# 726 final drive sprocket groove pin?



## amuller (Jan 3, 2016)

The only consistent problem I have with this old machine is with the way the final drive sprocket is pinned to the shaft. It is supposed to be a solid 1/4" "groove pin" but that had sheared. (Probably why I was given the machine....) I have been using grade 8 1/4" bolts, but these only last a few hours before shearing. I've been assuming these are at least as strong as a groove pin but maybe I'm wrong about that. I've been thinking about drilling out the shaft and sprocket for a 5/16" or 3/8" pin or bolt but that would be a bit of a pain. Suggestions? Is this a common problem with these machines? Thanks.


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## micah68kj (Oct 8, 2011)

You must have something else going on. That's one of the *last* things that would break. Something out of line stuck or something hanging up? :smiley-confused013:
Groove pin. ... Are you meaning a roll pin?
This?


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## SnoThro (Feb 20, 2016)

Either replace the split pin that was there or try something like a Spirol pin which is essentially a split pin that's been rolled like a cigar to give it more strength. I'd only drill it if the hole is wallowed which will allows the drive play to hammer any pin or bolt until it breaks. If you do have to drill i'd go the next size up on a split or spirol pin as you'll have a lot more intermediate sizes as opposed to removing a lot of material to get a 5/16 bolt to fit.


Grade 8 and Stainless are harder and thus more likely to break than bend when put under load or hammered.


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## amuller (Jan 3, 2016)

SnoThro said:


> Either replace the split pin that was there or try something like a Spirol pin which is essentially a split pin that's been rolled like a cigar to give it more strength. I'd only drill it if the hole is wallowed which will allows the drive play to hammer any pin or bolt until it breaks. If you do have to drill i'd go the next size up on a split or spirol pin as you'll have a lot more intermediate sizes as opposed to removing a lot of material to get a 5/16 bolt to fit.
> 
> 
> Grade 8 and Stainless are harder and thus more likely to break than bend when put under load or hammered.


Well, I have sheared two today. I need to solve this or the machine will have to be retired.


Obviously the 1/4" grade 8 bolts aren't the answer! The hole is too close to the sprocket plate for 5/16" nuts/bolt heads.


I expect the holes in the the shaft and the sprocket hub are somewhat wallowed. Likely, enough that a 1/4" spirol pin won't stay in place. But I can go try to buy one locally and try it.


Obviously the 1/4" grade 8 bolts aren't the answer! The hole is too close to the sprocket plate for 5/16" nuts/bolt heads.


Maybe drill for a 5/16" spirol pin or groove pin?


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## UNDERTAKER (Dec 30, 2013)

amuller said:


> Well, I have sheared two today. I need to solve this or the machine will have to be retired.
> 
> 
> Obviously the 1/4" grade 8 bolts aren't the answer! The hole is too close to the sprocket plate for 5/16" nuts/bolt heads.
> ...


* If you are going to retire it. I will take it off your Hands to use as a parts machine 4 "SR". :yahoo::yahoo::yahoo::yahoo::yahoo::yahoo::yahoo::yahoo::yahoo:*


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