Re: [CAD_CAM_EDM_DRO] re: thomson shafts was Re: Cnc Project-- combo router- plasma cutter

----- Original Message -----
From: <ballendo@...>

> 2)The rails and bearings are fairly priced, IMO. The "highway
> robbery" occurs in the shaft SUPPORTS and bearing MOUNTS.
>
The ten foot length requires continuously supported rails with open
bearings. The aluminum support extrusions cost more than the rails.

> 3) The newer super-duper-ball bushing allows the same loads to be
> carried by a 1/2" shaft as used to take a 3/4" shaft. It "looks" weak
> to an experienced eye, but the engineering calcs are there to back up
> the claim.

I must admit being guilty of overbuilding things. A review of the load
capacities for linear rails convinced me that 3/4" or even 1/2" rails are
more than adequate (though 1.5" looks better). The machine is for our use
so who cares what it looks like. Thank you for the reality check.

> 4) The industrial people are moving to the "ground linear rail"
> systems (like THK) in DROVES. Check to see if these are close enough
> to (or better than) the "thomson" prices to be a viable alternative.

If the popularity has increased these may have come down in price since I
last checked. I'll give it a look.

> 5) Present yourself as an INDUSTRIAL user! Who will be buying a LOT
> of stuff! Not as a home shop guy making "one machine for my garage"!

We are an industrial user, though not big enough to command good pricing.
However, the local Motion Industries rep has given us some good deals
lately. I guess he knows I'm consulting with a major corporation and have
friends in high places. A little name dropping couldn't hurt.

I tried for years to get a McMaster catalog, and though I was spending over
$1000 a month with them they wouldn't send me one. Then a client (ABB
Corporation - 215,000 employees) called them on my behalf. Got one the next
day.

Doug