Re: Cutting forces and Acetal nuts - Anyone?

Arvid,

This is tough to answer without more specifics, but think about
this...

If you were cutting the materials you have in mind with a handheld
tool,like a woodworking router, how much force would you use?

And how fast would you cut? Would you try to cut all the way through
in one pass, or use multiple depth settings?

As you answer these, you may start to get a "feel" for the forces you
need.

I remember being in the same place many years back. I called the
Forest Products Lab in Madison, WI ; and asked what forces were
necessary to cut various types of wood at different thicknesses...

Then I set up a fish scale and CAREFULLY used it to pull a router
through the types of things I was planning to cut. I timed myself
cutting given distances to determine how fast I was moving through
the material. In other words, what was my "typical" feed rate. (I had
the advantage of having spent a lot of time cutting things manually,
which was why I was building a cnc in the first place!<G>)

Finally, I cheated. I looked at existing CNC machines aimed at the
low and slow market (only a FEW back then under $20K; now there are
scads). What I found is that real work can be done in most of the
materials you mention at "handfeed" type cutting speed (50-90IPM)
using 30-60 pounds of force. A far cry from the needs of heavy metal
cutting.

Hope this helps,

Ballendo

P.S. You can work at this the other direction, by determining your
desired chip size at the material's optimum cutting speed, figuring
the rpm of your spindle, which will give you your "best" rate of cut.
Then you can "do the math" to be sure you can achieve this speed
given the motor and structure characteristics. Motor manufacturer's
usually have a "calculator" to help them sell their stuff. It does
all the engineering calcs, and points you to an entry in their
catalog. You then either order from them, or use the motor specs
found to get what you need somewhere else...

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "bitnick78"
<arvidpublic@h...> wrote:

> I wrote:
>
> *snip*
> > I want to be able to cut wood, MDF, Delrin, perhaps make my own
> > PCBs, and preferably also cut aluminium panels and the like.
> *snip*
>
> Anyone have any idea what kind of forces this kind of work will

cause

> at the lead screws?
>
> *snip*
> > What I am worried about, and have not been able to find much
> > information about, is what kind of cutting forces that can be
> > expected from the kind of work I want to do. This particular screw
> > (or nut, actually) /that I'm about to buy/ has a "design load" of
> > 175 lbs (or about 775 N if you prefer). Will this be enough, or

am

> > I going to destroy it milling aluminium?
>
> Is anyone using Acetal anti-backlash nuts in a machine and doing
> light aluminium milling with it? If so, what's the specifications

on

> the screw/nut?
>
> > Thanks for your help
> >
> > // Arvid
>
>
> // Arvid