Desktop Gear Hobbing
Model Engineers' Workshop|May 2020
Toby Kinsey has designed this fascinating piece of gearmaking equipment
Toby Kinsey

One of my occupations is as a model maker for a small toy and games invention company. We often have to construct prototype toys and use small Module gears for various gearboxes and mechanisms. The deadlines are often quite tight and to avoid the wait for gears to be delivered, the company stocks a range of small plastic moulded gears in different sizes, from 9 teeth up. These are mainly 0.5 Module, but we do keep some bigger module gears as well. These are generally sourced from companies such HPC (ref. 1). But due to the way the world seems to work it is invariably the case there isn’t a gear with the right number of teeth for a particular job or there is only one gear left when you need two!

Another issue is the bores of even the small gears are quite large, 3 or 4mm being common. This leads to lots of machining up of little sleeves to reduce the bore down to suit the 1 or 2mm shafts we use.

I also work on my own personal projects at home, but lack of deep pockets has stopped me from building up a stock of gears in the way that a company can afford to do. This was a limiting factor on what I was able to do at home as again, you never seem to have the right gear for the job in hand. I was faced with the choice of having wait while I ordered a particular gear or “borrowing” gears from work.

The solution to the gear issue I came up with is desktop gear hobbing with the Mini Electronic Gearhob Setup, or “MEGS”, photo 1. Pushing a few buttons, photo 2, you can select the number of teeth of the gear you desire, and it will produce you a gear up to 30mm in diameter. See ref. 2 for a video of MEGS in action.

Gear Hobbing

The journey that led to MEGS began when I thought would be useful to have a way of making gears myself. Of the ways to make gears I thought, a small gearhob would be the thing.

As many of you will know, a gear hob works by rotating a blank of material at the same time as a cutter or hob is rotated about an axis 90 degrees to the axis of the blank. The hob has spiral groove cut round it like a thread, with gashes cut to provide a cutting edge, photo 3. The blank is rotated in proportion to the cutter, i.e. cutting a 10-tooth gear the blank needs to rotate at 1/10th the speed of the cutter spindle. The beauty of hobbing gears is you only need one cutter to cut any size gear for any given module, unlike cutting gears on a mill using a dividing head and involute cutters. Where each cutter will only produce the right teeth form when cutting gears with a limited range of number of teeth. You can get an involute cutter that will cut a gear of between 12 and 14 teeth. You will need another cutter to cut the next few sizes up and so on. Which all means you will need a range of cutters to cover all eventualities. Another advantage of producing my own gears was that I could produce a long length of a particular gear and then part if off to just the right thickness, as and when needed.

As I was only going to need to work in plastic or the odd bit of brass I wouldn’t need anything too substantial. But looking around on the web the options seemed rather limited.

There were commercial hobs, but these were a bit too mighty in both construction and price.

College Engineering Supplies, (ref. 3), sell the castings for a small tabletop hob. The requirement to make a fair few gears for the hob just to function was slightly off-putting. It also looked like it would take quite a long time to complete and it would be handy to have something producing gears fairly soon.

Continue reading your story on the app

Continue reading your story in the magazine

MORE STORIES FROM MODEL ENGINEERS' WORKSHOPView All

Readers' Workshops - Patrick Cubbon

Patrick Cubbon describes his workshops – a portable one from 1963 and the current accommodation

2 mins read
Model Engineers' Workshop
May 2020

Desktop Gear Hobbing

Toby Kinsey has designed this fascinating piece of gearmaking equipment

9 mins read
Model Engineers' Workshop
May 2020

The John Stevenson Trophy 2020

Many readers and forum members will remember John Stevenson, a contributor to MEW but best known for his larger-than life presence on the Model Engineer forum.

3 mins read
Model Engineers' Workshop
May 2020

From the Archives: Twist drill Sharpening by the Four Facet Method

Giles Parkes, MEW Issue 64, February/March 2000

4 mins read
Model Engineers' Workshop
May 2020

Dividing on the Warco 220 Lathe

Peter Shaw describes a mandrel dividing attachment for this popular lathe that can be adapted to fit many other benchtop machines

8 mins read
Model Engineers' Workshop
May 2020

Choosing Steels

Stub Mandrel offers some advice on choosing the right steel for the job

7 mins read
Model Engineers' Workshop
May 2020

A Storage Story

Robin King shares the lessons learned from his experience of workshop moves

8 mins read
Model Engineers' Workshop
May 2020

A Simple Drill Grinding Aid

A newcomer to our hobby was having trouble sharpening drills, so Howard Lewis made a simple aid for him

2 mins read
Model Engineers' Workshop
May 2020

Yet Another Bodge-Up!

Peter Shaw finds a use for some aged homebrew slot drills.

5 mins read
Model Engineers' Workshop
March 2020

Workshop Press Tooling Part 2

Will Doggett makes a set of tooling for his press tool described starting in issue 285

5 mins read
Model Engineers' Workshop
March 2020
RELATED STORIES

Jim and Carolyn Phillips — Don't stop being active

Jim and Carolyn Phillips are local legends.

7 mins read
The Good Life
February 2021

Retirement Brings With It Extra Time

Make The Best Of It

3 mins read
The Best of Times
February 2021

DECADE OF iPAD: HOW THE TABLET CHANGED THE WORLD

In 2010, Apple CEO Steve Jobs took to the stage to announce a device that would revolutionize the way we read, watch, learn, and work. Ten years on, the iPad remains one of Apple’s most iconic products, ushering in a personal computing experience that continues to evolve at speed.

7 mins read
Techlife News
Techlife News #478 *Special Edition

Filling an Empty Space and Enhancing a Cabochon

I often look for a special feature within a slab when choosing the shape to cut into a cab.

2 mins read
Rock&Gem Magazine
January 2021

EXTRAORDINARY BOATS

HELEN FRETTER ON KARMA

5 mins read
Yachting World
January 2021

UNSTOPPABLE with Tracy Tutor

As our long time readers know, a number of our cover photoshoots have taken place in phenomenal luxury residences here in NYC as well as other locales around the country. So it's no surprise that we love reality shows that focus on luxury real estate. The OG of these programs includes BRAVO's Million Dollar Listing. Both NY and LA focuses not only on the housing market in those cities, but also follows the brokers to understand what their lives and interactions are like as they are closing multi million dollar deals.

8 mins read
Athleisure Mag
November 2020

Papi's Sign

“I saw a butterfly,” my mother said with a shy smile. It was the first time I’d seen her smile since my father’s death the week before. After a seven-year period of steadily declining health, he’d passed away in his bed at home, surrounded by his wife and three daughters. It was a peaceful end to his suffering, but saying goodbye was still difficult. We all missed him terribly. Especially Mami.

3 mins read
Mysterious Ways
December/January 2021

WINTER OF DISCONTENT

The hot stove could quickly turn to deep freeze

4 mins read
Baseball America
December 2020

HALLE'S NEW LAD WAS A CAD!

Cheating past could catch up to singer Van Hunt

2 mins read
National Enquirer
November 30, 2020

Two engines, four-wheel drive: Citroen's 4x4 is unique … just check the trunk

Automakers have devised quite a few ways to get power to all four (or sometimes more) wheels underneath off-road vehicles, but only a very select few have accomplished that task with two engines.

2 mins read
Four Wheeler
January 2021