machining worm gear wheels

This video demonstrates how I made a set of worm gear wheels using the free hobbing method.
In the first part of the video a gear hob is made from silver steel. We set up a dividing head for helical milling to mill the threads of a triple-start worm screw.
The teeth of the actual wheels are first pre-cut with a regular involute cutter and finished with the custom made gear hob.
- intro 00:00
- taking measurements 00:58
- machining the gear hob
-- grinding a stylus (D bit/single flute) cutter 01:13
-- basic turning operations 04:40
-- drilling "eccentric center holes" 07:15
-- final turning operations 08:00
-- setup for helical milling of the threads 09:08
-- helical milling ("roughing") with end mill 10:08
-- setup for triple-start thread 11:46
-- finishing the threads with stylus (D bit/single flute) cutter 18:37
-- milling relief angles (still photographs) 22:00
-- milling cutting edges 22:57
-- finished gear hob 25:02
-- heat treated gear hob 25:20
-machining the worm gear wheel(s)
-- basic turning operations 25:25
-- milling a radius 27:28
-- pre cutting (gashing) the teeth with an involute gear cutter 29:48
-- finishing with gear hob (free hobbing method) 35:36
- finished parts 43:28
- cutouts 44:41
This is the video on the restoration of the "target lathe" • Ehrlich Lathe Restaura...
and the lathe after restoration • Old "Oskar Ehrlich" La...
The worm wheel installed: • 20220113 185001

[@halfnelson6115]

I keep waiting years to see a double throated worm/wheel on KZbin. I still haven't seen it. It's becoming a mythical part for me.

[@HaraldFinster]

That would be quite an interesting challenge for a home shop. I would probably make a "regular" pair of worm/wheel first and make a cutter from the wheel and use the wheel to cut the throated worm. Ideally both the cutter and the worm should be driven synchronously an the machine. It might be possible to "hob" the worm freely by just driving the worm? I found a video showing the process, actually kzbin.info/www/bejne/npXbnZ9_e5V3maM

[@carmelpule8493]

Congratulations for your dedication. There is a lot of hidden logic and mathematics in all this. I enjoyed seeing you caring about the details. I am a very old man and this week I kept myself busy thinking about making the worm in the shape of an " hourglass" Globoid worm to fit into the round circumference of the wheel, so that more teeth are captured at the two ends of the worm. I decided to make a wooden model, as I have not got the machines to do it, so I make a hand made wooden model. I made the " hourglass worm" wooden shape at the root and then slowly I glued bits to form the complex thread on the worm which resulted in caved thread on the end of the worm. I can never make a real one, but at my old age it is enough to appreciate all these mathematics, form and functions, in addition to the skills and workmanship of those who have the machines to make them. Congratulations once again wish I could go back to all this but I cannot now. I can only appreciate what others do. Well done, and thank you for uploading your work Here is what I did with wood, " very roughly" kzbin.info/www/bejne/hYe3gIaFgNWrbKs

[@wyliemacbean1157]

Hello, just like the comment below. It is all about the little things which really are the big things. Math, setup, test runs, assessment of small test pieces, seeing correct speeds. I love your channel and the videos are of great quality and content. Maybe at the beginning or end you could add the speeds, feeds, measurements and the math that is needed. Thank you and Cheers. Wylie

[@HaraldFinster]

Thank you very much for your kind comment. Adding info on the speeds and feeds is a good suggestion. I will keep it in mind.

[@FZ1nbiker]

A fantastic piece of engineering on some awesome machinery. Your video making is also a work of art!

[@brucewilliams6292]

Thank you for taking the time to make such an in depth video. You are truly a master.

[@jasonmoore1333]

Whew!!! I had to smoke 2 cigarettes after watching this gratuitous masterpiece of MECH PORN.... ART AT ITS FINEST.... #SATIATED SUBSCRIBER!!!

[@metusa666]

Thank you for the video it has given me new ideas how to cut a worm gear

[@dustyduds3953]

Very helpful video for my current project. I did not think I needed to gash the blank with a gear cutter (I initially used a slitting saw) but now after several failures and watching your video; I know that I must gash with a gear cutter. Thanks for posting this video.

