Re: Advice on turning a part
What about drilling it to the nearest size down, say 12.5mm then use an adjustable reamer to finish ?
Re: Advice on turning a part
For the pinion, the hole is probably a nominal 12.7mm - or half-inch as us old-timers know it! Easy enough (but not necessarily very cheap) to get a reamer for that. Biggest issue is maintaining concentricy. Personally, I would hold it by the teeth in a collet. You can make a one-off collet which will be very accurate even if you only have a tired 3-jaw chuck. A drill to open out the hole might work but a small boring tool would be better, whether or not you use a reamer for final sizing.
From what I can see, the shaft is more difficult. Even if it's not hardened, I'm not sure how you will hold it for turning which you will need to do before cutting the thread Possibly another home-made collet would do. Assuming it's just for a securing nut rather than an accurate location surface, a die would do the threading job but there will be a groove between existing thread and shoulder that might give a problem. If it is hardened - make another one from scratch?
Re: Advice on turning a part
Quote:
Originally Posted by
Neale
Easy enough (but not necessarily very cheap) to get a reamer for that. Biggest issue is maintaining concentricy.
You are correct, but I was thinking of a morse taper reamer held in the tailstock, same with the drill.
I can't believe I didn't realise it was 1/2", damn mm have warped my brain.
Re: Advice on turning a part
Problem is holding the pinion concentric. With a worn three-jaw, plus locating on teeth, the hole is unlikely to end up in the middle. A home-made split collet can fix that. And a worn lathe probably doesn't have an accurately set tailstock, hence suggestion of a boring tool. It's easy to start over-complicating, isn't it? It's what I would do, but I have the tools to hand. There are probably folks out there who would hand-hold the pinion and use a drill press (but please, don't try that one at home...)
Re: Advice on turning a part
Hi Charlie
If you have a 4 jaw chuck you could get some silver steel rod or suitable drill shanks, place 4 in the spaces between the gear teeth and use a clock to set to the drill/rod outer dia, that will get the gear running true, bore it if you can, run @ a slow speed so you don't burn out your boring tool, if it wont cut you could anneal it and then machine it.
Mike
Re: Advice on turning a part
thanks for all the advice i only have the basic stuff and only a 3 jaw chuck, sounds like im best of trying to find some one to do it for me as its going to cost me a bunch just to get the mentioned tools and im not that sure my lathe is all that accurate any more.
Re: Advice on turning a part
Hi Charlie
was just having another look @ your wee jobby, the dia of the boss looks smaller than the one shown with the key in it, what sort of wall thickness would you be left with if you opened it up to 1/2" ?
Mike
Re: Advice on turning a part
no they are the same size just one is a fraction shorter.
Re: Advice on turning a part
Try to run a file in the bore of the gear to see if it is possible to machine it, i think your best option for the pin would be to remake from silver steel, harden/ temper and polish the shaft.
Mike