Hobbing a Helical Gear (Differential Method)

Рет қаралды 23,437

Күн бұрын

Robert Hermann Pfauter (RHP) invented the method of hobbing helical gears by adding a differential mechanism to the drivetrain of his machine. The slight retarding and advancement of the workpiece by the differential is THE SECRET... bit.ly/3onfQon
He made the hob head rotate on the vertical column of his machine for the helix angle- in concert with the differential - the hobber produces helical gears. With the formulas and setup schematics in the owners/operators manual the machine can cut right-hand and left-hand helical gears.
These advancements added to his hobbing machine's capabilities to make spur gears, sprockets, spline shafts, ratchets and worm gears making a differential equipped Pfauter a very Universal Machine Tool.
Timestamps:
0:00 Types of Gears
1:24 Gears and History
2:45 Pfauter
3:52 Modern Pfauter
5:57 Machine Setup
9:05 Pfauter Logo
10:36 Differential
12:09 Scallop Surface Finish
13:14 Wrap-up
Helical Gear Manufacturing Characteristics:
One Hob can cut right-hand AND left-hand helical gears
At angles from about 7° to 45°
for tooth counts ranging from about 20 to the limits of the machine(at least 130T)
RHP's first GE patent was in 1897, and his US patent in 1900. Advancements in CNC hobbing equipment came late compare to mills and lathes. In the early 1970's some of the drivetrain components were simplified with electric motors and rotary encoders. So any machine you buy prior to this date will be all mechanical.
There were many hobbing machine manufacturers making machines prior to 1970 and surprisingly there is a very active market for these machines. Some brands of interest:
Pfauter-Obviously, Mikron-instrument gears, Barber-Coleman - American still being serviced by Bourn & Koch, Gleason-bevel gearing, LIEBHERR, Gould & Eberhardt, Fellows-Shaper...
If you have a mill, get a lathe
If you have a lathe, get a mill
If you have both, get a hobber!
REAL GEAR MAKERS LOOK HERE bit.ly/2ViRr9J
Use our online calculators to make gears: gear blanks, arbor sizes & gear measurement...
Use our online calculators to calculate change gears for your old hobber/shaper
Get a larger hobber from Gibbs Machinery bit.ly/3Ajv5Es
Get a small instrument hobber and tester from George Tahan bit.ly/3AknaXj
Get the Hob from Ashgear (talk with Brad Jerris) bit.ly/3fH58a4
The Pfauter (code name Jersey) used in this video is a RS00 Model, made in about 1950. Refurbished with all new bearings & seals. Nothing special, easy to source and commonly available. We spec'd bearings by Timken. Gear Oil Pump-resurfaced, bench checked and reinstalled. New stud post (scissor) for the differential gear cluster, new quadrant studs and hardware. Rebuilt operator panel to allow for more & modern pushbuttons. All new PLC and VFD's drive the machine, just a few dozen lines of ladder logic make it function safely
References:
Gears From The Greeks - Derek de Solla Price: amzn.to/3rkfoJT
Interesting Gear schematics can be found in Tony Freeth's 2012 research paper:
dlib.nyu.edu/awdl/isaw/isaw-pa...
Pfauter - Hobbing, The engineer’s pocket book for Hobbing with Pfauter's Hob Cutter Catalog
Julius Springer Approximately 1930 (In German If anyone knows the exact date please let me know)
Pfauter - Hobbing, Volume 1, Springer-Verlag, 1976 (In German)
amzn.to/3hOwZXa
Jesse Ramsden (1735-1800) Science, Technology and Culture, 1700-1945
amzn.to/3wXfVTq
Sir Joseph Whitworth, A Pioneer of Mechanical Engineering"
amzn.to/3wQoz61
evolventdesign.com/blogs/hist...
British Patent Number 6850 from the year 1835 aka (GB183506850A)
Woodbury, Robert S, "History of the Gear-Cutting Machine"
amzn.to/3eCRsMO
Video Credits
The CT and PTM data that the AMRP have made publicly available can be found here www.antikythera-mechanism.gr/data
Gleason Corp - Pfauter Training Video - Encyclapedia/GE-EN Dictionary
www.gleason.com/en/encycloped...
Chris Maj - Helical Gearbox clip
Pfauter US Patent (1900)
patents.google.com/patent/US6...
NASA Reference Guide on Gearing
evolventdesign.com/blogs/hist...
Please SUBSCRIBE 🔔 We have developed useful content to help the machinist community with gears and gear machine tools. With our free resources centered around skills/tools/knowledge, you are now enabled to make any high quality gear you would ever need
The history of gears is surprisingly interesting - the process of milling and hobbing gears plus the transmission of torque and movement all find a place here. We will open the "Secret Gear Case" to YT as well through this channel - a personal mission
/ villagehobber
Disclaimer:
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Пікірлер: 73

