Intro to aluminium extrusion

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mdf

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#235920 9-May-2018 16:56

I have a project in mind that I think would be well suited to aluminium t-slot extrusion. I've never used the t-slot stuff before and am not even sure what terms I should be googling to learn more. Everything I have tried so far seems to pop up with office furniture related links.

What I want to build is basically a t-square, but with the ability for the blade (the long bit) to be loosened and moved along the stock (the short bit) and re-tightened. Once re-tightened, it should be back to a true square/90 degrees. I want to see if I can figure out a better approach to a table saw fence. My current wooden one is okay, but there is definite play in it an a couple of bits are just slightly off true.

I think I've figured out that 4020 t-slot should work well, but I'm still trying to work out the range of various fasteners and things.

Any guidance on what I should be looking for (or the terms I should be googling would be appreciated).

Also, any local suppliers and hints on how to work with it wouldn't go astray - is an aluminium cutting blade on a drop saw or table saw sufficient? Or should I be using a grinder and abrasive cut off discs?

mkissin

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#2012974 9-May-2018 21:28

Minitec is the common brand you might be looking for. They have pretty much everything you could ever want, but it's not the cheapest. We've used it a bit at work for building test rigs.

SMC is the only NZ reseller for Minitec (AFAIK), but there are a heap of other equivalent brands that might have differing quality.

neb

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#2013031 9-May-2018 23:57

Local suppliers will cost you an arm and a leg compared to getting it direct from Aliexpress/eBay. We're talking as much as ten to twenty times more expensive locally. I realise they have to warehouse the stuff and manage it locally, but selling a $1 part for $20 is pretty outrageous.

As for what you need, that's a pretty open-ended question, for starters you'll want a pile of T nuts, just get a pack of fifty or so from China, then black M5 hex socket screws to fit the T nuts, to join things up perhaps L-shaped interior connectors or brackets (be careful with these, some use M4 grub screws not M5 + T nuts), some plastic end caps, and then you can buy various lengths of 4020 online.

If you want to get it locally, try Mecha4Makers or CNCKits.

neb

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#2013042 10-May-2018 00:02

As a separate reply, there are about a bazillion tutorials on making your own table saw sled online, generally out of wood, why not use one of those? 4020 extrusion and equivalent is mostly used for building frames for equipment and devices, things dealing with static not dynamic loads, I'm not sure how it would hold up to being moved around a lot on a table saw.

frankv

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#2013080 10-May-2018 08:26

If you want the parts to be removable from the extrusion, get ordinary T-slot nuts. These are a bit less that 5mm wide, so they can be put in via the slot and then rotate to hold it. If you loosen them, they can be rotated to align with the slot and you can take things apart. They can be a bit of a pain if you're screwing into them blind (behind another part) because you can't tell if they're properly aligned across the slot or not. So, if the parts aren't going to be taken apart, get square nuts. These are 10mm on each side, and you have to put them in at the end of the slot and slide them into place.

mdf

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#2013357 10-May-2018 13:13

Thanks all. Will look into it more. Sounds encouraging. And if nothing else, I get something new to play with.

neb: As a separate reply, there are about a bazillion tutorials on making your own table saw sled online, generally out of wood, why not use one of those? 4020 extrusion and equivalent is mostly used for building frames for equipment and devices, things dealing with static not dynamic loads, I'm not sure how it would hold up to being moved around a lot on a table saw.

This is for the rail and the fence on my table saw (see previous post for link to pics) rather than the sled. I've spent plenty of youtube time looking a homemade rails and fences, which inspired the design of the current one. While the fence I made isn't too bade, the j-frame rail isn't perfectly straight and has a little bit of flex it in. This was fine when I first put it together, but much to my surprise, I seem to have advanced my woodworking to the point where I actually notice when cuts don't come out true. The plywood j-frame was a good start since it doesn't expand and contract as the humidity changes, but I can never get it perfectly true with the tools I have (I don't have a jointer). I was trying to figure out a better way to use an aluminium panel on it to compensate, but then it occurred to me that maybe a solid bit of aluminium might be better. This is my currently thinking (excuse the 5 minute sketchup job):

A length of extrusion would be fixed to the front of the bench saw as a rail. Another bit (probably more extrusion but maybe something else) would have a finger wheel and bolt going through into the t-slot of the rail. Tightening the finger wheel would pull the sliding bit into the rail tight and (hopefully) square. The fence would be fitted to the sliding bit.

I was thinking to make the whole thing out of aluminium since its relatively light and already true. I'd place some plywood or maybe plastic at the bottom of the fence so it's not scraping along the cast iron of the saw bench top. I'm not sure what kind of fixings to join pieces are available though. The corner brackets for example would be fine in the triangular reinforcing bit on the sketch, but would prevent the sliding bit pulling in square if I tried to put them on the underside of the fence.

Having looked at the sketch, I'm now thinking 8040 might be better than 4020?

neb

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#2013553 10-May-2018 18:55

frankv:
If you want the parts to be removable from the extrusion, get ordinary T-slot nuts. These are a bit less that 5mm wide, so they can be put in via the slot and then rotate to hold it.

Those aren't ordinary T-slot nuts, the standard ones are sliding T-nuts which use friction to hold them in place, the drop-in ones are less robust even than that. Given that a table saw sled is going to have a fair bit of stress put on it, I really wouldn't use either. What about getting a 3mm alu flat bar (Bunnings have them), stacked as required and use a countersunk screw to attach it to a piece of hardboard, and then an alu L-bracket as a fence?

Some sort of diagram of what it is you're after would probably help with the advice here...

neb

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#2013561 10-May-2018 19:06

mdf:
This is my currently thinking (excuse the 5 minute sketchup job):

Ah, that helps a lot. So I'd go for alu stock rather than T-slot stuff, check out what Bunnings have under the Metal Mate brand. The only tricky bit is going to be the adjustable portion.

neb

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#2013565 10-May-2018 19:15

To answer my own question, just did a quick Google on what a pre-made rail and fence costs. Holy bleep those things are expensive, I can see why you'd want to DIY it.