Dividing on the Warco 220 Lathe
Model Engineers' Workshop|May 2020
Peter Shaw describes a mandrel dividing attachment for this popular lathe that can be adapted to fit many other benchtop machines
Peter Shaw

Users of this lathe will no doubt be aware that limited simple dividing by 2, 3, 4, 6 and 12 can be accomplished using the pre-drilled holes in the mandrel flange along with a simple accessory which bolts onto two pre-drilled and tapped in the headstock housing. If you have not got one, then drawings for this accessory were published in MEW 135, February 2008.

Divisions of 2, 4 and 6 are quite useful on their own as along with a suitable filing rest, one can produce spanner flats on a bar, a square end on a bar or a hexagon for use as a nut. But what if you need to divide by 8, say for a cover with 8 fixing holes? Well, you could rig up something to engage with the 32 teeth gear wheel semi-permanently mounted on the mandrel inside the gearbox. This same device would also give you 16 and 32 divisions if you need them.

Life gets somewhat more difficult, though, if you want something else. Suppose you want to mark graduations around a disk with a M6 tapped hole through the centre with a view to being able to adjust the device, whatever it may be, by 0.1mm. M6 has a pitch of 1mm, therefore, if you could divide the disk into 10, then you could adjust by 0.1mm and hence problem solved. But how do you do it? Or, as I did recently, I wanted 40 long graduations of 5mm length around the periphery of a ring, with a further 40 short graduations of 3mm length to subdivide the main 40 divisions. The answer is to use a dividing mechanism mounted on the rear of the mandrel and which uses the lathe changewheels as the master device. Even so, there is problem in that I required 80 graduations, and the largest changewheel available is 64 teeth. The answer is to use the 40 teeth wheel and a detent which either slots in between two teeth (thus giving 40 graduations) or sits astride a tooth (thus giving a further 40 graduations spaced between the original markings). Taken to it’s logical conclusion, the greatest number of graduations this method can give is 128 (2 x the largest changewheel of 64 teeth). Even so, there are a number of divisions which cannot be achieved, and for these it will be necessary to use some form of gearing using two or more changewheels. The design presented here is the simple version using a single changewheel.

The essential ingredients of such a device are firstly some means of rigidly attaching a changewheel to the rear of the lathe mandrel, and secondly, rigidly attaching a detent to the lathe itself such that the detent can lock securely into the changewheel thus preventing its rotation whilst suitable marking of the workpiece proceeds. It was this latter ingredient which caused me most concern as I ended up using the gearbox cover itself to locate the detent. This cover, being hinged could be considered to be somewhat flexible and hence could contribute to some inaccuracy, however, on my lathe, once the gearbox cover lock is engaged, it does seem reasonably rigid. The cover itself is reasonably thick at about 1.75mm; indeed, it is thick enough for there to be three 4mm tapped holes which are used to hold in place the protective shield for the end of the mandrel. Finally, the actual strain on it is, I think, quite small, and in the end it worked satisfactorily.

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

Totally Scrappy Scarf

Using less than 12 yards per row and simple single crochet and chain stitches, this stash-busting scarf is a perfect way to brighten up a winter outfit!

2 mins read
Crochet World
February 2021

Patchwork Puppy

Popular from the moment it was first published in the April 2012 issue of Crochet World, this cute puppy is such a fun project to make! Make up a bunch to sell at craft fairs or to give as gifts.

5 mins read
Crochet World
February 2021

STOP SUCKING AND JUST BREATHE

Air-saving tips and strategies to make every tank last

4 mins read
Scuba Diving
May 2020

CUTTING A FINE FIGURE

Master craftsman and national awardee, Amrit Sirohiya infuses imagination and creativity into the ancient art of gemstone carving to create breathtaking pieces that find takers from the world around, while also contributing to preservation of the art.

4 mins read
MARWAR India
March - April 2021

Delight in detail

Lighten your load and mood by carrying this pretty and compact bag designed by Carolyn Calderon

4 mins read
Simply Crochet
Issue 107

Sennheiser Momentum 3 Wireless

THIS LATEST VERSION updates the Momentum 2 Wireless, which is still on sale at £300.

2 mins read
Hi-Fi Choice
Yearbook 2020

Sculpting with success

CREATE GREEN STATUARY– AND MAKE IT A-MAZE-ING!

2 mins read
Better Homes & Gardens Australia
January 2021

HOUSE SITTER

This cute chair pair will make your kids feel right at home!

2 mins read
Better Homes & Gardens Australia
February 2021

Bon NOËL

This stylish blanket-stitch cushion is a great way to add a festive touch to a sofa or dining chairs

1 min read
WOMAN'S WEEKLY
December 08, 2020

RUSTIC makes

These natural decorations are so quick to make and you can even find some of the materials in your own back garden

2 mins read
WOMAN'S WEEKLY
November 10 - 17, 2020