Machining a Worm Gear - Gashing and Hobbing

[@robertbarr8001]

Your videos are beautifully, simply and thoroughly explained. Thank you.

[@machiningmoments]

Thank you!

[@machiningmoments]

The worm was cut (threaded) on a lathe. It is similar to an Acme thread (actually a Brown and Sharpe thread). This particular thread is a single start.

[@machiningmoments]

My pleasure, thanks for watching and posting! I should have another one for you in the next few days.

[@mog5858]

very well done i never new that the hob drived the blank as well as cutting it i feal that i might be able to tack bilding a small worm drive now. thanks for your time great work keep it up.

[@machiningmoments]

Some gears are cut (gashed) with an involute gear tooth cutter, the issue is that it not likey has the same form as the worm (usually similar to an acme form) requiring the hobb to finish the correct form. Due to the lead angle on the worm the milling machine table or head will require swivelling for a proper mesh.

[@machiningmoments]

Good luck with your worm drive and thanks for your post.

[@machiningmoments]

There is a slight helix to it to accommodate the lead angle of the meshing worm. It is also enveloping or throated because of the radius that the worm sits in. Good question, thanks.

[@machiningmoments]

Essentially yes, it also makes the work load easier for the hobb.

[@machiningmoments]

A universal-horizontal milling machine is used and the tooth spacing is controlled by the hobb.

[@Gottenhimfella]

When you (in the clip) talk of "tilting" the table: is that American for swivelling? Where I come from, tilting implies away from the vertical, which could not be used to align the cutter with the lead angle of the helix. (ON EDIT: I've since searched all the comments and see that you do talk, in one of your comments, of swivelling the table or the head, not tilting)

[@machiningmoments]

Glad you like it. Thanks for posting!

[@glassglowz]

Excellent video! How did you make the worm though?

[@stanleyrodgers3375]

Nicely done! What errors would have been caused in the worm gear geometry if it had been finished to depth using the involute cutter instead of the hob?

[@Gottenhimfella]

Even if the profile was correct, it is not possible to make the right shaped toothspace with a milling cutter which spins about an axis which is fixed in space relative to the workpiece. Thing about it this way: if you pressed a blob of clay into the toothspace on a hobbed wormwheel, then took it out, the resulting shape would not be a "solid of revolution" with respect to ANY axis. A solid of revolution is the sort of shape you could replicate on a lathe or a potter's wheel. It's the volume swept by revolving a flat profile, one of whose sides is a straight edge, about that edge (the "axis" referred to above). The blob of clay would instead look like something made in a lathe and then (before it had time to set) twisted or warped.

[@machiningmoments]

Other than calculating the gashing depth (which is cut shallow), you need no calculations for hobbing. The hob is "full-form" as soon as you reach throat diameter you have the proper size and profile. Thanks for your note.

[@j.r.5130]

Thanks for making this video, it was very interesting. Would the dividing head be a 40:1 worm gear as well?

[@machiningmoments]

Yes it is 40:1, must (not all) dividing heads are 40:1.

[@machiningmoments]

You likely could get away without using an involute cutter as the form is created by the hobb. You would have to use care to not overshoot the finished form.

[@AbhinavSG]

this is a great video coz it is very informative & the explanations made are to the point & precise. I was looking forward to watching the HOBBING Operation, which is missing. Will appreciate a link to the 'HOBBING of the Worm Gear' video. Keep up the good work. :)

[@marshalcraft]

very cool, im considering this for making a cnc machine to get the precision needed.

[@Srk7028]

thanx for the video., is this worm wheel is spur or helical gear type?which type worm wheel is this ?

[@machiningmoments]

If you Google "Machinery Handbook by Industrial Press" you will find it. I believe the current edition is the 29th. Thanks for your post.

[@machiningmoments]

Yes helical gears is another story, honestly the math is very involved and would take me a while to go through. The Machinery handbook is a good reference, I also use Technology of Machine Tools author Krar (I think). I will research gear cutting info for you. A lot of it is older.

