Cutting Tool Generatin -- new name

[philbur]

Yes but for some applicati ons shaft center distances can be important, without to much back-lash.

I'll have a go at making a brass M1.5 - 30T gear tomorrow (oops, today).

Phil:)

All I really wantr to ensure is that a gear cut with such a tool will meash with other gears of the same module, so the more important thing is if a gear made with the tool will mesh with that reference gear, not if the tool does. A deeper root for example simply gives better root clearance .

[ArtF]

Phil:

  Root depths and such wont impact backlash or center/shaft distances . The only important issue there is tooth width.. the formula for tooth width doesnt vary from maker to maker. Root depth really impacts the strength of teeth more than anything else. As long as clearance is equal to or greater than required, no issue "should" exist. ) .. that should is always an important issue.

Art

[philbur]

Art:

I understan d about root depth, we are maybe not talking about the same issue. I was still harping on about the risk of using the wrong full feed depth.

As a matter of interest what is you source reference for the involute profile.

Phil:)

[ArtF]

Phil:

  Oh, of course. My Bad. The depth will of course have an effect of shaft dist..tho ugh not roll meshing..

  My reference s on the involute profile are too many to list, but then, they all agree. The involute itself
is a mathmatic al item that is resolute, no-one can play with that one. So long as the formula for the base circle is kept standard
across makers, the gears must mesh. The Base circle is the most important item in all of it really. And its always the pitchdiam times the
cosine of the pressure angle. The pitch diameter is always the teeth * module, again a constant except when profile shift is in effect or in a helical,
which has the pitch diameter stretched as well. SO since the pitch diam, and the base circle are predefine d constant formula's, the involute
too is a never changing formula.. .. ie..

x = (Gear.Base Diam/2) * (cos(ang * PI/180) +  ang * PI/180 * sin( ang *PI/180 ));
y = (Gear.Base Diam/2) * (sin(ang * PI/180)  -  ang * PI/180  * cos( ang *PI/180 ));
 
   for any ang that fits withing the constrain ts of the visable involute from root to tip ( or base to tip if root is less or equal to base.)

 Art

[philbur]

Hi Art.

There is still something not right about the Z height when doing the profile. I had to rerun the profiling code again with the Z height lowered by 1 mm to get it to complete the profile.

Phil:)

[philbur]

Here's a cutter ready for use. 5mm diameter - 1.5 module - 25 teeth, hardened and tempered.



Phil:)

[ArtF]

Excellent . Ill be facinated by the gear it makes.

 Still too high eh? Thats amazing, I told it to go to 1.6 times the depth just in case.
Ill revisit that math to see where I dicked up..

Art

[philbur]

Art:

Oops, possibly my mistake on the Z height. Just discovere d tonight that I had make the cutter from 6mm stock, but the code was for 5mm stock.

Anyway I carried on with cutting the gear, just to confirm how the cutter would work. It didn't. The brass blank ate the cutter, so I rechecked the hardness on the tip with a file. Seemed pretty good so I checked further up the cutter with a scriber. It was somewhat soft. I need to take more care with the heat treatment . I didn't expect the brass to be such a challenge, although it is of unknown origin.

Anyway I'll redo it all all tomorrow.

Phil:)

 Still too high eh? Thats amazing, I told it to go to 1.6 times the depth just in case.
Ill revisit that math to see where I dicked up..

Art

[ArtF]

Phil:

  Ahhhh, well... shot happens.. murphy rules.

  I did check my math on the height, all looks well, and I verified it with known values precalcul ated.

Pity about the hardening . But I guess thats one of the sore spots in the process. Good luck with the next attempt.
Let me know if you think of something that I can do to make it all easier.

Thx
ARt

[John S]

Phil,
Don't temper if using brass, a quick lick across the flat faces put's enough heat into the extreme edges to temper them.
If you temper then grind it makes it too soft.

Art / Phil

Just got a big job out the door tonight so I should have a bit of time to play this week before I need the machine for another job.

[ArtF]

HI John:

  Dont complain, I get the feeling the busy are the lucky these days.

 I think your timing is good, the latest troubles we fixed really needed
to be done, thanks to Phil, I think the cutter now seems good. Minor issues perhaps?

Art

[alenz]

I was just thinking (gets me in trouble) about the code to make a fly cutter tool. Maybe take the tool cutter wizard code and break the profile portion into two parts. (Break at Y=0). For example run one half with G0A9, then the other half with G0A-9. Only problem is that the tip would not have enough (any?) rake to prevent the heel of the tool from rubbing. Maybe mount the RT with a slight cant from the X-axis?  The stock (for a Sherline) would be ¼ X ¼ X 2 ½ square and therefore wouldn’t need nor use the stock squaring code.   The actual cant angle would be a function of the effective fly cutter radius and tool thickness (stock would be precut).   Unfortuna tely however small that cant angle is it will still compromis e the flat pattern outline.
Two questions:
1.   In the real world, (assuming that this would even work at all) would this error be noticeabl e?
2.   Am I in total left field and there is already an easier and more direct method for cutting a fly cutter?
Historica lly for me, the 2nd is more likely <grin>
Al

[philbur]

Hi Al, I think the issue with the tip clearance could be solved with a file, or the program could turn the cutter 90 degrees and then profile the clearance angle.

I guess the ultimate would be a program that milled you a B&S type cutter.

Phil:)

[philbur]

I think what happen was I didn't take sufficien t care in heating enough of the bar-stock to the correct temperatu re, so by the time I got it in the quench the bar-stock had already sucked the temperatu re of the tip down.

Phil:)

Phil,
Don't temper if using brass, a quick lick across the flat faces put's enough heat into the extreme edges to temper them.
If you temper then grind it makes it too soft.

[philbur]

Hi Art:

Here's the latest attempt:



I made two cutters and broke both by the third tooth. Another Oops. the cutters are very delicate because of the thickness and with no tempering they were very brittle.

Other observabl e faults, I pre-slit the blank with a saw that was a bit on the thick side, also the DOC with the slitting saw was a bit to much, consequen tly the profile at the root is a bit buggered. This was on purpose, for a first attempt I didn't want to over stress the cutter, ya well.

I'm not use to making and using such delicate cutters so I need a bit of practice. A watchmake r would have less of a problem.

One other thing, the produced code has an M3? followed by a M6 but no M3! to restart the spindle, potential Oops. I'm not sure the M6 is necessary? I forget many things but putting the right tool in before a start isn't normally one of them.

I think overall at this size (and in brass) the method is capable of producing usable gears, providing the cutter survives.

Phil.