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  1. #41
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    SeaMoss? I got about 2 sentences into your post before the light bulb got really bright- too familiar to be anyone else! All in all- SM is correct- its not that big a deal to tangentially hob the worm wheels with a single tooth fly cutter in a hobbing machine with a tangential head. Smallest one I've ever done was a 1 module 24 tooth in bronze for a customer who had specified a part from Japan that turned out to have a 26 week lead time. As far as the worms, I would have them ground on a CNC thread grinder from the solid. Its not that expensive if you make 6 of each or so. Finding literature on the tangential hobbing process is not too available but G&E made specialized worm hobbers that used this method- the model designation was TWG as I recall.

    As far as you 6 DP hob not being correct, worm cutting usually requires axial pitch hobs- not normal pitch, and that's where you are mistake.

    Worm hobs are a special case, where the hob will only cut one specific worm configuration for a given size worm diameter and pitch.
    Last edited by Dan from Oakland; 03-18-2017 at 09:11 PM.

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    First off, it occurs to me that you think I am advocating grinding the Worm Wheel. I am not. I was specifically referring to the Worms he was desiring to make.

    Quote Originally Posted by SeaMoss View Post
    He isn't having a problem making a new worm. He is having a problem making the wormgear.
    Then maybe you should re-read the very fist post in the thread where the OP states fairly clearly -

    Quote Originally Posted by Hobby Shop View Post
    I'm missing all the worms & worm gears for my K&T 2CHL.
    As for small diameter single thread grinding, you have been away or off your meds for too long, as there are a number of machines capable. It's a moot point, because I was not advising making a Worm Wheel that way, despite your flawed assumptions. You might take a minute and actually read what was written, without an agenda. If you do, it will be very quickly and clearly apparent where you went awry.

    As for the rest of your drivel, as humorous as it is to some of us reading it I honestly have neither the time nor inclination to play into your mastabatory self aggrandizment. It's not clear if you're old and cranky, lost and angry, off your meds, or simply a douche. But I won't have to read it any further having put you on the ignore list. Wonderful widget that is.

    Have a great weekend, despite yourself.

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    Quote Originally Posted by Zahnrad Kopf View Post
    First off, it occurs to me that you think I am advocating grinding the Worm Wheel. I am not. I was specifically referring to the Worms he was desiring to make.
    Not exactly. In fact, not even remotely but ...

    Then maybe you should re-read the very fist post in the thread where the OP states fairly clearly -

    I'm missing all the worms & worm gears for my K&T 2CHL.
    Nah. I think I should jump ahead to post #25 where

    Quote Originally Posted by Hobby Shop
    I can cut the 8TPI worm easy enough on the lathe.
    Viola, cello and double bass, worm is now out of the problem area. This was before you entered the discussion. And in fact, he is correct, even if his engine lathe doesn't have the required feeds, any cnc lathe can do the job. Or it could be thread milled, or it could be thread ground, or it could be put in a 4th axis on a cnc mill and a shaped end mill in the collet and you could create it that way. In fact, I think there was a machine that worked something like that. Making worms is not generally a problem.

    All those methods create slightly different geometry on the worm, btw, but in this case that's of no matter. If you want to go crazy, read Buckingham on the subject.

    Anyway, then Hobby Shop went on to make some rather bad assumptions

    Is it ok to gash the 96T worm wheel with a 25P #2 14.5pa cutter. Then, finish hob with a 3/4"-8 acme tap or should a 25p hob only be used?
    I really don't understand how he planned to do that And why, if you have a hob, would you be considering gashing the part to begin with ? Mr Hobby Shop, no offense, but you could use the advice of a guy who has run some hobbing machines. As Dan mentioned, a wormgear is a special case where the hob has to match the worm. You can't just feed through it along the axis of the bore like with a spur or helical. A few moments looking at the parts will show you why.

