New shaft in Oilite bushes?

[Martin KyteParticipant @martinkyte99762]

Posted by old mart on 27/04/2021 14:08:07:

Chrome plating is not a recommended surface to run with bronze. Hardened steel is best if you can achieve it.

In defence of Duncan all motorcycle forks are or at least were, hard chromed and cylindrically ground and run in bushes, not at all the same as decorative chrome plated.

regards Martin

[duncan webster 1Participant @duncanwebster1]

Here's some guff about application of oilite It says shaft should be harder than the bearing, but then doesn't tell you how hard the bearing is

Normalised EN8 has HBN at least 150,EN8 hardness

tin bronze (gunmetal) is 75 bronze hardness

Steam locos, at least the ones I worked on, had EN8 pins/axles with leaded bronze bearings

If you want to go one better then EN19 is 223 HBN EN19 in the S condition, still machine-able, but don't go welding it

[Richard S2Participant @richards2]

For the price of a length of 3/4" silver steel, which has a Brinell hardness of about 270 in the raw, it would save a lot of work. You probably won't even need to harden/temper it any more either.

I've used it for my counter shaft on my ML7 and several other machines and it's fine and durable

[Tony Pratt 1Participant @tonypratt1]

Word from the wise [me] just use unhardened steel, Silver, mild or some such & leave it soft, it will last many years. If you try to harden the shaft you are in for a world of pain, i.e. distortion & scaling. Let us know what you decide.

Tony

[MikelkieParticipant @mikelkie]

Posted by Nick Clarke 3 on 31/08/2020 22:03:28:

Posted by old mart on 31/08/2020 21:32:48:

While you are about it, why not make an extra shaft, then you can be sure that the first one you fitted will last forever.

Such cynicism I expect from the young, not someone signing themselves as OLD Mart! 😂😂

Edited By Nick Clarke 3 on 31/08/2020 22:05:05

The "OLD" in Old Mart means he spoke of a lifetime experience

[Andrew Moyes 1Participant @andrewmoyes1]

Thank you all for your thoughts. You have persuaded me to take the easy route and use ground silver steel. That’s on order together with the Oilite bushes.

It’s interesting to note that while the original ¾” dia mild steel crankshaft and bronze bushes are badly worn, the much smaller 3/8” dia crankpin which is hardened and runs directly in the cast iron connecting rod is perfect with no play.

I have replaced the motor bearings with SKF ballraces and converted the flat belt drive to poly-vee. The saw should be a useful addition to the workshop when finished.

[HopperParticipant @hopper]

Posted by Richard S2 on 27/04/2021 16:06:06:

For the price of a length of 3/4" silver steel, which has a Brinell hardness of about 270 in the raw, it would save a lot of work. You probably won't even need to harden/temper it any more either.

I've used it for my counter shaft on my ML7 and several other machines and it's fine and durable

I didnt even go that fancy on my ML7 countershaft. Piece of bright mild steel bar (1020 grade under our system) has been running happily in Oilite type bushes for several years now. Probably not copping the hammering a power hacksaw would put on it but will definitely outlast me at the current rate. Main thing is to oil the bushes every time you use the machine. Your crankpin running in cast iron could get away with rarely being oiled but those sintered bronze bushings rely on the oil being kept up to them.

[Nigel Graham 2Participant @nigelgraham2]

IanT –

I would not recommend lapping a shaft in an 'Oilite' bush. A plain bush yes, but not sintered.

A lot of machines used plain cast-iron bearings with mild-steel (probably EN3 or similar), and these can give a very long life if kept reasonably well lubricated..

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