@ActiveAtom 2 жыл бұрын

Nice topic, we love and very much appreciate your focused knowledge on the gear cutting and usage topic, good to see learn a lot about how the machine cuts these hob gears and it is a real joy to be here with you, hello to the beach please from the high-desert.

@EvolventDesign 2 жыл бұрын

Glad you enjoyed it!

@EvolventDesign 2 жыл бұрын

The beach said hello

@Mike40M 2 ай бұрын

Some fifty years ago, I worked teaching machine tools at university level. One test was to using trigonometry calculate how to make helical gears. When the math was done, they had to set up and run a hobbing machine, possibly a Pfauter. Very easy to tell if they passed the test. If they had made the math wrong, it started looking good but ended with a smaller diameter blank.

@EvolventDesign 2 ай бұрын

That is awesome! Thanks for being a teacher. Class work and shop work - thats the most effective way to teach and learn

@TheKnacklersWorkshop 2 жыл бұрын

Hello Andrew, Many thanks for this video... I find the whole gear cutting process extremely interesting... Take care. Paul,,

@EvolventDesign 2 жыл бұрын

Glad you enjoyed it

@OldIronShops 2 жыл бұрын

Very nice video Andrew love the history to bring up.

@EvolventDesign 2 жыл бұрын

Thanks very much, I enjoy learning about the very interesting history surrounding machining in general and share... Glad you like it.

@OldIronShops 2 жыл бұрын

@@EvolventDesign I'm on board with you there.

@dizzolve 2 жыл бұрын

beautiful machine, nicely refurbed

@EvolventDesign 2 жыл бұрын

Thank you very much!

@dannywilsher4165 2 жыл бұрын

WOW, very interesting. I like learning about anything mechanical. Thanks for sharing!

@EvolventDesign 2 жыл бұрын

Thanks for watching. Glad to hear from you.

@RRINTHESHOP 2 жыл бұрын

Nice machine, thanks for sharing about it.

@EvolventDesign 2 жыл бұрын

You bet, fun to do. It is an interesting project and the process is fun on these machines setup.

@johnwenzel9252 2 жыл бұрын

Interesting. Thanks for sharing!

@EvolventDesign 2 жыл бұрын

Thanks for watching!

@richardbradley961 2 жыл бұрын

THANK YOU . REGARDS RICHARD.

@fareshammoudi9187 2 жыл бұрын

Thanks Sir for the clarifications, Are you familiar with the Y3150 Machine? I bought one recently and I was told that I need to connect a different Bushing (Bigger) for helical gears?

@EvolventDesign 2 жыл бұрын

Possibly, I think that machine looks and operates very much the same as the Pfauters. I could not say about the bushing, you would need the owners manual as that may be machine specific. For the all hobbers i have seen, it must be equipped with a differential in the drive train to make helicals.

@sarahdelacruz5208 2 жыл бұрын

I have a question. You said that the scallops go away after running the gears for a little bit. Is that why certain machines recommend changing the oil after the break in procedure? Metal from the gears and other various machined parts contaminate the oil and thus require an oil change ?

@EvolventDesign 2 жыл бұрын

Yes, but it is just one reason to flush the gearbox. There are also deburring debri, and other potential shop dust that can get into a gearbox if left open for much time. For higher quality gearboxes the gears are ground and should not have any scallop debri. It is good practice all around regardless of the quality of gears used.

@thomasutley 2 жыл бұрын

Super overview. I’d be curious to learn how you determine the helix angle of a gear you’re replacing. Seems like it would be tricky to measure!

@EvolventDesign 2 жыл бұрын

You can measure the helix angle using some simple metrology tools(sine plate etc), but to test the gear completely for runout you need some special arbors on a gear tester (Vari-Roll). It is definitely a next level measurement.