    There are really two practical methods to make small quantities of wormgears. Have an infeed hob built or have someone single-tooth it tangentially. If there is a market, the infeed method is way faster and any hobber can cut the parts for you and you could come back later and make more, pretty cheaply. If it's a one-off and you will only ever make the one, price and delivery would be lower and faster going single-tooth.

    If it's just as a project then all the other elderly labor-intensive methods would apply, but you won't get as good a roll as you do with the proper methods. Just remember that the space in your wormgear needs to match the cutter, and a lot of your ideas about hobs and cutters will explain themselves away.

    Quote Originally Posted by bigmouth
    As for small diameter single thread grinding, you have been away or off your meds for too long, as there are a number of machines capable.
    I'm not quite sure what you mean by "small diameter single thread grinding" but if you mean threaded-wheel generated grinding, a la reishauer, go ahead and name one machine. There aren't any. There is no use for them. The very concept is silly.

    It's a moot point, because I was not advising making a Worm Wheel that way, despite your flawed assumptions. You might take a minute and actually read what was written, without an agenda. If you do, it will be very quickly and clearly apparent where you went awry.
    Yes ?

    Quote Originally Posted by bigmouth
    Typically, the OEM will have tooling made to their specs and desires, kept on hand, and sharpened as needed. This should be Hobbed, or Thread Milled, but Grinding is perfectly acceptable, albeit a bit overkill for your desires. Mostly due to the economics of it.

    Your best bet if you insist on doing it yourself is to do it the way they most likely did in a pinch. On a Horizontal Mill, using a universal dividing head and gears to drive it.
    I liked this part, too ...

    Quote Originally Posted by pompous bigmouth
    Not even the same ball park. Not even the same kind of ball park. "D" Class Hobs are lowest of the low, barely qualifying to be "not scrap" and used solely for preparation of subsequent operations.
    What a crock.

    As for the rest of your drivel, as humorous as it is to some of us reading it I honestly have neither the time nor inclination to play into your mastabatory self aggrandizment. It's not clear if you're old and cranky, lost and angry, off your meds, or simply a douche. But I won't have to read it any further having put you on the ignore list. Wonderful widget that is.

    Have a great weekend, despite yourself.
    Surprising how people will go on for paragraph after paragraph explaining how they are not going to respond to you



    Quote Originally Posted by Dan from Oakland
    SeaMoss? I got about 2 sentences into your post before the light bulb got really bright-
    Ja, me here .... need some Makinos so came here to put up a wanted ad, got sidetracked by the gear talk. And the *&^%*^ who was supposed to come pick up the floor in our old office (typical China story) was four hours late !! so ended up passing time ... . Seemed to be a cnc kinda place so that old American Tool term popped into my head

    its not that big a deal to tangentially hob the worm wheels with a single tooth fly cutter in a hobbing machine with a tangential head. Smallest one I've ever done was a 1 module 24 tooth in bronze for a customer who had specified a part from Japan that turned out to have a 26 week lead time.
    Except for having a hob built, do you know of another way ? Would you want to figure out the geometry to contour it in a fourth-axis ? Eeek. And the dividing head method, probaly good for kids in metal shop to learn how but in real life, not so practical ...

    Remember those 12T 63* helix angle instruments of torture ? In a Barber-Colman 3 with no diff ? For $3.50 each ?

    If I am ever that stupid again, please shoot me.

    As far as the worms, I would have them ground on a CNC thread grinder from the solid. Its not that expensive if you make 6 of each or so.
    Do you use Grind'em down in Redwood City ? I bet Julius is up in that Big Machine Shop in the Sky ...

    Finding literature on the tangential hobbing process is not too available but G&E made specialized worm hobbers that used this method - the model designation was TWG as I recall.
    mc------- ! I gotta coupla gleeeeesoons for ya !

    Attachment 194011

    Give ya a good price

    Just to prove the sickness hasn't abated, saw a 24" version of this out in the jungle. Wasn't too bad, I bet we could get it cheap and fix it up, whatta ya say ?

    Should Hobby Shop use this one ?

