Gear Cutting on the Mill

[Arbo]

I am considering trying to make some gears. My setup would be a rotary table and tailstock, with the blank mounted on an arbor and held between centers. I have never thought about this before, so I don't know what kind of cutter i will need. Do they make end mills to cut gears? Or, is it designed like a slitting saw with the correct pitch angle on the cutter? A little help on this one please.

[J Tiers]

1) See machinery's handbook

2) There are a series of cutters made to cut the profile for each of 8 groups of tooth counts, since the profile varies.

3) it is cheaper, but takes longer, on the shaper. The cutters for the mill cost about $25 per each, imported from Chin-Chin land. More if you want US etc.

[SGW]

Like a slitting saw, more or less. Check the MSC catalog www.mscdirect.com for involute gear cutters. Since the shape of gear teeth varies with the number of teeth (the teeth of a 16-tooth gear aren't the same shape as the teeth of a 100-tooth gear), strictly speaking you ought to have a separate cutter for each number of teeth. As a practical matter though, a set of 8 cutters will cover the entire range, each cutter dealing with a range of teeth (12-14, 15-20, or whatever). You can buy the cutters individually, you don't need to buy the complete set. So...buy the cutter(s) for the gears you plan to make, with the pressure angle (14 1/2 or 20 degrees) you want.

Ivan Law's book, "Gears and Gear Cutting" is really good.

[hms50]

If you don't have a shaper, and don't want to shell out the $$ for cutters, you can make a fly cutter. The results will be dependent on how carefully you make the cutter.

Good Luck
hms50

[jeastwood]

I've just been doing some gear cutting for a clock I'm making; perhaps my experience will be of use to you.

I also used a rotary table (RT) mounted vertically. Rather than build or buy a tailstock, I created a jig to be mounted and centered on the RT, that would hold the gears to be cut, along with backing for them. This need for backing or support during cutting may be a place where the jig has an advantage over holding on centers with a tailstock. It's a good idea to have a blank of almost the same diameter mounted along with the wheel you're cutting, in order to support it and provide a more rigid setup. Possibly this is more important for single point cutting tools than multi cutter commerical tools. The cutting I was doing was with a tool I ground and held like a fly cutter in the mill.

My jig has a base about 2.5" dia. Around the perimeter are 4 holes to allow bolts to reach down to the T nuts in the RT.
Above the base the jig is turned to a smaller diameter; choose this diameter based on the diam. of gears you'll bee cutting. It should be a bit smaller than the smallest wheel; this provides support during cutting.
Finally, another turning provides an arbor over which the gear blank fits; obviously a close fit to keep things concentric. I tapped the top of this turning to allow a bolt and washers to be mounted on top of the gear, snugging it down during cutting.
This jig also allows you to mount the gear even more securely if desired: you can drill and tap a hole through the gear blank and on into the jig body. I did this due to a caution from the clock designer on making sure the gear doesn't slip during tooth cutting. It's easy to plug the hole later and sand it down to be nearly invisible.

If you need this arbor to be different diameters, you can always use a bushing, and/or turn it down if need be.

[Arbo]

I'm missing something here...Are you holding the tool bit stationary (like a fly cutter) and using the table axis to act as a shaper. ie.no power to the spindle? I just cant see how a fly cutter type tool is going to cut teeth on a gear. Maybe I'm completely stupid. Thanks in advance.

[SGW]

Think of the flycutter as a single-point slitting saw with a weird tooth profile.....

[neonman]

Rudy Kouhoupt has a comprehensive vidio on the subject. He advertizes in HSM. My only disapointment about the video was that he makes no mention about how to make the fly cutter profle. Still a great video for beginners wantng to cut gears.

neonman

[lynnl]

Ivan Law's book describes how to closely approximate the involute form on unhardened tool steel (e.g. drill rod), which can then be hardened. Very interesting book. What's really fascinating is a device he made to provide the relief on the cutters.
John S. has also made one and posted links or pics on this board (in motion as I recall). Maybe when I grow up I'll be able to do something like that.

[coles-webb]

Here are a few links. You may want to buy a book on the subject first. "Gears and Gear cutting" book 17 of the workshop practice series is reasonably priced and good.

http://www.metalwebnews.com/howto/gear/gear1.html

http://members.cruzio.com/~lehrian/B...tingTools.html

http://www.transatlanticpub.com/cat/workshop/gears.html

http://www.enter.net/~depack/gearcut.htm

http://www.aardvark.co.nz/pjet/gears.shtml

http://www.ul.ie/~nolk/gears.htm

http://easyweb.easynet.co.uk/~chrish/worms.htm

http://www.drgears.com/Books/Titles/0852429118.htm

http://www.lathes.co.uk/hommel/page5.html

http://www.mjdtools.com/books/42209.htm

http://www.littlemachineshop.com/pro...ProductID=2057

Mike