@elanjacobs1 2 жыл бұрын

With some not quite simple math and a healthy amount of educated guesses. You start with the number of teeth, OD and pitch (just getting to the pitch and pressure angle can be a bit of an exercise when half the teeth are worn away). Once you have those details, you can work backwards to what the helix angle should be, then you physically measure the part and see if it matches up. If it doesn't (not uncommon), you have to then figure out what the addendum correction factor is. Sometimes, when parts are badly worn, the only way to be confident is to calculate a diff gear train, set it up in the machine and run an indicator over the part and measure how far off you are and re-calculate the gears. It can quite literally take a couple of hours to get to the answer in some cases.

@mabmachine 2 жыл бұрын

Some really great information in there. I find gear making fascinating. So far I've only cut spines on shafts which are essentially very long spur gears, but its been fun none the less. I'm curious if you know how this machine compares to the old Gould & Eberhardt or Brown & Sharpe US made hobbing machines? Thank you for sharing. -Mike

@EvolventDesign 2 жыл бұрын

Both share the same drivetrain, have not seen differential mechanisms on the G&E's. The G&E's that I know are very solid and reliable with massive cast iron bases. Have not seen a B&S hobber to know. But I do know B&S as a very technically solid machine tool builder and they likely have the differential. Pfauter had the patent on the differential, but I am not sure when it lapsed and others could use it. It took until the early 70's before CNC entered the hobbing world - much later than in mills and lathes.

@EvolventDesign 2 жыл бұрын

After looking through my history books, I found the earliest example of a B&S hobbin machine (horizontal) in 1915. This was apparently their first attempt, and they had studied the Pfauter machines extensively. Pfauter's patent in 1900 and manufacturing of machines significantly pre-dated the B&S efforts. The 1915 B&S machine does not appear to have a differential.

@umerramzan3375 2 жыл бұрын

Thank you dear, sir

@EvolventDesign 2 жыл бұрын

So nice of you

@adrianschaap4807 11 ай бұрын

Hi Andrew. I have a question about the differential mechanism highlighted in green. Do you have more knowledge on this? As I am struggling to cut helical on my machine..and suspect this part to be the problem. Question, if the diff lever is activated, with machine off, should it be possible to stop rotation of the diff gear train by hand if I turn the input shaft(f) of the rotation gear on the index side? Is the diff(included/excluded)lever suppose to lock the diff mechanism's worm gear onto main index shaft(f) inturn turning the worm on diff shaft(D) rotating the diff gear train.

@EvolventDesign 11 ай бұрын

Adrian- Short answer is I think you are correct in your conclusions above. The differential is a cluster arrangement of 4 mitre bevel gears (°45). The order of power transmission is: 1) Power input 2) Differential 3) Output from differential has a worm gear on the shaft 4) But it also becomes the input shaft to the INDEX change gear box. 5) then abcd for the INDEX gears 6) the output shaft has a worm on it that ties to the feed and differential gearbox 7) There is an engagement knob that ties to the output shaft of the differential gearbox and it engages a worm back to the wormgear in #3 above. 8) If it is not engaged, it will not function to make a helical. The function of the differential is to slightly slow or retard the relative motion of the INDEX ratio> To add a partial tooth. You then must tilt the hob head to the correct angle and it will generate the desired helical gear. The setup seems a little complex the first time around, but the more your do it the more it makes sense how things are working. Hope this helps. Andrew

@EvolventDesign 10 ай бұрын

kzfaq.info/get/bejne/jNKhgsV_uJ_IfHU.html

@bobanppvc Жыл бұрын

Is differential powered directly from motor or from feed gear i cant see?

@EvolventDesign Жыл бұрын

They are both powered from the motor. The order is Motor, Index Change Gears, Feed & Diff are linked behind the gearcase, then the power is split. One shaft goes to the platter worm gearbox, the other goes up the spindle to the hob. The truly interesting part is the diff connects back to the shaft that is connected to the motor before the Index Change gears.

@jetenginethrust863 2 жыл бұрын

Nice, thanks for sharing. I'm trying to find out the pitch/Module/DP or a gear I have from a power wheelchair motor gearbox. I thought it was a 1.5 Module but I was wrong, so now it's back to square one. I need some metric and inch helical gear teeth gages like a set of thread or feeler gages. McMaster-Carr has some but they are very expensive approx $300.00 for the inch & $280.00 for the metric just to use prolly once, no thanks.

