Chain Sharpener Gravity Spring

[Wood Doctor]

I figure that this thread title would catch your eye. Who ever heard of a gravity spring for a chain sharpener? Seems like every three to five years the return spring on my Oregon 511A snaps suddenly with a loud pop and the wheel sometimes crashes down on the chain being sharpened. This just happened to me again, so I decided to make a temporary invention after ordering a new one. The idea was to replace the spring with gravity to help pull the wheel back up after each cutter was sharpened:

Using a 1/4" bolt, I attached an 8-lb splitting wedge to heavy pull cord on one end and looped it through a pulley that I fastened with a screw eye to the back of the sharpener's mount with a 1 x 1 oak stick. I tied the other end of the cord to the handle on the sharpener. Here's another view with the sharpener in the grinding position:

The counter weight takes the load off the grinding wheel, similar to what the spring does. The cord is just long enough so that the weight almost reaches the floor. The back view shows the attachment. I used one bolt in a threaded hole and that allowed me to pivot the stick to the exact position for tightening:

It may seem goofy, but this invention works so well that I could almost say good bye to the sharpener's spring. Thanks for looking. Comments welcome.

 

[Chainsaw Jim]

I wonder if taking some temper out of the spring would help. It seems they're too hard and brittle.

 

[Wood Doctor]

I wonder if taking some temper out of the spring would help. It seems they're too hard and brittle.

Good point. I also wonder if they have any data showing how frequently these return springs snap. I doubt I use mine as much as some shops do, so commercial sharpening shops may break one or two springs a year. Replacing them is not exactly a cakewalk either.

 

[kingOFgEEEks]

I like it.

 

[cease232]

Nice job. Must be newer springs. My old 511a spring has never been replaced.


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[Wood Doctor]

Nice job. Must be newer springs. My old 511a spring has never been replaced.
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Hard to believe but this will be my third spring. Two have already given up. Heck, maybe I use it more than I think. One thing for sure, when they snap, it's about the same sound that a 22 rifle makes and the motor and disk drop like a stone.

 

[huskihl]

Could put a junk Chinese one in it. Lol. Mine has been fine for 2 years now.

Junk Italian crap, anyways

 

[srcarr52]

Could put a junk Chinese one in it. Lol. Mine has been fine for 2 years now.

Junk Italian crap, anyways

It's saying, "Go get a coffee!"

 

[Wood Doctor]

Could put a junk Chinese one in it. Lol. Mine has been fine for 2 years now.

Junk Italian crap, anyways

I have you beaten so far. This spring lasted for 4 years. It might be an Italian spring, but who knows? The original that came with the 511a also lasted for 4 years. Therefore, I got about 8 years out of two springs. Regardless, my invention would probably outlast them all.

 

[beaglebriar]

A friend of mine with a little dealership down the road has his rigged up with a rubber tarp strap stretched between the grinder and the ceiling. Must be more reliable than the spring because it's been that way for as long as I've known him. He sharpens a *s-wordpile of chains..

 

[Wood Doctor]

A friend of mine with a little dealership down the road has his rigged up with a rubber tarp strap stretched between the grinder and the ceiling. Must be more reliable than the spring because it's been that way for as long as I've known him. He sharpens a *s-wordpile of chains..

The rubber tarp strap might also work rather well. The return force would go up the further the disk dropped. In my invention, the return force remains constant and the motor picks up leverage the further down it goes. However, that works a bit to my advantage because at the halfway point, the motor and disk barely move and will hold balanced about 4" up from the chain.

It takes a little getting used to, but the motor's weight when near the contact point with the chain's cutter applies some pressure that assists in the grinding. The rubber tarp strap (and the spring for that matter) are always pulling the disk and the motor away from the chain. I suppose I could add a few pounds to the counterweight so that the motor's weight is perfectly balanced when the disk meets the chain's cutter...

 

[Wood Doctor]

Just thought I would close out the thread with good news. I received the replacement spring today and installed it. Yes, it took a few tools and some know-how, but it's back in normal operation. That also gave me a chance to clean up all the iron grinding powder that was scattered all over the place. I also redressed the grinding stone.

To be sure it all worked again, I found a used chain and sharpened it. Looks good, so all systems are Go! Dang, guys, I still like this 511a. It's been my friend for years.

 

[RI Chevy]

Cool. Good deal.