Freebie - Gear Hobb

Hey Ron,

I have no interest (read...roooooom), but I think this is very nice of you to do.

Have a good day. Take care.

Brian Laws>I obtained a gear hobb as part of an auction lot and have no use for

MAN, I'd really like this hob.

FWIW, Don Foreman is me helping build a control box so you can hob gears on any bridgy type mill if you also own an indexing head and step or servo motor to drive the head.

Karl

no, i don't need it, but talk about a small world: i live in 94523...

--joel

Karl was the first respondent and will get the hobb.

Ok What does it do?

Reno, Paul

It's the cutter used in a hobber to make the teeth on gears. Damned expensive for new ones.

Looks interesting enough. Is there a way to do that on a lathe? Thanks Reno, Paul

Paul, The "free" hob is a special purpose hob. .2992 CP is 10.5 DP which is a non standard gear Diametral Pitch. If you don't have a Gear Hobber, a lathe could be set up to hob gears although it would take a great deal of work to do it. I saw an article from an Australian Model Magazine on how a guy did it. Far easier is to use a horizontal mill with a universal table. There was an article in HSM awhile back that detailed a horizontal mill setup. The gear hobbing essentials are: The work (gear blank) must be feed into the rotating hob at an angle equal to 90 deg +/- the helix angle of the hob (the reason for the universal table). This is the small angle (about 1 or 2 degrees) usually etched on the hob. As the work is fed into the rotating hob the work must also be rotating. If your are cutting a 60 tooth gear the hob must rotate 60 times for each rotation of the gear blank. As you can see the hob spindle must be connected to the work via change gears and some type of reduction box. The setup must be rigid with virtually no slop. Any setup you can dream up that meets the above criteria will hob gears.

Joe H

Not without a lot of "work-around". Hobbing cutters are intended for continuously rotating the workpiece, the teeth on the cutter are cut in a spiral, as the workpiece rotates, the teeth come to where they're supposed to.

Using one of the formed milling cutters and some way of indexing works, but it's anything but fast. Plus, as the shape of the teeth changes with the number of teeth, the the cutters have to be for a certain range of teeth, meaning a lot of them are required to go from say 10 teeth to 60 teeth. Hobbing them, the tooth form of the cutter is straight, and the rotation of the workpiece forms the involute, one cutter will do for any number of teeth. Not that it's perfect, the angle of the hobslide will change the involute, and sometimes it can be stubborn about coming in. In the specs that were posted is an angle, this is the angle that the slide should be set at, plus or minus any degree of helix, but usually it's only a starting point. The actual setting will normally be somewhere a few minutes of angle from the marked one.

The main advantage of a hobber, you can stack blanks on an arbor, start it going and come back when the noise stops. I've run groups of them, from as few as three hobbers, to as many as ten, depending on the jobs being run.