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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Plexiglass drilling-tips please
Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled
in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Roger in Vegas Worlds Greatest Impulse Buyer |
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Roger Hull wrote:
Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Roger in Vegas Worlds Greatest Impulse Buyer You can use regular twist drills but you gotta keep 'em COOL or the Plexi will melt and leave a raised ridge around the holes, or worse, melt so much that the hole becomes oversized. Keep the drill speed low and don't try and "punch" the drill through with too much pressure. If the Plexi is horizontal you can build a low dam of modeling clay around the spot you're drilling and put a little water in it to help keep the drill cool. If you've got some extra Plexi, you might want to PRACTICE a little until you know you can drill the workpiece properly. HTH, Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "Truth exists; only falsehood has to be invented." |
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Roger Hull wrote:
Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Roger in Vegas Worlds Greatest Impulse Buyer 90 degree included angle, 90 degree relief |
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Roger Hull wrote in
s.net: Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Roger in Vegas Worlds Greatest Impulse Buyer Make sure that both sides are masked: if the original covering paper has been removed use masking tape to insure that both sides are masked where the holes are to go. Masking will reduce chipping as the bit enters and leaves the material. |
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"Roger Hull" wrote in message s.net... Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Roger in Vegas Worlds Greatest Impulse Buyer Use a drill press and go slow. Excess pressure will make it crack. Cracking was my biggest problem with plexi. Stev |
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Roger Hull wrote:
Any tips appreciated. One mo Clamp the piece down. If drill passes through it will pull the piece up and ... crack! Nick -- WDR Fernsehen: "Ein Computer arbeitet so lange Befehle ab, bis keine mehr vorhanden sind." Muss ich die dann irgendwie nachfüllen? |
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"Roger Hull" wrote in message s.net... Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. IIRC, that material undergoes a tremendous expansion rate on temperature change, so suggest drill oversize if the piece is very large at all--otherwise, it will crack--or else your fastener heads will break off upon weather changes..... What exactly is the application ??? -- SVL |
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""Nick Müller"" wrote in message ... Roger Hull wrote: Any tips appreciated. One mo Clamp the piece down. If drill passes through it will pull the piece up and ... crack! Another, place a pirce of wood under the plexiglas before clamping to aviod the drill breakout. -- www.billcotton.com Nick -- WDR Fernsehen: "Ein Computer arbeitet so lange Befehle ab, bis keine mehr vorhanden sind." Muss ich die dann irgendwie nachfüllen? |
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The material is very prone to cracking. I have good luck using a
step drill (Unibit). (top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) "Roger Hull" wrote in message s.net... Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Roger in Vegas Worlds Greatest Impulse Buyer |
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I always reduce the grind angle on bits I use for drilling plastics. I
picked up a set of mid quality drill bits at Harbor freight, and used them for various items, and when they needed resharpening, I just gro9und them to a lesser rake angle and put them asside for plastics. Less rake and reduced pooint angle keeps them from grabbing and chipping the exit side of the holes, and really makes a nice clean hole.....I use center cutting endmills as well in some cases, for larger holes. ============================================== Put some color in your cheeks...garden naked! ~~~~ }((((o ~~~~~~ }{{{{o ~~~~~~~ }(((((o |
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With hole diameter less than thickness, there shouldn't be a lot of
problems. You will probably have some chipping as a regular drill exits. If the hole is very near the edge, you may crack the material hole-to-edge. If you can buy a drill bit specifically made for plexiglass, most of these problems will disappear. Any plastics supplier will have the drill bits. Tim. |
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Along with all the other tips don't use any kind of oil on it. If you
do it will crack. Maybe not right away, but it will for sure crack. No doubt about it. Water is really best for a coolant. ERS |
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Eric R Snow wrote:
Maybe not right away, but it will for sure crack. Really? I always used cooling fluid (water + oil). But I never realized that this might be the cause for cracks. Yes, I had some/many fine but _only_ after glueing. I always thought that it has something to do with the way I glue (UV-hardening glue). astonished, Nick -- WDR Fernsehen: "Ein Computer arbeitet so lange Befehle ab, bis keine mehr vorhanden sind." Muss ich die dann irgendwie nachfüllen? |
