What's the most rigid way to join 80/20?

[jcdillin]

Originally Posted by digits 1) Please don't rub it in - Ebay UK is useless for anything CNC - my rails/screws/motors will have to be new 2) Even if your frame wasn't perfectly straight before mounting those rails, I'd bet the frame flexed to fit the rails rather than the other way round

Yeah even here it's hard to find stuff on ebay everyone else bids it up so high that it's hard to afford on my budget.


lol your probably right!

[studysession]

Originally Posted by jcdillin Also another note, don't bother buying their expensive T nuts and bolts, I use standard 5/16" carraige bolts from home depot. I get 100 nuts and bolts for about the same as it costs for 10 T nut and bolts. The heads fit perfectly into the channels and work great.

Thanks for sharing. I am ordering 8020 material for a setup I am building. The pic's look great.

[digits]

Well, having actually played with a shed load of aluminium extrusion and 350 t-nuts, I have learnt a few things, but also have some more questions for those in the know:

All the brand-new extrusions that I have bought (Hepco & Bosch) have been very squarely cut. This has actually made square butt-joints possible, but I still haven't used them much in my design as my gut feeling is that stacking extrusion can give stronger joints.

The cast 90 degree aluminium corner brackets are pretty solid, but they are a pain to use with T-nuts as the nuts rarely want to rotate so that they are perfectly at right-angles to the slots. This has a negative effect on rigidity, so it is very important to get right! The other problem with the cast brackets is that they obviously don't provide any clamping directly where the profiles meet, as they are offset from the joint - which seems to mean that you'll need at least two brackets per joint to achieve any torsional rigidity. Finally, and this is significant IMHO, the brackets are about £10/$20 each with fixing hardware.

What I haven't tried so far is drilling into the profiles - I know they do have fixings that are designed to slide into a T-slot and then be tightened using an allen key via a hole drilled through from the far side of the profile, but what I want to do is to use T-nuts and through bolts to bolt two profiles together with the bolt head on the outside of the profiles for easy adjustment. Has anyone done this, and if so, does drilling holes through the T-slots significantly weaken the profiles? Also has anyone tried drilling through the profile edges/centres, rather than the T-slots - e.g. to mount something with a 1.5" bolt pattern on extrusion with a 1" gap between T-slots?

Cheers.

[hippy]

Originally Posted by digits Well, having actually played with a shed load of aluminium extrusion and 350 t-nuts, I have learnt a few things, but also have some more questions for those in the know: All the brand-new extrusions that I have bought (Hepco & Bosch) have been very squarely cut. This has actually made square butt-joints possible, but I still haven't used them much in my design as my gut feeling is that stacking extrusion can give stronger joints. The cast 90 degree aluminium corner brackets are pretty solid, but they are a pain to use with T-nuts as the nuts rarely want to rotate so that they are perfectly at right-angles to the slots. This has a negative effect on rigidity, so it is very important to get right! The other problem with the cast brackets is that they obviously don't provide any clamping directly where the profiles meet, as they are offset from the joint - which seems to mean that you'll need at least two brackets per joint to achieve any torsional rigidity. Finally, and this is significant IMHO, the brackets are about £10/$20 each with fixing hardware. What I haven't tried so far is drilling into the profiles - I know they do have fixings that are designed to slide into a T-slot and then be tightened using an allen key via a hole drilled through from the far side of the profile, but what I want to do is to use T-nuts and through bolts to bolt two profiles together with the bolt head on the outside of the profiles for easy adjustment. Has anyone done this, and if so, does drilling holes through the T-slots significantly weaken the profiles? Also has anyone tried drilling through the profile edges/centres, rather than the T-slots - e.g. to mount something with a 1.5" bolt pattern on extrusion with a 1" gap between T-slots? Cheers.

Forget the t-nuts and go with 5/16 carriage bolts. A 1lb bag at Menards goes for about $1.25 for 3/4 to 1 1/2 inch.
Theres plenty in a bag.
I'm using 3mm x 3inch x 5inch steel plating for corner brackets and it works very well with the carriage bolts.
And yes, in my opinion stacking two extersions (80/20) and bolting them together is way stronger if you use steel plating.

[digits]

I recently changed suppliers, and while the new bits and bobs are almost identical to the old ones, they go together more easily, and seem to be more rigid - which is nice