worm gear cutting success

According to Ken Sterling <kens_at_sys_matrix_.net>:


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    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.
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On Tue, 11 Jul 2006 23:31:53 GMT, "Tom Gardner"

Tom-I've been looking all over for the cable that goes from my camera to the computer. As soo as I find it I'll post pics to the dropbox. ERS
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Eric, It's right *there*, to the left of the phone on the top of the desk - geeeezzzzz- I gotta find *everything* for you.... Ken.
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    [ ... ]

    Assuming a standard digital camera with removable media, you can generally get faster transfers from a USB interfaced card reader (most will fit several types of cards), or (in my case) I put the CF cards in a PCMCIA adaptor and shove that into the PCMCIA slot in the computer, because I don't run a computer with USB for my normal operations.
    I've never actually *used* the USB cords which came with my various digital cameras. :-)
    And these card readers seem to be priced between $6.00 and $18.00, depending on sales at the time you get it. At that price, get a spare, and keep it where you can find it again. :-)
    Enjoy,         DoN.
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On 13 Jul 2006 05:36:07 GMT, snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:

My current camera uses compact flash..and Ive picked up 3 readers at second hand stores , all totalling less than $5 for the 3. Each are USB..so I can keep one at home, one at my work RV and one in the laptop case.
Pretty slick and most will do various other formats, one at home does PCMCIA, compact flash, smart card, mem stick and something else I dont recognize
Gunner
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On Tue, 11 Jul 2006 23:31:53 GMT, "Tom Gardner"

Greetings Tom, Everyone else too. I just uploaded the pics and a text file to the dropbox at www.metalworking.com . The files are below: Worm gear cutting.txt Worm gear blanks. Worm gear fixture 1 Worm gear fixture 2 Worm gear blank on fixture Worm gear setup Worm gear cutting 1 Worm gear cutting 2 Worm gear cutting 8mm Worm gear finished There is only one text file and all the others are jpg files. I included the gear cut with the 8mm x 1.25 tap so I wouldn't leave out the rest of the world. I chose the 8mm x 1.25 tap because I had a high spiral one in that size. Cheers, Eric
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Thanks for those, Eric. It's a helluva lot of fun, isn't it! Seeing the thread (rack?) form *automatically* on the blank is a real hoot. I'm interested that you didn't pre-turn the "hole", that is, the groove for the tap to run into. Any particular reason for that?
Cheers -- Jeff R.
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wrote:

Just 'cause I didn't want to. Sometimes, I've read, the gear can end up with one extra tooth if it isn't gashed first. But since I just needed a large reduction, and not a particular one, I just went for it. In all I hobbed three worm gears with the 3/8-16 tap and they all ended up with 50 teeth. ERS
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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.
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On 16 Jul 2006 01:37:52 GMT, snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:

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
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    [ ... ]

    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.
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On Tue, 11 Jul 2006 23:31:53 GMT, "Tom Gardner"

Tom- You may have missed my other post. But the pics are in the drop box. Look for files starting with "Worm" ERS
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On Tue, 11 Jul 2006 23:31:53 +0000, Tom Gardner wrote:

I just ran into this website yesterday http://www.buildyouridea.com /
Has some interesting stuff in it.
This one http://www.buildyouridea.com/hardware/fine_feed/fine_feed.html
has pics of the author making a worm gear for a HF mill/drill using something akin to this method with the mill itself.
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On Mon, 17 Jul 2006 16:05:19 -0500, Marc Britten

He even used the tap to index the part. Thanks for posting the links. ERS
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On Tue, 11 Jul 2006 16:15:43 -0700, Eric R Snow wrote:

You can use one of your ANS thread worm gears to drive the blank to cut the acme. Just match the ratio. Ain't it amazing how fast they cut?
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From what I have read about this method I think the main problem is in getting the circumference of the blank to divide correctly into the number of teeth so that once the blank goes around it will start in the same tooth spaces. It seems that the spacing is only correct at the pitch circle so the blank is a little too far around when starting. Feeding at full depth from the side of the blank is supposed to make it easier but sometimes it syncs right and sometimes it doesn't. Coarse gashing of the teeth supposedly can make it work reliably but then it isn't near as simple.
For the acme thread it might help if you can first cut a shallow V thread for the acme tap to follow.
Don Young
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Several amateur telescope makers have done the exact same process but made a special tap for it instead of using a regular tap. The process is to first make a threaded rod (large diameter with relatively fine threads) and then split the rod into two, one to be used as the tap and one as the worm. The tap piece then gets cut for the cutters on the face and is then fed into the wormwheel piece. For the older line frequency drives, the number of teeth was usually 359 theeth (an odd number that actually is pretty close to the needed rate for the differeence between the sidereal rate and the normal clock time) and when you measured everything right, you got that number of teeth on the wormwheel. Often, the wormwheel is roughed out with a hacksaw so that the number of teeth is done and the majority of the material is already removed so you don't end up with having to cut the whole tooth at one stroke. Doing a worm and wheel this way usually ends up with a fairly low tracking rate error (theroetical rate vs. what happens), usually on the 1 arcsecond or less error.
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