Re: Why dovetails?

My Bridgeport has an aftermarket table. It is mounted on linear
rails rather than dovetails. While I would never run it at that
speed, I clocked it at well over 200 ipm so they must be doing
something right.

Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "mandras76" <mandras76@y...>
wrote:

>
>
> Hi,
>
> I'm new to this group and in fact new to CNC machining altogether. I
> have some experience in wood- and metalworking, and am in the

process

> of converting a Proxxon MF70 micro mill to CNC.
>
> In doing so, I'm dreaming of a larger mill already... I'm thinking

of

> building one from scratch, rather than converting a non-CNC mill,

let

> alone buying a CNC mill. Somehow I imagine that a design where the
> workpiece is at rest (or on a rotary table) and the spindle moves
> would be easiest and best. This would make the mill of my

imagination

> very similar to a CNC router, only somewhat stronger and stiffer.
>
> There must obviously be something wrong with this idea since this is
> not a design you normally come across among metalworking mills. Is

it

> because dovetails are so much better than any other kind of linear
> movement? I was thinking of triangular rails with ball bearings

loaded

> against each side, would that be less stiff compared to a dovetail?

I

> don't need the stability of a Bridgeport because I have all the time
> in the world and can take shallow cuts, but please tell me if my

idea

> is unsuitable even for my humble needs. It needs to be cheap in the
> first place, but also capable of cutting metals, at least non-

ferrous

> ones.
>
> Thanks a lot, and please excuse me if this has been discussed

before.

>
> András