[@keldsor]

In fact I plan to use a big TAP to do the job - this way the Worm gear - I think - will match the Worm - IF I cut the Worm with a die matching the tap - right ?

[@machiningmoments]

You bet, each axis has a (ball) screw. When it rotates it moves the table towards/away from you, left/right, up/down.

[@mikeherron8652]

I have a grizzly lathe with a broken worm gear driven gear, can you make one? Just much smaller than this video. Any help would be appreciated

[@machiningmoments]

The biggest thing you are up against is the hobb. The hobb will cut the worm gear. The hobb in the video is controlled by the diameter of the worm in this scenario. It is also a Brown and Sharpe worm thread... what I'm saying is it will depend on your situation. There are a few videos on line with a tap (hobb) in the spindle of the lathe cutting the worm gear. If you have enough of the old gear you cut the diameter, you can calculate circular pitch which will equal linear pitch (hobb, tap) if its throated that would be controlled by tap diameter. Thanks for watching and your questions. Good luck

[@ravneetsingh7606]

thanks for the reply ...can you please guide me how to set the different ratios(5:1,10:1,25:1) between worm and worm gear

[@timjonminers]

Would you be able to do a video on hobbing helical gears on a lathe? Many home machinists find this difficult

[@machiningmoments]

Jonathan Barnes I'm on holidays at the moment, I'll look at your suggestion when I get back. I'm half way through a video on differential indexing someone else wants. Thanks for the suggestion and stopping by.

[@timjonminers]

Brilliant, thanks. Great videos by the way.

[@machiningmoments]

Thanks for your kind words, I appreciate suggestions.

[@timjonminers]

I've bought a hob, assuming only the hob needs to be driven, in which case I would be able to use just my lathe. Is this the case or do both hob and workpiece need to be powered, meaning I would need an auxiliary drive mechanism?

[@machiningmoments]

If the hob is the correct form only it needs to be driven. The difficulty in a lathe is you need to drive the hob (held in the spindle) against the gear blank (held on the tool post/fixture on the carriage) it needs to freewheel, introduced at the proper angle and fed into the hob to obtain the proper tooth depth. It will help guide the hob if the gear blank has rough teeth "gashed" into the gearblank.

[@uchepuche8391]

The blank is it concave machine ???

[@machiningmoments]

The concave shape is cut into the gear so the worm can sit in it.

[@uchepuche8391]

@@machiningmoments the concave blank is first machine in the lathe before gear cutting,sorry for my armature questions am just new in machining,thanks for your attention.

[@uchepuche8391]

please is very important your response

[@machiningmoments]

Yes the gear blank is first turned on a lathe with the concave center then it is placed in the milling machine to have the gear teeth cut in the blank.

[@uchepuche8391]

@@machiningmoments thanks very gratefull

[@BoffinGrusky]

Outstanding!! Thanks fpr posting!!

[@JCruise007]

Where can i find the Machinery Handbook ??

[@marshalcraft]

linear movement would be a ball screw or lead screw yes?

[@DieselCrawler86]

What is the tattoo on your hand? are you are hard core gang bike that doubles as a machinist?

[@machiningmoments]

In this example the form would be incorrect as the worm was cut with a Brown and Sharpe form rather than a DP.

[@altaroffire56]

Can this be done in a vertical mill? If so, would the vertical mill be more or less convenient than a lathe?

[@machiningmoments]

There are vertical setups to cut gears, they are called gear generators.

[@marshalcraft]

wouldnt i use a larger diameter worm gear with a ball screw?

[@ccfoam]

Nice Job! I would really like to see a worm being made. Any chance you need one? Thanks! Chuck

[@machiningmoments]

Hey Chuck, sure next time I cut one. It is really straight forward the pitch equals the circular pitch of the worm gear (I think it was 1/4 inch), the lathe is set to 4TPI and it is cut as a Brown and Sharp thread. Thanks for the feedback!

[@machiningmoments]

Good Luck!

