CNC Router V1.0 (For Cutting Multiple Materials)

[GEOFFREY]

Why is it not possible just to drill a bigger hole in the bottom face of the tube and nut up to the underside of the top face? G.

[JAZZCNC]

Why is it not possible just to drill a bigger hole in the bottom face of the tube and nut up to the underside of the top face? G.

It is possible Geoffrey but to be honest it's not needed. Mostly I use 4 or 5mm without any problems but in the past I've fitted rails to 3mm box with no issues. The fine pitch gives enough threads engaged and because of the number of bolts you don't need to swing on them to tighten down.
I just use spring washers with loctite on threads and never have any trouble. The rails on my machine are into 3mm box and have been on for over 6yrs without any bolts coming loose so it works well enough.

[Wobblycogs]

When I started building my first frame I (stupidly) decided to bolt it together, I was worried but stripping threads etc so I did some experimenting...

The test piece was 4mm steel box section drilled and tapped for use with regular M6 socket screws. With a screwdriver and a hex head I couldn't do the bolts up tight enough to strip or damage the thread in the box section. With a regular Allen key I generally couldn't damage the thread, after repeated re-tightening as tight as I could do by hand I did manage to make a couple of the test holes a bit loose. With a cheater bar on the Allen key I could strip the threads and using a drill driver without torque limiting I could strip the threads. My conclusion was 4mm box + M6 was more than strong enough for what I was doing.

I also experimented with some 3mm box + M6 and concluded it wasn't good enough. You can get a thread in it but it's clearly not much good. M5 worked and M4 (which is what I suspect your rails will be using) was fine.

[biketrialsdave]

Yet again, thank you for all the help! I think I may end up going for something like 60 x 40 x 3mm box section as this is within the capabilities of my welder and isn't too expensive.

[Clive S]

Yet again, thank you for all the help! I think I may end up going for something like 60 x 40 x 3mm box section as this is within the capabilities of my welder and isn't too expensive.

If you can go with 4mm all the better for drilling a tapping. ..Clive

[biketrialsdave]

Hmm if I can get away with 100A/2.5mm electrodes then maybe. Although it is an added cost...

The rail I have takes M4 bolts so thats 4.28 threads for 3mm and 5.71 for 4mm... I think the rule is 1x the diameter?

[biketrialsdave]

Started work on the base...

[JAZZCNC]

Hmm if I can get away with 100A/2.5mm electrodes then maybe. Although it is an added cost...

The rail I have takes M4 bolts so thats 4.28 threads for 3mm and 5.71 for 4mm... I think the rule is 1x the diameter?

Listen trust me it will be fine. One more added point My machine was mounted vertical for well over a year and other than hanging from the ceiling you couldn't put more stress on the bolts has they had all the weight of the gantry bearing down on them and they didn't even flinch. Go for it won't be problem.!