Piston Hone (question for Ramon?)

[Allen Smithee]

I have just come by a kit for an external hone for pistons (at least that's what I want it for), at a very nice price. The accompanying drawing is attached. It looks nice enough, although the drawing took a while to get my mind around (like why is the lower circular spacer 0.313 long when the gap it's spacing in is shown as 0.375"? Surely it would be better if it was a only couple of thou shorter than the gap?). I'm considering a couple of tweaks like brass-bushing the pivot holes and using a grubscrew rather than loctite to retain the pivot pin. But that's just normal tinkering.

The only time I have ever used one of these before (30ish years ago) it was subtly different. This one seems to be designed to have the honing stone set at a specific gap and be progressively adjusted down to size as honing progresses. The one I used before had the adjustment collar *between* the jaws (with a locking nut) to provide a "hard stop" and an adjustable spring pressure via a second knurled collar outside the jaws where this one has the "hard" adjustment. It also had a much finer thread so that it was easy to set the stop in increments of half a tenth or so.

I have very little experience in using these so hand those who have give me their views? Which type is better/easier/more-accurate to use? I won't be starting on this for another couple of months (at least), and I could easily make either type from the bits in this kit so all views/experiences would be appreciated - I mentioned Ramon in the title because of his superb "lapping and honing for dummies" threads which I've been avidly reading!

AS

Edited to correct for defective memory with massive apologies to Ramon!

[Allen Smithee]

On reading it again I realise that my verbal description of what I mean isn't as clear as it might be - I'll draw the two and post the drawing for clarity.

I'm also a little surprised that the lower V-block attachment screws go into the thinnest part of the material - I'd probably move these to the quarter-width position (one on each side) to get more thread engagement.

AS

[Jo]

Maybe a couple of pictures will help you think about it.

Jo

[Jasonb]

And I think its Ramon's lapping 'n' honing thread.

Unless you are making multi cylinder engines I can't see much point in a stop. You will usually be honing it down until it just starts to fit the cylinder so its really a case of hone a bit and test, hone a bit more and test again, etc. Infact you probably do't really need a screw, just hand pressure will do.

J

[Allen Smithee]

And I think its Ramon's lapping 'n' honing thread.

I was indeed - I've corrected that and offer my apologies to Ramon!

AS

[pgp001]

Just for comparison here is my genuine Delapena version.





Phil

[Allen Smithee]

Here's the quick powerpoint sketch of what I'm talking about. The upper one is the design as drawn, and the lower one is my memory of the one I used a few decades ago.

I take your point about piston sizing Jason, but would the hard-stop version makes it easier to do (say) crankshafts?

Dunno! Perhaps I'll make the bits for both versions and see which configuration works more effectively.

AS

[Allen Smithee]

Maybe a couple of pictures will help you think about it.

I'm fairly sure that one was made from the same kit, Jo!

AS

[Allen Smithee]

Phil - what are those two ground bars for in the wooden box?

AS

[Jo]

I'm fairly sure that one was made from the same kit, Jo!

AS

It was indeed  I brought it to enable me to hone the R&B crankshaft big end journal, which if I recall correctly was why Bruce Davey originally designed this one.

Jo

[Jasonb]

I take your point about piston sizing Jason, but would the hard-stop version makes it easier to do (say) crankshafts?

Yes it could help on a longer shaft to keep a constant dia.

For those with less of a casting fettish, Model Engine builder had a nice design for scratch built versions.

http://www.modelenginebuilder.com/issuetwentyfive.htm

[petertha]

Link to self-made external hone set with nice pictorials & description.
http://thebloughs.net/series/external-hone-2/

[pgp001]

Phil - what are those two ground bars for in the wooden box?

AS

They are some sort of setting bar as far as I know, I was told to put the bar in the tool as the stones and anvils were being tightened into position in the jaws to ensure they were square.
If anyone know differently I would be pleased to hear from them as I did not get any instructions with the kit.
I have used it though, and it makes a superb job of sizing a diameter in a very short time.

Phil

[Allen Smithee]

Link to self-made external hone set with nice pictorials & description.
http://thebloughs.net/series/external-hone-2/

They are interesting because they are the "hard stop" kind I've used in the past - if nothing else it's comforting that my memory wasn't making things up (again!)...

AS

[Allen Smithee]

Phil - what are those two ground bars for in the wooden box?

AS

They are some sort of setting bar as far as I know, I was told to put the bar in the tool as the stones and anvils were being tightened into position in the jaws to ensure they were square.
If anyone know differently I would be pleased to hear from them as I did not get any instructions with the kit.
I have used it though, and it makes a superb job of sizing a diameter in a very short time.

Phil

Ah, thanks - that makes sense. Something to ensure that the stone and V-block are parallel.

AS