Helical Gears

Have you a universal milling machine?

Not "easy" but not impossible.

You pretty much need to have a universal milling machine (one that has a swivelling table) and a matching universal dividing head (one with a set of gears to drive the head from the table cross feed)

After that, it's a matter of figuring out what you need for a helix, what you need for a cutter, and generally, figuring out which gears your set is missing that you need to make. :-)

After all that, it is just repetition of the same stuff that you went through cutting a spur gear, except that the part will twist as it traverses across the cutter.

Cheers Trevor Jones

Pretty much?

Well, that depends on your ability to lash things up.

You kinda need a horizontal spindle. if you want to follow along in the books.

You can sorta maybe get away without the swivelling table, if you can accurately swivel a vertical head over to the helix angle of the gear. That gets you either working blind, with the cutter on the back side of the work, or rapidly running out of travel, working on the front side of the work. Way easier to use a swivelling table. Then all the books you might find that cover the subject, will make sense.

You do need a universal dividing head. And a pile of gears for it.

Lotsa guys doing the CNC thing, too. There was at least one helical gear on the Sherline site.

Take a look in Machinery's Handbook, among others, for info on helical milling. Probably the Machine Shop Practice books, too, but I don't have them handy to check. My edition of Technology of Machine Tools, a common senior high school/college text has some basics as well as some of the formulae to work out your gear train.

Helical gears is just helical milling of a gear tooth form. One more thing to keep yer head around.

Cheers Trevor Jones

"Pretty much" "Lash things up" "Kinda" Sounds like you don't treat helical gear cutting as anything but a bodgeup. Woodbutcher are you Trev? I'm amazed you didn't throw in instructions for creating gears with a hammer and chisel, accuracy wise that would be right up there with the rest.

Tom

Well, lacking any useful inputs from yerself, whatsa guy to do.

Not a woodbutcher. Not beyond firewood, anyways. Still got all my toes, so that's working out.

I build parts for airplanes. Sheet metal, machining, a little CNC. My workplace is a mainly manual machine shop, with a pretty decent budget for everything but manpower. I have done some helical milling, mostly decorative. It was while I was being trained. It was thought that at the very least, we should have some experience with it, whether we were ever going to use it. I also work metal in a hobby shop at home, and appear to have a better grasp on the realities of home metalworking, than you do. Apparently. If the guy was in a shop where he had access to the full kit, I'd figure he would not be asking on a recreational metalworking newsgroup. I have seen what CAN be done with limmited kit and lashups, and it's pretty nice stuff. At the end of the day, the part on the table counts for more than the tools in the shop. Espescially as a hobby.

Suit yourself. All you have provided to this is smartass comments, rather than anything useful. Have you considered actually contributing, or are you going to carry on talking out of your ass?

:-)

Yup! Lash-ups, Pretty much, and Kinda, will cover a lot of ground. Every guy that ever taught me anything was quite able to lash up a set-up when the "right" tool was either busy, or in some cases, was in a different country. Sometimes Kinda is as close as you get to the way the textbook shows it, and Pretty much, is the appreciation that gets shown to the guy that can make a safe part that otherwise keeps an airplane down.

FWIW, I have seen what can be done with hammers, chisels, and files. If you could do that, I'd respect you.

Cheers Trevor Jones

With your head buried in wood chips, it obviously passed you by, that I had already asked the OP whether he had a universal mill.

If he hasn't, then you can jump in with all the mickey mouse methods known only to yourself. The chances of him then making 2 helical gears that will mesh at the necessary centres and on parallel axes will be fairly remote. As far as I'm concerned, anyone who wants to cut helical gears and expects an internet education to provide it, deserves all the assistance you can provide.

You consider my comments smartass? Perhaps if you weren't so slovenly in your explanations of gear cutting, you could have expected a better critique.

After all I was only originally querying your vague: "pretty much" comment.

Tom

Nope. It had not passed me by that you had asked. Nor had it passed me by, that the OP had only just been succesful at gear cutting spur gears.

Wanna cut out the shit slinging at each other? It'd probably help get this whole op back to the topic at hand. It WAS you casteing aspersions on me, remember.

Dunno what your background is, but if you have made it in any way in a machine shop, without having to resort to a lash-up or mild (or not so) bodge in order to get a job done, I figure you are living a charmed life. Or you don't cut all that much metal.

He needs much better explanations than what he has been given, but, for the amount of information he provided, the info he has got handed to him, is fair. That it can be done, and that there are a few different options, depending on his equipment available or not available. Other than that, I could have spent a great deal of time retyping formulae and a lot of text that would be pretty meaningless to him or anyone else looking to try the stuff, and been no further ahead for the trouble taken. But I did actually provide him with some input, which is still more than you did.

Ante up. Provide an answer to the posters question. Something not so slovenly perhaps. Or is that not so much your style?

I think he would be better off finding a library full of Model Engineer back issues and having a couple long sits in the reading room with those, than he would sticking to the industrial texts. They (the many and talented writers for ME) at least understood that stuff could be done, with, or in many cases, without the "proper" equipment.

Cheers Trevor Jones

I'd rather wait and see if he responds to my question. If he hasn't got a universal mill, end of discussion. When it comes to helical gears, lashups don't cut it. Of course he may have the odd hobber or gear shaper or planer, tucked away. However, if he did, this discussion wouldn't be taking place. Finally I see we can agree on something, a book beats a pc screen any day garnering and absorbing info. BTW a milling machine would be my last resort to cutting a helical gear and I speak from the experience of using all of the above.

Tom

Well, at least we agree on one thing.

But to cease any information, just because the poster may or may not have a particular bit of kit, well, that seems a bit tight to me.

What do you figure that he'd be willing to speak up and ask any more questions, after this little exchange, too.

I know that it can be done, with other equipment than a hobbing machine, or a universal mill and universal dividing head.

It just depends on how much desire there is to get it done.

There is a great picture in the Sherline Book, Tabletop Machining, showing a helical milling set-up that made a 45 degree helix gear blank for a model enginge distributor drive gear. If the term lash-up does not come to mind when you look at the picture, I don't know what words better describe it. Unfortunately, I do not have a scanner, or I would fire a copy of it online somewhere.

Tabletop Machining is worth the read. It IS really a big advert for Sherline (Hey. They wrote it!) but it shows a LOT of stuff that can be done, and generally it is done without the ways and means that a traditionally trained Machinist would not try.

If it can be done on one machine, it can be done with another. Just have to follow the basic principle, and work from there.

Cheers Trevor Jones

Cheers Trevor Jones

Wow. I never thought it would generate this amount of correspondence!

All I have is screw cutting lathe, vertical slide and a dividing head and a computer in the office.

Many thanks.

Well, as the saying goes, "Never give up!".

:-)

The Brit Model Engineering lot are a really good source for info on getting things done with next to no equipment. Sometimes, it boils down to deciding whether it is worth the effort or if it is cheaper just to dig out the stuff from a catalog. If it is available.

Dig around online for "Tee Publishing" and "Hemmingway Kits".

Lot's of good reading around.

Cheers Trevor Jones

There's another way. Standard Bridgeport vertical mill. Mount the right gear cutter on a stub milling arbor in the spindle. Set up the dividing head on an angle. I have a very old dividing head that has a swivel so it can point upwards at an angle from the table. Using the machine's X axis travel, sweep an indicator along a test bar in the dividing head and adjust the angle until it is correct for your helix angle. Now, you need a CNC control that can control X, Y and the dividing head. It needs to make synchronized movement of X and the dividing head when the cutter is engaged in the gear.

Jon

LOL