On Wednesday, May 20, 2015 at 12:21:43 PM UTC-7, F. George McDuffee wrote: snip
In your example you won't have concentricity issues because it's a one and done with all variables being controlled in one op. That's the way to go if you can.
In my case, we make some gears using pinion wire running it on a lathe. We buy the wire which is drawn through a die.
The supplier threads one end of a bar as shown in this photo and then pull through die.
Here are a couple gears I make and a different sized pinion wire:
The issue with buying pinion wire is concentricity. The OD is rarely concen tric with the pitch and minor. Concentricity issues cause major backlash is sues in assemblies that don't have backlash compensation Using a round 5C c ollet doesn't work, you start off by not being concentric.
In our case I had Hardinge make us some collets that chuck on the pitch dia meter, shown here;
This way all the critical dimensions are concentric with the ID and OD turn ed features.
The next major issue was how to deburr the parts. Using ThinBit tools to ma chine the OD dimensions and they are great tools better than any other but under microscope there still left microscopic burrs on the teeth which is n ot allowed by the customer.
To remove the burrs and polish up the parts, after a lot of searching I fou nd a "Magnetic Finisher" that does a wonderful job. The machine shop size i s about $27,000.00. Since we are making small & micro miniature parts for t his product line I found a Magnetic Finisher that is used for polishing rin gs and cost less than $500.00.
Similar to this one;
Sounds like it's beating the parts up but it's not. Will add more informati on on this deburring and polishing machine later.
Sandvik makes milling gear cutters with inserts. It's one of their specialties. They're trying to replace gear hobbing with gear milling in a lot of applications. They even have agreements with Gleason to co-develop gear milling.
One of their really interesting projects is their uP-Gear system for "milling" spiral-bevel gears on a five-axis milling machine. At that point, you have to scratch your head over whether it's really milling, or if it's actually gearless generating.
Very cool stuff. Not much there for hobbyists -- the prices will make your ears flap.
What is the potential to use *ONE* of these inserts in either a "fly cutter" in a mill or insert holder in a shaper? I have made several gears but my limiting factors are the high costs of the store bought numbered cutters and the difficulty of hand grinding a "line out" HSS tool bit.
Either square lathe tool bits or small end mills ground to the numbered involute profile both inch and metric module could be a viable hobbiest/repair tool concept. Anybody care to make a guesstimate of what it would cost to cnc grind number an involute profile [or the circular arc equivilant
] with clearance on a
1/4 to 1/2 square HSS bit and/or appropriate size HSS end mill?
Also does anyone have a trick to set the c/l of the tool on the c/l of the gear blank in either a mill with fly cutter or shaper?
"F. George McDuffee" wrote in message news: firstname.lastname@example.org...
When I turn the locating stub arbor that snugly fits into the gear blank I leave a centering point or plug on the end. A point is good when I can find and mark the cutter centerline, otherwise a plug the same width as the cutter tip helps with visual alignment.
I've been buying involute gear cutters on ebay , average price is about $25 for singles , around $150 for a set of 8 .
I use the cutter to make a light cut on the end of the arbor , then rotate
arbor and machine it flat , then make one pass with the gear cutter on CL . I then use that cut to center the cutter for later sessions . I recently figured out that not all of my cutters are the exact same thickness ...