Bandsaw tension spring ???

[DaveO]

Has anyone ever replaced the stock bandsaw tension spring with an aftermarket spring like this one -
Cobra Coil Bandsaw Tension Spring

I have been having problems getting good tension on my Griz BS. I am getting a curved cut during re-sawing with a 3/8" blade and the tension tightened all the way. I fear that my spring is just compressing and not transferring the tension to the band.
If anyone has done this I would appreciate any heads up on the impending pitfalls, and thoughts as to if the change made a improvement or not.
TIA, Dave

 

[junquecol]

I put the Carter one from Woodcraft on my Delta 14" some time ago. The stock spring had seen it's best days. Don't do a lot or resawing though.

 

[DaveO]

Bruce, did you find that it made an improvement?? Reduction in the amount of cranking on the tension knob to get proper tension, or just a better cut ???

Dave

 

[GregSmith]

Haven't tried the aftermarket springs, but I had a problem with the same Grizzly bandsaw. I kept losing tension and then finally the adjustment locked up. Turns out the adjustment nut was jumping threads and the blade would lose tension. When it finally stripped out, I broke the knob off the top and had to use a pipe wrench to get the thing apart. :-x
A guy at work made me a replacement in the machine shop and it works great now. Resawed some 6" Poplar today and it works great with the factory spring.

 

[DaveO]

Greg, I don't think that is the problem that I am having. I took the whole assembly apart today, and the threads look perfect. I can tighten the tension knob until it stops and still be able to deflect the blade with my finger about 3/4" to either side.
The only other thing that I can think that could be going on is that the stop on the rod that is lifted by the tension quick release lever has slipped and I am not starting with enough tension and can't crank it up enough to compensate. I will check that out tomorrow, and see if there is any room for adjustment.

Dave

 

[junquecol]

Bruce, did you find that it made an improvement?? Reduction in the amount of cranking on the tension knob to get proper tension, or just a better cut ???

Dave

My old spring had simply had too many trips under tension. It had two settings, none and colapsed. So ANY spring was an improvement. If you don't have an Iturra Design Catalogue, by all means get one. They are free, but because of such they are incrediably slow in arriving. It is the bandsaw bible. They only have an 800 number, no web site as I best remember.

 

[Travis Porter]

I bought the one from Iturra, but I think it is the exact same one as Carter. IMO, it made a big difference. IMO, if you are putting your tension up all the way, either the blade has stretched or your spring is shot. I would believe the latter more so than the former.

 

[toolferone]

The Carter spring at WC is only $20, but on sale 20% ($15.99) off until March 2nd. FYI

 

[DaveO]

Blade stretch is a possible cause, the blade isn't new but it also isn't heavily used. I see no movement as I am tightening the tension knob, just the spring compressing. I will probably try both the spring and a new blade.
Hey Tom, do you deliver :lol: :lol: :lol: :lol:
Dave

 

[rhett]

What is the TPI of the blade you are using. I had a similar problem with my Powermatic. Found that the blade I was using just had to many teeth to effectively clear the dust. I have since switched to a 1/2 inch 3tpi hook-tooth blade and had excellent results.

 

[toolferone]

Dave, I was thinking about the saw on the way home and I am not sure we fixed it. It is still possible the old blade was stretched some or mismade. If you put a 1/2 or 3/4 blade on will you be able to tension it? I think it still might be necessary to either change the spring or remove that blade release and use the tension knob the original way.

 

[DaveO]

Tom, I will have to try that out. But I thank you for coming over, delivering the needed parts (spring and new blade), bring Sophie to play with Ava, and helping me to get my saw running right. With what we did, it is performing like it used to. I will try the tension adjustment with some other blades, and hope that we got it fixed.
Ava wants Sophie to give her a call sometime to come by and hang out again :-D :-D They're so grown up :lol: :lol:

Dave

 

[sapwood]

Hope you guys got 'er going right. Woodworkers Journal had an interesting article on bandsaw tensioning this month. The gist of the article was to "Bust the Myth" that folks should replace original springs with stiffer ones. They claimed to have tested various springs and tension gauges. Their conclusion was that OEM springs tensioned to the manufacturers markings are generally accurate. A spring is maxed when the coils touch. Further tensioning can result in breakage/bending of tensioning system or stretching blade. A fully compressed spring is not broken, nor has it failed. The operator has exceeded the design limits of the saw.

The article was researched by Mark Duginske and Aaron Gesicki and I'm not endorsing nor condemning the article. Just relaying what I read :mrgreen:

Roger

 

[Toddler]

That sounds about like what Nick Engler says in his book. He also says running with the spring fully compressed is bad because it means any shocks are transmitted directly to the bearings and the frame, and not softened by the spring.

My Steel City has two tensioning springs. I think they're the same as the ones used on their 18" and 20" saws and that there's some serious overkill built into the saw. Maybe it means I'll never need to maximally compress the springs.

However, all that doesn't mean you don't ever need to replace a spring. Dave is far from exceeding the design limit on his Grizzly with the blade width in question. Metal does fatigue and even spring steel can take a set if you leave your blades tight all the time. Hopefully a new spring or unstretched blade is all that is needed.

Todd

 

[Gofor]

Y'All forget the speed at which Dave works. As fast as he turns out projects, the wood is moving a just below Mach 1, which can induce friction heat just from the air movement!!. Poor blades are stretched to the limit and just can't hack it!!
Just a note, they do sell tape measures made of non-stretching fabric that can also be used to measure the overall length around curves, like for a bandsaw. Look for a surveyers' tape at the local borg. (Most seamstress tapes are only 60" long so won't work). A lot of real estate agents have them because they are easier to use and rust free. Call a realtor and after she measures your house for square footage, and before you tell her you decided you really don't want to sell, ask to borrow her tape to measure the max/min length for the saw.:rolf::rolf: Of course a piece of the strapping material used to band pallets will also work.

Go

 

[gator]

Greg, I don't think that is the problem that I am having. I took the whole assembly apart today, and the threads look perfect. I can tighten the tension knob until it stops and still be able to deflect the blade with my finger about 3/4" to either side.

Dave

I'm jumping in here a little late but I have been in Florida for the past week. The fact that with the tension all the way tight and you sitll have 3/4" play in the blade would tell me that the blade is too long. It could either be stretched or just plain too long from the git-go. If your old spring allowed you to bring the top wheel all the way up to where it almost touched, or touched, the top of the upper cover that also tells me the blade is too long. If the spring fully compressed and the top wheel wasn't up to it's full available height, then the spring might be the culprit.

George

 

[DaveO]

What was going on was a wierd situation. It appears as Griz. just modified an existing BS design and added a quick-release lever to the tension system for the 0555Z. The way it was set-up the bearing surface for the tension was the quick release lever assembly. The spring wasn't actually in play with the tension system. I could completly compress the spring and not have any change in the tension. Not the best desgin:BangHead: Tom came over and we adjusted the assembly so that the bearing surface was the spring and not the lever. The lever still provides some tension release but not enough to change blades, I'll have to manually crank down the tension for that. But now the saw is cutting like it use to, a new 3/8" 6TPI blade re-sawed 5" Maple into a uniform 1/8" slice, with the original spring :eusa_danc :eusa_danc . I still have to see if our adjustments will still allow me to get proper tension with a larger blade, but if not I can make those ajustments as needed, now that I know how it all works.
Dave