# How to cut a 36 diameter wood gear?



## Edward King Solomon (Apr 11, 2014)

I cut the pinion gear at 7.5 inches on my bandsaw. It is 3 inches thick (it's 4 section of 2x6 glued and bolted together perpendicularly).

However, now that I'm about to cut the 32 inch main gear (flywheel) which weights 46 pounds, two very particular problem are about to arise. 

First, the bandsaw table is not even 1/4 the size of the wheel.

I can overcome this by raising both of my drill press tables (with a level) to the exact height of the bandsaw table. The bandsaw and two drill presses are placed in an equilateral triangle position.

Second, the force required to move this wheel will often knock the bandsaw blade of the pulley. This already happened twice with the 7.5 pinion. I can't imagine what an object with 16 times of much mass will do to the blade when it hits it on the flat sides.

My current plan is to build a small three legged table on wheels (very low on height, and adjust the height of the bandsaw with shims under an OSB plate. to match the height of low table. However, this will require a lot of bending, so if someone knows an easier way, please share it!

Picture of pinion gear for treadle lathe:


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## woodnthings (Jan 24, 2009)

*You need a table extension*

What size is it, 36" or 26"?
Get a36" square piece of high pressure covered particle board, like Formica. This will make it easy to spin the blank because it's quite slippery. Support the board by what ever means so that it's level across from the bandsaw table. You can make a slot the width of the blade to allow it to sit on the bandsaw table.

Secure it so it can't move in any direction.
Drill a center hole direct out from the cutting edge of the blade at the radius you want...13"... and place a bolt through your blank and into the hole in order to spin the blank.You will have to have a "start opening" on the radius of the blank to allow the bandsaw to make it's first cut, not much wider than the blade.










Then just spin the blank as you cut all the way around. 
You might want to have a hole at 14" to remove most of the waste on the first cut, then follow it with the hole at 13" .


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## Edward King Solomon (Apr 11, 2014)

Although it's an improvement from my idea, I'm not cutting a circle, I'm cutting gear teeth. I can cut along the tangent in the way you described to cut away the excess above the addendum, but when I actually have to cut the teeth, the tangent will not be parallel to the blade, in fact it will nearly be perpendicular when I reach the end of the dedendum. This is why I was considering a wheeled table. In the picture above, the disc would slide off the table when I turned its tangent perpendicular to the blade.

However, Formica would be a good idea for the table surface. I might actually have to create a jig that pulls the disc into the bandsaw while rotating the disc at the same linear speed (the very definition of an in-volute gear).

Wait. Maybe I can make a rotating table extension...


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## co-dan (Apr 4, 2014)

What about using a jig saw instead of the band saw? That would mean you could attach it to a table to support it and turn and cut each tooth.


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## woodnthings (Jan 24, 2009)

*drill out your dedendum ...what ever that is?*



Edward Solomon said:


> Although it's an improvement from my idea, I'm not cutting a circle, I'm cutting gear teeth. I can cut along the tangent in the way you described to cut away the excess above the addendum, but when I actually have to cut the teeth, the tangent will not be parallel to the blade, in fact it will nearly be perpendicular when I reach the end of the dedendum. This is why I was considering a wheeled table. In the picture above, the disc would slide off the table when I turned its tangent perpendicular to the blade.
> 
> However, Formica would be a good idea for the table surface. I might actually have to create a jig that pulls the disc into the bandsaw while rotating the disc at the same linear speed (the very definition of an in-volute gear).
> 
> Wait. Maybe I can make a rotating table extension...


If that is the bottom of the gear's tooth, then drill all those using a similar jig on your drill press to keep your distance from the edge identical. Now you only have to cut the teeth. The teeth are not straight in, but have a slight crown or curve...right? 

That would lend itself to making a template for a hand held router with a guide bushing or a flush trim bearing bit. Accurately layout the shape of several teeth, make your template from 1/4" hardboard and use the predrilled holes as a reference. Secure the template and rout your way around the circumference.


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## Edward King Solomon (Apr 11, 2014)

woodnthings said:


> If that is the bottom of the gear's tooth, then drill all those using a similar jig on your drill press to keep your distance from the edge identical. Now you only have to cut the teeth. The teeth are not straight in, but have a slight crown or curve...right?
> 
> That would lend itself to making a template for a hand held router with a guide bushing or a flush trim bearing bit. Accurately layout the shape of several teeth, make your template from 1/4" hardboard and use the predrilled holes as a reference. Secure the template and rout your way around the circumference.


Aha, cut a few teeth into a hardboard and use it as template for the trim router to follow. Clamp template, cut some teeth, remove clamp and move template to next set of teeth. 

Now we're talking son!


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