DougW Posted July 16, 2020 Report Share Posted July 16, 2020 Idler gear on the LC is worn, it has a pressed in phosphor bronze bush. I want to make a new bush , common grades on EBay are SAE660 and PB102. Any advice on the suitability of these ? Going to try making it a heat shrunk in press fit, then ream to final size. Note "try" "O" Level metalwork steam engine was a long time ago. Happily been making spacers for the last few years, this is the first "precision" lathe job I`m going to attempt at home. Quote Link to comment Share on other sites More sharing options...
Swarf Posted July 16, 2020 Report Share Posted July 16, 2020 25 minutes ago, DougW said: Idler gear on the LC is worn, it has a pressed in phosphor bronze bush. I want to make a new bush , common grades on EBay are SAE660 and PB102. Any advice on the suitability of these ? Going to try making it a heat shrunk in press fit, then ream to final size. Note "try" "O" Level metalwork steam engine was a long time ago. Happily been making spacers for the last few years, this is the first "precision" lathe job I`m going to attempt at home. To be honest either would do quite well, you might find the PB more pleasant to machine though. It's bloody abrasive on your tools and also very 'snatchy' so make sure everything is clamped nice and tight! 1 Quote Link to comment Share on other sites More sharing options...
DougW Posted July 16, 2020 Author Report Share Posted July 16, 2020 1 hour ago, Swarf said: To be honest either would do quite well, you might find the PB more pleasant to machine though. It's bloody abrasive on your tools and also very 'snatchy' so make sure everything is clamped nice and tight! Cheers Swarf, PB102 on order. Adjustable reamer needed next, but might be able to scrounge that off Father in Law. 1 Quote Link to comment Share on other sites More sharing options...
Swarf Posted July 16, 2020 Report Share Posted July 16, 2020 Just now, DougW said: Cheers Swarf, PB102 on order. Adjustable reamer needed next, but might be able to scrounge that off Father in Law. Horrible things, adjustable reamers.....😂😂 1 Quote Link to comment Share on other sites More sharing options...
porter_jamie Posted July 16, 2020 Report Share Posted July 16, 2020 what size is it? Quote Link to comment Share on other sites More sharing options...
DougW Posted July 16, 2020 Author Report Share Posted July 16, 2020 7 minutes ago, Swarf said: Horrible things, adjustable reamers.....😂😂 How would a real engineer machine the ID of the bush pressed in to the idler gear to be a good running fit on a shaft that my Aldi digital vernier says is 15.15 mm ? Asks a clueless numpty. Quote Link to comment Share on other sites More sharing options...
DougW Posted July 16, 2020 Author Report Share Posted July 16, 2020 (edited) 5 minutes ago, porter_jamie said: what size is it? Quick measurement this morning before work , existing shaft OD 15.15 mm, gear ID that bush pressed into 17.04. Quickly made with Aldi vernier for getting suitable bar. Edited July 16, 2020 by DougW Quote Link to comment Share on other sites More sharing options...
Swarf Posted July 16, 2020 Report Share Posted July 16, 2020 1 minute ago, DougW said: How would a real engineer machine the ID of the bush pressed in to the idler gear to be a good running fit on a shaft that my Aldi digital vernier says is 15.15 mm ? Asks a clueless numpty. I'd get a micrometer on the shaft first, to get an accurate reading. To be honest I'd look at boring it on the lathe if you can hold the gear true enough? 1 Quote Link to comment Share on other sites More sharing options...
porter_jamie Posted July 16, 2020 Report Share Posted July 16, 2020 well, yes i was wondering how you were going to keep it concentric - it is a gear after all. and what clearance do you want to run? i wonder if the usual if in doubt a thou per inch would work? 1 1 Quote Link to comment Share on other sites More sharing options...
DougW Posted July 16, 2020 Author Report Share Posted July 16, 2020 14 minutes ago, porter_jamie said: well, yes i was wondering how you were going to keep it concentric - it is a gear after all. and what clearance do you want to run? i wonder if the usual if in doubt a thou per inch would work? I think I would struggle to get that in my little boxford lathe chuck. Current fit is "Floppy", just measured around 1.5 mm of deflection at the circumference of gear, if that makes sense. Doesn't seem to have been a problem, but might soon start catching clutch, I am thinking. Internet seems to suggest this is common. Idler gear drives tacho and kickstart gear engages with it. Looking for clearance to give an improvement in fit from "Floppy" Quote Link to comment Share on other sites More sharing options...
Swarf Posted July 16, 2020 Report Share Posted July 16, 2020 2 minutes ago, DougW said: I think I would struggle to get that in my little boxford lathe chuck. Current fit is "Floppy", just measured around 1.5 mm of deflection at the circumference of gear, if that makes sense. Doesn't seem to have been a problem, but might soon start catching clutch, I am thinking. Internet seems to suggest this is common. Idler gear drives tacho and kickstart gear engages with it. Looking for clearance to give an improvement in fit from "Floppy" No reverse or soft jaws for your lathe? Quote Link to comment Share on other sites More sharing options...
DougW Posted July 16, 2020 Author Report Share Posted July 16, 2020 Just now, Swarf said: No reverse or soft jaws for your lathe? Not clear from photo, but very little depth to clamp reverse jaws in. I have no soft jaws. Quote Link to comment Share on other sites More sharing options...
porter_jamie Posted July 16, 2020 Report Share Posted July 16, 2020 this kind of thing 1 Quote Link to comment Share on other sites More sharing options...
Swarf Posted July 16, 2020 Report Share Posted July 16, 2020 (edited) Aye, that.....^^^ so you could grip outside the teeth. Do you have a mill or a pillar drill? Edited July 16, 2020 by Swarf Quote Link to comment Share on other sites More sharing options...
DougW Posted July 16, 2020 Author Report Share Posted July 16, 2020 16 minutes ago, Swarf said: Aye, that.....^^^ so you could grip outside the teeth. Do you have a mill or a pillar drill? I have a Clarke Pillar drill, fair amount of play in shaft. Quote Link to comment Share on other sites More sharing options...
Swarf Posted July 16, 2020 Report Share Posted July 16, 2020 21 minutes ago, DougW said: I have a Clarke Pillar drill, fair amount of play in shaft. 🤔 IMHO your best bet will be to get some soft jaws to suit your boxfords chuck, and bore them to suit the gear. That'll give the best concentricity. 1 Quote Link to comment Share on other sites More sharing options...
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