Duncans Metal Pages
VDH - Simple indexing
Last updated: 13 Nov 2018


For this section, the dividing head will be expanded to allow indexing from pre-drilled plates.  The whole situation is still 'chicken and egg', because the micro-attachment is required to drill the plates, which are are required to drill the main gear, etc. etc.

Worm bracket

Casting1 28-Mar-2005: Nothing special about this one although I did manage to screw up machining the cylindrical surface.  I will remind myself in future that 1-5/8" is definitely not 1.5625" and will use the calculator to turn fractions into real numbers...
Casting2 The part machined casting is now in the milling machine to get some of the flat surfaces machined.  The mill will also be used to bore/ream the 3/8" diameter holes in the casting.

Worm and Sleeve

Worm1 03-Apr-2005: This is the method used in the book to get the boss on the sleeve to stand proud of the gear by 0.001".  The cutting tool is brought up to the gear and wound back by 0.001", after which it is retracted and the gear removed to allow the shoulder to be machined to the right size.
Worm2 I'm just using an endmill here to machine the relief for the bolt hole.
Worm3 The worm comes pre-machined which saves quite a bit of setup time.  A centre hole is being made on the end of the bar after which the bar will be mounted between centres.
Worm4 The finished worm ready to have the fit checked.
Worm5 The worm, sleeve, and gear all installed in the worm bracket.  Everything turns smoothly so I'm quite pleased.

Micro worm wheel

Micro1 08-Apr-2005: This arrives in part machined condition, a recess for mounting the plates needs to be machined and a handful of holes to secure the plates.  Here it's being "clocked" to ensure that the recess is machined concentric with the bore.
Micro2 09-Apr-2005: Something of an experiment going on here...  Thomas describes the use of a jig in his book to drill the holes for retaining the plates, but I'm trying an alternative method of using the X/Y wheels on the mill to move from the centre of the bore.
Micro3 It worked out well, although the worm bracket (using the same method) had the hole 0.100" out of place as I forgot to subtract half the width of the centre...  Another hole has been drilled and tapped on the other side, so the plates will have their "12 o'clock" position 180 degrees out from where they would normally have been.

Sector arms

Sector1 09-Apr-2005: A paper template is being used to get the shape right for the sector arms.  The strip of steel supplied with the kit has been cut into two sections, and bolted together through both the handle holes and the centre.  A slitting saw has been used to get the initial shape of the straight edges.
Sector2 Cut to shape, and now in the process of being filed.  It didn't work too well on the circular areas, it would have been an idea to make up some 'filing buttons' from some thicker steel material to get a really nice profile on this part.
Sector3 The 0.950" bore is being machined on the mini-mill with both strips of steel being machined at the same time.  I did initially try this in the lathe but the whole lot moved on the faceplate, so the clamping arrangement I used was not too good...
Sector4 A trial fit on the machine, it does look a bit better than I feared it might.  Next, there are a couple of parts to make up to clamp the sector arms together.


Plunger1 14-May-2005: This is the nut on which the plunger arm sits, would have been easier with a dividing head and it didn't turn out too well.  It will do the job for now, but will eventually have to be re-made.
Plunger2 This has to be the worst bit - machining the silver steel plunger.  I didn't do a very good job of making this, the operation is sticky and there are concentricity errors - another one which will do for now, but will have to be re-made.

Making the 60 hole plate

Plates1 14-May-2005: Some offcuts of cork floor tile are used to hold the plate in, this allows machining to take place right up to the edge of the plate.
Plates2 The centre hole is initially drilled, although the final operation is to bore to size as the hole size must be accurate.  A small chamfer is put on one side of the plate to make it easier to get on the micro worm wheel.
Plates3 Using the centre finder to work out the centre of the plate for drilling the mounting holes - this task needs to be repeated in the X and Y directions a couple of times as the only references we have here are curved ones.
Plates4 We now have three plates, but none of them have any holes in them.  A washer with a 3/32" hole has been clamped on to make a "1 hole plate".
Plates5 This allows 60 divisions to be made, and hence a ring of 60 holes.  Having 60 holes will then allow us to divide into 3600 which is needed to make the 100 graduations on the dial for the micro-adjuster.  Incidentally, the plate being drilled will end up as plate 3, the 60 holes (and micro-adjuster) will allow plates 1 and 2 to be drilled.
Plates6 Plate 3 mounted on the VDH to give any division capability when the micro-adjuster is used, and even without it can divide by 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 30, 36, 40, 45, 48, 50, 60, 72, 75, 80, 90, 100, 120, 144, 150, 180, 200, 225, 240, 300, 360 and some higher numbers.  Maybe I should finished off the sector arms...

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