Hex Blind Hole in Polyester Resin

[Chris TriceParticipant @christrice43267]

Sorry, I thought it was a one off. Wouldn’t it be easier to cast real Allen screws in silicone moulds. I’m still not sure exactly what the raw material is we’re talking about. Is it purely polyester resin or fibreglass reinforced. From experience, fibreglass kills HSS very quickly so the tooling route won’t necessarily last plus polyester is brittle and chips easily.

[JasonBModerator @jasonb]

But then it won't look like bakerlite as the resin will take on the colour of the metal filler at least all the times I've used the metal fillers thats what happens, the pigments won't be strong enough to hide the metalic look.

These are polyester resin in one form or another machines, taps, mills fine

Unreinforced so no fibres to blunt your tools

They are not allen screws the hex hole fits over a metal shaft and then the outside is shaped to form a knob/toggle

 

Edited By JasonB on 27/10/2014 15:15:13

Edited By JasonB on 27/10/2014 15:16:02

[NishkaParticipant @nishka]

Jason is exactly right these are switch knobs that are 'pinned' to a hex shaft of a switch. They need to look exactly like the originals.

The link to the Col.849/TM polyester resin rods is the very sort of material I am thinking about. This is unreinforced polyester rods.

Thanks for the ideas guys.

[NishkaParticipant @nishka]

If the part I required was a one off, then the idea suggested by Chris, of recasting would probably be the root I would take. However,for several hundred it may not be very practical.

[Russell EberhardtParticipant @russelleberhardt48058]

Bakelite was a resin (phenol formaldehide) mixed with wood flour as a filler. If it was cream coloured it would probably have been filled urea formaldehide. Polyester resin on its own would tend to be brittle and should be filled. A common filler for plastics these days is talc which would give it better strength and colour. The original part would have been moulded so there would probably be draft angles so a 1/2 deg. draft on the hexagonal core is unlikely to be a problem if you cast it.

How is the part fixed to the hexagonal shaft?

Russell.

P.S. The biggest worldwide use of talc is now in the automotive industry.

[JasonBModerator @jasonb]

Another sacrificial allen key later and we have this

Just hollowed out the end , stoned off the burrs and shoved it through from the other side to give the left hole, some breakout on exit and tight to remove.

2nd hole was done with some clearance very roughly ground behind the edge a lot easier to drive and remove, was slightly off on the pilot hole so edges nearest are a bit round but others fully cut. Thats a 6mm key into a 6mm hole in Corian which is not unlike the properties of Polyester rod.

If doing it this way do as I said above but a 3/16" hole will do down the middle. Either hold the rod in a collet or bore a block of metal to hold it so there is no risk of bursting

[NishkaParticipant @nishka]

Thanks Jason, that looks just the job.

The bored out block of metal would also serve to centre the hex broach tool, as well as prevent bursting of the rod.

Brill, now all I need to do is order the material and start making holes!

[Chris TriceParticipant @christrice43267]

OK, I see what we're talking about now.

[Chris TriceParticipant @christrice43267]

Could an Allen key shaft not be drilled slightly deeper than shown with something like a carbide centre drill so that the entire hexagonal edge was sharp?

[JasonBModerator @jasonb]

That was my intension until the carbide slotting drill snapped only used the key as it was a test, milling some silver steel to a hex would be better as I originally suggested with a deep hole and CSK end like this which I tried in mild steel first but it was too soft

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