Odd tension spring size Powermatic 140

[Tyler Keniston]

Hi all.

I am considering replacing the tension spring on my Powermatic 140 bandsaw. It is circa 1960 and I believe it likely the spring has seen better days. I immediately checked out Iturra and Carter, but the dimensions for my spring are odd. The rod inside the spring is 1/2". OD (or hole fit) seems to be around 13/16" inch and the length is around 2 3/4".

Does anyone know about getting spring in this odd sizing?

I am thinking I could (and might have to) get away with the 3" iturra spring and simply replace the 1/2" rod with a narrower one. It just bums me out a tiny bit to downsize the rod from the original (I like the look of the hand crank and like things to be beefier than they probably need to...
Any suggestions?


Thanks,
Ty

[Mike Cutler]

You might want to size a Carter Cobra Coil. Changing that rod may not be as easy as it appears. There is a T-Nut in the tensioning mechanism that may need to be changed.

Unless your spring sat fully tensioned for a very, very long time. Young's Modulus and Hook's Law says it's probably still be good.

[Tyler Keniston]

"Unless your spring sat fully tensioned for a very, very long time. Young's Modulus and Hook's Law says it's probably still be good."

Yeah this is one of those things I have heard lots of differing information about, and not being educated on the matter enough myself, I can't help but err on the side of needing a replacement in the chance it does help. Perhaps it will not I don't know for sure.

I'm not worried about replacing the rod, I've taken the whole assembly apart before no problem. I don't remember a T-nut but perhaps i'm forgetting (do you mean the square nut?).

The cobra is similar in dimensions as the iturra, only not as long.

-ty

[Mike Cutler]

Yep, the square nut, sorry about that. When I changed the spring on my Jet I also replaced the rod, and had to make a square nut for the new rod.