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"Roger Hull" wrote in message s.net... Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Roger in Vegas Worlds Greatest Impulse Buyer Use brad and spurr bit at slow speed with wood under it. Do it all the time! |
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Nick Müller wrote:
Eric R Snow wrote: Maybe not right away, but it will for sure crack. Really? I always used cooling fluid (water + oil). But I never realized that this might be the cause for cracks. Yes, I had some/many fine but _only_ after glueing. I always thought that it has something to do with the way I glue (UV-hardening glue). astonished, Nick I don't think the oil CAUSES the cracks, but, as I understand it, the machining produces microcracks. The oil gets into these and causes them to spread (propagate). Eventually the whole area around the hole or cut just about crystallizes and crumbles from all the little cracks. Tapped holes are especially prone to this. Anyway, it DOES happen. Water does indeed seem to be the safest coolant/lubricant. ANY residual oil is asking for trouble. I have tried wax, and this does not seem to have the same degree of problem as oil. Perhaps some, but I've not decided one way or the other yet. Some micro-cracking is normal. Like many things, the plastic can have internal strains that are released during the cutting process. This may aggravate the cracks. Sometimes the plastic can be annealed to relieve this effect. It is heated evenly to a temperature below it's melting point, and allowed to set for a while, then slowly cooled. This may reduce cracking. I've not done this, and usually get decent results without needing it. What I do that DOES help a lot ... AFTER the cut is finished, seal any cracks(most are invisible at this point). This can be done with either heat (fire polishing)if it's an open surface, or a solvent chemical like Methylene chloride (liquid acrylic cement ... nasty stuff, use suitable gloves and good ventilation) which can be used even inside a hole. Even lacquer thinner may work fairly well (depends on the brand, as all are NOT alike). The solvent needs to melt the surface slightly, thus fusing any tiny cracks into the main body of the plex. A drop into a small hole should work fairly well. Let the plex dry and harden before trying to use the part. Some minor rework may be needed after for critical surfaces. Dan Mitchell ============ |
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Daniel A. Mitchell wrote:
but, as I understand it, the machining produces microcracks. ACK The oil gets into these and causes them to spread (propagate). Sounds reasonable. So I accept your oily oppinion. :-) Like many things, the plastic can have internal strains that are released during the cutting process. Oh yes, they do! I think Plexiglas XT (extruded) is worse than the GS (or G? anyhow, the casted one) Sometimes the plastic can be annealed to relieve this effect. I did this and it helps. But you can make it wrong too. 60 deg. C for several hours is OK, 70 deg. C will make new wraps. :-( What I do that DOES help a lot ... AFTER the cut is finished, seal any cracks(most are invisible at this point). Polishing helps most. 240 grit, then 400 grit whet, then a special Plexi-polish. For glueing, polishing is not required, the 400 whet is good enough. or a solvent chemical like Methylene chloride (liquid acrylic cement ... nasty stuff, use suitable gloves and good ventilation) which can be used even inside a hole. I had bad experiences with acetone. It introduced cracks (_very_ fine, but a lot). I think that the plexi swells a tad with the solvent, deforms and when the solvent vapors you get the cracks. Not a proven theory, just my experience. So I stay away from _any_ solvents (except for glueing, but there the solvent vapors much slower). Thanks for the insight, Nick -- WDR Fernsehen: "Ein Computer arbeitet so lange Befehle ab, bis keine mehr vorhanden sind." Muss ich die dann irgendwie nachfüllen? |
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I always regrind bits to almost no rake (bit scrapes instead of cuts) and=
use a mix of water and dish soap on it when drilling. Holes are clean, no breakout on= bottom (use back board on bottom of course). If you go to a place that sells "drill bits = for plastic" just look at the way they are ground. Otherwise they are just regular twist = bits. regards, Joe.=20 On Tue, 24 May 2005 11:59:05 -0400, "Daniel A. Mitchell" = wrote: Nick M=FCller wrote: Eric R Snow wrote: =20 =20 Maybe not right away, but it will for sure crack. =20 =20 Really? I always used cooling fluid (water + oil). But I never = realized that this might be the cause for cracks. Yes, I had some/many fine but _only_ after glueing. I always thought that it has something to do = with the way I glue (UV-hardening glue). =20 =20 astonished, Nick=20 I don't think the oil CAUSES the cracks, but, as I understand it, the=20 machining produces microcracks. The oil gets into these and causes them=20 to spread (propagate). Eventually the whole area around the hole or cut=20 just about crystallizes and crumbles from all the little cracks. Tapped=20 holes are especially prone to this. Anyway, it DOES happen. Water does indeed seem to be the safest coolant/lubricant. ANY residual=20 oil is asking for trouble. I have tried wax, and this does not seem to=20 have the same degree of problem as oil. Perhaps some, but I've not=20 decided one way or the other yet. Some micro-cracking is normal. Like many things, the plastic can have internal strains that are=20 released during the cutting process. This may aggravate the cracks.