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Hi. I just started to make 9" letters out of mdf (moisture resistent) board. I am using a templet and a 3hp inverted router to cut 1/2" mdf (MR) BOARD. I am dulling bits in a few letters. I have 3 settings to cut in 3 passes, but I am affraid of getting cut lines on edges if I use the settings. I am cutting with solid carbide 1/4" spiral upcut bits from CR ONSHRUD at over $20.00 a piece. What can I do to get a lot more life out of a bit?
 

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Welcome to the router forum.

Thank you for joining us, Tim.
 

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Hi. I just started to make 9" letters out of mdf (moisture resistent) board. I am using a templet and a 3hp inverted router to cut 1/2" mdf (MR) BOARD. I am dulling bits in a few letters. I have 3 settings to cut in 3 passes, but I am affraid of getting cut lines on edges if I use the settings. I am cutting with solid carbide 1/4" spiral upcut bits from CR ONSHRUD at over $20.00 a piece. What can I do to get a lot more life out of a bit?
Hi Timothy and welcome!

That's not a lot of mileage out of your cutters! Are you trying to rout the letters out of a solid slab of MDF? If so you are wasting a lot of time, energy and carbide doing that - you need to start off by tracing round your letter with a pencil. Rough out the letter with a bandsaw, scroll saw or jigsaw a little over the line - a little less than 1/2 the diameter of the cutter (or under 1/8in for a 1/4in cutter) - before "attacking" the piece with the router. A couple of things to note about spirals - they run cooler and wear less if you can clear the swarf out of them - so hook up a vacuum cleaner or shop vac to your router - they were originally designed to feed at high speeds on CNC routers, so they can take a much deeper and faster cut than same size straight cutters. In fact if you feed too slowly, especially without dust extraction, the bits heat up and go blunt. This is partly because of friction between the edge of the cutter and the material (and that edge is a lot longer than on an equivalent straight cutter) and partly because uncleared waste tends to churn in the cutter (continually recut) causing excessive heat build-up and premature blunting. MDF is a very soft material and you should find that if you reduce the cut to 1/8in or less and hook up a vacuum it is possible to make your trim cuts on the letters with a spiral on the router in a single (or at most two) passes

Regards

Phil
 
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