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Member postings for DC31k

Here is a list of all the postings DC31k has made in our forums. Click on a thread name to jump to the thread.

Thread: Old School Drawing Exercises and 2D CAD
01/07/2020 20:49:10
Posted by SillyOldDuffer on 01/07/2020 17:40:18:

Score double for solving it with only a compass.

If you can solve it using a magnetic thing, surely that deserves considerably more than double.

If you can solve it using a pair of compasses, that also deserves more than double as drawing the straight lines that form the angle bisectors and whose intersection defines the inscribed circle centre is quite challenging using an instrument for drawing circles.

Referring back to the original challenge, I am dubious that any railway would be constructed from simple circular arcs tangent to straight lines. AIUI, transition curves are always necessary (and drawing those, whether manually or on a computer, is somewhat tricky).

Thread: Tungsten carbide for shapers
01/07/2020 18:27:12
Posted by Bo'sun on 01/07/2020 17:08:34:

Isn't that the function of the "clapper box"?

If the clapper box was the complete answer to this issue, why were so many machines (shapers and planers) fitted with tool lifters?

Thread: ISO Container for Workshop
30/06/2020 06:41:52

Immediate thought is 2 x 20 foot might be so much easier. Transportation, equipment for installation, access and space for installation, foundations are all simplified with a smaller unit.

Thread: The fit of tapers
28/06/2020 06:47:12
Posted by pgk pgk on 28/06/2020 06:13:39:

Surely that's down to quality of component fit, durability of material and assuming identical expansion coefficients?

Perhaps we can reframe his question: for any two particular pieces kept at a reasonably steady temperature, if you dismantle and remantle them repeatedly, how close to 'the same' do they go back together? For the sake of clarity, assume they are both steel.

To the OP. Do some experiments yourself. Poke a Morse something into your lathe spindle and zero an indicator on it. Remove it and insert it again. Check indicator reading.

If drawbar-mounted, see if drawbar torque affects results. Analyse effect of percussive seating of item.

Camlock lathe spindles have a taper mounting. I believe the spec. talks about the gap between the back of the chuck and the face of the spindle and mentions a number around 0.001" so you can infer taper-seating repeatability from this.

Look at milling machine spindles: things like classic 7:24 tapers are not face-seating, but more modern ones (possibly HSK, but you need to check) do seat on both the face and the taper, so the specs. and information on these will give you some useful pointers.

Thread: boring head and tools
19/06/2020 21:02:28

Now we have started looking at alternative holders, ChrisB' sketch reminds me of a style of holder I have seen that has two projecting pins that locate in the two vertical holes in the head and somehow puts the cutting edge horizontal.

I have a hazy memory that either the bar itself or a separate insert then fixes to this piece. I wonder if that was aimed at assisting with the balance issues. I cannot remember where I have seen it though.

OK. Found something similar at:

Thread: Gear software
19/06/2020 20:43:06

All good suggestions. Could I add one more thing please?

If he is to go the 'print out' route, try to print a line of a known dimension on the same sheet then check it with a ruler. If you calculate the gear diameter beforehand, you can even use the printout itself.

Some printers have issues with scaling and especially if printing something near to the size of the sheet of paper can do unexpected things. You need to check in both X- and Y-directions until you are confident that printing something 100mm dia. actually comes out on the paper as 10mm diameter.

Thread: boring head and tools
19/06/2020 20:37:13
Posted by Martin Connelly on 19/06/2020 20:27:21:

You could make a tool holder that fits in the side and takes the standard tools to hold them further out but oriented the same as the standard holes in the bottom of the head.

I was just about to suggest the same thing to him. Put 'Wohlhaupter UPA3' into Google and look at images or look at:

Edited By JasonB on 19/06/2020 20:41:31

Thread: Colchester Bantam MK1 Help Needed (Shipping Disaster!)
18/06/2020 09:31:41

See this thread:

and download the comprehensive information provided by Muzzer here:

Study it carefully and you will then know which parts are unique to the metric machine.

Short answer: leadscrew, halfnut, cross-slide screw and nut, both dials, topslide screw and nut are unique. Other parts interchangeable. Bare saddles and fully-populated imperial aprons available on eBay.

Thread: How to cut a tri-lobe bore in a change gear (Schaublin style bore)
16/06/2020 08:46:25

Sorry to post again.

The image at:

is a screen capture of the technical catalogue of which used to be available as a pdf download. I can no longer find it there, and cannot work out how to find it on my old computer, but it is at:

This contains comprehensive info. on the profiles and their geometry and is probably the best you will get without buying the DIN itself. Since it is a manufacturer's catalogue, I do not think there are restrictions on distribution.

If someone with access to Scribd would download it and put it in a more accessible location, I would be very grateful.

16/06/2020 06:50:01
Posted by John Haine on 16/06/2020 06:44:44:

Schaublin were obviously keen to stop people using generic change wheels! I'd be tempted to convert to use round holes like the rest of the world.

I think you rather misunderstand the Swiss psyche. If you read up on the polygon profile, from an enginerding point of view, it is the best thing since sliced bread.