@EvolventDesign 2 жыл бұрын

Yep, here’s a way to come close. Hopefully you have some good calipers or micrometers to measure the OD. If so make the measurement, count the teeth and the you can use our calculators trial and error to make an educated guess. Link in bio to our website and calculators.

@TheJohndeere466 Жыл бұрын

Do you know how to calculate the measurement over pins for a helical gear?

@EvolventDesign Жыл бұрын

yes

@TheJohndeere466 Жыл бұрын

@@EvolventDesign I need to make two 12 tooth 6dp 20 degree Pa helical gears with a helix angle of 13.398 degrees and they need to operate at a center distance of 2.200" I got a calculator from zak gear but my calculation always comes out too small and the gears have excessive backlash. One thing the calculators asks for is the normal arc tooth thickness on pitch diameter. To calculate this I multiply 2.200 x 3.1416 and divide by 24 since the gear has 12 teeth. Is this correct?

@EvolventDesign Жыл бұрын

Send drawing with your plans , contact info and phone number to: Contact@evolventdesign.com

@EvolventDesign Жыл бұрын

James-send me an email so I can get with you on the solution.

@gulfnepaleurope Жыл бұрын

Very Informative Guru I want to know what are the difference setting for cutting right hand and left hand helical gear cutting settings to be done on Hobbing machine. Also when to use the lead angle given in Hob cutter? Please reply me sir, i want to know this very soon please.🙏🙏

@EvolventDesign Жыл бұрын

Thanks for watching. There are many different machines out there-It is spelled out in your owners manual.

@gulfnepaleurope Жыл бұрын

@@EvolventDesign Thanks for your reply. I hope to know just as a example for your machine so that it may somehow relate to other machine setup process.

@EvolventDesign Жыл бұрын

Yes, that will be a future video. Please support me on Patreon. www.patreon.com/evolventdesign

@gulfnepaleurope Жыл бұрын

@@EvolventDesign Ok sir, sure. I promise you I will support you. Right now i am on short travel to abroad.

@likeit173314 2 жыл бұрын

I Have An Old Hobbing Machine Niles RF-4 Can You Tell Me The Helical Constant Of Machine I Don't Have Any Manual If Machine

@EvolventDesign 2 жыл бұрын

I have only ever heard of a Niles RF3, but no manual. Not sure of a method either. Let me find the RF3 info and get back with you-it may be in German.

@likeit173314 2 жыл бұрын

@@EvolventDesign Thanks For Your Reply ! Yes it may Be RF-3 Or RF-5 Please Try For Me I am Waiting Your Reply Thanks Once Again

@dattatrayapundalik8315 Жыл бұрын

Please give me differnsiyal gear formula to orijinal pautar machine

@EvolventDesign 10 ай бұрын

kzfaq.info/get/bejne/jNKhgsV_uJ_IfHU.html

@bhupender3799 2 жыл бұрын

Sir wat is pfouter rh2 lead formula

@EvolventDesign 2 жыл бұрын

Hope this answers your question for the RS2 Machine Index Constant = 24 (from Becher and Korner Example 11 pg 23 GE edition) The Lead Angle is scribed on the end of the HOB.

@bhupender3799 2 жыл бұрын

@@EvolventDesign sir wat is lead formula plz tell the answer

@sachinbsotari4396 2 жыл бұрын

Differential constant value how calculate

@EvolventDesign 10 ай бұрын

kzfaq.info/get/bejne/jNKhgsV_uJ_IfHU.html

@haythamdraz9800 2 жыл бұрын

How you convert from spur gear to helical gear pls

@EvolventDesign 2 жыл бұрын

For manufacturing > watch our spur gear videos and you can see how they are done vs this video for helicals. For design, that is a very different question and one new issue with a helical is the side load that will require some sort of solution/bearing for the thrust they create. Thanks for watching.

@haythamdraz9800 2 жыл бұрын

@@EvolventDesign thank you for your interest sir but i mean thise machine cause i have typical one wfzw mwm500*5 my problem is not how to calculate the helical but how to adjust It on this machine cause even i adjust the angle and all the calculation it also make spur not helical so may i have not connected the differential or i hv something i dont know. If you can offer me the manual instruction i will be glad

@EvolventDesign 10 ай бұрын

The machine needs to have a differential gear train It is calculated in this video kzfaq.info/get/bejne/jNKhgsV_uJ_IfHU.html