[@HaraldFinster]

Thanks for your kind comment. You might be able to work with a slitting saw as long as you slit deep enough but not too deep. You just need initial "teeth gaps" to synchronize the hobber. Long ago I made a set of gears for a thread dial. Although I turned the blanks to the theoretically correct diameter, the number of teeth turned out to be incorrect in some cases.

[@michaelmcallister3429]

Well done sir. The filming and narration was excellent.

[@HaraldFinster]

Thank you Michael. I wasn't quite sure about the narration as some people complained about my German accent. I am glad that you enjoyed the video anyways.

[@thomassalgert9976]

Das ist noch wissen und Handwerk vereint.Super Video und sehr gut erklärt.Danke. ;-)

[@IFA_P3]

Ganz großes Kino! 👍 Fertigung und Dokumentation gefallen mir sehr!

[@alirezaalemrajabi3328]

Such a great Video! Thanks a lot, it taught me many things and removed my ambiguity. Keep doing well, dear Harold.

[@michaelnordin3006]

I have to say, watching you spend all this time making a perfect gear then only to run a mill through it, not once but like 5 times was tough to watch. Lol

[@HaraldFinster]

:-)

[@Thermo88]

Thanks alot really appreciate your in depth video ❤

[@davidiansykes]

that is a nice piece of work and thanks for showing us how

[@noneofabove5586]

Excellent job

[@rodneykiemele4721]

That was a fantastic video, very impressive, very informative. Thank You very much. I’m subscribed.

[@HaraldFinster]

Thank you very much for your kind comment and your subscription. I am glad you enjoyed the video!

[@oldfarthacks]

Thanks for the video. Quite the project. I'm sure that you learned a few things along the way and that is the real reward, the knowledge. By the way, the parts are pretty.

[@vat_1989]

Beautiful video, thanks a million for this

[@Freetheworldnow]

Amazing project!! Great skills! Beauty full equipment and tooling! Well done! Excellent vidéographie! Thanks for sharing!!! GOD Bless.

[@HaraldFinster]

Thank you very much for your kind comment, Pierre. "Great skills!", well, to be honest, not everything went as planned and I had to try out different approaches. I didn't show the entire adventure with all deviations in the video in order to keep the length acceptable.

[@oldfarthacks]

@@HaraldFinster Very understandable. But the nice thing is that you without a doubt learned some new things along the way and that is the real reward.

[@jimsvideos7201]

Very well done indeed.

[@mftmachining]

Excellente Arbeit, Hut ab.👍

[@glennmorrissey5309]

Great tutorial, thank you very much!

[@markramsell454]

Good job and all in one vid!

[@nhcreator6563]

Nice work your a smart guy

[@alansmith5690]

First class work.

[@TheSuntravel]

Klasse Video und sehr lehrreich

[@Mauri59g]

Ottima lavorazione professionale👍👍

[@DK-vx1zc]

EXCELLENT!. Thanks for sharing.. subscribing

[@jocker621021]

simple but great 🎉

[@HaraldFinster]

Thanks, Rony!

[@jeremycable51]

I dont have a dividing head yet this had to build a direct indexer using at first the original gear that was partially stripped then a plastic gear I cut and ran in the machine that was just a little oversized that gave me a excellent profile and size to copy then made it in aluminum it’s been working great

[@HaraldFinster]

Good idea. When I made my first gear on the lathe, I just printed the required "index holes" on a piece of paper and glued it onto the drive pulley. So I could use the chuck of the lathe as a simple "dividing head".

[@scambroselauntrellus3681]

Impressive.

[@ikhffolo63]

عمل اكثر من رائع.

[@soryegetun529]

thanks for the video it really helped a lot. I have a presentation homework about manufacturing of a worm gear in my mechanical engineering course :)

[@HaraldFinster]

Hi, that's great. I am glad that my video was helpful!

