Re-facing Slide Valve & Ports

[Soot n' Cinders]

Thanks Tristan, I wonder what the abrasive on the 3M paper is? Are your cylinders and valves cast bronze?

Dan, cast bronze is the material offered by Blackgates in England as a premium material over cast iron. This material has been used successfully for many years by others. I am pretty sure my problem stems from a lubrication problem.

David

I believe its aluminum oxide, I would have to look though. My cylinders are cast iron and my valves are bronze bar stock

[hoppercar]

Bronze to bronze is a very poor bearing surface. You can remachine or lap them flat again, but even with good lubrication it will soon wear out again. You should always use iron to iron, or iron to bronze...but never bronze to bronze

[Bill Shields]

There is bronze and there is bronze..some combinations are quite good for bearing applications.

Aluminum Bronze and /or Phosphor Bronze on 'other bronze' actually makes quite a good bearing combination for our application(s).

[hoppercar]

I suppose that could be..but you can Google it and learn about the coefficient of friction bronze...I suppose there are alloys that might be allright together, but generally you don't see bronze to bronze out in industry for that reason, the poor wearing. Iron to iron or iron to bronze is the standard. ...normal bronze castings as the type used in the live steam world, are Not suitable bearing surfaces when used together

[Builder01]

If cast bronze is so poor for a bearing surface, I wonder why almost all of the companies in England offer cast bronze for cylinders and slide valves? Very curious.

David

[Builder01]

Tristan, aluminum oxide, thank you!

As for my cast bronze cylinders and valves, seven days is probably not quite enough time to get new iron castings and machine them in time for my open house event!

Even when I get them refaced, I'm probably not quite ready to throw them in the scrap bin just yet.

David

[hoppercar]

For the same reason you do not see a lathe bed cast in bronze, with a bronze saddle and a bronze tailstock....machinery builders do not put sliding bronze surfaces together...

[Harold_V]

The abrasive of choice for non-ferrous is silicon carbide. It's much harder than aluminum oxide, which will also work, just not as aggressively.

H

[Bill Shields]

Giggle...

Not using bronze for a machine tool frame (or any sizable component there of) has very little to do with its suitability as a bearing surface.

Think about the mechanical properties of bronze and all the reasons why it is unsuitable for anything much larger than maybe a small toaster.

[hoppercar]

Soyour saying there is no reason to be concerned about a bronze saddle on a lathe sliding and wearing on a bronze lathe bed?...

[hoppercar]

My final comment on the subject...after 52years as a machine way scraper and fitter...I have seen my share of people fitting bronze sliding surfaces.together...its is always a disaster...bronze to bronze is poor....bronze to iron or steel is better...iron to iron is the best

[Bill Shields]

I am saying that bronze is low on the list of materials from which you should make a lathe - but the LEAST of the concerns is the sliding surfaces.

Stop and think WHY CAST IRON is used (or Meehanite if you are familiar with name) as opposed to Bronze.

Young's modulus of CI is almost 2X that of Bronze.
Coefficient of thermal expansion of Bronze is 2X that of CI