BuildingAfloat

[Jonathan]

The sacrifice will be rapid speed which to quote John S only any good for "dick slapping".

That and bed surfacing. It's much more useful to have high acceleration, since this dictates how fast the machine can go round corners which is important for toolpaths with fine detail.

Like Jonathan I urge you to use ballscrews and the difference in cost if bought from china won't be very much and really lead screws can't be compared with even cheap ballscrews unless high quality lead screws which cost more than ballscrews.!

Use 16mm as well not 12mm.

Yes and yes...

though I have seen 8'x4' machines with 12mm

Seeing them doesn't mean they're any good! Unless you need a rotating nut on a 16mm screw (which is pushing it for 8') you'll need at least 20-25mm ballscrews on an 8' axis to get sufficiently high critical speed.

Also the BK/BF blocks from china are ridiculously cheap and I see no point in making your own.?

I make them myself since then I know the quality of the block and bearings is good and I don't want to limit my design by having to fit standard size blocks in. But for your average machine and particularly without the tools to make them yourself the blocks from China are excellent value.