[@peterfitzpatrick7032]

12:05 Instead of using the hex collet block for indexing, would it not have been more accurate to offset the mill table by 1x p ... ?? 🤔 Very enjoyable video ! 👏 😎👍☘🍺

[@HaraldFinster]

Peter, yes, excellent suggestion. That would be the same principle as used for cutting multi start threads on a lathe. (Well, at least one of multiple solution.) I did not think of this for several reasons: (1) originally I intended to use the dividing head to set the 120° degree offsets between the individual threads. This turned out impractical due to the (in the world of spiral milling) relatively "flat" pitch. This required driving the shaft of the dividing head directly instead of the usual "deviation" via the dividing-plate and the worm gear. By the way: Walter even offers a dividing plate sitting on the spindle for this purpose, but I don't own this special attachment. (Rule no 1: you can't have enough tools ;-) ) (2) I had to cut eccentric curves for the reliefs of the cutter ( 22:03). This required a setup with the collet block anyways. In retrospect I think that a simple straight relief would have done. (3) I also planned to spiral mill the V-grooves of the treads for relief. This did not work for geometric reasons (I did not think of beforehand.) Thank you very much for your thoughtful comment. Highly appreciated!

[@peterfitzpatrick7032]

@@HaraldFinster thanks for the detailed reply Harald ... for me, THIS is what the internet & YT in particular was made for... entertainment AND education ... all in one... 🤗 Also, as a hobby woodworker , the motto "you can never have enough tools" (or clamps😂) is so true... 🙄 Its amazing what you can do if you are creative and think "outside the box" I remember many years ago making these racks and pinions for sliding metal doors on waste skips (dumpsters) ... they didn't need to be super accurate and I , a 20 somethin kid starting out on my self-taught engineering carreer (65y.o. now) thought they'd be a piece of cake to do on my Elliot shaper !! ... ahh to be soo naive .. 😂 Suffice to say , I got them done but man oh man 😤 !! Cutting each individual tooth gap in those 1 metre long x 1"sq. BMS racks was a ball-breaker... and then of course they bent like prezels , my first real lesson in releasing internal stress ... 🤓 I made up a makeshift dividing head using a division gear at the far end for the pinion-planing job... they actually turned out okay and my customer was delighted... The things we do when we don't know we "can't do that" ... 😬 😎👍☘️🍺

[@HaraldFinster]

@@peterfitzpatrick7032 Can't agree more. Thanks for sharing your experience. With regards to stress relief: this is true even for "stable" stuff like steel. Recently I made a gib from "stress relieved" cast iron. I had to mill it down from about 12 mm to 8 mm. It bent like a Banana. Fortunately I anticipated this and left enough material to mill it straight again. About "naive": again, can't agree more, and I think that this video is a good example: I agreed to making this worm gear for a friend. My first naive plan: turning the hob on a lathe was just impossible due to the (in the screwcutting world) steep thread pitch. So, the rat-tail began. 🙂 But I enjoyed it very much and it gave me the opportunity to film many different techniques. I would love to see your work on video, by the way!

[@peterfitzpatrick7032]

@@HaraldFinster Not a vid maker, I haven't the personality for it... I'm retired from machining at this stage, (I just dabble at it now, when my farmer neighbours break their agri-equipment, removing a sheared off bolt in an expensive silage baler part earns me a God-like status amongst them 😂) My father was a cabinetmaker & none of his 9 children followed him into the trade... so my forays into woodworking have been a sort of homage to him.. not that I could hold a candle to his skillset... 😕 😎👍☘🍺

[@mrcpu9999]

I enjoyed this... Keep making more. sub'd.

[@jeremycable51]

Where the hell was this video at when I needed it four weeks ago lol

[@HaraldFinster]

My apologies, that it took me so long 🙂

[@deconteesawyer5758]

@@HaraldFinster Two peoples devided by a common language. "treading " "silver steel" Those two got a bit wet crossing the pond.

[@craigtate5930]

Really nice work here...I have been working on a worm gear/wheel lately as well from scratch ...basically flying by the seat of my pants you might say

[@carlostapa9084]

Magnificent !!

[@HaraldFinster]

Thank you very much. I am glad you enjoyed the video.

[@taranson3057]

How long did it take you to make the hobb? It looks like it could not have been easy and my guess is that it took a full day. Great job! Enjoyed the video and the presentation.

[@HaraldFinster]

Thanks a lot for your interest and your kind comment! Making the hob took a long time, indeed. I estimate that the spiral milling took 10-15 hours.

