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Cylinder Honing

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Reggleston:
Recently did a cast iron cylinder bore on the mill using a fine feed with a light cut to achieve what I thought was a smooth surface, based on my wife's touch and mfg. engineering experience she concluded it wasn't all that smooth. So I decided to try to improve the cylinder finish using a brake cylinder hone system using my electric drill with generous application of good old brown Sulphur  based cutting oil. Within a short period the bore was greatly improved. As this engine will run on compressed air only I will try a Delrin piston in the improved cylinder finish. First Delrin piston tried in the machined surface ID pretty well abraded the Delrin piston in short order.

Wondering if anyone else has experienced using the ID cylinder hone for any metal/ringed piston or Delrin piston application? Did it improve the ringed piston fit with the honed cylinder or better left without honing?

Roger B:
As I understand different material combinations require different surfaces. I have used diamond paste lapped cylinders with aluminium or cast iron pistons and cast iron rings. These require a fairly open surface for oil retention. O rings or polymer pistons may require a different, much smoother, surface to avoid abrasion. It is also important to ensure all traces of the abrasive are removed. I use an ultrasonic bath with a strong degreaser.

Ye-Ole Steam Dude:
I use a brake cylinder hone tool and believe that the oil retention in the cylinder is much better.

Have a great day,
Thomas

Brian Rupnow:
I use a 3 stone brake hone at moderate speed, with light oil on a steel cylinder and dry if it is a cast iron cylinder. This is really only used to take out any machining marks, and to leave a light "cross-hatch" for oil retention. This is all that is needed if you are running cast iron rings. If you are running cast iron rings, the fit of the piston into the cylinder is not as critical as when you are running no rings at all or a Viton o-ring on the piston. I have a set of barrel laps that I use with #600 aluminum oxide paste to lap my cylinders that are running a viton o-ring. The lapping procedure removes 95% of machining marks that are left by the 3-stone hone. I run a bit of 2 cycle oil with my naptha fuel, and that seems to keep the viton rings happy. When running no rings at all, I hone and lap the cylinder, then machine the piston to about .0005 to 0.001" oversize and lap the piston into the cylinder---a very finicky and somewhat dangerous procedure.

Art K:
I will echo what Brian said. I have used a barrel lap. The paste is something I got from my dad. Clover brand silicon carbide grade A, whatever that means. It gave a really good finish. Ran it in the lathe a very slow speed worked best.
Art

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