Gear question

Want special lathe tool form cutter to cut gears.
After an extend lapse, I want to complete a set of change
gears for my EMCO Compact 10 lathe.
formatting link

formatting link

I have hand ground the gear tooth profile and this works
pretty well, but I am hoping to improve on this process by
getting several 1/4 square lathe tool bits profile ground to
the required profile [1.0 module]. In his book _Gears and
Gear Cutting_
Law provides a method of closely approximating
the involute curve using constant diameters, thus it would
appear that it should be possible to simply grind the
required radius on both sides of a lathe tool blank using a
surface grinder [which I don't have] with a wheel dressed
with the correct diameter/radius.
formatting link

formatting link
{spreadsheet download and cartoon}
formatting link

I have two machines that I can use.
(1) The Emco lathe with the milling head, and
(2) An Atlas 7B shaper.
From prior posts I know that several people have machined
their own gears, so I am hoping for some good advice.
(1) What does the group suggest for tool material. Is the
additional cost [8X to 10X] for the premium steel such as
T-15, MoMax, etc. over the no-name M2 justified?
(2) In your opinion, which machine [lathe or shaper] is
the better bet?
(3) Because of the light duty and ease of machining I am
planning on making the gears out of Aluminum. Which alloy
6061T6511 or 7075T651? [7075 is considerably higher price at
about 4X for the same size blank]
formatting link

(4) Do any of our posters know if these form tools are
commercially available, and if so an URL or phone number?
(5) Can anyone suggest a shop that would be interested in
grinding 4 of these tools, (2) #2 and (2) #3
(6) Does anyone care to venture a guess as to the price?
(7) Would there be a commercial market for these tools if
they could be priced about like other lathe form tools?
formatting link

