worm gear cutting success

Tom- You may have missed my other post. But the pics are in the drop box. Look for files starting with "Worm" ERS

According to Eric R Snow :

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Pretty work. A few minor points, however:

1) The system will have renamed the files on receipt so they have the embedded spaces replaced with underscores (to be more friendly to non-Windows systems.

2) The ".JPG" is needed for downloading the images by name, instead of just going to the web site and browsing.

Here are the full and final names:

====================================================================== Worm_gear_blank_on_fixture.JPG Worm_gear_cutting_8mm.JPG Worm_gear_blank_on_fixture.JPG.1 Worm_gear_finished.JPG Worm_gear_blanks.JPG Worm_gear_fixture_1.JPG Worm_gear_cutting.txt Worm_gear_fixture_2.JPG Worm_gear_cutting_1.JPG Worm_gear_setup.JPG Worm_gear_cutting_2.JPG ======================================================================

3) It would have been beneficial to have named them so they would display in your intended sequence, eg:

Worm_gear_00_cutting.txt Worm_gear_01_blank_on_fixture.JPG Worm_gear_02_cutting_8mm.JPG Worm_gear_03_blank_on_fixture.JPG.1 Worm_gear_04_finished.JPG Worm_gear_05_blanks.JPG Worm_gear_06_fixture_1.JPG Worm_gear_07_fixture_2.JPG Worm_gear_08_cutting_1.JPG Worm_gear_09_setup.JPG Worm_gear_10_cutting_2.JPG

Of course, you would have selected a different sequence, but why not name them so the filesystem sorting orders them properly for you?

4) I suspect that Steve will go in and shrink the images. I *like* the level of detail, but several of them could have benefited from cropping to show only what you were making and as little of the surrounding as possible. Examples are the

"Worm_gear_blank_on-Fixture.JPG" and similar ones, which have a lot of large area red background (felt?) which does not serve much, and could result in much smaller images for people to download. Some of them were large enough to trigger a problem in the Opera browser which I use which causes corruption on the later parts of long downloads. This forced me to go to using wget to download them (and thus to deal with all the file name problems).

Again -- pretty work.

Is the sleeve free to turn on the stripper bolt, or is it rigid and just serves as a bearing for the gear blank?

I would probably not have turned the shoulders on the blanks until after cutting the teeth, which would do the cleanup of the burrs at the same time.

Thanks, DoN.

Greetings DoN, First, thanks for the compliments. The dropbox sent me an e-mail with all the changed file names with underscores, like you posted. I've only posted pics to the dropbox a couple times and am still learning. I did take the pictures at lower resolution with my camera but after looking at them in the dropbox I see that some cropping is indeed in order. The first blank I made was done the way you said you would do it. The subsequent ones were not. The cutting pressure from a tap being used as a hob is much higher than a cutter that was made to be a hob from the beginning. It pushed hard enough on the brass to deform it to the point that I re-faced all the parts before chamfering. So it depends on what kind of cutter is being used. For a light duty worm gear hobbing with a tap is a good way to go. For a worm gear that's going to see high pressure turning a hob with an acme profile makes more sense. That's the next project. Making a hob. ERS

According to Eric R Snow :

[ ... ]

I understand.

Live and learn. :-)

O.K. So it is experience which told you to face them before hobbing. Good enough.

O.K. Good luck, and please keep us informed of the results. DoN.

Eric, I understand what you are doing and the method used. I have never done this myself, but a question come to mind... On wormwheels I have seen, (most, anyway) the teeth are angled to match the angle of the wormgear. If the angle is significant on the wormgear, and you had straight teeth on the wormwheel, it is possible that there would be no engagement at all.... which brings me to the question... What would be the easiest way to jig up the wheel on the compound to the correct angle? (Nice work, by the way). Ken.

Greetings Ken, First of all lets get the definitions right. Worm wheel and worm gear are the same thing. Worm gear systems consist of a worm and worm wheel/worm gear. The hob for cutting a worm gear looks like a worm, excepy that it has teeth instead of a continuous thread. Similar to the high spiral tap. This hob will automatically generate teeth on the gear with an angle that matches the helix angle of the worm. So, with a hob that is shaped like the worm, there is no need to angle the worm gear. You can use a spur gear as a worm gear. The point of contact will be tiny and the pressure high because the gear will have straight teeth which do not curve up to surround the worm. And, as you have observed, the worm will need to be canted over to the same angle as the helix angle of the worm. Worm gear systems can also be hobbed with the worm at an angle to the worm gear. This may be done to get the worm shaft out of the way of something. For example, a low rotary table could be made this way to allow room for the handwheel. Now, I'm no gear expert by any means so if there are any mistakes above any experts reading this ought to post a correction. Eric

SNIP

Hey Ken,

I hope you get an answer, but I would like to be able to follow this thread and discussion at a later time too. I am having a problem deciphering your terminology.

