Tiller Sheared rotary tiller hex shaft

[brooksto]

I have a 5' rotary tiller that is branded southeast IMCO. It was purchased used so im not sure the age, and i cant find any parts diagrams or dealers. The problem is the hex shaft that runs from the pto gear box to the chain sprocket has sheared off at the sprocket end. What are my options for getting this repaired?

 

[brooksto]

 

[zzvyb6]

Me, personally?, I buy a new chain sprocket, buy a new solid ROUND shaft and put it back together with a shear pin in the hub. I suppose you could find a welding shop to extract the broken off insert and put it back together just as easily. But first, I'd want to know why this broke: lots of excessive strain, shock load, slip clutch too tight, no slip clutch, wrong shear pin or abuse. Until you know, it's going to happen again and again until something changes.

Doesn't look like 'bad' metal or 'defective part'. Looks like 'overload'. Were you tilling the railroad right of way again ?

 

[brooksto]

The hex shaft runs through the pto gearbox to the sprocket. It is turned down round on the sprocket end to go through a bearing, then threaded for a nut to hold the sprocket on. This is a heavily used tiller before we bought it and used it for several years. Im not sure why it broke, I was making a quick pass of already broken soil to try and get a finer top layer for planting, really lightly skimming the surface when the tines just stopped turning. It has had much harder loads on it than that. The hex shaft seems to run straight through the pto gearbox, with an extra 8 inches or so out the other side. I wonder if that extra would allow for a machine shop to turn down another round threaded end. Does the hex shaft just drive straight out of the pto gearbox? It doesnt seem to want to budge but im afraid to pound on it too hard if somthing internally in the gearbox is holding it in place.

 

[jenkinsph]

I would remove the gear box and shaft from the tiller and get it on a bench where you can fully disassemble it. There is a good chance you can turn down the shaft to fit the chain sprocket as you mention or start with a new piece of hex shafting. Hex shafting is readily available, let me know if you can not find it. Some machine work will be required.

Almost all tillers have a thrust tube that runs from the other side of the tiller to the gear box, hope you have this and it is removed in the picture.

I agree with finding what caused this overloading of the shaft. Do you have a slip clutch or shear pin of the proper rating? Make sure the slip clutch is not rusted or frozen stuck.