seeing through Lexan, darkly

[Bruce Seidner]

I have been decifering the differances between plexiglass and lexan and lexan is described as less brittle. There is an adhesive, Weld-On 45 from IPS corp that folks making windshields for home made aircraft are favoring. (And I thought wood working was dangerous.)

I want to make a TS blade hood and can think of some other applications, but have no experience with this material. It comes in any number of thicknesses and 3/16" and 1/4" are not too pricey but for all I know anything short of 1/2" is an accident waiting to happen.

I assume it cuts with a special blade and that there is some plastic fantastic web-source for all things someone working with this stuff would find usefull. I will continue looking for primer and diy oriented information but thought I would tap the collective genius in this forum.

Thanking all in advance.

[Alan Schaffter]

I have been decifering the differances between plexiglass and lexan and lexan is described as less brittle. There is an adhesive, Weld-On 45 from IPS corp that folks making windshields for home made aircraft are favoring. (And I thought wood working was dangerous.)

I want to make a TS blade hood and can think of some other applications, but have no experience with this material. It comes in any number of thicknesses and 3/16" and 1/4" are not too pricey but for all I know anything short of 1/2" is an accident waiting to happen.

I assume it cuts with a special blade and that there is some plastic fantastic web-source for all things someone working with this stuff would find usefull. I will continue looking for primer and diy oriented information but thought I would tap the collective genius in this forum.

Thanking all in advance.

The info is all on the web, but just off the top of my head:

Plexiglass (a brand name) is an acrylic and the more brittle of the two.
Lexan (a brand name) is a polycarbonate.

With care, both materials can be machined relatively easily and successfully with normal WW machines (bandsaw, tablesaw, jointer, router, sander, drill press), though special blades, drill bits with different angles, etc. can be purchased. Both materials can be solvent welded by clear chemicals available from from IPS, Tap Plastics, Acme Plastics, etc. The solvent welding chemicals typically used are watery and often applied at the edges of a joint with a hypo needle and flow between the pieces by capillary action when bonding straight flat pieces. The solvent also comes in a higher viscosity "glue" for bonding parts with less-than-perfect edges.

Instead of solvent bonding, both materials can be drilled, tapped, and bolted together for disassembly later. Both come in clear and various semi-transparent and solid opaque colors and with metalicized coatings. Both can be filed, scraped, sanded and polished after cutting for a perfectly clear edge. Flaming works for this also. Both can be heat formed or heat vacu-formed, although I believe Plexiglass is the preferred material for this. Both materials are very suitable for prototyping, etc.

Both materials can be purchased at a discount and in smaller quantities from surplus houses and on Ebay. Plastics fabricators often sell cutoffs directly or on Ebay.

I have used both extensively- for ww jigs, waterproof U/W camera and light housings, science fair projects, TS blade dust shrouds and guards, prototyping for my last invention, and yes, even homebuilt aircraft parts (yup did that years ago).

http://www.ncwoodworker.net/pp/data/1403/medium/PB050012.JPG

[Jim O'Dell]

Bruce, I made one out of some 1/4" material left over from the previous owner. It wasn't brittle, so must be Lexan. I used it for the sides. The top that was curved I used some PTEG scrap that Ed from Clear Vue sent me. The Lexan drilled and even tapped pretty good. I've made 2 so far, the last one replaced the first which got scrapped for the hookup and the screws. There is a picture of it here: http://sawmillcreek.org/showthread.php?t=14427&page=6 About 2/3 down the page. It uses a 4" hook up that is a 4" round to 4 X 3 gutter downspout fixture. Works great with S&D 2729 4" pipe. I used a plastics blade on my TS to make the straight cuts, and my 1/4" blade on the BS for the curves, and a lot of filing. Jim.

[Lee Schierer]

Acrylic can shatter if struck sharply or dropped and is much more prone to stress cracking when compressed under a screw head. Polycarbonate is going to be much more impact resistant and less likely to crack. I would go with Polycarbonate if it were my guard project.

[Tom Vanzant]

Bruce,
Polycarbonate (Lexan) drills and taps very nicely, but use lock washers... Lok-tite and similar will craze the Lexan.
Tom

[Bruce Seidner]

Once you get the right lingo the Google goes so much faster. Thank you one and all.

But while I can be personally quite thick at times, what thickness does Lexan need to be for a robust inlet. I don't expect it to stop 45caliber bullets point blank but I don't want to have to fuss about it either.

[David Hawxhurst]

1/4" is probably strong enough, but 3/8" or thicker is easier to work with has more than enough strength. i use 3/8" for fish tanks up to about 30 gal and 1/2" for tanks up to 55 gal size.

[Greg Portland]

PETG is easy to form (cold bending or heat bending) and is shatter resistant. Also, it is clearer and cheaper than polycarbonate.

[Alan Schaffter]

PETG is easy to form (cold bending or heat bending) and is shatter resistant. Also, it is clearer and cheaper than polycarbonate.

ClearVue used PETG for their cyclones.

[Bruce Seidner]

PTEG is great stuff. I will try to find it locally. With shipping it would be less expensive to purchase a store bought blade intake and then enlarge what I am finding to be shop vac sized ports. This one can be had from Penn State for $25. Though, it lacks the beard of Alan's more mature inlet. Maybe as it ages...

Alan, what is your thinking about the surround that you use? Is this about allowing more distance from the piece and still create some boundary and/or does it increase the volume of air while controlling the dispersion of the dust?

[Alan Schaffter]

PTEG is great stuff. I will try to find it locally. With shipping it would be less expensive to purchase a store bought blade intake and then enlarge what I am finding to be shop vac sized ports. This one can be had from Penn State for $25. Though, it lacks the beard of Alan's more mature inlet. Maybe as it ages...

Alan, what is your thinking about the surround that you use? Is this about allowing more distance from the piece and still create some boundary and/or does it increase the volume of air while controlling the dispersion of the dust?

The reason I used a soft (bristle) surround was because I don't like the way most 100% plastic surrounds mount. They must pivot or articulate (usually via a parallelogram mount) to lift up over stock being cut and then don't conform to the stock as they ride over it. That leaves open sides where dust can be ejected. My bristle shroud doesn't conform perfectly either, but is much better than most.