Emco Compact 8 dimension request

The Compact 8 gears are module 1: the pitch circle diameter being equal to the number of gear teeth. Missing some of the gears on my lathe, I reproduced them from POM-C/Delrin/Ertacetal. It's a great material that cuts like butter and won't wear down your tools. Often used for gears, they also run a lot quieter than metal ones and it's a relatively cheap material.

A standard, complete set of gears (auto-feed and thread cutting) for the C8 contains: bus(2*)/z20/z25/z30/z35/z40/z50/z55/z60/z65/z70/z75/z80(3*). Gears are 8mm thick with a center hole of 14mm. The keyway width is 4mm by 1.5mm deep. When cutting gears, a rule of thumb to indicate the outer diameter of the gear 'blanc' you're going to cut, is to take the number of gear teeth (z) + (2*module). So for a gear of z80 that would mean starting out with a blanc with an outer diameter of 80 + (2*1) = 82mm. Depth of cut is measured by 2,25mm * module. Hope this helps.
 
I just checked what I have downstairs, and I get the same 1.257 inch outer diameter for the 30 tooth gear.

For the 25 tooth gear, I get 1.056/1.057 inch with calipers in the middle of the gear face, and 1.060 inch with mics. There's clearly some sort of burr on one face of that gear. Note that this measurement is with 2 teeth against one anvil, and one tooth against the other. I believe this number would then be smaller than the actual outer diameter.

I'd stick with Okidoki's numbers for the blank sizes. As you may have guessed, I'm unaware of how to measure the true OD for the odd tooth gear.

TomKro
 
Thank you Tom!!! That's just what I wanted to hear to confirm the clearance needed! Between yours and Okidiki's info, .... time to get busy ;) Thank you both again!!:encourage:
 
Okidiki, by any chance do you have the CAD files for those gears or did you use a dividing head to cut them?

Edited to add if you did use a dividing head can you point me to the tool you used please:<)

Thanks!
 
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Steve,

Not sure if this came up before, but the key on the keyed bushings for the Emco are smaller than the Grizzly style bushing (I think you had two different threads on Emco dimensions? Or maybe I haven't had enough coffee this AM... ).

I purchased a few of the Grizzly bushings a while back. It looks like their bushing have a key width of about 0.191 inches. The grizzly one piece keyed bushing has the key sitting about 0.072 inches above the bushing OD. It looks like the Grizzly keyed bushings can be trimmed down to Emco dimensions. They're only $2.25 a piece, so hard to pass up.

TomKro
 
Yes Tom, you are correct... I discovered that as well! I made some from the drawings you supplied but changed the key to the Grizzly version because I had a broach that size already. I have the power feed working now but only the .008 per rev option , which is faster than I would like, great for roughing, but now I want to get it to the .004 per rev for finish cutting. On a side note, I modified a Bridgeport quill feed wheel/handle, ( about 6" dia.) with a crank knob, mounted to the tail end of the lead screw, and all I do is engage the power feed lever and crank it which gives amazing control and finish results!

Steve
 
Steve-F said:
Okidiki, by any chance do you have the CAD files for those gears or did you use a dividing head to cut them?

Edited to add if you did use a dividing head can you point me to the tool you used please:<)

Thanks!
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Hello Steve,

I don't have any CAD files of these gears, only some dimensions like in the previous message. I don't own a cnc-mill in which CAD-files may be useful. Perhaps you can use the spur gear generator in Inventor's assembly environment to produce some dxf files. I made my gears using a rotary table combined with a set of involute cutters, but I've also seen people making gears using a single point HSS bit fixed into a boring head. That last method can be an inexpensive method since you don't need an arbor for holding involute cutters, the cutter set, etc, but it's challenging to cut an accurate tooth profile on the HSS bit and also the single point cutting will cause more force on the work piece (with POM it shouldn't make much difference, but with metals the noise production will be significant). Involute cutter sets don't have to be really expensive though. I've seen some sets for approx. $65, but you can also buy cutters separately. Hope this helps and keep us posted on your progress :)
 
Thanks for your reply Okidiki! I just happened to do as you suggested and joined the Engineers Edge web site and just that! I just downloaded all the files for the full set using spur gear generator they have, now I have just cut them. Thanks again so much, very helpful !! :eagerness:
 
Hey steve,

I really like this topic! if needed any other dimensions, feel free to ask me aswell.
Do you have any more info about your self made tailstock base? Really like the quick lock idea!
 
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