I will be cutting several sheets of plexiglass (4’x8x1/8″). I have done some home work here on the Knots and elsewhere so am aware of most of the things to look out for (keep the wrapping on till the end, possibly use a zero clearance insert, support the sheet with a wood backing when drilling, make the holes clearance size: that is bigger than the screw etc).
My final question is about the blade. Am I correct in thinking carbide teeth with the more teeth the better? What is the best configuration and hook angle for the teeth?
Can anyone recommend a specific blade.
Mant thanks for any help.
Replies
Most of the blade manufacturers make blades specifically for cutting plastics.
John W.
The blade I use on the table saw is an 80 tooth triple chip grind with a negative rake.
In other words there are 3 different profiles ground into the teeth and the tooth
has a negative slant to it instead of leaning forward as most blade teeth do.
It works well. The zero clearance insert is important as well.
Tom
Plastics are much more abrasive than wood. If you use a woodworking blade, even if it has the correct geometry, to cut the acrylic you will dull the blade quickly.
Blades made specifically for plastic cutting use a harder than normal carbide to increase the blade life. The extra hard carbide is very easily chipped however, so be very careful when installing the blade, don't accidentally hit it against the arbor or bump it with the blade wrench when installing the blade.
John W.
Thats new info to me John - thanks - will look into it. However, I don't doubt your information or experience, but I cut plastic sheet for a living, (see link) and I use regular ATB blades as well as negative hook ATB and triple chip and I never really noticed that the acrylic dulls them any faster than MDF or Ply. I run big jobs (1/2", 3/8" and 3/4" Plex) through my cheap 60 tooth positive ATB and don't see that much problem.
What I have found to be very important, is that sharpness is more important than geometry or hardness of carbide. Even if a harder carbide blade with correct geometry (triple chip, negative hook, etc.) is a little dull, the melting effects in the cut are far more detrimental than a simple positive hook ATB blade that happens to be freshly sharpened. I use every blade I have - when the first is dull, I use the next one, and so on, then I send 'em all out at once to be sharpened (actually I sharpen them in-house on my T-saw cuz I have a sweet diamond sharpening blade to hit the inside faces - super job - but thats another story)
So unless your a pro, and need long, long life in a blade - get a good triple chip and you'll be fine.
BTW, on any large sheet cutting I need to do on 3/16" or thinner plex, I use a scoring knife and a drywall T-square. Fast, quiet, and you don't get all that static-charged dust all over you and the sheet. Scoring blades will even work on 1/2" stuff if you score deep enough.
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
Dr. D,
I got the information from Freud a few years ago, and it seemed to make sense, but I don't cut enough plastic to have tested it out personally.
My thinking, in answering the original question, is that if you are going to buy a new blade, you might as well get one fine tuned for plastic rather than buying a woodworking blade that is close but may not cut quite as well or last quite as long.
I'd be interested on the fine points of how you sharpen your blades in house.
John W.
Edited 3/11/2004 3:06 pm ET by JohnW
Points well taken, John. Say - you're not the John Welsford of Australia, the highly respected boatbuilder and designer that posts on other woodenboat forums are you? I read John Welsfords articles on http://www.duckworksmagazine.com all the time and love his points.
Anyway, my shop space neighbor is a stained glass artist and he fenagled a load of used diamond blades from a Norton supplier, assuming he could cut glass with them - not. These blades were way, way too fine - they were continuous rim diamond composite edge blades. I converted an old 1953 sears tablesaw into a wet diamond saw for cutting my glass laminates just to make use of these blades, and when they burned into the glass even when wet, I bought a coarser tile blade and it worked like a dream, so I just ignored these fine blades that my neighbor had - about 20 of them.
Then I needed to sharpen a cheap old 7-14" blade for cutting aluminum, and thought I'd chuck one of these fine diamond honer blades in. The blades were 9" DIA and about 3/32" thick, and the continuous diamond faces were about 5/16" which would get right into the gullet of the saw blade in order to "face" them. If you grind the face of carbide teeth, you really don't change the geometry much, so I gave it a shot, and PRESTO !!! Super sharp in minutes. I did a few other 10" blades and they all sliced through the wood and plex like they were pro-sharpened.
I simply lay the blades flat on the T-saw table and kiss them against the inside face of the diamond hone at the original angle, then mark the center hole of the blade so I can follow the exact position on each tooth. I face every other tooth (point of the ATB grind "up") then flip blade over and grind the other teeth - real logical at this point.
That's when I realized that my neighbor actually got a load of carbide sharpening blades, not glass cutting blades. Let me know if your interested in one of these blades. - JB
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
Hi Dr D,
Just a clarification, please. Do you use the converted tablesaw that runs wet to sharpen your blades? Does the process need to be a wet one, or will it work well done dry? I gather that wet would be safer as regards toxic dusts. Thanks.
Bugle
Understandable question - I never thought of using the wet saw to rough shape dull blades, but I know that its too coarse - about 100 grit. The honing blades I use on my normal T-saw are about 400 - 600 grit, I'm guessing. I hit them with WD-40 and rub the carbide dust out of the blade every few teeth to keep the carbide from clogging the grit face. I have heard that airborne carbide dust is highly toxic, so the WD40 is good to contain it, as well as being a good cutting fluid. - JB
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
This is completely off the wall compared to the others. I use a $7 Oldham plywood blade on my tablesaw to cut 1/8" plexiglass. It seems to work fine. The scoring knife, t square idea sounds better though, given the dust, noise, etc. of the saw.
As always, great stuff.
Many thanks to all for your feedback
Hey Mike, I work in a theater and we use plexi at times, usually for light boxes. Typically I never bother changing out blades for plexi, I just feed it in on the slow side. We've done the scoring with a straight edge and razor blade on 3/16ths thick plexi, but it was prone to cracking. If you support the plexi very well a jig saw will also work. Hope this helps
Datachanel
Doing things the hard way
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