South bend 9A back gear fix

[mark smith 20Participant @marksmith20]

Hi, Im currently fiddling about with a spare South Bend i own ,I bought a back gear repair gear section on ebay for the small gear end .

I only noticed yesterday that the back gear  itself is a boxford part and although the gear spacing and gears are correct the whole part is longer by around 5mm on the left hand side and a gap is left on the right side as well when fitted.

I removed a few mm from the left hand side of the back gear shaft.

Turned away the small broken gear section and glued the repair section on the right side whilst temporarily in place to make sure the gear teeth are in line .

Whats the best way to pin the replaced back gear section to the shaft??

Also should i make a spacer for the right hand side gap or push the right hand side bushing right in and redrill for a split pin as the original taper pin will now be out of line.

Hope im explaining this correctly. See pics.

 

 

Thanks

Edited By mark smith 20 on 25/10/2016 14:31:48

[mark smith 20Participant @marksmith20]

[Ady1Participant @ady1]

I cut a keyway of 3/32 in the shaft of my Drummond and new cog and dremeled off a bit to use as a key. I had an extremely tight interference fit as well, which only gave way when I got a serious chuck jam up, making the keyway necessary

The new system unlocked the chuck and has

held up fine so far

[mark smith 20Participant @marksmith20]

Hi Thanks, Key way is a good idea but ive already glued the gear section on ,so dont really want to take it off again.

Would drilling 3 equally spaced holes on the end ,centred right on the seam between the gear and the shaft core hold enough if i insert 3 round pins???

A couple of more pics .

There is also the annoying gap to the right , i guess ill just have to re drill the bushing further in and use a roll pin (taper pins are a pain to fiddle with).

[Chris Evans 6Participant @chrisevans6]

I have done a similar repair to a groundkeepers lawnmower and used two countersunk screws on the seam/jointline. Drilled and tapped/countersunk then fitted with studlock. It has not failed in two seasons of mowing a football pitch.

[mark smith 20Participant @marksmith20]

Hi, Think i may try it, i supposed its no different than the grub screws you see in taperlock pulleys, im only trying to avoid the gear rotating on its shaft and i cant see it moving with screws or pins in .

[Ady1Participant @ady1]

I suppose pins would work because you have plenty of meat(metal) and I presume it's made of steel or good cast iron

I couldn't do that with mine because it's T6 aluminium and high torque jobs would "push" the two parts away from each other as they tried to roll around the shaft and were lifted by the circular shape of the pin

[BazyleParticipant @bazyle]

If you have glued it unless you used Gloy it will probably hold until you overstress it. Might save you breaking off a tooth.

[Jeff DaymanParticipant @jeffdayman43397]

Hi Mark, the joint between this gear and shaft is one that sees high torque. I would be more likely to drill 2 or 3 holes through the hub , blind, just shy of the central shaft hole, and fit some short dowel pins with loctite. Leave a wee bit of pin sticking out , if it clears everything nearby, to help pull the pins if ever needs be.

A couple of hard dowels in blind holes thru both parts will transmit almost as much torque as a key, and are much less likely to start a crack than a keyway.

I'd be concerned about fitting screws or pins in the shaft to hub joint line, dutchman-pin style, this thins the material locally and could "roll out" or jack the hub outward, or jack the shaft inward, under high torque. If it jacked inward it may jam on the shaft.

Just my $0.02 as a fellow 9" SB owner. Your mileage may vary.

Still have to fix several broken teeth on my back gears some day. The breakages happened long before I owned it and I've owned it for more than 25 years…. and use back gear all the time, with no troubles. I try and go gentle on it though, in back gear. JD

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