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Member postings for JA

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

Thread: Springbok completed
01/01/2022 09:40:14

Simon

Looks great, very fine. I trust it will run well and reliably.

Please excuse me asking, how long did it take you?

JA

Thread: How do you find someones 'profile'?
31/12/2021 13:07:22

Not posted

JA

Edited By JA on 31/12/2021 13:11:04

Thread: Myford Lathe Service
27/12/2021 19:49:55

Roger

Do you still have the old single phase motor? If so, you could fit it to the lathe and get used to using the machine. Inverters and infinitely variable speeds are just nice to have. After all almost no lathe had such a drive until recently and many good new lathes are sold with just a single phase motor, belts and pulleys.

JA

Thread: Endless Repeats
26/12/2021 14:53:37

Endless TV repeats at Christmas, what do you expect. What I miss are the Marx Brothers films.

As for the news, any news, it is always biased.

JA

Edit: Question mark removed.

Edited By JA on 26/12/2021 14:55:05

Thread: A Merry Christmas to All
25/12/2021 09:02:33

Happy Christmas to one and all.

Eat the sprouts, drink the wine but stay away from the minced pies. They won' t do you any good.

JA

Thread: DRO's and mental agility
23/12/2021 11:57:05
Posted by Jon Lawes on 23/12/2021 08:50:53:

The tip I got from this website with regards to measurements on the lathe is how much easier it is with a left handed digital caliper; diameters can be checked far more easily even though I am right handed!

Left handed digital calipers??

I have a feeling I've missed a "trick" here.

JA

22/12/2021 18:02:46

I have Newall DROs on my Myford lathe and vertical mill machine. Both are set to inches. I fitted the milling machine with a three axis DRO after using the DRO on the lathe. On the lathe it is nice to have but I find all three axises on the milling machine absolutely invaluable.

My new small lathe, metric, is not fitted with a DRO and I have not missed using one. After a life time at work using both imperial and metric units I will happily use either (or both, bad practice) without problems.

JA

Thread: Maths problem just for fun
20/12/2021 17:34:41

Goat in field - my method:

O is centre of paddock

AP is the fence with P as the tether point.

goat in field.jpg

I halfed the "model".

The area of a ribbon of grass is R x T x OPA (angle in radians). The first ribbon starts when R = T/2 (very close to P) and its area is the start of the total area. The next ribbon has R = R (previous) + T and the resulting area is added to the previous total area. And so on.

Obviously there is an error because the end of the ribbon does not match the fence. However if T is small this is small. Some will recognise this as integral calculus.

This only calculates a general area, it does not know when to stop. However if a spreadsheet is used (the obvious way of doing the above) you just run the sheet until the required area is reached.

The angle OPA can be easily obtained from trigonometry, the triangle OPA is isosceles and can be split in two to give right angled triangles. Therefore Cos(OPA) = AP / (2 x OP) = length of tether / diameter of paddock. This is very easily incorporated in to the spreadsheet.

Quite enough of this.

I wish everyone a Happy Christmas and just hope next year is better than the last two.

JA

18/12/2021 15:34:17

Martin

I remember trying to solve the problem about 45 years. It was a Christmas problem set at work. Using nasty integral calculus I did get an answer. It took hours and many sheets of paper

With a spread sheet it is not difficult, no Pythagoras and just a right angled triangle (Cosine). I made it 28 yards and 35 inches but that is approximate because of the method. On the computer it takes less than 10 minutes of setting up the spread sheet.

JA

Thread: The New Normal Christmas?
18/12/2021 12:39:27

Lateral flow tests can be ordered on the internet from a government web site:

https://www.gov.uk/order-coronavirus-rapid-lateral-flow-tests

The pack of seven is promptly delivered by the GPO (unlike most of the post, not a criticism). The one I received was different to the ones I got from by local pharmacy. I wonder why pharmacies were drop out of, or left, the system.

