Well, my CNC buddy is out of town this weekend – off to New Orleans and Mardi Gras.  Rather than wait patiently until he returns and do something else, I tried cutting a gear by hand.

I’ll just tell you now: don’t ever try it!  At least not without a scroll saw.

Cutting Teeth By Hand

The Saturn gear has always presented me with a worry.   The teeth (all 147 of them) are small; smaller than any router bit that I have.  My friend says he has some small ones but I haven’t seen them and so I’ve never been certain if we can do this one or not with what we have.  So, in his absence, I tried to cut it manually on my bandsaw.  Actually, aside from being boring, it wasn’t all that difficult.  As you can see by the photo, I just had to cut a lot of short straight lines.  They are technically a section of an involute curve but when they’re this short, they look almost straight and considering the amount of control I had over my bandsaw, they ended up straight anyway.

I used my circle cutting jig which came with my band saw to cut the thing to final diameter. For making the Mercury gear and this one, I bought a new 1/8″ blade.  It has a pronounced drift to the right so I had to tinker with the circle jig to compensate.  I just cut it too big, then cut the teeth, and moved the jig to final diameter.

Then I tried to waste out the spoke sections.  This is where I realized just how much trouble I was in for.

To cut an elaborate hole out of anything requires that you have a small saw blade that you can thread through a pilot hole and reattach it and start cutting.  If not a scroll saw then a coping saw comes to mind.  I tried that and had a pretty rough time of it.  I’m not sure if I just don’t have much experience with the tool or if I was holding it wrong in the vise but I got nowhere with that.  I have a jeweler’s saw (like a teeny coping saw) but could not find the blades.

Trying to Drill Out the Waste

I switched to a forstner bit and tried to drill out the waste – thinking that I would come back and sand it smooth later.  This worked OK but left a lot of wood yet to remove. It worked although I had to switch to smaller bits in order to get as much of the waste as I could. I only have two forstner bits so that didn’t take long.

I then tried using a sanding drum in my drill press and while this works well, it doesn’t go very fast.  It’s great for what it’s designed for and that is sanding out saw marks.  Removing material: not so much.  So I went inside to think about it for awhile.  It occurred to me that I had watched a video series on inlay once (in fact the same friend with the CNC router loaned it to me).  To cut the shell pieces for inlay work, you use a little shelf-like thing called a “birds mouth” which has a “V” cut in it.  You hold the work on this flat piece over the “V” and use a jeweler’s saw to cut right there while the material is supported on three sides.  You can almost see it behind the gear in the lower photo below. Further, if you place it at the right height, the ergonomics are pretty good and it’s easier to control the saw.  I quickly went and made such a thing out of a scrap of old 2×4.  (Remember kids: always keep a 2×4 around the house; they’re good for a lot of things.)

Spokes Looking BetterThis seemed to work fairly well.  It was getting late and the cars were in the shop (garage!) so I couldn’t really get comfortable.  I was trying to cut all this with a rear-view mirror gouging  me in the back.  So I went inside for the evening but as you can see from the photo, I’m making progress.  I’m hopeful this system will work and I can get the rest done in a timely manner.

One final word.  The bird’s mouth needs to be clamped down (obviously) but I don’t have any direct means of doing that in this geometry.  I don’t have a holdfast and I suspect that most woodworkers don’t either.  This made things a bit awkward but I can probably think of something.

But one thing is for certain: I’m not going to try and cut the Mercury drive gear.  Patience is a virtue so I will develop some until my friend gets back.  Plus, it’s going to take me that long to finish up the Saturn gear.

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