# Gear Making



## Nebraska Kirk (Jan 26, 2016)

I made my very first gears yesterday!!  They are for a sheet metal "slip-roll".  The Bridgeport worked pretty well, I set the cutter speed at 135 rpm and played with the power feed on the X axis until it seemed to be cutting well, not too fast and not too slow. It still took a while  to do the 4 gears at 14 teeth each.


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## Deerslayer (Jan 26, 2016)

Nice work!


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## ch2co (Jan 26, 2016)

Well done!  What size slip rolls are you making? Do you have any prints?

CHuck the grumpy old guy


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## Chipper5783 (Jan 26, 2016)

Nebraska Kirk said:


> I made my very first gears yesterday!!  They are for a sheet metal "slip-roll".  The Bridgeport worked pretty well, I set the cutter speed at 135 rpm and played with the power feed on the X axis until it seemed to be cutting well, not too fast and not too slow. It still took a while  to do the 4 gears at 14 teeth each.
> 
> View attachment 120481
> View attachment 120482
> View attachment 120483


Good job.  Gear cutting can be sort of addictive.  David


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## brino (Jan 26, 2016)

Hi Kirk,

Great work!

-brino


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## kvt (Jan 26, 2016)

looks like you did a great job.   Now what are you putting them one.

Ken


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## dave2176 (Jan 26, 2016)

I'm impressed. Is it done in a single pass or do you need to take multiple passes at each tooth?


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## FOMOGO (Jan 26, 2016)

Those look great. How is the gear your cutting held on the shaft it's mounted on, press fit? Is the cutter set at 90 degrees to center-line of the gear for each tooth while being cut? I'm really missing my shop. Thanks, Mike


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## Steve Shannon (Jan 26, 2016)

That's impressive. Could you do all four at once, or do a long gear and then part it into four?


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## Nebraska Kirk (Jan 26, 2016)

I am not making a sheet metal roller, these gears are replacements for an old roller, the original gears were TOTALLY shot from rust.  I cut each tooth in a single pass. With a 10 pitch the cutting depth is only .216"

Mike, yes, the gear blank was just a press fit on the mandrel, but tight enough there was no danger of the cutting pressure moving it.  These are just plain spur gears so, yes, the cutter would be running at 90 degrees to the gear. 

Steve, all 4 COULD have been cut at once, but I don't think my mandrel would have been long enough. I suppose it is possible to make one long gear, cut all the teeth and then part them off, but these being my first gears, I just made them individually.   I doubt much time would have been saved anyway, it only took 2-3 minutes to press the completed gear off the mandrel, press on the next blank and mount back between the centers of the dividing head and tailstock.

At some point in the future I will have to make at least one helical gear that I know of.  I have an antique 4-cylinder, twin camshaft engine that uses an idler gear between the crank gear and the two cam gears.   Since this idler gear is meshing with 3 gears, it is getting 3 times the wear and consequently the teeth are worn until they are so sharp you could shave with them!  I have looked for a better replacement gear, but all the other ones I have found are just as badly worn.


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## Steve Shannon (Jan 26, 2016)

My question was not meant to be critical and I apologize if it sounded that way. I would love to learn how to cut gears. I've watched nearly every you tube video on the subject, but I haven't seen any where someone was making more than one of a particular size.  Boring a long gear blank like that might offset any savings anyway. I would think a person would turn the blank and then groove it below the gear teeth root. Then cut the teeth and finally finish parting it off. That would avoid having to make an interrupted cut. 
I have a couple helical gears that are each missing a single tooth. When you do cut the helical gear I would love to see how you do it. 


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## Nebraska Kirk (Jan 27, 2016)

Steve, not to fear, I did not consider your questions to be criticizing, merely  legitimate questions from someone wanting to know.  A helical gear will be more involved... the power shaft of the dividing head will  have to be geared to the leadscrew on the table so that as the table travels in the X axis it will rotate the dividing head to form the helix.  Careful calculations have to be made to determine the lead of the helix and to get the correct gear ratio to form that helix.  The cutter also has to be set at the angle of the helix. Then there is the task of determining what cutter to use. The normal pitch (pitch of cutter used) will vary with the helix angle. The Machinery's Handbook gives the procedure and formula necessary to determine the normal pitch. Finally, the correct number of cutter in that pitch must be calculated.  The proper milling cutter to use for spur gears depends upon the pitch of the teeth and also upon the number of teeth, but a cutter for milling helical gears is not selected with reference to the actual number of teeth in the gear, as in spur gearing, but rather with reference to  a calculated number that takes into account the effect on the tooth profile of lead angle, normal diametral pitch, and cutter diameter.  Clear as mud!? That is why I have a copy of the Machinery's Handbook, all the mathematical formula and tables are in there!

Videos of the machining process.


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