Reply to
F. George McDuffee
Loading thread data ...
Suggest buy them instead--Sterling ( stock drive products ) should have whatever you need reasonably priced although you might have to machine out the bore and press in a new hub.
formatting link
Reply to
1. You are going to be cutting aluminum. M2 ought to be fine.
2. and 4. You can use either, but I would look on Ebay to see if you can get a gear cutter that you can use. I did a search on Ebay for gear cutter and found 400 items.
Note you may not find a gear cutter that will work to cut gears that are compatible with your existing gears. But so what. You can make gears to replace your existing gears. You just need a complete set of gears. They do not have to be 1.0 Module.
3. I would use the cheaper alloy. If any of the gears fail you can make another one.
5. and 6 I have no idea.
7. Module 1.0 gear cutters can be found by searching on the internet. I suspect one could use a 24 or 26 DP gear cutter and cut gears that would work with Module 1.0 gears. But surely someone that actually knows something about cutting gears will chime in here. ( Unless they have all quit reading RCM because of all the OT posts ).
Reply to
George, I'm really confused. I cannot see you making any gears with the equipment you have. I think you will find it an exercise in frustration. Gears of any description are not easy to make. Good gears require the proper equipment. I never make parts that I can buy. Buying is almost always cheaper. If you are doing this as a hobby, I suggest you have far too much time on your hands. Steve
formatting link
formatting link
formatting link
formatting link
Reply to
Steve Lusardi
That depends on what other (non-powered) tools he may have.
There is the pride of accomplishment to consider.
And looking at the second URL this being done by student machinists as part of their learning process.
Interestingly enough -- there is something about this web page which crashes Opera -- though Mozilla Firefox shows it with no problem -- just too small a font for my current eyes. :-)
This suggests that other tools are available.
Blending the various radii might be a bit tricky. I have a surface grinder, but not a radius dressing tool.
Cartoon? Where?
The lathe can be used for turning the gear blanks. The milling head could be used for a form cutter in an appropriate holder, or the shaper could be used with the form cutter -- but the problem with the shaper is getting a consistent depth of cut.
But for either, you need a dividing head or perhaps a rotary table with dividing plates. The problem may be getting one small enough to fit either machine. I've got a Rockwell/Delta 7" shaper and know how difficult it is to fit extra tooling like dividing heads onto it.
You should have asked this *after* mentioning the material. Given that you are going for aluminum, I think that even the M2 will suffice.
Which one can you fit your dividing head or rotary table onto in an orientation which allows access to the work area of the gear to be?
Personally, I would consider the milling head on the lathe (really, don't just call it a lathe when you are intending to use the milling head) with a selection of involute gear tooth milling cutters on an arbor. (Check which ones you will need for the tooth counts which you are making. You don't mention which tooth counts you will need to make -- but if the counts are widely separated enough, you will need a different cutter (either the milling cutter or the form cutter) for each tooth count.
formatting link
formatting link
No guess here. How fast will the teeth wear and deposit on the meshing teeth? One thing to bear in mind is that you absolutely *don't* want two aluminum gears meshing -- alternate between steel or cast iron and the aluminum. Aluminum on aluminum will gall badly leading to a *very* short life for the gears.
I seriously doubt that they are.
Not I.
Probably more than the cost of involute gear tooth cutters bought as milling cutters.
formatting link
formatting link
Highly unlikely. No commercial use. Commercial shops who *have* to make gears instead of purchasing them (because they have some kind of unusual feature) and don't have the production quantities needed to justify a gear hobber would be purchasing the involute gear tooth cutters (likely a full set of eight with spares for the most commonly used sizes) and certainly not single-point form tools. The production rate difference would be too much of a penalty for the form tools.
Personally, as a hobbist, for gears which I need to make (or repair), I have purchased the gear tooth mills -- and I have a horizontal spindle milling machine so there is sufficient rigidity to drive them well.
Hmm ... another possibility with the shaper. Simply grind a rack form tooth (no involute shape needed), and set up the gear blank so it is rotated as the cutter steps across the blank, so it is turning and producing the true involute shape as it passes. You will need to sit and wait as it passes through a single tooth fully before resetting the blanks to cut the next tooth. It will take *lots* of time, but you will get the right gear tooth shape with a simple to produce tool. Something like an Acme threading tool if cutting 14-1/2 degree pressure angle, or somewhat more blunt if cutting a 20 degree pressure angle. The real trick is setting up the mechanism to rotate the blank at just the right speed as you step through the tooth position. I think that this would be done with a drum with a steel cable running around it with the cable's centerline at precisely the pitch diameter.
Good Luck, DoN.
Reply to
DoN. Nichols
Strange -- how about the other pages on the site? Nothing fancy and no special features on any of them, just box stock M/S Front Page 2000. All pages work fine with both FireFox [v 3.6.6 latest download] and M/S Exploder on my computer.
formatting link
will allow you to adjust the font size. Font at 100% is about right on my monitor.
Upper right hand corner of the spreadsheet. Shows in both M/S excel and Open Office spreadsheet for me.
also see
formatting link
I also have a B&D RTX electric die grinder. Some sketches indicate that it may be possible to mount this grinder in a frame to generate the two radii on both sides of the tool. I have some small mounted stones and a set of the diamond pins from HF and these allow very easy freehand grinding of hook and chip breakers in 1/4 square HSS. Also ground up a "bullnose" finishing tool with considerable hook for the shaper using a 7/16 M2 blank. Worked fine and gave a very nice finish.
I was expecting to rig a positive stop for the shaper down feed. Further consideration indicates that I will most likely do all the operations in the mill mode on the Emco including rounding the blank and thinning the outside edges of the gear to 9m/m. The dividing head can be mounted vertical or horizontal and used as a rotary table. LMS [Little Machine Shop] had some blank 2MT arbors with 1" diameter heads. I plan on modifying one of these to use as an arbor in the dividing head to mount the gear blanks.
formatting link
The dividing head I purchased will just fit on the Emco, and the Atlas 7B will require a table extension to support the dividing head, and a "short" tool post to clear everything.
Being a real cheapscrew, I generally get the sale stuff from Enco, but even this is getting expensive.
The dividing head just fits the Emco, so this looks like the better option. Could fit the shaper, but will need to rig up a table extension.
#2 [55-134 T] and #3 [34-54 T] cutters will cover the range of interest. { FWIW -- while it may be a typo on some of the foreign sites, it appears their cutter numbers are "backwards" to U.S. usage} I managed to locate a 2MT arbor with drawbar that is the correct size for the 1.0 module B&S style cutters [apparently 16 mm hole as these are all imports], but from a UK supplier. As indicated in an other post in this thread, I also located a source in India that makes gear cutters like an end-mill. Downside is the difficulty in sharpening compared to the form ground B&S style, but I already have both Weldon endmill adapters and ER25 collets for 3/8 and 1/2 shank endmills.
formatting link
formatting link
Thanks for the reminder. The aluminum gears worked well with the CI gears, but most likely would not be satisfactory with another aluminum gear. That leaves 11L44 and sheet plastic such as nylon.
formatting link
formatting link
I was thinking of the home/hobby machinist, and possibly the "one-off" repair shops where parts are no longer available.
Indeed. See
formatting link
I considered this but the effort required to construct the indexer/rotator and rig the shaper seems very high. I could see this for the hobbiest that makes lots of gears in strange sizes and profiles, e.g. cycloid. This looks like an interesting project for CNC that would rotate the dividing head so many "clicks" for each stroke of the ram, assuming fine automatic feed. Easy to change the number of "clicks" for changes in diameter/tooth count.
Thanks for the feedback.
Reply to
F. George McDuffee
Similar to above I recall as being called using a "pitch block", and though generally it's used for gear grinding I see no reason why a single hss tool blank having a rack form couldn't be used in a planer / shaper instead....
We had used a round chunk of aluminum and a couple pieces of steel banding...and I can't remember exactly how the arc was swung in relation to the wheel stroke axis or even how the gear was indexed for each tooth but pretty sure the wheel was dressed to a rack geometry and had perhaps 5 "teeth"
Reply to

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.