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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: What is "Mathematics"
30/05/2022 18:52:30
Posted by Nigel Graham 2 on 29/05/2022 22:38:56:

Sometimes I think rather waspishly that a "pure mathematician" is one for whom the best mathematics has no physical, let alone practical, application at all; but are there in fact any branches of maths like that?

It is a good question, but one aspect it glosses over is the issue of time: there are innumerable branches of pure mathematics which at the time they were first written down had no practical application, but in the future have become very important. So, if you study the history of pure mathematics, you would not want to bet on anything never having a practical application.

As just a small example, consider quaternions (4-dimensional numbers). They were written down by the Irish mathematician Hamilton and absolutely derided by some of his contemporaries (e.g. [Lord] Kelvin). Yet in computer graphics today they are very useful.


On a slightly different note, the relationship of mathematics to societal norms is interesting to study - in earlier days, the concept of infinity was almost verboten as discussion of it by mortals was considered trespassing on something belonging only to the divine.

Thread: Again - another whatsit
28/05/2022 20:00:53
Posted by Ian P on 28/05/2022 11:57:24:

...the single visible hex--headed bolt looks to be the only fastening holding the narrowest ends of the slotted plates to the part carrying the handle, so the bolt would need to be very tight to prevent rotation.

What is to say that there should be no rotation about the bolt? Maybe being free-swinging about that point is an intended feature. Consider how it would feel in the hand if that joint were rigid - very unbalanced. With a free joint, holding it with the handgrip horizontal, the main body would hang reasonably vertically.

There is something hidden behind the ball of the handle, possibly a fine adjust mechanism (like on a pair of trammels or vernier caliper).

The bolts in the slots (small, horizontal holding the indicator and large vertical) might have square shanks on them stopping rotation of the parts they retain.

There is a great deal more left-right adjustment on the shiney-holding arm than on the indicator holding part.

28/05/2022 19:50:10
Posted by SillyOldDuffer on 28/05/2022 09:58:52:

Might be for accurately positioning a large diameter job on a giant lathe to reduce run-out?

Your sketch appears to require a plunge-type indicator. The one in the photo looks like a lever-type indicator.

The indicator is a little unusual in that it has a rectangular body, but the dial is on the larger side of the body rather the more usual small side.

If looked at from the right hand side, I am trying to work out if there would need to be some care taken so the two shiney bits and the indicator tip form an isosceles triangle.

Maybe someone can think this through a little and see if that is the case - perhaps if it used as a comparator against a master, the relationship does not matter.

Thread: 3 way toolpost
27/05/2022 09:02:13

It's a three way toolpost, so what is more natural than one thread per way?

Thread: Looking for uncommon propane tank fitting
24/05/2022 15:33:57
Posted by JasonB on 24/05/2022 15:16:53:

in stock here

That is 50% more expensive than the one he considers to have a non-sensible price.

What it does do is to provide the Sievert part number, 720740. I believe CuP alloys are a Sievert dealer.

24/05/2022 15:03:53
Posted by Bill Phinn on 24/05/2022 14:09:58:

So, DC31K, in addition to the POL female x 1/2" BSP female adaptor in your link I'd need a 1/2" BSP male (presumably RH) x 3/8" BSP female LH adaptor

I do not know. In neither your original post nor in the item to which you linked is there any mention of a left-hand BSP requirement.

We might be able to infer that the notches in the LS Engineers one denotes the LH feature of the POL thread, but if you are now saying the BSP thread needs to be LH, it is back to square one.

Thread: Looks a lot like plastic
24/05/2022 07:28:14

Is the white part not an insulator or thermal break so the heat does not transfer down the tube supplying the gas?

I was under the impression that in a properly functioning burner, the flame does not touch the orifice from which it emerges, so the heat transfer to the aluminium part is through the surrounding atmosphere. In that respect the aluminium is a good choice as its thermal mass, high surface area and good conductivity will keep it cool. Short of copper (not easily found in box section), what would be better?

Thread: Looking for uncommon propane tank fitting
24/05/2022 07:18:28
Posted by Michael Gilligan on 24/05/2022 06:34:36:

I think the non-POL female thread in that is 21.8mm left hand, so not what he wants.

He could try this:

and a 1/2" to 3/8" George Bush, the 1/2" to 1/4" one being of course George Bush Jr.

Thread: What are SILVER STREAK Wedges?
22/05/2022 11:28:21

22/05/2022 09:43:49

HSS: cutting something. Balanced: high speed rotation. Guess: spindle moulder.

Thread: Fix my (new) Lathe
20/05/2022 17:26:37
Posted by not done it yet on 20/05/2022 17:02:55:

JB’s seems OK with about ten times the clearance you have measured.

I wonder if the OP has his numbers mixed up. Do they make a 0.01mm feeler gauge? That is less than half a thou' in old money.

Thread: Operators manual
15/05/2022 16:06:37

It looks as if your machine belongs to the extended family of far-East machines such as those sold by Warco, Armadeal, Chester, Arc, Axminster, etc. They are also sold in the US by Jet and Grizzly.

