Lexan for jigs

[upand_at_them]

I see most crosscut sleds use 3/4" plywood for the base, but why couldn't I use 1/4" Lexan instead? It's a stable material, isn't it?

Mike

[Toller]

I used 1/4" ply. Worked fine. Lexan "should" work, but plastic can shatter and throw out shrapnel. I would avoid it.

[Teamcasa]

I would think it would work but after some use it would scratch up badly. I'm unsure of its stability with heat. It melts easily. I use 9mm Baltic Birch (3/8") Plywood. Stable and strong.

Dave

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[willim]

upand_at [e-mail] wrote in news:1156283102.389344.3920 @p79g2000cwp.googlegroups.com:

Lexans attribute is that it does not scratch as easily as other plastics. I use 3/8 all the time for jigs. It is used as trays and stuff for wheelchairs.

1/4 is a little thin for a sled but I think it will work if you are careful. Chamfer edges, holes and slots; cracks will propagate.

Bill

[CW]

Lexan shatter? Unless you freeze it, it's less likely to shatter than the piece of oak you're cutting on the sled you built.

[TBM]

Really? Oak must be pretty shatter prone, because I have seen many of peices of Lexan or acrylic sheeting shatter. I tried to cut a peice with a CMS once, wasn't pretty.....

[Tom]

Where can one purchase Lexan and what sizes does it come in?

[Edwin Pawlowski]

1/4" will probably flex too much for a sled

[Sergey Kubushin]

Yesterday I was milling some parts of 3/8" Lexan sheet. On my metalworking vertical mill with a regular 2 flute end mill for aluminum. What I can say Lexan is amazing stuff. Tough, not melting, not brittle, pure pleasure to work with. 1/4" deep 1" wide single pass cut is very smooth, shavings from the mill are clean and don't have a slightest sign of melting. Aluminum is much worth--it DOES melt and sticks to a mill. Regular 6061 alloy machinability is considered fair. I would give Lexan "Excellent" grade. Pure pleasure. It would definitely made fantastic jigs. Much better than oak.

[LRod]

Really? Acrylic yes, but you'd be hard pressed to get Lexan (polycarbonate--different stuff altogether, I believe) to shatter. Post pictures if you do. In fact, it's used to make shatter proof features, even bulletproof in thicker construction.

[gkemper]

It had to have been acrylic which will crack/shatter very easily. It does have the benefit that it doesn't scratch very easily.

Lexan on the other hand will never shatter even hitting it with a sledge hammer, but will easily scratch.

When lexan was first introduced they made frying pans out of it to show some of it's properties.

Gary

[CW]

Any plastics place. It's quite common. 4x8 sheets. Thickest I've seen it was

2".

[CW]

So, which was it? Lexan (polycarbonate) or acylic. Completly different stuff. I know, it was clear stuff, right?

[Toller]

Acrylic is much brittler (is there such a word as brittler?), but I have had lexan shatter when cutting it with a CMS. It sent some pretty impressive shards out.

[Lew Hodgett]

You got frying pans, we got individual size pie plates.

Put it in a vise to try to crack it.

No luck, it bent but didn't break.

BTW, like TeamCasa, I'm a birch ply kind of guy for sled bottoms.

Lew

[TBM]

Both.

[gkemper]

Try flaming the edges of the cut material with a torch.

The only drawback to lexan is that it scuffs and scratches easily. If you are looking for a satin type of finish just steel wool it.

Other than that it is great stuff!

Save the Acrylic for display cases for which it is great for. It won't dull after repeated cleanings.

Gary

[lwasserm]

Really, lexan (polycarbonate) is very different from plexiglass (acrylic) in how it reacts to stress & strain. Plexiglass will shatter quite easily but lexan usually deforms. You can actually bend the thinner stuff in a sheet metal brake.

[dingbat]

Normally Lexan (polycarbonate) will bend into a pretzel long before it shatters, but there is one way to make it brittle. Lexan is mechanically tough, but chemically it's weak. Lots of common chemicals, including household solvents and detergents, can change its behaviour like this.

I used to work on big production-line machinery. One toolroom had a mis-match between its very expensive 1/2" Lexan safety shields around all the CNC machines and the cutting fluid they were using. Eventually there was a mishap on one machine and a chunk of metal came loose. It hit the screen and went straight through it, shattering the glazing like a Hollywood saloon window. They had to change cutting fluids, then replace every screen in the place.

Normally I'd have scrounged the scrap, but this stuff was so embrittled that plant maintenance couldn't even unbolt the screen panels from the frames without most of them cracking or breaking.

I'd also advise against Lexan for jig making. You don't need that level of impact resistance and the stuff's a pain to work with.

[B A R R Y]

I usually have piles of plywood and MDF cabinet offcuts available for jigs. I would have to purchase Lexan to use it. Wood is easier to shape, brad nail, and glue for a quick jig. Typically, I'll buy Lexan, UMHW, plastic laminate, metals... only when I have a specific requirement, and only if it'll be for a many-use tool.

Look in any metal shop,, wood shop, plastics shop, etc... Most shop jigs will be made from whatever materials they often work with, because they have some, they work with the material often, and the correct tools and sundries are already handy.

The bottom line is if you like to spend time and effort building pretty jigs, Lexan would probably work fine. Aluminum is nice, as well. On the other hand, if you make many jigs on the spot, specifically for an operation at hand... There's nothing wrong with either approach, it's a personal choice.