Return-Path: Sender: (Marvin Kaye) To: lml Date: Fri, 29 Nov 2002 11:45:26 -0500 Message-ID: X-Original-Return-Path: Received: from mail.indian-creek.net ([209.176.40.9] verified) by logan.com (CommuniGate Pro SMTP 4.0.2) with ESMTP id 1891129 for lml@lancaironline.net; Fri, 29 Nov 2002 11:29:12 -0500 Received: from VAIO (sl15.du.indian-creek.net [209.176.40.31] toucan@78055.com) by mail.indian-creek.net with SMTP (IOA-IPAD 3.70a/96) id 63DA800 for ; Fri, 29 Nov 2002 10:29:12 -0600 X-Original-Message-ID: <000201c297c4$6daec670$1f28b0d1@VAIO> From: "Jim Cameron" X-Original-To: "Lancair Mailing List" Subject: Drilling and machining plexiglass X-Original-Date: Thu, 28 Nov 2002 18:08:52 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0037_01C29709.350DEC80" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2720.3000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 This is a multi-part message in MIME format. ------=_NextPart_000_0037_01C29709.350DEC80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable First, plexiglass is not always plexiglass. Every manufacturer (and = probably every batch) has a different composition, sometimes very = different. Some formulations have a lot more styrene in them, extruded = rod and cylinders, e.g., and these are much worse to work with. They = crack and craze and chip, etc. Sheet material from name manufacturers = like Rohm & Haas or DuPont is infinitely superior to the unbranded stuff = that comes from Mexico or Asia. Dimensions are always approximate; due = to variable shrinkage during polymerization of the sheet, a nominal 1/4" = sheet can be anywhere from 0.210" to 0.280" in thickness. Any cutting or machining of plexiglass will induce stresses in the = material, and the more unrelieved stress, the more likely the material = will craze later on, or even crack and break. The ideal treatment is to = anneal the material after all the machining is done, but I doubt many of = us have the ovens that would be needed for doing, say, a windshield. = Also, the temperature is critical, so most home-type ovens would = probably end up melting the material. All of that said, the best procedure is the one that will produce the = least stress. Abrasion is better than any cutting action with a = percussive component. A band saw is better than a saber saw, and so = forth. Lubricate with water, with dishwashing detergent a good additive = (a few drops in a cup of water). The only solvent that doesn't seem to = affect it is ethanol, but I would only use that sparingly for removing = adhesives and other gooey stuff. As for drill bits, the ones ground for = plexi have zero rake, so they really abrade the material away rather = than cutting it. The main risk with a normally ground bit is when the = bit starts to come out the back side (or bottom) of the hole. As soon = as it pokes through, it wants to grab, usually with disastrous = consequences -- chattering, shattering, and other such events. Plexi's a funny material, and requires its own special set of tools and = techniques. DuPont and other quality manufacturers have good tech = bulletins on working techniques, and also have most of the info posted = on the web. Jim Cameron Lancair Super ES N143ES ------=_NextPart_000_0037_01C29709.350DEC80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

First, plexiglass is not always = plexiglass. =20 Every manufacturer (and probably every batch) has a different = composition,=20 sometimes very different. Some formulations have a lot more = styrene in=20 them, extruded rod and cylinders, e.g., and these are much worse to work = with. They crack and craze and chip, etc. Sheet material = from name=20 manufacturers like Rohm & Haas or DuPont is infinitely superior to = the=20 unbranded stuff that comes from Mexico or Asia. Dimensions are = always=20 approximate; due to variable shrinkage during polymerization of the = sheet, a=20 nominal 1/4" sheet can be anywhere from 0.210" to 0.280" in=20 thickness.

Any cutting or machining of plexiglass = will induce=20 stresses in the material, and the more unrelieved stress, the more = likely the=20 material will craze later on, or even crack and break. The ideal = treatment=20 is to anneal the material after all the machining is done, but I doubt = many of=20 us have the ovens that would be needed for doing, say, a = windshield. Also,=20 the temperature is critical, so most home-type ovens would probably end = up=20 melting the material.

All of that said, the best procedure is = the one=20 that will produce the least stress. Abrasion is better than any = cutting=20 action with a percussive component. A band saw is better than a = saber saw,=20 and so forth. Lubricate with water, with dishwashing detergent a = good=20 additive (a few drops in a cup of water). The only solvent that = doesn't=20 seem to affect it is ethanol, but I would only use that sparingly for = removing=20 adhesives and other gooey stuff. As for drill bits, the ones = ground for=20 plexi have zero rake, so they really abrade the material away rather = than=20 cutting it. The main risk with a normally ground bit is when the = bit=20 starts to come out the back side (or bottom) of the hole. As soon = as it=20 pokes through, it wants to grab, usually with disastrous consequences -- = chattering, shattering, and other such events.

Plexi's a funny material, and requires = its own=20 special set of tools and techniques. DuPont and other quality=20 manufacturers have good tech bulletins on working techniques, and also = have most=20 of the info posted on the web.

Jim Cameron

Lancair Super ES N143ES

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