RE: [CAD_CAM_EDM_DRO] Re: Smithy Granite

>Chris, what is the tolerance and what kind of details are you trying
>to machine? What size are your parts, X-Y-Z extents? The answers to
>these questions will have a big impact on getting a straight answer
>as to whether or not a benchtop or 3-in-1 CNC mill will work or not.

I need something like 6x12x2 inches of cutting area. The tolerance
claimed on this machine is .0005, which I think is quite good.

>Do you need tight hole location AND size/finish?

Tight? Nothing serious - I make exhaust and intake automotive parts, so
it's not like there will be a 1 mm hole .5 mm away from another one...
if that's what you mean.

>You may find that the best solution is to rough the material out with
>the plasma, and then finish it with a mill. The plasma is far and
>away a better tool for removing large chunks of metal within the id
>or OD of a flange. It is not too good at spotting and drilling a
>precise bolthole circle around the periphery of the flange, and the
>edges will always be a little jagged looking. You might need to
>leave .06-.1 inch all around for mill cleanup, but if you have to
>mill that contour without the plasma, it will take much longer,
>require full flood coolant, and wear out many endmills.

In all reality, I don't even need a plasma CNC as I could free hand
something close to a quarter inch off - I mean if looked at that way, I
could do the majority of things by hand and then put that rough piece on
the mill and clean it up and get it where I need it - is this an idea?

>If the parts are round (and I'm imagining them to be 5-7 inches in
>diameter), you may be able to use the lathe portion of the Smithy to
>finish OD & ID, and mount an indexing control to the spindle and a
>driven tool on the compound for a bolt circle, without having to
>change setups from lathe to mill. You will still want to burn the od
>& id with the plasma to start the process.

That's what I found to be appealing of the Smithy... having the lathe
would be really nice...

>If you just have a few parts, maybe you can use a drill jig for the
>bolt hole circles, and just finish the od & id on the lathe.

I'm thinking the same... or think of this - what if I made a jig that
would hold the plasma torch onto the chuck of the mill, turn the mill
motor off, and use the plasma to cut roughly with it, and then take that
jig off, and put a nice cutting pit with coolant running to finish it up
- I just thought of that... what do you'll think?
Thanks Fred!