[@eXactModellbau]

Schönes Video! Gruß Larry

[@HaraldFinster]

Danke - auch für den Hinweis bezüglich "stylus" vs. "D bit" "single flute" cutter

[@robertoelvir155]

Buenas tardes colega, excelente idea. Una consulta: se gira la mesa de la fresadora y a cuántos grados o no se gira?

[@HaraldFinster]

Hi, the table of the milling machine is fixed. It does not turn. During the gashing process (the pre cut of the teeth with the involute cutter), the work was tilted in order to get the correct angle of the teeth. Hope this answers your question.

[@VammasKersantti]

I liked a lot

[@HaraldFinster]

Thank you for your kind comment. I am glad that you enjoyed the video.

[@timogross8191]

Was the hob diameter identical to the worm diameter? I would have thought the hob needs to be larger than the worm (addendum of hob similar to dedentum of wormwheel). Outside diameter of the worm should not touch the inner flat of the worm wheel?

[@HaraldFinster]

What an excellent thought! You are certainly right. Honestly: I did not think about this and made the diameter of the hob identical to the worm. It works anyways, but I wouldn't consider power feeding the lathe slides a "high end" application.

[@terrorbobby1989]

Hey Harald. Super Video. Wie lange hast du denn daran gearbeitet?

[@HaraldFinster]

Hi, danke 🙂 Mitte September habe ich begonnen und war Mitte Dezember fertig. Gearbeitet habe ich hauptsächlich an den Wochenenden. Neben den im Video gezeigten Arbeiten waren allerdings auch noch einige "Nebenarbeiten" erforderlich. Beispielsweise musste ich die Werkzeugschleifmaschine zunächst betriebsfähig herrichten - u.A. waren die Lager hinüber, und ich musste eine Anpassung für die Diamant-Topfscheibe herstellen. Ausserdem konnte ich den Spanndorn für den Direkt-Antrieb des Teilkopfes nicht finden und habe deshalb einen eigenen Dorn gefertigt. (Natürlich ist das Ding zwei Wochen nach Fertigstellung des Projekts wieder aufgetaucht - übrigens in Anwesenheit von Marco, für dessen Drehbank ich die Zahnräder gefertigt habe 🙂 )

[@Build_the_Future]

What temperature did you harden the hob at and for how long? What kind of steel work best for that?

[@HaraldFinster]

Hi Eric. I used "silver steel" (1.2210 / 115CrV3 / BS-1407 ) which is designed as a tool steel. I attempted to use Borax (the same as commonly used as a flux) to prevent scale formation. This did not work too well though. The work was heated up to cherry red. i.e. approximately 850°C which is slightly above the recommended temperature 810-840 °C for oil quenching / 780-820 °C for water quenching. I quenched it in water. Admittedly, this was a mistake, as the sudden temperature drop caused a crack. The work was annealed to approximately 200°C - 250°C. Fortunately the crack did not progress any further and I was able to finish the job. Edit: sorry, I did not answer your question about the duration of the heat treatment: I just used two propane torches and heated the work up to cherry red. Then the part was quenched immediately. Hope this answers your questions.

[@therestorationshop]

Great video! Why was turning on the lathe impractical? I'm not 100% sure at the moment but I think my only option will be on the lathe.

[@HaraldFinster]

The required thread pitch of approx. 18 mm was pretty "steep". Although I could find a suitable set of change gears for this, it turned out that a lot of force was required to move the leadscrew and the carriage. My lathe has a lead screw with 4 TPI, i.e. a pitch of approximately 6.2 mm. The 18 mm pitch of the worm would have required a 1:3 speed up between the spindle and the lead screw. With the gear train engaged I could hardly turn the chuck manually because of the required forces. So, in short, you will be perfectly fine with a lathe as long as the required pitch is not to steep.

[@therestorationshop]

@@HaraldFinster Thank you for the great explanation. Hopefully my 100+ year old Hendey lathe will be able to manage.

[@HaraldFinster]

@@therestorationshop I wish you good luck and would be interested to see the process. Your channel looks interesting - subscribed!

