Gallery, Projects and General > How to's
Cutting Spur Gears -- A neat technique
xo18thfa:
Several years ago, I did a series on cutting spur gears using the methods in the “Workshop Practice Series” book #17, “Gears and Gear Cutting” by Ivan Law:
Mr Law's method works great. You can follow his techniques without deviation. However, recently I found another method to cut gears that approximates involute tooth using only one cutter to form gears of any size within the diametral pitch. The method is described by "Helicron" at his website.
http://www.helicron.net/workshop/gearcutting/
I followed Helicron's technique with good results.
First step is to make the cutter tool. My lathe is not rigid enough to make the cutter as Helicron shows. Instead mine is a single point cutter with most of the blank removed before forming the cutting teeth.
The steel for the cutter is alloy “O1”. O1 is the most widely used tool steel and is available from McMaster Carr and other suppliers. O1 is very easy to work with and harden. Shape and form the tool to the desired size. Heat with a torch to 1400 degrees F, which is cherry red heat in room light. Plunge in oil to quench. I used some leftover salad oil from the kitchen. Leave in the oil quench about 30 seconds, it cools down slowly. Quenched tool steel is too brittle at this point and needs tempering. To temper, suspend the tool in a small pot of salad oil on the kitchen stove. Heat to 350 degrees F using a candy thermometer to check the temperature. Leave it in about 10 minutes, pull out and let air dry. The O1 steel comes out very hard and will cut just about anything.
For an upcoming project I want to cut some 48 diametral pitch gears with 52, and 16 teeth. First, the 52-tooth gear. These are from 1/8” thick flat brass bar. First, make a shank from length of 1/2" diameter steel in the lathe cut and turn a 5/16” diameter boss. Thread the end to accept a nut. Gang up four pieces of brass stock on the shank.
Turn the ganged stock to the final diameter for the gear. In this case 1.125"
To cut the gears I used my little, homemade Harold Hall dividing head. It is a “direct indexing” head that uses the change gears from the Atlas 6” lathe for indexing. The spindle hole is tapered with #2 Morse Taper (2MT). A 2MT collet holds cinches stock tightly in the dividing head be means of a draw bar.
Secure the 52-tooth lathe change gear to the spindle of the dividing head. Mount the dividing head to the mill table. Use a 1/2" 2MT collet to chuck the gear blanks. Chuck the gear cutter in the mill spindle and use a height measure device to set the gear cutter height.
Adjust the depth of cut and start cutting. depth of cut on 48DP gears is 0.045". Advance the dividing head spindle one notch on the indexing gear.
Finish the 52 tooth gears by soft soldering an appropriate hub. Drill and tap for a set screw.
Next time we will cut the 16 tooth gear and do something with the results.
bertie_bassett:
nice work
that method is one im planning on using again in the near future to make change gears for my lathe.
last time i tried it didnt quite work, think my cutter wasnt very accurate. and had issues with working out the depth of cut
couple of questions:
a multi tooth cutter would have been easier on your lathe surely? its just a series of v's at the correct spacing. cuting just one tooth as you have must have been quite clunky as it went round and id have thought harder on your lathe?
also from memory you only need about 5 teeth, anymore dosnt help as they dont do any cutting ( unless your cutting a gear with hundreds of teeth.
AdeV:
There used to be a series of videos on YouTube by a guy called Hobbynut, showing how he used a very similar technique to make gears on his Sherline lathe & mill. I think I downloaded them somewhere, no idea where they'd be now, I'm pretty sure they've gone now. I can't remember if his cutter required indexing, or if it was a free-running hob, though.
Even so, liked the write up on Helicron's site, that definitely gives me the confidence to have another go at gear cutting!
John Stevenson:
Yes those Hobbynut videos were very informative but as you say they have gone now.
There is a DVD by Jose Rodriguez on gear cutting doing the rounds, about £30 a pop.
Don't bother it's absolute $hite
He's using some home made mill made from licorice root and drinking straws, the video is out of focus and any close up could be a shop of anything [ probably blancmange ]
But the biggest fook up is he gets Pi wrong all the way thru all his calculations so all his calculations are off.
Since when is Pi 3 416 ??
PekkaNF:
--- Quote from: John Stevenson on February 22, 2017, 03:20:59 PM ---....
Since when is Pi 3 416 ??
--- End quote ---
Imperial PI? Metric is standard :lol:
Pekka
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