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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: 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.

06/09/2020 19:41:02
Posted by Michael Gilligan on 06/09/2020 18:14:08:

.... being available from four Hall sensors and one rotating magnet.

The crux of it seems to be on page 10 of the datasheet.

The Hall sensors give a continually varying analogue output.

This is amplified, then goes through an A to D converter and then there is an inbuilt CORDIC that calculates the angular position.

I guess that for every 'tick' of the encoder, there must be a unique set of four values from the Hall sensors.

The headline cost of $10 seems good but how much value does the time to make the PVC housing, the magnet and PCB consume? And compare that to a 1024ppr encoder available from a source, which will be moderated if mentioned.

Thread: Welder buy
04/09/2020 08:14:24
Posted by Nicholas Farr on 03/09/2020 23:33:44:

Hi Stevegtr, you may wish to peruse this Argoshield

That is a good link and perusal of it may help to dispel some of the misinformation above your post.

Perhaps its parent link, BOC's guide to shielding gases in general, might be even more instructive:

Thread: All things Beaver Mill
04/09/2020 08:05:21
Posted by Lex Davis on 04/09/2020 04:36:26:

I think that the spring is either in the Quill casting or the feed gearbox housing on the left, it is not on the handle side of the head.

It is on the handle side of the head.

Look here:

post by Paul Major 09/02/14 23:03:40, sixth photo of post.

The spring is inside the left hand gear.

Thread: Harrison M300 - am I going crazy?
02/09/2020 11:28:51

It is quite rare for the carriage handwheel to be graduated.

Some high end machines and clever manufacturers do it but it is not the norm.

The reason is that the the apron moves due to the action of a pinion on a rack fixed to the bed. For the wheel to have sensible graduations, the rack would have to be of circular pitch specification (i.e. its teeth some easy rational number of chosen unit apart).

For length measurement without DRO, a (micrometer) bed stop and spacing pieces can help. I believe Harold Hall published something on this, so check his website or early back issues.

Another option, liked by the Myford brigade, is a graduated wheel on the end of the leadscrew and use that with the half nuts engaged.

Edited By DC31k on 02/09/2020 11:30:22

Thread: Harrison M300 Apron
02/09/2020 11:19:26

Go into back garden.

Cut stick from hedge.

Whittle it down until it is the same diameter as the shaft you are removing.

Insert from opposite end to which you are removing shaft.

Thread: UK availability of 1/8" Dia shank End mill/Slot drills
31/08/2020 17:50:52

What you are looking for is difficult to find in this country. If you can relax one or both of 1/8" and HSS, you may have more success.

3mm shank carbide is the nearest-easily-available over here.

One specific size, 1/8" dia. 1/8" shank, is not too difficult to find, but smaller sizes are not at all common.

Peatol sell small imperial HSS cutters but they are 3/16" shank.

If you have to have what you want, and have any American friends, MSC sell them:

Thread: Change to the Code of Conduct
27/08/2020 07:48:55
Posted by JasonB on 27/08/2020 07:21:02:


In the interests of properly following your own CoC, should you not blank out the logo on the drinks-can-for-scale as it may imply endorsement of a non-forum-funder's product?

Thread: Chamfer Block
25/08/2020 19:26:26

1/4" woodworking router and a bearing-guided bit. Sleeve bearing OD to adjust width; use router's height adjustment for depth.

Thread: Bantam Gamet Dials
24/08/2020 19:48:43

Thread: Harrison L5 taper turning attachment
22/08/2020 16:19:26

There is a large number of Harrison manuals at the 'usinages' site:

(this link may not be the correct page - they are listed in alphabetical order and Harrison starts on page 3 of 8 on my browser).

I do not know if the L5 one has the TT attachment in it, but you could also try the L6 and 140 one.

I can only speak for Colchester TT attachments and they do use a different leadscrew (longer and splined at the handle end). Can you partly dismantle your own lathe and see if they are identical or different to what you have?

Thread: Plain lathe gearing for 'bastard' metric thread
21/08/2020 07:43:47
Posted by not done it yet on 21/08/2020 07:37:52:

Back gear will make no difference to the lead screw pitch. Lead screw turns from the spindle. Thread pitch will be the same whether in normal drive or back gear.

In general you are correct. But for a Little John, I do not think so.

Kindly go and look at the manual mentioned above and assess the situation.

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