DIY Linear Bearings

[JAZZCNC]

Ok - it looks like i'm looking in the £200 ballpark which is a lot more than the DIY route...but I know i'm not looking at like for like here.

I'll carry on drawing up the rough design & then look at the exact rail lengths involved.

Send Chai an email for quote here [email protected] with lengths and number of bearings and you may find it's bit cheaper.
Either way i'd wait and save up a bit before take the DIY route because you will end up disappointed and wasting money trust me.!!

Another thing to consider is the small extra investment will pay back big time further down the line when your ready to upgrade because you'll easily sell the machine and recoup most the cost (If done well you'll make money). DIY route you'll struggle get anybody to look at it and even then they'll want it for nothing.!!
Also look at it this way your first DIY effort ended up in the bin so any outlay was lost.!! . . . . For the slight extra cost of doing with better materials it would still be alive, same goes here but this time you do plan on using better materials but will let the machine done with crappy DIY bearings. . . Better but only just.!!! . . .Not worth skimping on IME.

If i'm using aluminium profile for the table sides (I think the sides are 80x40 from memory), whats the best way to attach the supported rail to them given that the mounting holes won't match the slot spacing?

You can just tap the profile but a better way is to fasten 10-12mm strip of aluminium with counter bored holes down centre and fasten into slots then fasten rail to that by drill/tapping into it.
Problem with fastening straight to profile is there's not much material and the threads strip.!!

Edit: Have you considered using steel.? It's much cheaper than Alu profile, stronger and taps no problem so no messing around.