CNC Router V1.0 (For Cutting Multiple Materials)

[JAZZCNC]

Just pulled it out the garage, its the one in the link below. Very cheap and cheerful. Only a 100A output.. What sort of thickness steel box section would be best to use? 3/4mm?

http://www.metals4u.co.uk/welding/we...sp?prd_id=3124

4mm will be better than 3mm but either will work. With 100A you'll be limited to 2.5mm rods which will be better suited to 3mm.

[biketrialsdave]

I will find all my gear and get hold of some scrap metal sometime this week! :) It's always good when you find a reason to use an untouched tool! Out of interest, how are people bolting their linear rails to box section? Bolt all the way through both sides?

[Clive S]

I will find all my gear and get hold of some scrap metal sometime this week! :) It's always good when you find a reason to use an untouched tool! Out of interest, how are people bolting their linear rails to box section? Bolt all the way through both sides?

You can't bolt all the way through as it would squash the box section without spacer tubes I used 5mm box section so just drilled and tapped it but others have glued a steel plate inside the box section with gorilla glue and then drilled and tapped. As Dean says you don't have to be super accurate because you can use epoxy on the top with a moat between the rails so that it levels out on the same plane.
When and if you come to this step just ask as quite a few people on here have used it. I used the Wests System which is ultra slow curing ie 15 -20 hours and so levels out very well ..Clive

[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.