    Attachment 194012

    Now, as far as grinding a wormgear, hmm. IF you could get a small enough wheel on this (one of those internal belt-driven thingies like the Detroit form grinders used to use ?) and IF the dresser could reach it, these things are awesome (my hip new vocabulary word for today !) The wheel will swivel to any angle, you can grind the teeth and then rotate and dress the wheel to grind shoulders or bearing surfaces in the same operation, I guess you could grind both internal and external, shoulders bearing seats and faces all in one chucking. Only one anda half mil or so

    Attachment 194013

    Sorry to get sidetracked (well, maybe not that sorry ) ... it's just that I've had too much of the pompous ignoramus blabla recently. I'd be willing to bet my Cleveland cut more gears in an hour than Mr Zahnrad has cut in his life. What a crock of poo ... bla bla bla, I'm so super, bla bla bla, this is so special, bla bla bla, you little peons bla bla bla ... And then a bunch of misinformation. Puke :p Had enough of that for one life ....

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    Anyway, then Hobby Shop went on to make some rather bad assumptions

    Is it ok to gash the 96T worm wheel with a 25P #2 14.5pa cutter. Then, finish hob with a 3/4"-8 acme tap or should a 25p hob only be used?


    I really don't understand how he planned to do that
    And why, if you have a hob, would you be considering gashing the part to begin with ? Mr Hobby Shop, no offense, but you could use the advice of a guy who has run some hobbing machines. As Dan mentioned, a wormgear is a special case where the hob has to match the worm. You can't just feed through it along the axis of the bore like with a spur or helical. A few moments looking at the parts will show you why.

    SeaMoss,
    You bet I screwed up when in said that. I've learned a whole lot the hard way since then. I'm a die maker and gears aren't my thing but I'm taking a shot at this. With the help I've been getting here and the books I've been reading, I'm on the right track now.

    I'll be making these gears with the equipment I have. It's going to be some work and maybe I'm fooling myself but I "think" I'll be able to make some quaility gears.

    I have a model 18H G&E gear hobber. The "H" stands for helical gear cutting. In the manual they talk about making worms and wheels but they don't go into any detail on how it's done.
    Even though the thread got side tracked, I really appreciate everyone's input. Unless someone suggests a different material, I'm using 4140 fatigue proof for the worms.
    I'd be in business if I could figure out to form relieve a hob.
    Andy

    Attached Thumbnails Attached Thumbnails img_4890.jpg   img_4893.jpg   img_4894.jpg  

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  6. #45
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    Quote Originally Posted by Hobby Shop View Post
    You bet I screwed up when in said that.
    Eh, we all gotta start somewhere

    I'll be making these gears with the equipment I have. It's going to be some work and maybe I'm fooling myself but I "think" I'll be able to make some quaility gears.
    More info ! Why didn't you say you had a G&E ! We (I use the term loosely) own that "brand". It's only a brand now because we haven't built one in a few years ... and the new guy, Send me an addy by pm, I can scan you some fun stuff.

    I have a model 18H G&E gear hobber. The "H" stands for helical gear cutting.
    Hmm. Not sure about that. They are all at least an H but maybe you are right, the HS is the one that only does spur. By the way, DfO owns one of those from 1913. Sometimes I think he's cracked but he thinks making parts for a 1913 auto on a 1913 machine is fun. Maybe it is but I prefer a newer hobber

    You should probably listen to him, he's the only one I've seen here who has a clue.

    In the manual they talk about making worms and wheels but they don't go into any detail on how it's done.
    Usually infeed. I don't remember any of the normal G&E's with tangential, except for the twg.

    Unless someone suggests a different material, I'm using 4140 fatigue proof for the worms.
    Sounds okay. If you want to really kill it, you can have them nitrided after. I have a vague memory that 4130 nitrides better.

    I'd be in business if I could figure out to form relieve a hob.
    Kids these days ! Buy a form-relieving lathe, of course !

