Author Topic: Piston Hone (question for Ramon?)  (Read 4575 times)

Offline ruzzie

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Re: Piston Hone (question for Ramon?)
« Reply #15 on: July 21, 2015, 12:49:32 PM »
Having spent many a year with my hands in smelly cutting oil on a Delapena honing machine (internal) which used cast iron sleeves used for truing the mandrels. The trick to truing was to use only enough oil to make a nice abrasive slurry so it cut the stone and guides; then when you honed your hole you use enough oil to flush the crap out so the stones cut the job.
So I would guess that is what the bars are for, just used the other way round

Offline Ramon

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Re: Piston Hone (question for Ramon?)
« Reply #16 on: July 21, 2015, 12:58:35 PM »

I haven't been on here for quite some time due to other distractions  ;) but as a result of our weekly chat's my friend Chris (Model steam) has just brought this to my attention.

I have two sets of Delapena external hones bought expressly for pistons and crankshafts. The round bars are indeed setting bars to bring the stones parallel but - as far as I am aware -  the bar is held in the lathe and rotated and the stones brought onto the shaft (well lubricated of course) as if in use properly - this will set the stones (particularly new ones) and take out any potential slight taper.

The nub is that having bought them (and a bench mounted internal hone) I still prefer to lap pistons down with a brass lap made for the relevant piston. Having used them (the Delapena) I feel that the external hone definitely has a tendency to barrel the piston blank as it moves over either end whereas the brass lap doesn't. They do work extremely efficiently however and produce a nice surface finish. I have used them on crankshafts but again there can be a problem getting up to the shoulder near the web.

I can't see a stop would be any great advantage - particularly, as Jason remarks, if making the piston (or a shaft) to fit a bore. Even on a multi cylinder I would still want to do that as opposed to 'interchangeability' though that said a stop could help prevent over doing things 'per pass'

If I were setting out again would I buy them? Probably not as the results achieved so far using the laps and methods described elsewhere have proved more than adequate for the task in hand - others of course may feel differently.

Hope that helps some - hope everyone is well too - I'm afraid I'm a hopeless cause being well and truly distracted at present but 'Forncett' isn't too far off so maybe that'll be the catalyst for revival  :)

Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Johnb

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Re: Piston Hone (question for Ramon?)
« Reply #17 on: July 21, 2015, 10:23:59 PM »
Good to hear from you Ramon - and well explained as ever! Enjoy your distractions  :)
John Browning. Member of Ickenham and District SME