New build – input/comments appreciated

[JAZZCNC]

I think a few of the boys have done it, most recently mr njhussey look at his thread

What you mean a few have done it I practicly invented it, all them other buggers just copied me. .

But he's right it does work well.! . . . . Not pretty but affective.!

I don't know if it is necessary, but I think the cover plate over the X-axis ballnut holder will stiffen the holder in the x direction.

Yes it's very necessary and I'd suggest something a little stiffer than that thin plate. Look a pic #2 and you can see the kind of stiffness i'm talking about.

Kingcreakys suggestion to use only a single Y-axis motor and use a belt instead, sounds very interesting. Obviously you save a motor and a driver and you avoid any misalignment between the two gantry sides. This is a fairly heavy machine.
Do you think that one Nema 23 motor is sufficient to do the job?

No for gantry this weight you'll really need nema 34 around 6nm with high voltage drives. The machine in Pic 2 uses twin screws joined with belts running a nema 23 on 70Vdc and while it very works well this is about the size limit of machine I'd fit it on.

Obviously the top cantilevers at the rear of the machine, after having extended them, will obstruct a belt. Extending them gave me an extra 153mm, so that the spindle could Work 70mm in front of the frame, which is a fairly small work area for dovetails. So I was thinking if I only extended the front end rails I could fit a belt and I would have 153mm length for the dovetails, which I think would be plenty.

Personally I would have a little at both ends. Think about the future or upgrades like 4th axis.? Passing the front with enough length will allow a very easy and neat 4th axis to built into the machine without impacting the cutting area.
The extra cost of longer rails or ballscrews won't be that much and usabilty of the machine is much higher. The extra functionality will return the cost 2 fold when you come to sell it or pay for it's self within a few jobs.

JAZZCNC - I noticed on your Pictures, that you are using a lot of proximity sensors. I was planning on using micro-switches, but maybe the proximity sensors are more reliable? Do you prefer magnetic, capacitive or inductance types?

Prox switches I use are inductive and they are much much better than low/mid end mechanical switches. Cheap as chips and very accurate.
I posted a video showing how repeatable they are.! . . Excuse my horrible voice!!