Is acrylic for templates hard on router bits? - created 06-27-2004
Mudd, chris - 06/27/2004.11:57:21
I am in the process of making a number of templates for the guitar I am building. I am using acrylic. This is the type that has the paper on both sides (very useful).
I am concrened about using up my router pattern bits before I get to use them on wood. Does anyone know how hard (or not) this material is on bits?
THANKS!
Chris
It'll be fine. You'll want to set the router at a lower speed, move it through the work pretty quickly without pauses, and try not to minimize cuts that surround the bit entirely. If you see the acrylic starting to melt, you're shortening your bit life.
and try not to minimize cuts that surround the bit entirely
Don't you mean to say that you should not make a route that surrounds the bit entirely?
No, but router bits (bearings) are hard on Acrylic.
Yeah, I did. Thanks.
Hi Chris. All we do all day is fabricate plastic. Run the cutter full speed with a decent feed rate and it will last really well. We get many hours of life out of out cutters. If you can, buy the acrylic with plastic masking. It works better. The problem with the paper masking is that the paper fibers are so much harder to cut that over time you will see notches in the cutter where it was cutting the paper. We are constantly moving cutters up and down to prevent this on paper masked products. Something else to remember, bit life is (in our experience) directly proportionate to the volume of material removed. So buzzcut the plastic away from the pattern on the bandsaw before you route it and everything go's faster. We make acrylic patterns for airplane guys and really like to use impact-modified acrylic as opposed to the regular stuff. It is a bit softer but much less notch sensitive. This makes it much harder to crack. Brand names like IMPLEX come to mind here. Plastic is hard on the bearings. The failure mode is to fill the bearing with hot dust that congeals on the balls locking the bearing and doing bad things. The cure is to soak the bearings/cutter in a jar of lacquer thinner. This dissolves the gummy junk and pulls all the smear off the cutter. If you need to know anything else, just post away and I'll get to it later today.... Scott.
Thanks for the info!!!
I have seen this go by before, but the paper wrapped acrylic is useful for tracng the template.
I will keep an eye on the bits hough.
THANKS!!
Chris
If you get some old paper backed acrylic sometimes the glue is REALLY stuck to the paper/plastic and difficult to remove. If you have problems pulling it off in one piece. Toss it in an oven and warm it up. 150f seems to release old glue really well. About the plastic backing, we trace outlines onto it with ballpoint pens, not a problem really.. Have a great day. Scott.
"paper wrapped acrylic is useful for tracng the template."
I prefer to use a carbide scribe after or instead of a pencil. I then take a Sharpie and fill the groove from the scribe with black ink. Now that's a line! A pink pearl eraser will remove the black from the surface instead of the groove. I can see where I am cutting now. The paper moves around when you are cutting so if you have a line on just the paper the line moves and the adhesive goes right on to my band saw wheels, damn annoying! If you are making more than two or three passes to cut a template then you need to remove more plastic before you start cutting.
Jeez should have read this post before I fried two good templates..
Sears hardware had a deal on plexiglass, bought a ton of it, but now I realize that I have to find some router that won't eat the plastic...
can you say hot plastic.
John,
You write that the bearings on the router bits are wearing down the acrylic template, is that correct?
Anders
"Jeez should have read this post before I fried two good templates."
I am sure I have fried more than two! It takes a few disasters before you get a handle on it, then it is easy. A carbide bit is one thing I can't do without, also a three cutter bit helps a lot. I use a 1/2"or 5/8" diameter three cutter first to get most of the corner edges close, (+1/4") then do the tightest radius last with a 3/8" or smaller bit. The big three cutter does not get as hot as the two cutters or the smaller bits. On the outside patterns cut it +1/8" with a bandsaw or jigsaw then use the router. On the inside patterns cut it +1/4" with a jigsaw or drill out most of it. One other tip, make two of everthing and keep the spares to cut new ones with because if you use them enough, you will booger one with the router sooner or later.
>>John, You write that the bearings on the router bits are wearing down the acrylic template, is that correct?
Like RP just mentioned the bearing can get hot, with acrylic templates you have to be very conscious about how much pressure you're applying once your bit is touching the template, it's really easy to melt it. Personally I make all my templates out of 1/4" to 1/2" MDF unless I need the visibility that comes with an acrylic template.
Want a good trick I've mentioned before?
Make your template out of 1/4" stock (this should work for acrylics as well), it's easier to cut and finish than thicker material. When you've got it perfect, glue your template onto a second 1/4" thickness and use a pattern following bit in the router to trim the new layer flush with your finished template. This will give you a 1/2" thick template without much of the fuss of working with and finishing 1/2" material.
I don't understand the problem here..... If you are tearing up the templates because the bearings are bad, get new bearings. If you are attempting to use router bits with solid pilots on them, they don't work, they will melt their way into the template. We change bearings when they won't stay clean and lubing them won't control the heat. This is usually around 90 minutes of contact time for the stuff we buy. Bearings are cheap and needn't be a problem.
Now the real cool solution to the problem is to use an overarm router setup where the pattern never touches anything that rotates, The bit comes out of the table and a stop pin concentric with the cutter floats above the cutterand indexes against the template. Simple to rig and it gets you out of the whole bearing/template/cutter mess. Scott.
This is very interesting for me as I have always used 3/4 inch ply, which is a bit rough,to say the least.
I'd really like to hear how the first template is cut ,after marking out. Is it with a router against a straight edge,terminating with the router bit's, or what?
I've read the thread carefully,but I can't find this specific information,Thanks.
P.S. Does anyone use sub templates? I used to ,then gave up because, when using 3/4 inch ply the extra depth wasn't needed,but what about acrylics?
"I'd really like to hear how the first template is cut,after marking out. Is it with a router against a straight edge,terminating with the router bit's, or what?"
Tom, for me it depends on if it is an inside or outside template. For an outside template it is rough cut on a bandsaw or jigsaw then sanded to proper dimensions with the best tool for the job. I have done a strat body template with 1/8" plexiglass before. It is pretty easy to get 1/8" plexi sanded close. If you use John Catto's method of gluing up a new piece underneath and pattern routing it, you can have any thickness you want. For inside templates I drill a hole for a jigsaw blade and rough cut it. I clean it up with files,sandpaper blocks etc. You can use a router and a straight edge on some cuts. Most of the time on the first one of a new type, I just use the tool that works the best to work the template to my scribe lines. I use the jigsaw,bandsaw or router for the rough cuts. Files,sanding blocks and scrapers to clean it up to the lines. If you use the 1/8" first and make the first one then all you need to do is use some spacers under that and on top of the next one to cut as many as you need.
"Does anyone use sub templates? I used to ,then gave up because, when using 3/4 inch ply the extra depth wasn't needed,but what about acrylics?"
I just use spacers and a thin template and cut whatever depth I need or I cut a thicker template the same way. I freehand cut most of what I need removed or drill it out with a forstner bit then use the template to finish up.
One other trick is to take an unused body tape it off and double stick plexi to the top of the body cavities. I drill a hole in the plexi over the cavity large enough for a bottom bearing pattern bit and rout out a template. Most body cavities have holes drilled in them to run wiring so, make sure the bearing does not ride into one or you will have a funny shaped template.