Duncans Metal Pages
Work head
Last updated: 13 Nov 2018


The Work Head

The work head is the movable device which holds the toolbit to or tool to be ground.

300: Workhead base

Base 29-Apr-06: First task is to make the 9/16" hole for the split cotter.  This must be done first as the cotter will be bored in situ.
Drill Drilling out the hole to 15/16".  Note that the cotter is bolted in place so it will also be drilled/bored.
Boring Taking out to final size with a between-centres boring bar.  The lathe is too old and worn to risk putting the workhead base in the chuck and boring it that way.
Spigot The workhead base has been clamped to the front bar so that the spigot can be machined.  Enough grip is provided by the split cotter to prevent slippage.
Graduating Graduating the scale in degrees.  This job is so much easier when you have the right tool.
Stamping And stamping the numbers on.  The strange arrangement here is the Universal Pillar Tool, or part of it, mounted in a V block.
Milling Here the workhead base is being milled to take the pivot bolt which attaches the tilting bracket.  This is very different to the mounting shown in the book and is a result of recent changes to the drawings.
Tapping The final task is to drill and tap the holes for the dust cover.

301: Rocking lever

Skim 30-Apr-06: The rocking lever is getting a very slight skim so it will sit flat on the backplate (it won't clear the bed of the lathe when held in the 4 jaw chuck).
Boring Here the hole in the centre is being cleaned up so that some measurements can be taken to work out the correct position of the cotter etc.
Complete Rocking lever and cotter with handle.  The other side has three M3 tapped holes to take the dust guard.  That's all I can do on this for now as I need to get hold of a 5/16 x 32TPI tap for the end of the lever.

302: Tilting bracket

Lining up 01-May-06: Lining everything up to drill the first hole and bore it true.  Everything else is going to be measured from the centre of the mounting hole and the front face.
Taper After drilling and facing the front, the boss at the rear is being faced and the 20 degree taper machined.  Both the front and back tapers, and the matching tapers on the shaft and split washer were done at the same time so at least they will match.
Finger Back to the front and the final sizing up of both the thickness and the tapered part of the end of the finger.
Grinding A small amount of material had to be ground out of the back of the casting to get a reasonable amount of swing.
Part complete It looks OK and seems to fit together without any binding or gaps.  The redesign of the mounting for the tilting bracket means that the bracket can be tightened without changing position.
Drilling The next step is to make a 9/16" hole for the cotter - this has to go in before the 0.500" hole is machined.
Faceplate 04-May-06: This is the faceplate setup to do the 0.500" hole.  On this setting the outer edge of the tilting bracket (scale marker) can also be machined.
Outside Machining the stop lug - the centre is giving some support for the interrupted cut.  The boss in the centre has already been cleaned up to a diameter of 1.000".
Reaming The centre has been drilled, bored true and finally reamed to size.
Milling All the turning work is done for now - the work has been left on the faceplate as it's easier to mill the edges square.

303/319/320: Rotating base

Since the original Chaddock design for the Mk I and Mk II, the rotating base is no longer made from cast steel.  The bulk of the base is a slice of 3-1/8" mild steel bar supplemented with a square section for the boss and a 1" dia length of mild steel bar for the spigot.

Base 07-May-06: The spigot has been machined and loctited into the rotating base.  The overall dimensions have been machined and a 3/16" wide x 5/16" deep groove machined in the side.  Still quite a bit of work to do on this one which will necessitate a special tool to cut the recess in the side of the base.  Need some more ball handles too - I'm 2 handles short for the picture...
Dressing 08-May-06: Dressing one of the wheels supplied with the Quorn kit to make up the special cutting tool for the recesses in the rotating base.  Trying to make the cutting tool made me realise that it would have been 100 times easier if the Quorn was already built...
Graduating 14-May-06: The recesses are now cut and the table is being graduated round 270 degrees.  This is a slow job with no room for mistakes.

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Warning: These pages consist of images and descriptions of equipment which can reach high temperatures creating hazardous and potentially dangerous situations.  These pages should not be taken as a step by step guide on how to construct any items or carry out any particular procedure, nor should any references to safety contained herein be taken to guarantee safety in all situations.