    Okay, more seriously, if you know what you need, look through Ash Gear's list of used/surplus hobs. Sometimes you can find something either the same or very very close to what you need in there. Wear your kevlar underwear when you order.

    If you end up making your own infeed hob, something like 8620 will work. Or you could use a through-hardening steel but I'd be concerned about ductility in that small a cutter. Hobs go bang bang bang. For ease in relieving it by hand, gash the teeth thinner than you would for a regular hob - I mean, not thinner teeth but bigger gashes so the teeth don't go as far back. And you can get away with straight gashes, don't need that helical shit for a one-off. You might get away with about 3/16" of depth ? or 1/4", anyhow. I wouldn't go less than that, bronze is stronger than you think and likes to grab, thinner teeth might break off. Then you can relieve the thing by hand. It won't be a Class A hob but it can work pretty good.

    For relieving, here's a trick that works decent - take a long quarter-inch allen bolt and cut off the head. Stick it in a dumore with the threads on the outside end. Nuts and washers, use small thin cutoff wheels, the non-reinforced kind. 2" dia or so. This is great for chamfering teeth (Redin does something similar) or you can use the flat part for things like you are doing. Blue it, make sure to leave the bluing on the face, grind up to the edge, all the usual stuff.

    For books, don't use Machinery's Handbook. Sorry, ugh. The Colvin & Stanley is good for basic diagrams of gear dimensions and terms, there are two or three main gear books - Darle Dudley edited Gear Handbook which is huge and has chapters on every kind of gear you can imagine, plus it's interesting. And another Dudley book, Modern Gear Design (I think ? bad brain) is a little more current, info on various machines and processes. Some others out there but if you have the slightest interest in gears, those two are worth the money.

    Not cheap tho now, I bet. Do they still have used book stores ? I got lots of good stuff there. People weren't interested in musty old dirty-hands stuff. Last time I was in the area my favorite ones were all cool hipster coffee shops. Man, that coffee is so good, awesome, d00d ! Gag me with a spooon.

    Disclaimer : I've been away from the US a long time. Things seem to have changed. But when I was a Young Idiot (tm), gear guys were a little different. They didn't mind spending time educating people who were really interested. So if you have any gear shops nearby, try asking them how to do this, how to do that. And like I said, if Dan here has time he's done all this. Someone who has actually done it is preferable

    If you give up on making your own hob, I can probably get you one made here for 1/4 the price of Ash. It'll be Chinese but they are accurate. They just don't hold up. But you are only making a few parts so who cares ?

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    I finally have some free time so I started making some chips. I need one last piece of info for the wheels but I can't find it anywhere. It's called the "arch gear angle" in this picture. The wheel throat radius is damn near the same width as the wheel. Some forum memebers measured the OD of their wheels. The OD's vary significantly between the same gear sets for the same model LL. I'm thinking it's not an important dimension but I thought I'd ask anyway. I'll order the Dudley book today.
    Andy
    Attached Thumbnails Attached Thumbnails img_5960.jpg  

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    That angle is for 99% of worm wheels, totally insignificant. Make your OD dimension and throw a 45 degree chamfer on both sides and you're good to go. I would not make the chamfer so wide as to make the transition from the throat radius to the OD a sharp corner as shown.

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    Quote Originally Posted by Dan from Oakland View Post
    That angle is for 99% of worm wheels, totally insignificant. Make your OD dimension and throw a 45 degree chamfer on both sides and you're good to go. I would not make the chamfer so wide as to make the transition from the throat radius to the OD a sharp corner as shown.
    Thanks Dan, Will do. I have enough to keep me busy for a while.

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    I can't find anything on VM for ATW Pacemaker formulas regarding change gears. One of the worm gears is 2-1/8 TPI. or .4705 lead.

    I have a 60T, 96T & 60T on the back of the lathe. I believe the 96T is just an idler so changing it won't do any good.

    If I take 60 X 2.125=127.5
    127.5/1.5TPI = 85
    Is it as simple as replacing the 60T for an 85T and use the 1.5TPI to cut the 2.125TPI?

