Re: [CAD_CAM_EDM_DRO] Re: Alum. Extrusion Manufacturers

At 02:39 PM 2/13/2002 -0600, CL wrote:

>Make all of your extrusion lineup with center openings capable of press

fitting

>Linear bearings. They get pretty standard in size. You just cut off a

length or

You need to watch out for the extrusion tolerances. Commercial extrusion
tolerance on, say a .625 diameter hole (a closed hole is the worst case for
extruding, because the metal has to flow around the supports for the part
of the die causing the hole and fuse back together) in the common 6063
alloy is +/-.016". An extrusion is like putty when it comes out the
extruding die. There is an inverse relationship between how quickly they
squirt it out and how accurate it is--slower being more accurate but taking
more machine time than "commercial" extrusion. And the parallelism between
the hole and an adjoining surface will have its own tolerance.

To hold +.001-.000 tolerance (straight and round) in the bore on an
extrusion I just had done (specifically to mount an INA linear ball
bearing) and keep it within .002" tolerance of an adjacent mounting surface
took a special holding fixture and a roller-burnishing after boring.

Best regards,

Randy
Randy Gordon-Gilmore ,----.___________ ______________ _________________
ProtoTrains // = = === == || == == == = || == == == = == =|
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