Question about mill travel

[Jon K]

I have been looking at smaller hobbyist mills like those from Grizzly. If it says it has 5.75" cross and 14" long travel, how big of a part can you make?

Is it 2.875" out from the center on the cross? Or, could I put a part at the center of the cross and go 5.75" out each direction to and away from me?

Thanks!

 

[jumps4]

you also have to subtract the size and length of the tool from this distance
and the distance from column to spindle
if you are using a 3/4" endmill to go around the outside as example then your max part size is minus 1.5" of your total travel without moving the part.
steve

 

[JohnAspinall]

I have been looking at smaller hobbyist mills like those from Grizzly. If it says it has 5.75" cross and 14" long travel, how big of a part can you make?

Depends on the part, the precision, and the tooling. What the working envelope says is that without re-mounting the piece, you can put the cutter center anywhere in a 5.75" by 14" rectangle.

Why is that not the size of the part? Just off the top of my head:

1. You might need to get the cutting tool center outside the part, if you were e.g. squaring up an outside edge.
2. You might never need to get the cutting tool anywhere near one region of the part, if you were e.g. finishing up that region by other means (or not at all).

Why does precision matter?

1. Because the loss in precision if you re-mounted the part, might or might not matter.

Can re-mounting the part always work (assuming that loss-of-precision isn't an issue)?

1. No. Another important dimension is how far away the column of the mill is from the table. If you have a 24" by 24" square, and you want to put some holes near the center, there's no mounting position on a little mill that will get you there.

Is it 2.875" out from the center on the cross? Or, could I put a part at the center of the cross and go 5.75" out each direction to and away from me?

The first. But don't think of it as a "cross". Think of it (the working envelope) as a rectangle.