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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: Turning and boring almost any* shape. *within reason
23/10/2020 08:27:59

A couple of questions:

Right now, it is effectively converting a closed shape into a series of (X, A) coordinate values, where I guess the A- increment can be arbitrarily small.

How easy would it be to make it turn 90 degrees and produce (Z, A) values? I am thinking of a face cam, as used in Brierley and Rush drill grinders.

Second, does it have any built-in idiot-proofing? If I sent it a circular hole with a keyway cut out, would it tell me to go away and pound sand due to the discontinuity in the profile? As a corollary to this, what is the most acute internal angle with which it is comfortable (e.g. an equilateral triangle-shaped bore)?


Thread: Measuring pitch diameter of clock wheel
10/10/2020 19:49:22

Let me start by saying I know nothing about cycloidal gears.

However, I have some familiarity with involute gears. In the involute system, pitch diameter is never measured directly. It is a number that is derived from other measurements of the gear (you measure the outside diameter of the gear and count the number of teeth - the pitch diameter falls out of manipulating these two numbers).

If you are measuring from the bottom of the tooth space, you have a good chance of being incorrect as the dedendum may incorporate clearance.

This page seems to me, a complete beginner on cycloidal gears, as good a reference as any and contains a number of subsequent references:

Thread: FC3 'disposable' cutters in ER Collet?
10/10/2020 11:08:31
Posted by Ian P on 09/10/2020 20:53:45:

Some of my ER25 collets (a mixture of cheap Asian and some quality European ones) have bores like your example but there does not seem to be a particular diameter value where the bore changes between the two types....

The diameter at which the collet is relieved also varies with the ER-series number.

For as close to gospel as you might easily obtain, have a look at Regofix' site as I believe they have dimensioned drawings.

For slimline, have you considered changing the closing nut? There are generally two types: the one with spanner flats or hex. and the type with a pronged spanner.

You could also buy an ER11 or 16 chuck on a straight shank and hold it in your ER25 chuck for reduced girth but increased length.

Thread: How do I disassemble Vickers dual metric/imperial dial?
07/10/2020 07:46:42
Posted by Oily Rag on 07/10/2020 00:03:05:

...the clever bit from memory was that they were identical tooth wheels but of slightly differing diametral pitch so giving a differential gearing.

I think your memory is perhaps deceiving you.

If the tooth wheels are identical, how is the imperial to metric conversion done?

In the Gamet ones, fitted to Colchester lathes, the two internal gears have different tooth counts (125 and 127), but cut on the same pitch circle so they mesh with a common planet pinion gear.

FWIW, the Gamet patents are available online, with patent-style exploded diagrams so this may give some insight into how the OP's one could work.

Also FWIW, it seems that Vickers offered these dials for Bridgeport mills, so some searching around this area might assist.


Thread: Horizontal Milling Attachments
05/10/2020 18:52:42
Posted by Nigel McBurney 1 on 05/10/2020 18:07:07:

...also attachments such as these are not that rigid.

Could you please expand a little on this statement.

At one end it is clamped to the ram dovetails so the ram does the same job as the overarm on a horizontal machine; at the other it has a death grip on a large diameter quill.

05/10/2020 14:32:48

A picture or a link to a picture of a Warco Economy would be useful.

All I could find was something that said it is the same machine as a ZX25.

A link to the Chronos offering would also help. Is it this: ?

Rotagrip will also sell one so it is worth looking for info., prices and pictures there also. Somewhere on their site, they have the full Vertex catalogue for download.

The attachment is designed for Bridgeport-style turret mills with a ram. You extend the ram and clamp the arbor support to the dovetails on the underside of the ram.

I think you may face considerable challenges in making this device work on your machine.

Thread: Martin Cleeve Swing Clear Retracting Toolholder
03/10/2020 21:35:20
Posted by Michael Gilligan on 03/10/2020 20:45:49:

Try here, Roger ... I re-posted the link earlier today



This is another old post of yours linking to his patent:

Thread: ER 40 Milling nose
26/09/2020 18:47:47

Have you considered how you will hold Morse tooling in the new spindle arrangement, particularly drill bits?

I have never drawn it up, but what size Morse taper would fit within the confines of the ER40 collet cavity?

Thread: Brierley ZB21
22/09/2020 07:32:40

There is also a ZB25 manual available at a price much more commensurate with its quality on eBay. The seller is fazerblazer and full seller contact details can be seen without logging in - Premier Machine Tools in Nottingham.

As for the cams, they are fairly easy to duplicate if you can find someone who has one to copy. Just put on a rotary table and map the rise every couple of degrees of rotation.

Find someone with a CNC machine with an A-axis and a touch probe and the mapping could be done almost automatically.

21/09/2020 21:56:18

AFAIK, the 21, 25 and 32 in the model name referred to the biggest tool that would fit through the spindle. In most other respects, the machines were the same, so a manual for any will do.

Tony at sells badly-photocopied incomplete manuals with thumbprints and distorted pages but on very good heavyweight paper.

You could look at this:

or look here:

Thread: Stuck SDS drill bit
20/09/2020 21:01:44

The diagram in the article to which Michael links is very useful:


The (normally rubber-like) end cap, not numbered in the diagram, but cut through by the upper and lower II section arrows, should just prise off. This will allow access to the collar that retains the balls.

