G/box mainshaft/output shaft bush

motoddrob

motoddrob

Hero member
Location
S/W Australia
A question for the machine heads on the forum.

How does one cut the spiral oil groove in the bushes in the output shaft?
Reason I ask is I just had a machinist mate fit and machine/ream those 2 bushes but he didn't know how to machine that groove which surprised me as he is usually very clever. He ended up cutting that groove by hand using a round bur in a air driven hand piece. Not very pretty but will still carry oil. Once home and closer inspection I noticed that the groove doesn't cross where the 2 bushes join so I'm now wondering how oil is suppose to reach the outer bush if the groove doesn't connect. I think the problem was the bur couldn't get in far enough from either end to connect across the centre join. If it is relatively simple I have a local mate with a lathe I can use to have ago at joining the grooves. It's what's stopping me from reassembling the gearbox and buttoning up the motor again. Or shouldn't I worry?

Cheers
 
Depending on your lathes capability the back gear can be set to give a very high feed rate and the scroll can be machined in as you would a screw thread. If the machine can't be set to feed fast enough then select a slow speed and feed by hand, one cut in one cut out at full depth will ensure the scrolls cross. Depending on which of my lathes I'm using this is the way I cut them. Best to do it before final honing or reaming to size then the honing/reaming operation will also nicely de-burr the scroll.


    Keith
 
                                                "Best to do it before final honing or reaming to size then the honing/reaming operation will also nicely de-burr the scroll."

Thanks for the reply Keith. The grooves were ground by hand with a small round burr before reaming to size.
As I said not pretty, but it'll carry oil. My main concern is the grooves don't cross from 1 bush to the other. Therefor the outside bush would be starved of oil.

I was a little surprised that my mate didn't know how to do that, his business is precision engineering etc.
Anyway it is what it is, just wondering if I should somehow cross the grooves from one bush to the other.

Or am I be just thinking too much again :o
 
Rob,

Actually, there should be a slight gap between the 2 bushes.  That way, oil can collect in the resulting groove and move on to the outer bush.

Always a bit of a moment when machining those scrolls.  Need to keep your wits, especially when doing the LH one, everything on the lathe works backwards!

piet

 
While I am on a roll with searching, there are a couple of photo's of the scroll in the bush here, you can see the crossover:

http://www.laverdaforum.com/forum/index.php/topic,89994.msg278933.html#msg278933
 
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