Bandsaw tension spring

[Jared Porter]

I have a Walker Turner 14" MBN935, 9BS6390 that I'm trying to get in working order.

The blade tension spring is 1"OD, .64"ID, wire diameter .174", length 1.4". I think the Walker Turner part # is BN22 or 310-1. I don't have any way of knowing how long the spring should be, how much it has compressed over the years.
I'm assuming the spring is shot because of the age and the likelihood that it was left tensioned. Anyone here with this saw or similar who knows what dimensions a good spring should have? I'm also looking for resources for replacements. I checked McMaster Carr but I didn't see anything that seemed close, plus I wasn't entirely sure what I was looking for.

Thanks in advance for any help.

[John TenEyck]

Ask over at OWWM.org. Someone will know. 'http://www.owwm.org/

John

[Jared Porter]

I did. I didn't really get what I was looking for, what length a new spring should be.

[John TenEyck]

From my perspective, the spring rate is the most important parameter. After that, I would put the longest spring in that will fit. It can't hurt, only give you more travel.

You can calculating how many lbs of force it will take to tension whatever the max. width blade is you intend to run on the saw, and that will allow you to pick a spring. Let's say you think that saw can handle a 3/4" blade. OK, to put 25K psi on a 3/4" x 0.035" blade will take about 656 lbs. It actually will take less because a 3/4" blade isn't really 3/4" wide due to the gullets, but that's a conservative number. So now you can look up springs that will give you at least 656 lbs force within their allowable compressed length. Pick something with an OD about the same as the old spring and fits lengthwise.

If you never plan to run a 3/4" blade then recalculate for whatever max. blade width and thickness you want and pick a corresponding spring. 25,000 psi x W x T = lbs spring force required.

John

[Tom M King]

Google die spring strength chart and you should find useful information, such as: http://www.industrial-springs.com/online-shop/technical-descriptions/die-springs