[@dizzolve]

5:15 hey what are those centers shaped like that for? I got some in a purchase but don't have a center that fits the bit cut

[@HaraldFinster]

Those are R-type center drills. They are especially useful if you turn between centers with a tailstock offset. A "regular" (A type) center drill forms a cone which has conical contact surface to the center as long as everything is in perfect alignment. If the tailstock is out of alignment (e.g. if you turn a cone) the cone of the center and the conical drill hole do not match. This might even damage the work or the center. With the R type you get an approximately ring-shaped contact between the center and the work. This gives more freedom and the center and the work don't jam. There wasn't any reason to use an R-type drill in my particular application. I just have plenty of them at hand as I got them cheap. (They are left handed by the way.)

[@billshiff2060]

I would have thought that the machine you have could have directly cut the teeth with the hob without resorting to the free hob method. Does your machine not synchronize the indexer with the spindle rotation?

[@HaraldFinster]

no, unfortunately it doesn't. The Thiel has separate motors for the spindle and the feed mechanism. This is nice as you can control the motor speeds independently via VFD but the drawback is that they are not in sync.

[@johndonlan5956]

I wonder if the same thing could be accomplished with a simple form-cut fly cutter?

[@HaraldFinster]

Good thought, John. Using a form-cut fly cutter with an involute would work for a very thin worm gear wheel. However the spacing between the teeth has to increase with the distance from the center plane o the wheel, i.e. towards the edges. If you watch the part where I gash (pre cut) with the involute cutter (32:20) , you will notice that the heads of the teeth are almost parallel. After the hobbing operation the heads are wider in the middle and more pointy towards the edges of the wheel. (44:00) Hope my humble English is understandable.

[@stephane-710]

Danke für das Video. Super ! Fertigen Sie auch Teile nach Anfrage ? Danke im voraus.

[@HaraldFinster]

Danke für den netten Kommentar und die Anfrage: ich mache das nur als Hobby in meiner Freizeit.

[@alleznape]

Why did you not just cut an ACME thread on the lathe for the hob? I don't have your equipment (or knowledge) and was planning to make my hob on the lathe while cutting my relief angles on the mill. Will I have a problem?

[@HaraldFinster]

Cutting an ACME tread was my initial plan. However the pitch of the three start tread is about 18 mm (approx 0.7"). Although I was able to find a suitable combination of change gears for this pitch (1:10), it turned out that a lot of force was required to move the carriage with the required gear ratio. Thus I decided to make use of the spiral milling capabilities of my dividing head. So, as long as your lathe is able to cut the required thread pitch you will be fine and I recommend using this technique as it is much easier, way faster and does not require any special tooling (apart from an ACME tread cutter which is easy to grind).

[@alleznape]

@@HaraldFinster Thank you!

[@ABKGRG]

Habe Dir mal ein Abo dagelassen. Sehr interessantes und lehrreiches Video!

[@HaraldFinster]

Dankeschön! Ich hab mich bei Dir auch mal "eingeschrieben", auch wenn ich nicht so der "Autoschrauber" bin. Das Video von der Säge war aber wirklich gut!

[@ABKGRG]

@@HaraldFinster Danke für die Blumen! Bei mir bedingte die Autoschrauberei, dass ich mich mal im Maschinenbau fortbilde. Mal sehen, die Fräse kommt bestimmt noch 👍

[@HaraldFinster]

@@ABKGRG Ein Leben ohne Fräsmaschine ist möglich aber sinnlos 🙂

[@ABKGRG]

@@HaraldFinster Völlig richtig, für mich war die Weiler LZ280 aber erstmal Neuland 😁 Aber wie es immer so ist, hat man erstmal das eine, braucht man das andere 👍

[@billshiff2060]

25:17 I don't understand how that line shows the relief? The relief of the cutter or the hob? It's too bad you don't have footage of the eccentric cutting of the hob relief cutting, the most critical part of a hob.

[@HaraldFinster]

Thanks for your very thoughtful comments, Bill! "how that line shows the relief?" I am referring to the relief of the cutter - not the hob. In the image the red line indicates the theoretical perimeter of the cutter's cone if it would be symmetrical with no relief. You can see a small gap between this line and the edge (which is not the cutting edge). "footage of the eccentric cutting" Yes, I agree that it is a shame that I lost this footage. Just to clarify: the relief angles of my hob are exclusively at the outer perimeter. Actually I planned to mill relief angles into the "grooves" of the hob too, but my intended method failed due to fallacy of thinking. I intended to spiral-mill the "grooves" with the single-flute cutter with the eccentric setup. This did not work. (Too complicated to explain why.)

