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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: CNC Gear Hobber
21/07/2020 08:38:06

Put 'stevenson gear hobber' into Google.

Read and digest everything you find (including the back issues of MEW).

Then you will be in a better position to understand the state of the art and crucially the boundaries/limitations of the method. It is this understanding, more than anything else, that will determine the success or failure of your venture.

Look at the electronic leadscrew thread here and on YT. Same basic principle of electronic gears rather than mechanical gears.

Software and encoders are 'industrial Lego' and are easily replaced.

Thread: Wohlhaupter UPA4 Boring and Facing Head Operation
13/07/2020 20:13:53
Posted by John Hinkley on 13/07/2020 19:24:04:

I can't see that there will be massive differences between UPA-3 and -4 models

There is.

That is why the manufacturer produces two manuals only. The first covers UPA1, 2 & 3. The second covers 4, 5, 6 & 7.

11/07/2020 21:23:06

Maybe less brief:

Possibility of help:

Patent images:

11/07/2020 13:29:18

Thread: Any body with experience of CNC PLC Controllers DDCSV 1.1 2.1 3.1 RMHV 2.1
10/07/2020 10:57:28,11598.0.html

Thread: Laser DRO sensor
08/07/2020 16:27:56

Have a search on 'ADNS 9800 arduino' for many ideas and working code.

Thread: Unknown Changewheels
05/07/2020 17:05:04
Posted by Pete Rimmer on 05/07/2020 15:10:10:
They are quite possibly Drummond gears. Quite popular though I never understood why.

Because they are 14DP and this size is difficult to find and difficult to find good quality cutters for making them. Used on Chipmaster, early Colchester (maybe Student & Master), Harrison L5 and derivatives (e.g. 140).

Thread: 63-tooth change wheel for Portass PD5
04/07/2020 21:22:43
Posted by Brian Oldford on 04/07/2020 20:04:34:
...whereas it's 94% for Mod 1.5.

Would you care to reconsider your suggestion of a metric gear specification in the light of the following, courtesy of

"Portass lathes date from the very early 1920s and were first badged as being made in the west of Sheffield "?

For clarity, I have greater than 94% confidence that it is Sheffield, UK.

Thread: Colchester Chipmaster
03/07/2020 18:58:14

Let's start slightly at a tangent: Chipmaster gears are 14DP, 14.5 degree PA, same as a Drummond or Myford M-type or Harrison L5 or 140 (and possibly an older Colchester Student or Master). The six-spline centre detail is discussed here:

There is someone on eBay called you_engraving who will cut these gears in delrin, including the centre detail, for what I consider a very good price.

Standard gears on a Chipmaster are 66t and 33t, giving 2:1 or 1:2 ratio. This does not change when you put the (55t/65t) metric translation gear into the train.

The theory behind it is: the relationship between 1.75mm and 1mm is 7:4 so if you put the location bar in 9, which gives multiples of 1mm pitch, alter the 2:1 (66/33) or 1:2 (33/66) ratios to 7:4 (63/36) or 4:7 (36/63) and flip the other lever between A, B, and C, one of the six possible combinations will give 1.75mm and another will give 3.5mm.

That ends the factual bit. Now everything that follows is potentially incorrect. It is a long time since I did the experiment so details are hazy and there might be a mistake below.

My pencil note in the handbook says 63/36 9C for 1.75mm and 63/36 9B for 3.5mm. What I cannot recall is if this was my initial calculation or is the final, correct result. I do remember that the first time I tried the gears, I did not get the expected pitch. I then either swapped the gears around or moved the A,B,C lever and it eventually worked. So what is written in my book may be correct or incorrect, but there are only six possibilities so it will not take long to find out which two are correct.

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

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