    This is not my picture but it's just like it.
    Thanks,
    Andy
    Attached Thumbnails Attached Thumbnails img_5999.jpg  

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    If 1 to 1 (60 and 60) cuts 1.5 TPI, then 85 and 60 will cut 2.125 TPI because 60 divided by 85 is .705882:1

    .705882 divided into 1.5 = 2.125

    In "lead speak" 1.5 TPI is .666666 and if you multiply .6666666 X .705882 you get .470 and change

    60 stud, 85 on input to QC, idler to suit if 96 too big

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    Quote Originally Posted by johnoder View Post
    If 1 to 1 (60 and 60) cuts 1.5 TPI, then 85 and 60 will cut 2.125 TPI because 60 divided by 85 is .705882:1

    .705882 divided into 1.5 = 2.125

    In "lead speak" 1.5 TPI is .666666 and if you multiply .6666666 X .705882 you get .470 and change

    60 stud, 85 on input to QC, idler to suit if 96 too big
    Thanks John.
    The 1:24 & 1:96 are pretty straight forward so I'll start with those 2 first. The 1:3 is a whole different animal. We'll figure that one out at a later day.

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    It’s been a while but I’m finally making chips. I needed a 1:96 worm for the 3CH LL.

    1st attempt) I made the mistake of thinking because this worm is 6TPI, it was an Acme thread. I thread milled 6TPI Acme in some CRS and it was a bust.

    2nd attempt) A much closer look to the small/finer details. I used 6TPI and the worm/wheel formula for DP. The tool tip, addendum, dedendum. OD, Pd, and whole depth was a perfect match to the OEM worm I had on loan. I ground the tool bit on the surface grinder and brought the tool to the OEM worm center line and it was spot on.

    The worm is O1 and turned on the P&W Model C (The best $600 I ever spent on a machine.)
    When it’s installed in the LL, it has the exact same backlash as the OEM worm. With 2 different wheels installed.

    When I tackle the worms and wheels for the 2CHL, I’m going to thread mill the worms and hob the wheels.

    Thanks again to the guys on PM for posting and giving advice and big thanks to rseddeg for making all the spread sheets.

    Andy

    The new worm is on the right in the pictures.
    Attached Thumbnails Attached Thumbnails e4196091-fd1f-494d-ad35-b79fe5177f7f.jpg   4738718e-e3ca-4c4b-8332-3c4b7dc6e582.jpg   e87ab983-6091-4b5a-9b29-17376d1a4cc3.jpg  

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    Here are the dimensions of the 3CH-2K 1:96 worm and wheel. My center distance might be a off a few thousands because the bushings in my LL are worn out. These worm numbers are spot on with the measured OEM. The wheel OD dimension is off .007” from a measured OEM wheel.

    The worm has a 2.313” bore x 2.500” long with a 1/4” keyway. The threads are undercut 5/8” off the ends.

    Center Distance 3.619”
    6TPI OR 18.850DP
    Worm Lead .167
    Worm Addendum .053”
    Pitch Dia. of Worm 2.145”
    Pitch Dia. of Wheel 5.093”
    Worm OD. 2.251”
    Whole depth of Worm .114”
    Worm Tool tip .052”
    Worm Helix Angle 88.583
    Gashing angle of wheel 1.417

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    I’m looking at the 2HL 1:96 picture Ramsay1 posted a while back. On the Worm, it looks like the under cut starts about an 1/8” - 3/16” or so from each end and 7 full threads are showing. I’m thinking the under cut is about .090” or so deep because the full depth is .086”.

    If the ends of the Worm are the same as the OD (without undercut or threaded to the ends), how does the Worm slide on to marry with the wheel? Example: when I install the Worm/wheel in my 3CH low lead, I put the wheel on first and just push the Worm in and it’s ready to go.

    I’ll try posting a picture later of what I have so far. Manage attachments isn’t working right now.

    Andy


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