Flush Trim with Router

[Scott Welty]

I have a metal shop next to my wood shop. The guys there took on a job and then realized their machine couldn't make the part I show here. It's 1/2 inch thick and about 16 inches long, with some rounded edges. The material is the very slippery plastic...don’t know the name. I'm wondering if I could use a flush trim bit in a router to cut these out of blanks. I could cut the shape out roughly on band saw, leave 1/8 inch and then use the one I have as a pattern to flush trim the piece. The sharp curve/hook shape at one end is a problem. I’m thinking maybe pre drill that and then cut/trim up to it?

Haven't tried it yet but also worried about double stick tape holding the pattern to the slippery plastic.

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Talk me out of it!

Scott

[Jamie Buxton]

Yup, a flush trim bit will do it.

If the double stick tape doesn't stick well enough, you could screw the template and the blank together. You'd be leaving screw holes in the part, but maybe that's okay with its intended use.

[Rod Sheridan]

I have used a shaper to flush trim plastic like that.

Make a larger wood template with a couple of dowels to locate the part, and a couple of Destaco toggle clamps to hold the plastic down.

Leave a good size lead in ramp, add a couple of handles to the template and away you go...........Regards, Rod.

Oven Stick Shaping.jpg

P.S. Here's an example, I'm shaping oven sticks.

[Grant Wilkinson]

The only thing that I could add would be to try to leave less than 1/8" around to trim off with the router bit. I don't know what your material is, but I've done fixtures out of starbond and HDPE (slippery plastic) and they are "gummy" on the router bit. I've gone down to no more than 1/16" over pattern size to reduce the problems of grabbing and melting.

[Bill McNiel]

The only thing that I could add would be to try to leave less than 1/8" around to trim off with the router bit. I don't know what your material is, but I've done fixtures out of starbond and HDPE (slippery plastic) and they are "gummy" on the router bit. I've gone down to no more than 1/16" over pattern size to reduce the problems of grabbing and melting.

Plus 1 on 1/16" max, melting can be an issue.

[Scott Welty]

Rod -
That's brilliant! Trim bit with bearing on the bottom. Got that. I'll need a couple more hold downs. I think 2 will hold the blank down.
Thanks,
Scott

[Lee Schierer]

Plus 1 on 1/16" max, melting can be an issue.

Slower router speed will help reduce the melting. Delrin, UHMW and HDPE machine pretty easily with wood working tools.

The part in the photo has holes in it that can be used for locating the part on the template.

[Rod Sheridan]

Scott, you're welcome.

Remember a couple of dowels to locate the part on the template, and perhaps some glued on sandpaper to keep the plastic from slipping.....Rod.

[Scott Welty]

Rod-
It occurred to me . .. How does the router get past the hold downs?
Scott

[Wayne Lomman]

Use a flush trim cutter with the bearing at the top. Put the pattern on top of the blank and screw it down to the bench or whatever through the holes. ( machine the holes first). This way you have a flat surface to go your hardest with the router. Cheers

[Scott Welty]

Thanks Wayne and may I say I love getting notes from Tasmania at 5 in the morning (my time)!

Scott

[Scott Welty]

Well, I don't have a bit with the bearing at the top. I've made a jig to securely hold the blank in place on top of the pattern so it can't slip sideways. I put a peg for one of the holes and a backstop along the straight edge that's not being machined. Now I figure the router itself will hold the piece down as my bit rides on the pattern underneath. Is this right?

4A3196FF-6A83-4ED0-BB4C-B843E5A61510.jpg5B41C991-6F5A-4917-A28D-01ABFED8F00E.jpg

Scott

[Wayne Lomman]

They say alarm clocks need to be annoying...
The pegged end will be fine but the other end needs to be held against the backstop somehow. If the work piece moves at all it will be undersize. Can you peg it through the most widely spaced holes? 2 pegs will solve the problem. Cheers

[Scott Welty]

Yes, I discovered the need for the backstop and have corrected. I also had to got get a longer bit. The one I had was exactly 1/2 inch in length and hard to align. Finally, I had to put some support for the router plate besides just the piece. It gets pretty narrow and with that bit if you tip the router it MIGHT dig in and climb into the piec. . . . yes this happened. I think I'm ready today. Kind of a big deal because I need to knock out 50 of these for my machinist friends. I've finished the hard part which was roughing them out on the band saw.

Thanks for all the help,

Scott

[Peter Quinn]

Looks great, best part of wood working to me, designing the jigs and fixtures to create success.