How to cut half circles in mass

[Emmanuel]

Greetings to all, 

 

I make wooden crosses much like the attached picture. I was hoping to get some ideas on how to make the half circle cutouts that you see are attached to the four ends of the cross. Each end has 3 half circles attached to it. 

 

Currently, I cut out each one individually on either a band saw or a scroll saw (my band saw broke so now I use my scroll saw). I then round them out by sanding on a belt/disc sander from 80 to 220 grit. 

 

I've gotten the desired results with the method I used above but it is very time consuming. I am currently making a group of 40 crosses which means 480 half circles (40 crosses x 12 half circles per cross)!! That takes a lot of time. The sanding part I think is inevitable, but is there any better way to cut out half circles in mass production? I was thinking there had to be some way of doing it with a drill press and a plug cutter. Any idea of how to accurately cut out half circles using a drill press, or any other machine?

 

I use 3/4" Walnut for the half circles and they are 1 1/2" in diameter. 

 

Any suggestions are much appreciated! 

 

Emmanuel

[wdwerker]

I have a Lennox hole saw with a fairly large slot in the side to make removing the plug easier. But you are going to need to cut the plugs in half to get rid of the pilot hole. It's kinda nessacary. You might be able to make a jig and cut the halves but if they twist it will jam up and bend the holesaw.

[Bill Tarbell]

how about this? (refactored to be done on your scrollsaw, of course).  After you've created the full circles, you can then clamp them to the edge of your bench and use a fine handsaw to cut them in half. Perhaps you can find a nail that's the same size as your saw kerf and then use that as the center spoke of the jig.  .. or you could use your scrollsaw to cut them in half if you're good at cutting straight lines.

 

 

 

[Eric.]

I'm wondering why you opt to glue the circles on in the first place, instead of making two templates, one for the vertical piece and one for the horizontal, and including the circular shapes at the ends in the templates.  Then you only have two pieces of wood to deal with in each cross, do your half-lap, and you're done.  That would be a much faster way.

[Jfitz]

Hello Emmanuel - welcome!

Good tips above. It might be helpful to let us know what tools you do have available. Drill press? Lathe? What's wrong with your bandsaw?

[Tpt life]

If you truly want fast half circles and not a pattern cut like Kiki suggests:

Buy a dowel, re saw in half, cut into sections. If this gives you less than a half circle then try this. Round over a half circle on the edge of a board. Rip the round off the stock and cut into sections. Don't cut little pieces into rounds. Round big pieces and then cut into sections.

[Indy Cindy]

Easiest way to cut a half circle is to divide the circle in two first while the wood is square, glue it back together, then cut the outer circle. You don't even have to cut the division first unless you want matched halves, just use two pieces of any straight wood big enough for each half. A common way to glue it is with a paper joint - put glue on the first half (usually wood glue), put on the paper (something like a paper bag), glue on the second half. CA glue could probably be used if it has an accelerator which makes it brittle. In each case a sharp blow should separate the two halves.

 

To cut the circles use a plug saw but take out the center pilot hole guide. You can do this with a drill press, just make sure your piece is clamped down well and enter it slowly so it doesn't skitter and give a rough cut.

[CessnaPilotBarry]

I would try Kiki's method...  I think the wood figure would look better that way, too.   Rout the pair of parts into shape, assemble, then rout the edge / face profile.   

 

If you use a plunge router for step one, you could do 2-3 laps with a 1/4" spiral bit at deeper depths, you wouldn't even have to rough out the blanks.   With a good spiral bit, you'd have very little sanding or tearout.

[Janello]

I have a Lennox hole saw with a fairly large slot in the side to make removing the plug easier. But you are going to need to cut the plugs in half to get rid of the pilot hole. It's kinda nessacary. You might be able to make a jig and cut the halves but if they twist it will jam up and bend the holesaw.

 

 

Lennox makes an arbor that ejects the plug by holding a knurled wheel atop the arbor. Pins move downward and push out the plug. When I was doing a lot of house plumbing it was an invaluable tool to use with a hole hawg. 

[..Kev]

Welcome to the forums Emmanuel!

 

I would take Kiki's idea one step further and make 1 pattern for the entire piece and flush trim it.

 

Good luck, sounds like you have lots of work to do.

[krtwood]

If you truly want fast half circles and not a pattern cut like Kiki suggests:

Buy a dowel, re saw in half, cut into sections. If this gives you less than a half circle then try this. Round over a half circle on the edge of a board. Rip the round off the stock and cut into sections. Don't cut little pieces into rounds. Round big pieces and then cut into sections.

 

The problem with this is you'd have end grain showing instead of the face grain.  You could temporarily attach or clamp together a bunch of small pieces, round it over and then take it apart.  Your pieces would have to be large enough that you'd probably be wasting as much material as if you'd done it the way Kiki suggested.

[wdwerker]

Glue up a stack of rectangular blanks just barely big enough, use a clean sheet of paper between each joint. Use cauls to make sure the stack is evenly lined up when you clamp. Or cut the blanks oversize and sawor sand the blank to flush it up. Use a 3/4" radius router bit to round over the stack then sand the half round stack. Split them apart and sand off the paper after they are attached to your crosses.

That will give you face grain instead of end grain.

[Emmanuel]

Kiki, that would be a good way but I do not use only one type of wood for the cross. The cross I am making is made of three different types of wood (maple, cherry, walnut): maple and cherry make up the actual cross and the walnut is used for the half circles. For some other crosses where I only use one type of wood I use the method you described, and even just use one template sometimes and have the cross made entirely out of one piece, which looks a lot nicer. 

 

John Fitz: I don't have many tools, but I am planning on buying a few more machines later. Right now I have: A table saw, Scroll Saw, Jig Saw, and Router. I am able to make the things I need with these tools so far. I started woodworking about 1 year ago and I just buy as I progress whenever I see a need for a specific tool. The next tools I was planning on getting were a lathe and drill press. My band saw was not a very good one and though it worked for a few projects it began twisting and turning on all of the cuts I would make. I tried to fine tune it to get it to cut straight and even took it in to the retail store I bought it from and had their technician look at it, but he couldn't fix it either.

 

I think I might try the dowel idea: Find a dowel the right size, rip it in half and then cut the pieces. Maybe a thin kerf blade would help keep it as close to a half circle as possible. 

 

Thanks for all of the replies. There are a lot good ideas. I am almost to the point where I need to begin making these half circles, so I will experiment a bit with some of the ideas suggested and let you know how it turns out. 

 

 

 

 

 

 

[Barron]

I would yue a circle template with a router and bearing guide to cut the circles, then cut the disks in half.

[Indy Cindy]

Make a template for your router with several elongated half circles. On a flat board follow it with a pattern bit. Then cut the half circles off in sequence with your scroll saw (the dotted line in my sketch).

 

[Coop]

I have a Lennox hole saw with a fairly large slot in the side to make removing the plug easier. But you are going to need to cut the plugs in half to get rid of the pilot hole. It's kinda nessacary. You might be able to make a jig and cut the halves but if they twist it will jam up and bend the holesaw.

Using the Lenox hole saw, drill/cut the appropriate size hole in a piece of 3/8" or so plywood. Clamp this ply to the wood that you want the half circles from. Remove the pilot bit from the hole saw arbor and use the hole in the ply as a guide. This will eliminate the pilot holes in the circles