JA

Thread: Maths problem just for fun
17/12/2021 15:12:00

I had another attempt, this time using coordinate geometry. The manipulation of the numbers is easier but you will alway end up with a quartic equation. These are very difficult to solve except by numerical methods.

I really can't resist setting a simple problem: Farmer Giles has a fenced, grass circular paddock, 50 yards in diameter. He wants to tether his goat to the fence so that it eats half the grass. How long should the tether be? He does not really care about the RSPCA so the tether is attached to the goat's mouth.

17/12/2021 12:02:23

My solution to the ladder problem:ladder 1ladder 2

Enough said.

JA

16/12/2021 20:07:50

I have just looked at the link. It is the same two solutions turned through ninety degrees.

It would be interesting see if complex numbers would make the solving easier. Too old for that now.

JA

16/12/2021 18:25:50

Agreed.

Wedge sum

I have met Buffer's problem before and it was deemed un-solvable. I have just written the equations down: three simulanteous quadratics. My evening meal calls. I am sure someone will solve it by the time I next look at the website.

JA

Thread: What do you use for heat treatment?
12/12/2021 12:17:16

I have considered buying an oven/kiln for many years but I don't know where I would put it in the workshop.

I do use my kitchen oven for tempering. For blacking very small steel nuts and screws a ring on the kitchen gas hob is used.

Otherwise I use a propane torch which is not ideal. I have case hardened successfully with it.

JA

Edited By JA on 12/12/2021 12:18:53

Thread: Silver solder resist
06/12/2021 23:03:10

Yes, yes. It works. If you have doubts use more than one coat.

After Dave's reply.

JA

Thread: Centering Microscope
06/12/2021 14:48:10

I used a standard Whitworth form microscope thread, probably RMS, since the design I copied used it. The thread is very strange, 51/64" x 36tpi. I did not even try to find taps and dies but screw cut all the threads, external and internal, with a single point tool. This was not difficult since only brass and good quality aluminium was used. However before cutting the threads it is wise to make a couple of thread gauges, particularly for the internal threads, from steel.

JA

Edited By JA on 06/12/2021 14:49:15

Thread: jury service
01/12/2021 19:53:15

I have been called and done jury service twice. Both times I was told I was not required before the full term of service. Not one of the cases I sat on was at all interesting. I did get off a three week messing murder case, along with two other potential jurers, by saying that my employer would be very unimpressed.

I believe every grown person should experience it. I found it incredibly interesting. I really did not know that people lived boring, disfunctional lives with some very strange ideas (that includes some of the jurers).

JA

Thread: Preferred slot for mounting a rear toolpost on the Myford S7 Cross slide
28/11/2021 11:37:49

I don't like the idea of a single bolt fixing. I think it would be done up quite tight to prevent the post turning during use. I am very aware of this on my set-up.

Is the base of your tool post and surface of the cross slide truely flat? If not the slide would distort when the tool post bolt is tightened. The fact that the problem occurs when mounted in the end slot, where the slide is less rigid, would suggest this is happening.

My set-up, shown, is left on the lathe unless I have to take it off.Rear tool post.jpg

JA

27/11/2021 12:50:40

Greensands

I use a late Myford rear tool post for parting off. It is clamped to the slide using three bolts, two into one tee slot and a long bolt, that clamps the swivelling head of the post, into the adjacent slot. Like you I use the furthest slots to give space on the slide. I have never had any difficulties with this arrangement.

I know that the slide is not very stiff and have had problems clamping parts, for boring or facing with a fly cutting, to it. I found that the slide can get stiff if you don't think about what you are doing.

Perhaps you could post a photograph of the arrangement in you album.

Just an aside, I have not be able to understand G H Thomas's explanation of the rear tool post for parting off. The more I think about it, mounting the tool up side down allows the swarf to fall away and not get trapped in the slot being formed during parting off.

JA

Posted before seeing ega's reply,

Edited By JA on 27/11/2021 12:53:16

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