How Would you cut these Curves?

Depends how meticulous you want to be and if you'd ever make another one of these. For me, as a hobbyist, something with complex curves interspersed with straight lines would be a real challenge to get acceptably smooth so I'd do it the more time consuming way. I'd make an MDF template. I'd work with it until I was satisfied, backfilling nicks and bumps with Bondo. If I really screwed it up, I can always start over. MDF is cheap. Then I'd go to the project piece, cut close to the line with a band saw and a thin blade. I'd finish it with the template double sided taped to the reverse side of the plywood project piece. I'd do it on the back with multiple small pieces of tape so that removing the template wouldn't pull off any of the face ply but, if it does, it'll be on the back and not the face. Then I'd use a router with a pattern bit. A lot more work but, for me, knowing my skill level, or, more accurately my preponderance for an "uh oh", it would work better on a complex piece.

When I first read the word clock, I was thinking gears and making smooth gear teeth in BB ply seems a real challenge. But this pattern is smooth. It's open on the bottom so a band saw cutting close to the line, then sanding looks the way to go to me. A pattern is in order if you're making others, but using a pattern will present the same challenges as cutting with the band saw on the original. It's all those inside curves. You will need either a small blade, plus a lot of sanding to smooth out the curves, or a little wider blade that will make a smoother cut on the long curves, but require considerable sanding in the tight curves.

I think you could cut with a wider blade for the long curves, leave extra space for the tight ones, then change blades and do the tight curves. Here's a blade guide for curves.
For sanding I suggest you glue sandpaper to sticks for final sanding. I think a spindle sander is too likely to gouge if you press too hard or have a lapse of attention or a distraction. Straight sticks and then sand a few rounded as well. Use a finer 150 to 220 grit so you have good control and can't over do it.

Did the pattern come in pdf form so you can print another copy? If not, I'd make a copy of the original, just in case, before starting. You can get 3M removable spray adhesive that won't spoil the surface when you lift it off.

That's my fifty cents.

The reason I didn’t mention a template before was because I would have the same challenge to make the template accurate. However I see the point here and I may go for it since I want the curves to be perfect.

This is the second clock I build, the first had 16 gears ranging from 9”OD to 1”OD. It is a challenge to cut all these teeth but I made my own 3 wheels mini band saw with a VS DC motor and I use either a Bosch 59.5” long blade with 6TPI 1/4” wide 0.012” gauge or a Vermont American blade 59.5” long, 15TPI, 1/8” wide, 0.012” gauge. I use the 1/4” blade for rough cut around each gear and the 1/8” blade for the teeth and of course lots of sanding... The current clock has only 9 gears. The band saw is happy with 1/8” thick material, it struggles with 1/4” and forget about cutting anything 1/2” thick; its purely for small hobby projects and luckily all gears I had to cut were 1/8” thick.

The patterns came thru mail from California, about 30 pages all actual scale which I print as needed and glue to the material. It turns out that my printer does not distort the scale of each pattern (I was told that some printers do change the scale not by a lot but enough to create problems during the assembly).

Home made tools are very interesting. For me, however, one of the best purchases I've made in the past few years was a medium size, 12 inch, Rikon band saw. It uses a 72 inch blade and is really nice and accurate and will handle pretty thick stock. I've even been able to resaw with it successfully. It is identical to the WEN (pix) which was a little cheaper. I have a 14 inch Laguna, but for fine projects I prefer the medium size bench saw. I usually run a half inch blade, but have a 3/16th blade for the fine stuff. The1/8th blade is too easy to break if you overtighten it. The picture shows the version with a stand. I have a number of WEN tools and they are very good, especially for the money.

kolias said:

I’m making a wooden clock as a hobby and the attached indicates part of the clock’s face. The plans I bought came in 8.5”x11” sheets in full scale and I had to cut/glue them together to form the parts. What you see in the picture is about 14”x12” wide which I will glue to 1/2” Baltic birch ply for the final cut.

None of the curves you see are proper circles and that’s the problem. If they were proper circles I would use my router on a jig I have which cut circles up to 36” OD but on curves how can I do the cut?

I could use my band saw for the rough cut and then use my sander to finish but I don’t think it will be perfect.

Any suggestions?
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Yes do as you stated.
It will be perfect and after years and years of doing this I can do any curve, perfect circle to any arc and make them so perfect I can mate glue up parts together by only sanding the edge of the mating sides.

You can always make a template and then use a flush cut bit or proper bit and bushing to get the exact shape too. Since you don't need mate parts, just cut and sand, you have it right. Safer, simpler, faster and no tear out.

My daughter and I made this Surmandel, it is an Indian Zither Harp( temporary strings). This was made just band saw cut and sand to line. She did the cutting and sanding as her first project using this Technique. I taught her, she followed it up with perfection after a few hours of practice. I think it came out great. I designed the shape from online pics I saw and used the same technique you are thinking of using. The edges look perfect and match our design. I attached pictures to show all the sides and curves. As long as your edges are smooth does it matter if your edges are a perfect match to the plan, probably not.

The straight sides on this harp were also done by bandsaw and sand to line on our edge sander.

Your edges look a bit tougher todo, still what you suggest will work fine.

If I were doing this, I'd do as others have suggested and make a template that you can then use with a pattern bit on a router table. I use this method all the time - even for one-off projects. As others have noted, a primary advantage of making a pattern of MDF is that if you screw it up, you can make another. Another significant advantage is that MDF is pretty easy to sand 'with the curve' (unlike plywood, in my experience). So starting with 3/16 or 1/4 inch thick MDF and either a scroll saw or band saw, that'll get you pretty close and a sanding drum/spindle sander would be the next step to get pretty close to the pattern. Then hand sanding along the curve will make it smooth - let your fingers (close your eyes...) tell you whether the curve is smooth. I suppose you could try 1/8 inch thick MDF, especially if you are only making one. In that case, then once you get the curve(s) smooth, you could coat the edge of the template with a layer of polyurethane (don't use water based...!). I have read this suggestion elsewhere - though I haven't tried it - it has the effect of strengthening the edge of the thin template (which might otherwise be thin enough that it could compress a bit on the edge).