[@rpchaitanya6044]

Sir, thanks for the informative video... all i need is calculations... machinery handbooks give general equations .. but practical calculations like calculating correction .. profile shift co-efficients are not explained well.please can u suggest some books or mail me the calculations if you have the one..?? Thanks alot...

[@ravneetsingh7606]

hi...can you please tell the machine used in this process of producing this worm wheel...and to maintain the teeth equidistant from each other...waiting for reply Thank you

[@pooleey]

How is the worm gear bronze mated to the steel center shaft?

[@machiningmoments]

The bronze is pressed on a steel hub which has a slide fit over a keyed shaft.

[@marshalcraft]

what if i wanted to be able to rotate one axis very precisely?

[@rubenarancibia7145]

can you do this in metrical units or you need to change the tools?

[@machiningmoments]

The process is similar, the cutting tool is basically the same...the big difference is metric uses "module" to select cutters and do calculations. Inch, imperial gears use "diametral pitch" to select cutters and do calculations.

[@rubenarancibia7145]

+machiningmoments I don't have much experience in manufacturing, thanks.. so the hobb you used here would be different if you were cutting a metrical gear rigth? because of the axial pitch, thanks

[@machiningmoments]

That's correct, the pitch (axial distance) is different inch/metric which means different hobbs are required. The module/diametrical pitch is used with tooth size and form. For not having a lot of experience you have really good questions!

[@joudymambu9608]

thanks is the trie solution teknik is the better

[@cyclejunk50]

thanks for the videos

[@machiningmoments]

Yes, if you are rotating a worm is the way to go. I thought it was a linear movement!

[@machiningmoments]

I'm not really sure why you want to use a worm gear to create a CNC machine.

[@arielpineda4532]

what is the degree of the worm gear teeth

[@JohnDoe-go2fc]

Why dont you make them out of steel like sterring units or rack and pinion as they do not wear out for many many years, these bronze gears were out quick. I had a bunch to wear out in garden tillers. If i had steel gears i would still be tilling!

[@HH-Machining]

Its made of bronze because it takes better heat away from the worm gear wich is made of steel.

[@arielpineda4532]

im asking because i make worm gear in my company but not match to the worm shaft , i set up my dividing head into 6.5 degrees .dia. of worm gear is 76.00mm number of teeth 28 pls reply to my comment. tnx

[@machiningmoments]

LOL it is the hand of the student that was making the gear.

[@russellbarnhardt]

Just kidding. This is so cool, thanks for the videos!

[@dianamccandless7094]

thank you! That answers my question ("Can I order a bunch of worm gears to be made that are only toothed on the TOP? The answer is NO)

[@machiningmoments]

Glad it was helpful.

[@rpchaitanya6044]

but in case of helical gears profile shift coefficients matter a lot.....

[@Bizzhatesme]

Looks like some severe runout on the cutter body.

[@machiningmoments]

One of the issues with horizontal milling (B-style arbors). The hobb takes care of it.

[@Bizzhatesme]

I have only had one that ran out more than .009 inch.

[@machiningmoments]

That should work.

[@rpchaitanya6044]

Thanks a lot..... :)

[@russellbarnhardt]

The spring winding video is way better!

[@uthidsangawong850]

Hob cutting worm gear must be turn free.

[@machiningmoments]

Yes

[@marshalcraft]

yes i will need a fare amount of luck, and even more knowledge from reading, youtube videos of people who have done it already, and frankly anywhere information can be found.

[@arielpineda4532]

and last ! i only use single fly cutter.

[@machiningmoments]

I believe the example in the video is 2.7 deg. If you know the pitch diameter of your worm you can do trig to calculate the lead angle. The worm and worm gear will have the same angle. A fly cutter will work fine.

[@joudymambu9608]

is good

[@machiningmoments]

Thank you

[@barryhill2978]

this is boss

[@josiahlevasseur4479]

I didn’t know Jordan Peterson was a machinist

[@machiningmoments]

I have heard before I sound like Jordan Peterson.

[@josiahlevasseur4479]

@@machiningmoments lol you sound exactly like him 🤣 love the videos

[@Soilift]

hahahaha!! :-)