So I have tried to ask Sienci if they can give me what length of rails I need to modify my MK@ from 30x30 to 16 (Y)x20 (X)…they refuse to help. Tell me they do not have the "Resources) to give me that assistance. I was under the impression they were engineers who actually created and built these machines and it should be simple enough to tell me what length to cut my rails to accomplish this feat. I replied that in an email and they will not even reply.
SO—do I just simply cut the rails shorter by the amount I want to reduce the machine and the lead screws, and then modify the $130 / $131 to the appropriate numbers?
I know most folks want bigger machines, but 30x30 is actually larger than anything I do and the space in my shop is wasted. I plan to modify it smaller, make a flip sytsem to enable me to flip the whole cnc up to the wall, then just bring it back down when I need to use it.
Hi Steve,
I think a good start is to collect a calculator, a measuring tape to measure up the machine you have and verifie how much longer the axis are vs the actual cutting area.
This picture might give an idea, but beware, it may include feet sticking out so take it as an indicating only and go with what you actualy measure.
Jens has some good tips and storys one post down.
I do not have a MK2 so take this with a grain of salt …
yes, I would reduce the rail and the screw by the same amount BUT … before you slice and dice, Have a look-see at the screw. Does it have an area where the screw shaft is reduced to fit into the bearing on that side? Do you have the capability of doing that work while keeping the shoulder in line /concentric with the screw? Be aware that on a lot of these kinds of screws (most certainly any ball screw which I don’t think yours is) there is a surface hardening treatment applied. You will need to make sure that what you are using for cutting is harder then the screw or you need to grind the screw end off. Whwn turning down the shoulder you should use a carbide cutter and it probably needs to cut deep enough to clear the surface hardening.
Of course it is also quite possible that the screw isn’t hardened.
As far as Sienci not answering your question - besides the fact that they have their own work to do, they would leave themselves open to all sorts of claims if the modification didn’t work out as expected. IMHO, it is not surprising that they didn’t answer you.
As a side story, many many years ago I bought a brand new Ford F250. Well I never thought that anyone could be so stupid as to not have a standard tow hook at the front of a work truck. There also was no optional tow hook available. I looked at the structure of the truck, found what I would have considered to be a suitable attachment point and contacted Ford to see if they agreed. Crickets … nada … absolute silence … and I didn’t want to replace the stock bumper with an aftermarket bumper that had a tow hook as part of it.
Not sure why you think they should help. Notwithstanding the resources required, I’m sure they don’t want the liability.
All their products are open source. The full drawings are available for you to view, redesign, and re-engineer if you wish.
Open Source 
- LongMill MK2 CNC
And the lead screw itself is here:
LongMill Benchtop CNC MK2 | 1030mm ACME Lead Screw (T8, 4-start)
It looks like a plain screw without any machined surfaces.
I’ll second Jens hardened steel comment.
And the first thing I would do is modify the software settings you propose to make it think it’s a smaller machine. If that works, you move on to step 2.