and other parts wear, but IME there has been no appreciable difference between the two approaches of relieving tension or not.
As I said in the earlier post, factual evidence is required, I have yet to see any.

Im guessing you haven’t read the linked thread I highlighted earlier. It answers your ‘sarcastic comment’

 

[TRITON]

Not sure about this on.off tension thing.
I've a basic RP 250 and its basically had the tension on the entire time I've had it, which is now over 20 years.
But far as im aware being in tension all the time is supposed to weaken the blade, by allowing it to stretch, but that said, and maybe in my own case and with a smaller saw, the tension isnt high enough to cause the blade any problems.

Plus, my bikes are full suspension, which due to the suspension shock unit have tension pretty much all the time. Being in tension doesnt seem to have caused the bearings any issues.

 

[rst rob]

Not sure about this on.off tension thing.
I've a basic RP 250 and its basically had the tension on the entire time I've had it, which is now over 20 years.
But far as im aware being in tension all the time is supposed to weaken the blade, by allowing it to stretch, but that said, and maybe in my own case and with a smaller saw, the tension isnt high enough to cause the blade any problems.

Plus, my bikes are full suspension, which due to the suspension shock unit have tension pretty much all the time. Being in tension doesnt seem to have caused the bearings any issues.

Brilliant if you have had no problems in twenty years with the same bandsaw think I'll take the risk.

 

[paulm]

Brilliant if you have had no problems in twenty years with the same bandsaw think I'll take the risk.

I've had my startrite for 35 years, never released tension except to change blades obviously, no problems with mine either !

 

[Daniel2]

My bandsaw (Agazzani Rapid 600), lives with the blade tensioned.
Made in 1985 (I bought it circa 2000), is still on it's original bearings.

 

[yetloh]

Speak as you find. I have had premature breakage on expensive bi-metal blades with tension left on but lost none since I got the de-tensioning habit, so it has saved me money. My bandsaw is not in daily use which probably makes a difference.

Jim

 

[deema]

Page 5 of the link highlights the difference between dynamic and static loading of bearings.
The decision to leave a bandsaw under tension is up to the individual, but the technical data is clear, leave the tension off.

 

[Spectric]

It just sounds wrong to leave a machine with the blade fully tensioned, rather than take any chance it must be better for all the mechanical components to be in an un stressed state when not in use. Just think of the rubber tyres, in use under tension they are rotating but under tension and stationary means that just part of the tyres are sitting there under load, if you leave a vehicle standing for a long period of time you can get flat spotting on the tyres due to only a small patch of tyre taking all the weight.