[@Andrew_Fernie]

I can only imagine how many hours were spent on this.

[@HaraldFinster]

The entire process took about three months.That sounds like a lot of time, however I had just a few hours during the weekends. And, honestly, not everything went as straight forward as shown in the video. Many small "side projects" were required. As an example I couldn't find the mandrel which allows driving the spindle of the dividing head directly. So I had to make my own. Needless to say that the original one reappeared when the project was finished. And, of course, capturing the work on video slowed everything down even more. But it was a fun project and certainly the most challenging I have ever done.

[@trailb4u]

Was it not nessesary to put cutting relief on your hob?

[@HaraldFinster]

Yes and no. There is a relief at the circumference of the hob. I attempted (and probably failed) to explain this at kzbin.info/www/bejne/mZabXop8rMZ8bZI . I intended to add relief to the sides (slopes of the "valleys" between the teeth) of the hob. I planned to set up the hob eccentrically - just like the setup used for the relief milling of the circumference - and spiral-mill them. This did not work for reasons too complicated to explain here. (Basically the eccentric setup creates a variable radius which would require a variable feed in x.) Fortunately the hob worked really well and left a beautiful finish. Thank you very much for your thoughtful comment.

[@ruicarlospratesdecarvalho5436]

Bom dia , amigão vc poderia me ensinar fazer as ferramentas para fazer rosca sem fim , ou mandar um vídeo traduzindo em português obrigado fica com Deus

[@HaraldFinster]

Unfortunately I can't help with that. I think that you need specialized machinery to make endless threads.

[@ruicarlospratesdecarvalho5436]

Oi, amigão que vc poder ajudar eu agradeço o meu sonho é ser um fresador de engrenagens ,

[@ruicarlospratesdecarvalho5436]

Meu ZAP 17 996 24 90 73

[@peterhornung3184]

Schade, daß das Video nicht auf Deutsch ist.

[@HaraldFinster]

Es gibt auf Wunsch deutsche Untertitel.

[@jamesballock1768]

Could have done it with the right size tap a lot faster.

[@HaraldFinster]

Yes, for sure! If I would have had the right size tap. Unfortunately a triple start tap with the required pitch wasn't available.

[@YoutubeSupportServices]

Not important!... Just a curiosity-thing. Asking for a "close-acquaintance" that won't stop irritating me! AND I'm ONLY asking because "it" won't stop complaining about constantly being "ignored", "blown-off" , and selfishly "used" for personal enrichment... AND when it does get any attention "it's" just being "picked-on" and/or "unwillingly-fingered":.. I tell ya, If it wasn't for personally needing oxygen and a rain-deterrent, I'd get rid of this "Nosy" burden!.. But I digress... So, question is: ... @5:16 the sound obviously indicates a diameter/speed adjustment... Did you retrofit the heart of a $50,000+ CNC machine into your lathe or was there a hand/finger involved in the audibly-noticeable RPM increase that coincides with the diameter-increase... or OR was this just meant to purposely entrap people with OCD that would notice this, and also realize the adjustment was in the wrong direction?(I.E. Should have slowed down.) or, OR, OR has my senses out-paced my ability to adapt again!...damit... it's probably that again...Sorry!

[@HaraldFinster]

Well spotted. Yes, I retrofitted the heart of a $50,000+ CNC into my 1950ies lathe :-) More precisely, the lathe still runs with the original 2 KW 3-phase motor, but I use a VFD to convert single phase to 3-phase AC as I don't have 3 phases in my basement.

[@YoutubeSupportServices]

@@HaraldFinster Just wish I could convert my lathe from a "coat/tool/hose/extension-cord-holding spectator to a running machine. a 20hp 3-phase isn't something easily powered from a 240v split-phase.... Oh how "wisdom" eludes us prior to it's untimely arrival AFTER BUYING A 3-PHASE GISHOLT #4 AT A REALLY REALLY GOOD "IF YOU CAN MOVE IT"-PRICE.

[@user-yl5ih3mx6z]

Лучше бы по немецки шпрехал. Непривычно слушать англискую речь с немецким акцентом.