In my experience, the "worm" is the spiral-shaped threaded driver. This would equate with Eric's "high-spiral tap". If this "worm" is of some arbitrary "large" size and formed like an auger, or as in an Archimedes Screw, it may well be called a "worm-wheel".

The "worm-gear" sometimes called just "the gear", is the driven member, and on large equipment is rarely a full brass blank, but rather a ring-gear fitted to a spider.

For a length of worm to be in 180 degree alignment with a worm-gear, (ie..to produce an output at 90 degrees to the input) the threads on the worm-gear will be at an angle, equal to the helix angle of the worm. If they are straight-cut, as in a spur gear, then in use the worm-gear could not be in 180 degree alignment, and would produce a "turn" in a gear-train at the helix angle of the worm (or the "tap" in this case).

If I'm not too far off-base, and not confusing the issue further, can you redo your question with this in mind?

Take care.

Brian Lawson, Bothwell, Ontario.

ps... maybe an interesting note.... In winding drum applications, especially of somewhat larger sizes, there is a tendency for high and sometimes excessive loads and wear on the thrust bearing(s) for the worm. We had stuff that had double drums, with double threads on a common worm. Not double-start threads (although it could be) but one thread left-hand, and one right-hand, and as a result there is almost no end-thrust at all. Pretty neat!

I just ran into this website yesterday

Has some interesting stuff in it.

This one

has pics of the author making a worm gear for a HF mill/drill using something akin to this method with the mill itself.

He even used the tap to index the part. Thanks for posting the links. ERS

Okay, my incorrect terminology. I apologize.... Worm being the "driving" member, and wormwheel/wormgear being the "driven" member. I now understand using a 3/8-16 tap to cut the teeth in the wormwheel and being driven by a straight toothed gear will work, albeit as mentioned pressure points may be high but would be fine in a light duty situation. I was thinking of Eric using a 3/8-16 tap and cutting

*angled* teeth on the wormwheel to match the pitch on an existing worm. Sorry for the confusion. Ken.

easy work-around and one used on several dividing heads is to place the worm at an angle to the worm gear equal to the helix [not pressure] angle of the worm.

Unka George (George McDuffee)

There is something to be said for government by a great aristocracy which has furnished leaders to the nation in peace and war for generations; even a democrat like myself must admit this. But there is absolutely nothing to be said for government by a plutocracy, for government by men very powerful in certain lines and gifted with the "money touch," but with ideals which in their essence are merely those of so many glorified pawnbrokers.

Theodore Roosevelt (1858-1919), U.S. Republican (later Progressive) politician, president. Letter, 15 Nov. 1913.

According to Ken Sterling :

[ ... lots snipped about cutting wormwheels on the lathe with a tap ... ]

Since you are cutting the teeth on the worm wheel by a tap which duplicates the thread of the worm gear, the angles will be *naturally* correct. The angle of the teeth on the tap will turn the wheel under it as it cuts, thus producing the angle.

Enjoy, DoN.

There was some discussion in the group about copyrights and

I don't have any good opinions about that but I rented "Making Gears the Easy Way" by Jose Rodriguez from them. Lots of good information and ideas in there. A bit odd because he made all his own machine tools, but all can be extrapolated to normal lathes or mills if you don't want to make your own machines.

So, DoN, if he's using a 3/8-16 tap to cut the wormwheel/wormgear, then he will have to use a 3/8-16 bolt (or similar) to be the worm as the pitch of each would then match? Ken.

Which is what I'm doing. Which is why a tap can be such a good hob. ERS

According to Ken Sterling :

[ ... ] [ ... ]

Precisely. That is what makes this system so great. Otherwise, you would need to have the blank turned by a gear train getting information from the hob's rotation. This is (obviously) a much more complex machine than the lathe which did the job for him.

Enjoy, DoN.