In the US, they will be described as 'diameter of swing' x 'distance between centres', both in inches, so the equivalent of yours would be 9 x 24. The US manuals tend to be very comprehensive. So, rather than looking for a manual with the correct title, find a picture of a machine that looks identical and use its manual.

I think this is the machine in question, so someine who recognises it could tell you the UK- or US-equivalent:

Thread: Ball bearing cups for bicycle hubs ?
10/05/2022 07:18:01

Mike makes a very good point above about the contact of the balls with the cup. If there are two lines of contact, one generally on the flat part, the other generally on the side, that means the dimension and finish of the curved part of it does not matter at all as long as it is of no lesser radius than the balls.

Consider the other part that threads onto the spindle and contacts the balls. Have a look at its contact patch. Maybe the balls themselves are simply in three point contact (unequal - 90, 135, 135 degrees), all that is needed to resist combined axial and radial load.

Find an off the shelf one, paint it up with marking blue and operate it a few revolutions to see what touches what.

Thread: Colchester Triumph 2000 - Topslide Leadscrew Threadform
08/05/2022 11:40:15
Posted by Colin Heseltine on 08/05/2022 09:31:53:

Does not make it easy.

It made it very easy (and thus more economic) for Messers Box, Den and Col.

No need to keep two sizes of leadscrew blank in stock. No need for inventory management so they did not get mixed up. Similarly for the cutting tools. Simllarly for the workholding devices. Agile manfacturing ability - at the flip of a lever on the machine either language leadscrew is produced. No need to make a batch of 20 and then call the toolsetter to alter the machine.

In prodcution manufacturing, cost is an issue. Why do so many French cars have M7 threads? Because M6 is too small to work and M8 in million-volume is too costly.

It would be interesting to look at some of the European manufacturers' machines that were available in imperial form and see what they did (e.g Deckel & Aciera mills, Schaublin lathes). Also interesting would be to look at current far-East machines and see what they do - they sell into both SI and Inch markets.

08/05/2022 07:28:21

Make it 29 1/2 degrees and then calculate the maximum possible error in both cases. Chew on that number a bit in the context of every other error and uncertainty in the making process, including the wear.

Thread: Thread gears for Warco GH-1322 lathe.
05/05/2022 18:11:13
Posted by Howard Lewis on 05/05/2022 11:53:15:

Reverting to the original query.

In a very early reply to this thread, Jason posted a link to the manual for the machine. I am quite sure the OP can and will read it. It would be possible to save yourself an enormous amount of wasted typing if you read the same manual. Among other things, asking other people what the manual says would not be required.

As well as full details of the gearbox and change gear settings and physical arrangement, the posted manual contains details of the leadscrew indicator fitted to the machine, from which the pitch of the leadscrew can be calculated. Given also that the lathe is in a school, I do not believe the class will have a great deal of interest in imperial threads.

04/05/2022 18:53:07

The spirit of John Stevenson came upon me and reminded me what he did with his Bantam: he removed the change gears altogether and replaced with a toothed belt and pulleys.

On the machine in this thread, you would just have to measure the pulley centres and choose a combination of belt size and tooth count to suit that distance.

04/05/2022 13:14:55
Posted by Thor 🇳🇴 on 04/05/2022 10:33:23:

The 42-127-120-42 combination of gears you give in your first post is for metric threading...

If the standard chart on the machine gives the feeds in mm per revolution, that suggests to me that it a native metric machine.

Why would you need a 127 gear to do metric threads on a metric machine?

Looking in the manual that Jason linked to, the 127 gear is shown behind the 120 gear when metric threading, so is not in mesh with anything. In addition, the 120 gear is only an idler between the two 42t gears, so the ratio is 1:1.

So, if the OP only wants to cut metric threads, he absolutely will not need the four gears above. Depending on the physical layout of the lathe and adjustment possible on the banjo, it may be possible to buy just a single 32t gear and use the 100t as an idler. If not, a pair of gears of identical but larger tooth count would do.

Edit: look for a piece of software called GearDXF if you want to go the 3DP route.

Edited By DC31k on 04/05/2022 13:15:59

Thread: Reilang Oil Can Nozzle Thread
01/05/2022 16:05:23
Posted by KWIL on 01/05/2022 12:29:36:

Thread OD 4.4mm dia thread, 0.8mm pitch (using pitch guage) Hex on spout 6mm A/F

Would you care to speculate whether the tube has enough thickness of body to enable its internal thread to be enlarged to M5?

The male thread on the nozzle would be easy to enlarge.

01/05/2022 08:01:02

The smallest BSP thread is 1/16" with an OD of over 7mm, so it might not be in that series.

There is a picture of spare parts for one model of can here:

Please confirm it is the part bottom left of the picture.

Have you any known bolts that you can use as a thread gauge to judge the pitch? How have you determined it is coarser than 0.75mm pitch? What is the actual OD of the thread?

Cut the end off the delivery tube at the bottom of the internal threads and thread it a known, suitable internal thread (you are extending it, so just extend it 10mm more). Turn down the nozzle, soft solder on a plain sleeve and apply male threads to match the new internal ones.

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