Re: [CAD_CAM_EDM_DRO] Denford Orac CNC

Hi John,

If you insist on playing with this lump of steel there are a number of
things that need to be done. The lump must first be normalised which
involves putting it in a kiln and bring it to red heat, then letting it cool
over night as slowly as possible. the underside is then machined flat to
avoid clamping it down and warping it. If you are going to remove 1mm of the
material from the top surface, remove .75mm with a fly-cutter or face-mill.
Then normalise it again and then surface grind the rest off. You should end
up with a flat, as near as it can be, surface. There should be no machining,
grinding marks left at this stage. The next process is to blue the surface
and scrape to a good surface plate.

Regards,

Terry


| I'd really like to have a go on a surface grinder. He mentioned milling it
| flat first and then grinding it. Is the surface grinder much more accurate
| than a good knee mill? The mill we have in school is a Bridgeport Series I
| Textron, I've not seen one of these before (Anyone have a link to some
| pictures or details on them?). I can see how a surfer grinder could create
a
| more parallel surface over a distance if it's travel is more accurate but
if
| the grinding wheel is aluminium oxide does it create a grain effect on the
| surface it's ground? Is it smoother or rougher than a face milled surface?
| Also, about how long does it take to level off say a piece 50mm by 200mm
| down by about 1mm?
|
| Thanks Sven,
| John H.