GearHeads Corner

I've finally got a new control box and have my 4th axis running.

Time to try cutting some gears, and I like the way this one works.

https://youtu.be/JDvCs82cpL8


Cheers and avageatday all.

Hi:

Attempting a search for small hobbs such as that one shows it seems
quite hard to find such things available.

Art

Hey Arty,

Thank you for the reply, ok they are called Hobs.

Arty, what would you recommend for rotary to cut gears using a 3kw spindle?

Also does Gearotic supports Hobs? or is that just standard?

I apologise for the lack of knowledge..

Cheers and avagreatday from the colonies downunder.....

Steve

Steve:

Hobs ( or it it hobbs) are a series of disks arranged so that
each disk off center contributes a small tangental cut to an
involute tooth as it rotates. Think of each disk as the machinist
set the task of making a single cut at a particular angle to
contribute to each tooths development. They are typically
sold in a range, one hob may be good for a particular range
of modules.

  Gearotic will use a single flute mill to reproduce that
process, it rotates the gear and moves the tool to a new
position so the end angle being cut is the same as the hobs
individual disks. It can emulate any number of hob disks
but 16 (8 cuts per side) is usually the default. This is called
tangential shaving and Gearotics 4th axis module will do
it for you. (See you-tube for the 4th axis video.).

  The video shows the process of how each tooth is formed
and if you use your imagination you'll see its basically
performing a hob function one cut at a time for 16 cuts
per tooth. This slicing on the tangent is the best way
to do a gear tooth unless you can do them in 2.5D standard
machining which will give a smoother finish.

The 4th axis module has been used industrially for gears up
to 3 foot in diameter, it can be slow but produces a pretty
good gear.

Art

Ty for such a quick and detailed reply, will have a look at the video ty very much!!!


Steve

More conventionally, hobs have the teeth on helical profiles, rather like a tap, and the gear blank rotates at the same time as the hob, with a ratio between the speeds so that the blank moves through one tooth angle per rev of the hob.  The hob is fed slowly back so that all the teeth are formed in one milling operation.  The benefit is that triangular teeth on the hob with a pitch equal to pi times the gear module, will generate involute gear teeth of any tooth count except for small counts where the teeth need undercutting.  You can use a tap as a hob.

JohnHaine wrote: More conventionally, hobs have the teeth on helical profiles, rather like a tap, and the gear blank rotates at the same time as the hob, with a ratio between the speeds so that the blank moves through one tooth angle per rev of the hob.  The hob is fed slowly back so that all the teeth are formed in one milling operation.  The benefit is that triangular teeth on the hob with a pitch equal to pi times the gear module, will generate involute gear teeth of any tooth count except for small counts where the teeth need undercutting.  You can use a tap as a hob.

Hey G'day,

Thank you for the courtesy of a reply, well bugger... that's something worth trying using a tap :)

Cheers and avagreatday...

Taps used to be a common way to DIY 3D printer filament "hobbed" gears.  These are used to push filament through the printers melting device, aka the hot end

Kirk

Mooselake wrote: Taps used to be a common way to DIY 3D printer filament "hobbed" gears.  These are used to push filament through the printers melting device, aka the hot end

Kirk

Another worthwhile idea to remember ty

Steve