As he says, a good clean and lubricate should solve your problem and endcap removal will allow you to check that the collar is retracting properly. The balls have to come out from the outside or they would fall into the chuck every time you remove the bit.

I have only seen it once before, and I hope it is not the issue here, but I once had an SDS drill bit that was improperly heat treated such that the hammering action mushroomed the end of it within the chuck. This made it very difficult to remove.

Thread: Type identification of a endmill tool holder (Hauser)
14/09/2020 14:37:31
Posted by Alexander Smith 1 on 14/09/2020 13:11:58:

...Schaublin P9 collet ...then hen's teeth are common in comparison

M. Georges Savoie must be feeding his hens something special then:

Thread: Strength of Beams
11/09/2020 08:40:04

I am glad that people are slowly coming to the conclusion that the question is unanswerable as posed.

For a given area of material, anything other than a regular shape (circle, equilateral triangle, square, etc.) can be made to have an almost infinite second moment of area.

Take the I-beam, for example. I read that gold can be hammered to 4 millionths of an inch thick. So use 1% of the material to make a web of this thickness and divide the rest of the material between the two flanges.

Totally impractical as a real-world object but fits the question very well.

A little thought on the first example given in the original post would show the form of the question presents difficulties.

You do not need to be Superman to deflect a rectangle on edge. Take a ruler and try it. Press not too hard and it will buckle out of the plane of the applied load. And that is the problem every real-world engineer has to face. Pushing on things in one way induces forces and effects in another.

A more simple example is compression. Intuitively, why would we expect a structure to behave much differently when we squash it as opposed to when we pull it apart? But it does. And this has been known since Euler's time.

So when we bend something, we have both tension and compression (and anyone who has ever cut a branch of a tree will know this) and the member subject to bending will inherit some of its behaviour from both of these.

11/09/2020 08:17:46
Posted by Sam Longley 1 on 11/09/2020 07:54:51:
Just one point-- They are not normally circular holes but hexagonal. That gives flat surfaces for the weld at the new meeting point.

It is horses for courses.

The traditional ones give long spans for efficient material use, good for single-storey warehouses and industrial buildings.

However, when it comes to multi-floor construction (office space), the circular ones are much more popular. They allow the myriad of building services to pass through the holes in the web rather than under the bottom flange. This means the overall structural depth can be reduced, allowing more than one extra floor (with its per square foot rent).

Where rectangular holes are needed, they can be incorporated, usually with stiffener ribs above and below the opening.

The march of technology has also had an influence. Traditional castellated beams were cut out of pre-existing rolled sections. Most modern cellular beams are cut from three plates and welded together. This gives you a lot more choice on both flange thicknesses and widths and also web height. CNC profiling and automatic welders facilitate this.

11/09/2020 08:05:50
Posted by duncan webster on 11/09/2020 00:02:28:

These ladies were known as 'computers'

I thoroughly endorse your recommendation of Gordon's books.

Not only do they deal with traditional engineering materials of concrete and steel, but also give very good accounts of building in stone, as well as interesting discussion of nature's own building materials, wood, bone and sinew.

On the 'computers' issue, applied to the US space program, the book 'Hidden Figures' is very good.

Thread: Change gear alternative material
10/09/2020 19:52:13

If you do go the Tufnol route, be sure you understand the different fauna under which it is sold (e.g whale, carp, etc.). For gears, you will need the type that is made like plywood, not the type that is made like a Swiss roll. There has been discussion here on this issue relating to Myford tumbler gears.

I do not know if it allowed now, so read this before it is moderated: there is a UK-based eBay seller with the username of you_engraving who makes various change gears in delrin at very reasonable prices. With Colchester gears, it is often the centre spline that is more difficult to make than the tooth spaces.

Thread: Left Hand Milling Cutter
09/09/2020 15:31:18

Would it be possible to do something to the mandrel to increase its holding force?

There are lots of solutions to stop Myford chucks unscrewing when the lathe is used in reverse.

Schaublin W-series spindles use a split clamp to secure the threaded-on chuck.

Look at how the track rod ends are clamped on your car.

Thread: Boring bars
09/09/2020 12:08:13
Posted by Ronald Morrison on 09/09/2020 11:56:09:

Hardened steel is more rigid than mild steel but solid carbide is even stiffer.

The rigidity of the bar is governed by two properties: the second moment of area (I-value), a geometric property, and the Young's modulus (E-value), a material property.

So which of these change after hardening please?

Thread: Split collet steel recommendation
09/09/2020 07:41:03
Posted by Mark Rand on 08/09/2020 21:03:08:

... that is about 100 feet/second!

The only time I have managed to hacksaw at this speed is as a passenger in a van on the motorway.

Thread: DIY Rotary Quadrature Encoder
07/09/2020 07:50:42

For the purposes of understanding its operation, I wonder whether it is helpful to draw the analogy between this device and some linear scales (Heidenhain and possibly Newall) that use a (n analogue) sinusoidal output instead of a quadrature pulse. The scales will resolve 1 um.

One big advantage of this sensor that struck me overnight is that it can be made into something with a very small length. If we have the end of the shaft as datum, all you need is the magnet thickness, the air gap, the chip height and PCB thickness.

I was dreaming of something that would go under my compound slide and feed into the DRO in the same way that a knee-quill adder box does on a mill.

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