[SPEEDRE]

I want to eventually extend my "z" from 3" of travel to, 6" of travel. So how long will the lead screw need to be? I can't quite wrap my brain around this obvious question. Not including the motor, what I have now for a lead screw is approx. 8" long. If that length is giving a 3" travel should an additional 3" be added to get 6" of travel, or will I need more. I had originally thought that a 12" screw would be sufficient to yield a 6" travel, but now I'm not so sure. Comments are welcome. This is what my machine looks like

[nlancaster]

From those pictures the limitation on your z-axis has nothing to do with the lead screw.

The gantry is only 3 inches from the spoil board. And the extension on the z-axis is only 3 inches below the lower bearing block.

[SPEEDRE]

Yes I know, I would have to add three inches to it but since there is no screw to contend with it is plain. So can I just add three inches in length to all the components of the "Z " axis?

[nlancaster]

Adding length to the z-axis will gain you nothing. That design, in the pictures provided, already has more then 3 inches of z-axis travel. Your z-axis limitation from those pictures appears to be clearance space under the gantry. To make full use of the available z-axis travel you would have to add taller gantry sides, and possibly a longer plate to carry your spindle.

[keebler303]

Adding length to the z-axis will gain you nothing. That design, in the pictures provided, already has more then 3 inches of z-axis travel. Your z-axis limitation from those pictures appears to be clearance space under the gantry. To make full use of the available z-axis travel you would have to add taller gantry sides, and possibly a longer plate to carry your spindle.

There are more reasons to increase Z travel than to increase workpiece thickness. What if he wants to drill 3 " deep with a 4" long drill bit and still be able to machine tiny features with a stub length 1/8" bit?

Conceptually, your travel will be the length of your screw, minus the mounts, the nut, the machined end for the motor coupler, etc. If you make the design longer, you still have the same number of bearings, nuts, etc. so every inch you add to the length of the screw will give you an inch of additional travel. If 8" gives you 3" travel then 11" should give you 6" travel.

In reality, you have to make sure your linear rails also have enough travel and you don't have any other interferences.

[keebler303]

See attached.

The bearings and whatnot occupy the same length regardless of the total length of the screw.

[wizard]

I'm a firm believer in the idea that questions aren't dumb.

I want to eventually extend my "z" from 3" of travel to, 6" of travel. So how long will the lead screw need to be? I can't quite wrap my brain around this obvious question.

All things being equal add the additional length you want to the threaded area. However if you change anything, the nut, motor mount, bearing mounts or whatever you may need to adjust further.

Not including the motor, what I have now for a lead screw is approx. 8" long. If that length is giving a 3" travel should an additional 3" be added to get 6" of travel, or will I need more.

Just how much of the current screw is used? Depending upon the engineering put into the current design you might have some travel to spare.

I had originally thought that a 12" screw would be sufficient to yield a 6" travel, but now I'm not so sure. Comments are welcome. This is what my machine looks like

Most likely the entire slide assembly will have to be redesigned. A quick look at the assembly ought to indicate if there is any additional travel potential for the Z saddle. That is a longer lead screw does nothing for you if your linear components don't support the travel you want.

[nlancaster]

But looking at those pictures his z-axis would seem to have about 4-6 inches of travel. That is what I am referring to.

[wizard]

But looking at those pictures his z-axis would seem to have about 4-6 inches of travel. That is what I am referring to.

It does look that way, which is why somebody needs to break out a tape measure to see what is really there and available to use.

[SPEEDRE]

Yep a tape measure did help. It seems I will have to build a new z axis carriage to do it. Onward and upward!