How to make a dozen copies of a "Moon shape" with a router?

[Greg L. Brown]

I need to make a dozen "moon shapes" (like a crescent shape), about 12" long, for a project for my daughter's room. My idea was to cut out the rough shape on a bandsaw then shape it exactly the way I want it with a sandpaper block or wood file. I was planning to use a 1/4" thick plywood for this part (the master template).

Once I have the "crescent shape" I want, I was going to use that as a template to cut out 12 copies using 3/4" plywood.

Can I do this with a router? My idea was to lay the 1/4" thick master template on top of a piece of 3/4" ply. Then I'd route around it and cut out the shape.

Can this be done on a router and what bit should I use?

Thanks,
Greg

[Jim O'Dell]

Easy enough to do, but I'd make the master out of MDF. Ply seems to crumble too much for me. Possibly I'm not using a quality ply, but I still think the MDF would make for a smoother master.
Then just use a pattern bit with a bearing to ride on the master. I usually use a 1/2" shank, 1/2" bit, but a 1/4" bit would create less waste. If you are using a router table, you need a bottom bearing bit. If free hand, use a top bearing bit. (I hope I have that right and not backward!!) It would be much safer to use the router table. Jim.

[Lee Koepke]

Jim,

When you use a router table, would you use a pin as a starter? I was thinking about something similar and couldnt find a comfortable 'dry run'.

[Will Overton]

I need to make a dozen "moon shapes" (like a crescent shape), about 12" long, for a project for my daughter's room. My idea was to cut out the rough shape on a bandsaw then shape it exactly the way I want it with a sandpaper block or wood file. I was planning to use a 1/4" thick plywood for this part (the master template).

Once I have the "crescent shape" I want, I was going to use that as a template to cut out 12 copies using 3/4" plywood.

Can I do this with a router? My idea was to lay the 1/4" thick master template on top of a piece of 3/4" ply. Then I'd route around it and cut out the shape.

Can this be done on a router and what bit should I use?

Thanks,
Greg

No, not really. After making the template, you want to trace it 12 times on the plywood and cut them out, outside the line (1/16" to 1/8"). Then, attach the template to each piece and use the router to trim them to the exact shape.

[Bruce Wrenn]

If was me (and it isn't) I would just cut them out on the band saw. But instead of "free hand," I would devise a couple of jigs to swing the two different arcs (inside and outside.) Clamp stock to radius jig, and cut inside arc. Then transfer cut off to another radius jig and cut outside arc. You could use toggle clamps from HF to hold parts. If I were doing them from a pattern using router, I would use guide bushings instead of bearing guided bits.

[glenn bradley]

This is definitely a great way to use template routing. As mentioned, trace the shape of the template and then cutout the moons within about 1/16" of the line. Double stick tape the template to the ply and use the largest pattern bit that you can; I find the larger the bit the smoother the cut. If it is just a crescent the diameter could be pretty big. My largest is about 1-1/4".

I often template route so I built a jig to hold the template and the work so I don't need the tape. Whether this is worth while for you to have available in the future is your decision.

[Prashun Patel]

You'll get the cleanest cut with a spiral trim bit. I'd use a bit with a bottom mounted bearing, because in a table, it can be a challenge to get a pattern bit (top mounted bearing) to raise up high enough in some tables.

Use a bandsaw to get within 1/8" of the layout line. If you don't, you risk a jagged cut or worse, having the bit grab and jerk the piece.

They do make pattern pins for the bandsaw, but in my experience, bsaw cuts still require smoothing and cleanup.


Last, I submit that if this is project for your daughter's room, then you might be thinking about painting the moons. If that's the case, MDF might be a good choice; the edges of plywood can be a challenge to make look like not-plywood.

[Jim O'Dell]

Very good point about the cuts to rough size then use the pattern bit. Much less waste. Jim.

[Greg L. Brown]

Wow I love this forum. Thanks for all the good suggestions. I don't have a router table, so it would be free hand routing. That means I need a bit with the bearing closest to the shank, correct (instead of at the very end of the bit)?

Thanks,
Greg

[glenn bradley]

Wow I love this forum. Thanks for all the good suggestions. I don't have a router table, so it would be free hand routing. That means I need a bit with the bearing closest to the shank, correct (instead of at the very end of the bit)?

Thanks,
Greg

It could still be done top or bottom mounted bearing depending on the bit. As you are going free hand I would use a 1/2" bit, shear-cut or better yet a spiral.

I would prefer the template on top and a bearing close to the shaft for hand work but you will not find that in a spiral (if you do, please let me know). Whiteside is my favorite but there are many good makers out there.

[Prashun Patel]

You can make a temporary table pretty easily - especially since you don't need a fence here. You basically drill a hole in a sheet of plywood - 1/2" would be fine and will give you more bit height than 3/4" - and then screw your router (without plate) to the bottom of the sheet. Then you support the sheet with 2 saw horses; clamp it.

Since your pieces are small, the flatness of the table isn't going to be a huge issue.

If you still want to free hand it, then you really have to secure that piece to the bench on something elevated but not wider than the moon. Double sided duct tape or carpet tape should work. Use cut offs around the piece to support the router base so it doesn't tip.

[Larry Fox]

If it were me (and it isn't), I would use solid wood and use a trick I read about and used for the curved shelves in my kitchen. Leave all the "blanks" slightly thicker than you need them and then face glue all the blanks together with a couple of sheets of newspaper between the layers. Cut and shape them as a single block. Once you are done, they will split apart surprisingly easily. You can then run them through the planer to clean them up and get to finish thickness. You are left with N identical copies where N is the number of blanks you glued together.

[Gordon Eyre]

I am often asked to create large letters; eg, E, A, P, etc., for a childs room decoration. I trace the letter shape I want onto 1/4 inch hardboard and then with a scroll saw (or bandsaw) I cut out the letter just outside the line. I then true up the letter with sandpaper or a file. This then serves as my template. I trace the letter onto the wood or MDF that I intend to use and cut it out in a similar fashion with a bandsaw or jig saw. I then affix the template to the wood with double sided tape and with a patterning bit in my router I true up the letter. Lastly I round over the edges of the letter with a 1/8" roundover bit. Little to no sanding is required.

[Will Overton]

Wow I love this forum. Thanks for all the good suggestions. I don't have a router table, so it would be free hand routing. That means I need a bit with the bearing closest to the shank, correct (instead of at the very end of the bit)?

Thanks,
Greg

Yes, that's the bit you want. Doing it hand held should not be a problem. Just raise the blank off the bench a bit and make sure it won't move around.

Or, clamp it to the bench so it partially overhangs. You'll have to move the clamps a few times, but it will work.

[Prashun Patel]

The issue with hardwood is that since his pieces are moon shaped, he'll have to be mindful of short grain situations at the points of the moon. He'll be working against the grain either on the inside or outside, which can lead to blowing out the corners unless he climbs into the cut.

I think ply or mdf is a safer solution in this case... Just my 2cents.