Gear Hobber

[MattM]

I've been thinking on building this machine:

. I bought the plans a few months ago and decided to order the castings. They are not available.

Would anyone be willing to sell their castings? Maybe a project that will never be finished and you would like to get a few bucks out of it? Just asking.

 

[Lo-Fi]

Which kit is it?

 

[MattM]

The Gear Hobber KIt

 

[DAT510]

Gear Hobber Casting Set

The gear hobber is a machine for producing gears by the hobbing process: a rotating gear blank is fed into a gear hob (in the shape of a worm). The maximum capacity is about 4” in diameter, 20 dp (diametrical pitch), 1.25 module down to 1/10” diameter, 120 dp, 0.2 module. The prototype uses...

www.martinmodel.com

Here another:

Gear Hobbing Machine Complete - College Engineering Supply

Designed on good machine tool principles, the machine incorporates dovetail slides and an Acme screw and nut for the auto feed cross slide The main components are cast iron, with mild steel used for shafts and small details. With the exception of the bed plate, most machining can be done on a 3″...

www.collegeengineering.co.uk

 

[MattM]

The Martin machine, which is the one I want is not available.

The English machine is not what I want.

 

[Winegrower]

Would this be better than just a set of cutters for each modulus or DP you wanted to cut? I’m making some mod 1.5 gears now and was surprised a set of 8 cutters was around $80.

Edit: looks like these machines might be a bit too small for mod 1.5.

 

[MattM]

Not much better but I want to build it just to watch it run. I can make and have made gears with my index head, gear cutters, and mill.

 

[Mitch Alsup]

Would this be better than just a set of cutters for each modulus or DP you wanted to cut?

Hobbing gears like shown will have lower (better) tooth-to-tooth symmetry than cutting each tooth all by itself (which is dependent on the gearing in the rotary table/spindexer/... and the precision at which the machines are operated.)
The Hobber is using 2 adjacent teeth to cause the current tooth to be cut symmetrically with respect to the adjacent.

High precision astronomy gears are hobbed, and then run worm-on-gear for multiple hours with fine lapping powder to get the sub-arc-second smoothness the drive needs. If the gear were 12" in diameter the tooth-to-tooth surface dimensions need to be way under 0.000,1" and surface smoothness in the millionths department.

 

[MattM]

Very interesting. I have no need for that level of precision.

The machine fascinates me and I want to see if I can do it. It is at the very outer edges of my amateur machining abilities and I may never complete it. I have the plans and have made the two shafts.

 

[benmychree]

And, hobs are not at all cheap.