What would you rather cut, something formed of a series of arcs that scales in a simple manner using a simple endmill and some knowledge of geometry or a horrible stub involute spline of 19 teeth that requires a complicated, dedicated and expensive cutter and a dividing head?

16/06/2020 06:41:59

The Schaublin gear centre is not a proprietary item. It is made to a DIN standard (DIN 32711).

Put 'P3 polygon shaft' into Google and enjoy...


For example,

There is nothing complicated about it that requires CNC mapping. It is just three pairs of arcs.

Easily done on a rotary table with a fixture, some travel stops and a cutter of any diameter less than that of the smaller arc.

Edited By DC31k on 16/06/2020 06:44:59

Thread: Where can I get a 3/4" strain relief bush?
15/06/2020 07:01:20
Posted by Andrew Tinsley on 14/06/2020 21:28:12:

There is an Ebay seller doing 5 plastic 3/4" BSP cable glands...

As Emgee says and the eBay picture shows, these are G3/4" thread, or 3/4 BSP. The 'size' number in a BSP thread is the nominal bore (ID) of the pipe so the glands will be both too big and the wrong pitch.

Non-American imperial conduit will have a BS31 imperial conduit thread on it.

Duncan's pitch measurement is explained by the proximity of 1.5mm and 1/16" on the number line. A 16tpi gauge will also fit. Measured over a low number of non-precision threads, it is difficult to determine which one is correct.

14/06/2020 18:40:40
Posted by Andrew Tinsley on 14/06/2020 17:48:29:

Using 3/4" cable gland gave me plenty of hits! Apologies for using up valuable forum space.

Your excitement may be premature. I just did the same search as I often need these and every 3/4" gland that comes up is 3/4-14 NPT.

3/4" BS conduit is 16tpi (see

Try one of these:

When I have bought them, they are always too long at both ends but that's nothing a hacksaw cannot correct.

Edited By DC31k on 14/06/2020 18:41:10

Thread: Wooden Gears
14/06/2020 16:25:24
Posted by JasonB on 14/06/2020 16:06:55:

I'm with Jeff on a good quality birch ply, no problem with short grain causing half the teeth to break off or the gear going oval if its not well seasoned when brought inside a centrally heated environment

Agree in spades. No natural wood of any species can have strong teeth on all four points of the compass. If the teeth at 12 o'clock are parallel with the grain, those at 3 o'clock will be perpendicular to it.

For a really well engineered wooden gear, maybe plies at 30 or 45 degree increments made from birch veneer would provide a good solution. Epoxy resin to glue the plies and a good squeeze in a cider press while it is curing.

Presumably he knows of Mattius Wandel and the site.

Edited By DC31k on 14/06/2020 16:26:33

Thread: 3 Phase in a Model Engineers workshop
14/06/2020 09:27:24
Posted by Anthony Gardner on 14/06/2020 00:02:56:

...What I really need is a wiring diagram

It may be worth a look through the stuff here if you did not already know of it:

Edited By DC31k on 14/06/2020 09:27:37

Thread: Non standard taps - what are they ?
03/06/2020 18:35:20

03/06/2020 17:28:30

I think the L'H'Z is indisputable and that your assessment is correct.

With regard to the thread angle, you might take a very close up shot, very square, and put into your album.

It can then be imported into a CAD program and lines overlaid to estimate thread angle (modern day poor man's optical comparator).

Thread: garden tractor wheel lug nuts and studs
02/06/2020 09:24:26

Remove all old studs and nuts behind hub.

Throw in skip.

Drill out all threads in hub with 1/2" drill.

Buy 1/2" UNF bolts and proper chamfered wheelnuts.



Optional: tack weld bolt heads so only one spanner needed.

Thread: Arduino/Stepper Motor Dividing Head
02/06/2020 07:12:06
Posted by Bazyle on 02/06/2020 00:02:14:

...I think it would be more in keeping with our type of machines to have simple switches rather than peering at little screens.

The issue with alternative user interfaces is the number on inputs required on the microcontroller. Three potentiometers as you suggest need three analogue inputs.

You could use a 0-9 thumbwheel switch (like on the electronic hobber) but each one needs four digital inputs (so 12 total for 0-999).

You could use a manual pulse generator (rotary encoder) with a click-to-select (three inputs). That would be great for later use as a jogging or continuous rotation device and most closely approximates a traditional handwheel on a rotary table. You could electronically build in the table stops so you cannot go past a set angle, good for putting a radius on the end of a part.

The 4 x 4 matrix keyboard works well with the resources of the chosen chip and its ubiquity means the component is very cheap. You could buy three or four spares for the cost of some of the other ideas.

As a challenge, perhaps build one with (binary) knife switches and Nixie tubes.

Thread: Sandvik Torx Plus Size
31/05/2020 14:13:04

Put the Sandvik part number into Google and you find lots of information on the item, including many photos which tell you it is a 6 IP (igloo postman) Torx plus item. Again, Mr Google will give you many other alternative sources for 6IP torx plus.

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