=20 Sometimes the plastic can be annealed to relieve this effect. It is=20 heated evenly to a temperature below it's melting point, and allowed to=20 set for a while, then slowly cooled. This may reduce cracking. I've not=20 done this, and usually get decent results without needing it. What I do that DOES help a lot ... AFTER the cut is finished, seal any=20 cracks(most are invisible at this point). This can be done with either=20 heat (fire polishing)if it's an open surface, or a solvent chemical like= =20 Methylene chloride (liquid acrylic cement ... nasty stuff, use suitable=20 gloves and good ventilation) which can be used even inside a hole. Even=20 lacquer thinner may work fairly well (depends on the brand, as all are=20 NOT alike). The solvent needs to melt the surface slightly, thus fusing=20 any tiny cracks into the main body of the plex. A drop into a small hole= =20 should work fairly well. Let the plex dry and harden before trying to=20 use the part. Some minor rework may be needed after for critical = surfaces. Dan Mitchell =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D |
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On Mon, 23 May 2005 19:30:22 -0700, Roger Hull wrote:
Hi, Gang: I have a piece of Plexi 1/4" thick that needs four holes drilled in it. Size yet to be determined, but under 1/4". I did this in school thirty years ago but not since and need a memory upgrade. Any tips appreciated. Here's a good web site on working with acrylic sheet. I found the info on thermoforming especially interesting. Here's the drilling section: http://www.bayplastics.co.uk/product%20guide/Altuglas-guidenavbar/prod-altuglass-tech(drill).htm |
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On Tue, 24 May 2005 11:59:05 -0400, "Daniel A. Mitchell"
wrote: Nick Müller wrote: Eric R Snow wrote: Maybe not right away, but it will for sure crack. Really? I always used cooling fluid (water + oil). But I never realized that this might be the cause for cracks. Yes, I had some/many fine but _only_ after glueing. I always thought that it has something to do with the way I glue (UV-hardening glue). astonished, Nick I don't think the oil CAUSES the cracks, but, as I understand it, the machining produces microcracks. The oil gets into these and causes them to spread (propagate). Eventually the whole area around the hole or cut just about crystallizes and crumbles from all the little cracks. Tapped holes are especially prone to this. Anyway, it DOES happen. Water does indeed seem to be the safest coolant/lubricant. ANY residual oil is asking for trouble. I have tried wax, and this does not seem to have the same degree of problem as oil. Perhaps some, but I've not decided one way or the other yet. Some micro-cracking is normal. Like many things, the plastic can have internal strains that are released during the cutting process. This may aggravate the cracks. Sometimes the plastic can be annealed to relieve this effect. It is heated evenly to a temperature below it's melting point, and allowed to set for a while, then slowly cooled. This may reduce cracking. I've not done this, and usually get decent results without needing it. What I do that DOES help a lot ... AFTER the cut is finished, seal any cracks(most are invisible at this point). This can be done with either heat (fire polishing)if it's an open surface, or a solvent chemical like Methylene chloride (liquid acrylic cement ... nasty stuff, use suitable gloves and good ventilation) which can be used even inside a hole. Even lacquer thinner may work fairly well (depends on the brand, as all are NOT alike). The solvent needs to melt the surface slightly, thus fusing any tiny cracks into the main body of the plex. A drop into a small hole should work fairly well. Let the plex dry and harden before trying to use the part. Some minor rework may be needed after for critical surfaces. Dan Mitchell ============ Take a look at a plexiglass pepper mill. They will be molded, with maybe a little machining done to hold the grinder parts. And then again, maybe not. However, it doesn't matter. They ALL develop cracks eventually. The oil from the peppercorns gets into tiny cracks, scratches, whatever, and cracks form. ERS |
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Eric R Snow wrote:
All the lids they made failed when stressed with the vacuum. Turns out they used coolant with soluble oil Thanks for the insights! Practice adjusted ... Nick -- WDR Fernsehen: "Ein Computer arbeitet so lange Befehle ab, bis keine mehr vorhanden sind." Muss ich die dann irgendwie nachfüllen? |
#22
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Use oil not water. Water beads up and doesn;t come in contact with
work. Oil give a crystal clear surface unless you get the thing too hot. I wouldn't go to fast as that let the heat build up. |
#23
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