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+--- Thread: cutting gears (/thread-585.html)
RE: cutting gears - dallen - 07-20-2012
thank you, my first try at cutting gears I did with a single point cutter that I ground and used on a piece of bearing bronze. The attempt that I made just before cutting the one in the picture I used too large of a blank it came out looking more like a metric module 1.5 them a 20 DP 14.5 gear.
I am going to make some blank patterns and cast some NiBrAl blanks and try making gears out of the bronze, if nothing else they will be pretty.
DA
RE: cutting gears - Sunset Machine - 07-20-2012
(07-20-2012, 09:02 AM)dallen Wrote: I have a question about your chart, it says that the number four cutter cuts from 26 to 34 teeth, but the cutter that I ordered is a number 4 and its marked 21 to 25 curious as to which is right or do different makers make the cutters differently.
Machinery's Handbook says #4 is for 26-34 teeth. Under a section on checking gears, it also says that there should be .387" across 3 teeth for a 20DP 25 tooth gear cut with no clearance, and mumbles something about arc thickness calculations for working any clearance in. The gear looks good, how does it measure up?
RE: cutting gears - dallen - 07-20-2012
I haven't measured it yet been off on other stuff, I did cut it like 5 thousands short of the depth that was called for by the Metal Shop Calculator that I downloaded.
Will try to measure it in the next day or to but will be out of town tomorrow.
RE: cutting gears - dallen - 07-21-2012
(07-20-2012, 09:08 PM)Sunset Machine Wrote:(07-20-2012, 09:02 AM)dallen Wrote: I have a question about your chart, it says that the number four cutter cuts from 26 to 34 teeth, but the cutter that I ordered is a number 4 and its marked 21 to 25 curious as to which is right or do different makers make the cutters differently.
Machinery's Handbook says #4 is for 26-34 teeth. Under a section on checking gears, it also says that there should be .387" across 3 teeth for a 20DP 25 tooth gear cut with no clearance, and mumbles something about arc thickness calculations for working any clearance in. The gear looks good, how does it measure up?
I measured the gear this morning across three of the teeth and got 3.91 so I'm a little on the thick side if I had of taken the cut to .107 it would of probably been right on.
RE: cutting gears - DaveH - 07-21-2012
DA,
Nah, it will wear that much
DaveH
RE: cutting gears - gramps51 - 07-22-2012
(07-07-2012, 10:59 PM)dallen Wrote:(07-07-2012, 10:43 AM)Sunset Machine Wrote: How'd you do for precision? Caliper across a few teeth in several places..
Lots of advantages doing these between centers. There's even a "re-do" possible, the drive dog is somewhat adjustable (opposing screws) and using it will enable you to remount the blank and recut teeth a little deeper if need be. Especially handy for recutting teeth damaged by another gear, or fixing broken teeth. I generally use a 1" x 6" round bar as an arbor, turned, centered and threaded to fit, preferring a shoulder for the blank to rest against and a large nut to hold 'er good.
I have a Chinese lathe made about 5 years ago that cuts a taper I can't make go away!!! My 70 year old Atlas is way more accurate. Now that my MFB is rebuilt I plan to do some gears so your experiences are a good learning tool for me and for you too I'm sure.
I didn't check to see if they came out right due to noticing that I was cutting them about a 80 thousands off of center.
I would make arbors that way but my lathe has a habit of cutting a slight taper which I have as yet get adjusted out, but the thing was made like 20 years ago in China and was treated really bad before I got it, hoping to get a new one pretty soon. But I do have a couple tapered arbors ordered that will be here in a couple days.
any hints, or tips that will help keep me on the straight and narrow of gear cutting will be listened
RE: cutting gears - stevec - 07-22-2012
Gramps, gotta agree with you on the Busy Bee Craftex 10 X 18 'cept I don't think it would even hold a decent sized boat.
RE: cutting gears - dallen - 07-23-2012
sorry for not being active here in this thread, but I have been doing some other things like the mag base revival which turned out pretty good if I do say so. And today I took the day off to run up to Tulsa and see one of my brothers and do some shopping at the tool supplier.
I do plan on getting back to the gear cutting as I want a whole set of gears for my lathe, by set I mean the gears that should of been with it when I got the lathe. So this thread will be active for some time yet.
Now thats out of the way, I have another question. If I was to use brass/bronze to cut gears out of what would be a good alloy. I'm leaning towards using NiBrAl 95800 I believe is the alloy number, reason for using it is I can get it at a dirt cheap price and I have worked with it casting some boat prop blades (another story for a different time)
anyone have any suggestions, warnings like don't do it that way or yea that will work, or your just plum crazy for casting gear blanks
DA
RE: cutting gears - Rickabilly - 07-27-2012
(07-15-2012, 02:01 PM)dallen Wrote: I plan on making the bores undersized then rebore them after the teeth are cut.
Just my £0.02 don't do it, there's no way to set up to the pitch circle which is the only thing that really matters on a gear, as long as the pitch circle is the right size and coaxial to the bore the OD can be miles out and 0.010" off centre and it'll still work fine on most applications.
My method is to set your arbor up as true as you can, and bore your gear to finished size, use the arbor as a reference when setting the cutter up on centre either with a square and guage block or by any other means and cut those teeth, in one go using a gear tooth vernier to verify tooth size.
Best regards
Rick
RE: cutting gears - dallen - 07-27-2012
Hi Rick
the way that I plan to do the gears is to bore the blanks out to shaft size then mount them on the arbor and put it in the lathe and turn to the working OD then mount them in the mill and cut the teeth on the blank. I am in the process of trying to purchase a horizonal mill which is older then I am by some years so its going to take some work to get it up and running (not to much I hope) my plans are to get it running and set up the indexer on it and leave it there till I get the gears cut that I am needing.
I would put it on the Mini MIll but its way to small to get everything onto the table, and I have other projects in the works that I hate to tie up my bigger mill with the indexer just to have to take it back off.
I missed out and a Cincinnati #2 Horizonal mill in and auction in kansas that sold for 210 dollars, but a machine that size is way overboard for me.
DA