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How best to cut wood clock gear teeth?

PostPosted: Wed Jun 25, 2014 4:32 pm
by Dave Van
Cutting a gear for a wood gear clock:

1/4 inch Baltic Birch plywood (quite thin)
8.5 inches in diameter

Long sharp teeth on the gear - lots of them.

Looks like plenty of potential for chipping and breaking at the ends of the teeth.

What's a good way to get a nice clean cut on this gear?

Excape-Wheel-Diagram.jpg
Wheel (gear) for wood gear clock. Looking for suggestions about how to get a clean cut on those long sharp teeth in 1/4 inch plywood.

Re: How best to cut wood clock gear teeth?

PostPosted: Wed Jun 25, 2014 4:48 pm
by 4DThinker
Use a downcut spiral bit that is small enough to fit on the first 1/16" or so pass, then finish the rest of the passes with an upcut spiral of the same diameter.
Depending on how old/dry the BB is your results may vary. We use bb plywood in every thickness available in the furniture classes I teach, and I've seen quite a bit of variance in how well bonded the outer veneers are. If you plan on putting a finish on the gears, you might apply it to the plywood before cutting the gears to help stabilize the surface.

Re: How best to cut wood clock gear teeth?

PostPosted: Wed Jun 25, 2014 5:35 pm
by FixitMike
After cutting the outline in multiple passes, make a single full depth pass to clean up the lines left by cutter deflection.

Re: How best to cut wood clock gear teeth?

PostPosted: Thu Jun 26, 2014 1:09 pm
by Dave Van
Thank you for your tips for cutting the clock gear. I'll give it a go!

Re: How best to cut wood clock gear teeth?

PostPosted: Thu Jun 26, 2014 2:01 pm
by Bob Jr
Dave,
When I cut clock gears from plywood, I use aircraft quality plywood. It has more plys, no voids, flat, and very little problems with chipping. Use a new, sharp bit with light pass depths. It takes longer to cut, but worth the wait. Applying a finish before the cut is good. Don't apply finish to the teeth after the cut if you want the clock to run.
Bob

Re: How best to cut wood clock gear teeth?

PostPosted: Thu Jun 26, 2014 3:06 pm
by ozymax
I have had good success with first running a shallow profile pass using a 1mm dia straight bit. This reduces any chipping of the face. Then I complete the profile to full depth using a 2-2.5mm dia upcut bit.
I then tune the gear teeth using some Olson scroll sanders in the scroll saw.
http://www.cwsonline.com.au/shop/category/-olson-scroll-sanders

Re: How best to cut wood clock gear teeth?

PostPosted: Tue Sep 16, 2014 8:40 am
by dhellew2
If you want to finish the teeth you can use polymerized mineral oil (teak, Tung, olive, etc.). Oils soak into the wood and leaves it silky smooth and slick. WARNING: DO NOT USE ANYTHING THAT SAYS TUNG OIL FINISH, THERE IS NO TUNG OIL, ONLY THINNED-STICKY-VARNISH, including Formby's and Minwax. For best results thoroughly soak the wood, let stand for 5 to 10 minutes then wipe off the excess. NOTE: I drench toy cars and trucks with Polymerized Tung oil (sometimes olive oil) and the wheels never stick to the axles even though there is no way to wipe off the excess.

When it's all finished if you want really slick teeth use DynaGlide; a high pressure wax based cleaner/lubricant product designed for saw blades, tables, joiners, shaper tables, and gun cleaner; it does not attract dirt or moisture.

Another method for cutting is to use a ball nose bit which makes a feathered edge cut, and a spoil-board (you will need to cut deeper to make the ball nose cut all the way through).
Use the smallest bit that will cut all the way through the wood, the downside is that small bits tend to follow the grain more than larger bits leaving a slightly rougher cut.
Slow down your feed rate.
You can use a wood hardener or mineral oil finish (fully dry) first to stabilize the wood.
Eliminate tabs, use double sided tape.
Use shallow cuts; make the first profile cuts offset outwards around 0.005", then make the last cut full depth in one pass inset 0.005"

Dale

Re: How best to cut wood clock gear teeth?

PostPosted: Fri Sep 19, 2014 8:57 pm
by Dave Van
Dale, Thank you for the tips! Lots of good info! Great tip on using the friction - reducing compound on the gears.

I have lots of baltic birch plywood so I can cut as many times as necessary until I get it right.