re: backtrack gantry mill was: Re: re:Re: What is everyone doing...

Marcus wrote:

>Hi Ballendo;What did you think of that Backtrack gantry mill?
>Looks awfully flimsy to me!! Brutal price too!!
>For 6 grand, I would hope for something a bit more substantial
>mechanically.

Marcus,

I think it represents some innovative use of some CHEAP, STOCK
Sherline components... Anyone could probably bolt one together in an
afternoon, maybe take a weekend... Tools needed(for the mech. assy);
drill& bits, countersink, or counterbore, allen wrenches, file.

It's is probably stiffer than it at first appears; but certainly is
not a bridgeport!

The X axis is 2 s/l 'lathe' beds bolted to an alum plate.
The 'saddles' carry 2 mill support blocks. At this point the 'flex'
will be that of the saddle/dovetail. The support blocks are "bridged"
by a third 'lathe' bed (looks like the 4400) which forms the gantry.
From here you are dealing with the 'flex' of this bed and the
typical "gantry" machine 'buildup' of tolerances affecting stiffness.

And the 20tpi leadscrews might be limiting to top speed, but I keep
remembering Dan M's post about the BLAZING 'gecko' sherline!

Would I buy it for 6 grand? No. But I might call sherline to see what
I could build it for... And THIS is why I posted the link...

Hope this helps.

Ballendo