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Will_D:
I am about to start work on Harold's grinding rest ( the advanced one [WPS #35]).

A long time ago I decided to stop using FC mild steels and the like and to use stainless 303 or 304. Carbide tooling allows us model engineers to handle stainless as easily as MS in the 80's.

Now a grinding rest built out of 304 would be an everlasting non-corroding wonder.

But, hang on a minute, this is a grindinding rest not a lathe. The forces are minimal but the machine needs to be rigid and stable.

Surely these days there must be some filled polymers/plastics that can be used for the bulky components (i.e the bits made from 32 and 50 mm square stock?

After all lathe ways are being resurfaced with "bonded plastic stuff"?

Or am I just mad?

Manxmodder:
Will,I use quite a bit of plastic of various forms,high density nylon,as seen in the Nylacast range here : http://www.nylacast.com/

Also sometimes use glass filled Nylon and Acetal copolymer. The problem with many plastic applications is the high expansion factor when temperature rises and resonance caused by lack of density compared with steels.......OZ.

vtsteam:
50mm sq stock sounds like a job for a quickie charcoal briquet casting furnace and scrap aluminum or zinc die-cast stock, to me.

Fergus OMore:
Will-D,
             Getting back to your original posting, I would mention that there is a posting here, where the drill grinder is plastic.  Actually, there was one, a lot further back that was just that and crap though it is, my lidl knife sharpener is plastic. The designs might be crap but the principle is sound enough.

Me, well I'm different. I've been messing about with a cheap ,low quality  Mig welder and have actually cut some hollow steel section and am welding up a sort of Tinker tool and cutter grinder. the original design was bloody heavy cast iron brackets but cost and one thing and another suggests bolted up and glued mild steel section.

So where does that leave us? First, I think that Mr Hall's design is sort of OK but nothing startling or complete for ordinary tool and cutter grinding. It is no better or worse than one old design in ME that was the forerunner of the fabricated Worden or the cast iron Kennet. I've built both!

Somewhere, I mentioned the Stent which is a baby Clarkson and whilst I built one from castings, I came across a fabricated welded up job in steel sections which, In my opinion makes rings around the quite a few competitors. Again, I like the Brooks which appeared in MEW 16 and 17, years ago and is utilises quite a bit of the arguably complicated Quorn.

Question? Can a Quorn be fabricated? The answer is Yes, an old friend long dead, built one. Can a Quorn be built of plastic parts? I would think so.  If you were wary about exotherms, you could do replace the cast iron with a ordinary fibreglass resin- from your local car accessory shop.

Clearly, my knowledge is dated and other alternatives seem possible- but I haven't tried them.

So it would be interesting to hear where you go.

Cheers

Norman

nrml:
You could 3D print  a grinding rest. The choice of plastics is huge. You could even use metal filled plastics, although I am not sure if it will offer any advantage over regular plastic other than being a better heat sink. I am sure it will cope with occasional hobby shop use. Even if it doesn't last, it can prove your design and allow you to refine it before making it in metal.

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