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Member postings for old mart

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

Thread: Back plate
03/06/2022 20:43:27

Go for the three milled flats then, they only have to be as deep as the ends of the jaws and will not matter with a small er32 plate. Shame about the thickness, though. I would stick a parting blade in about 1/4" and use the groove for a hacksaw guide. I bought some Starret blades for plastic and aluminium with 14tpi, but even with those it would take a long time to cut. If you go for partial parting, then use the tailstock to steady the work, it will be safer.

Thread: Metallurgy of Copper
03/06/2022 20:34:32

We used mostly monel on aircraft oxygen systems, I thought tungham was only for ground use. It was nearly 50 years ago, and as far as I recall, the fittings were made in the USA. Our old system was stainless steel put in before I worked there, and there was a funny story about it. When they fitted it, part ran through a small room used as an office up near the ceiling. The door opened inwards and there was a joint with the olive fitted backwards. It blew off when the pipe had a few hundred psi in it as the system was being tested for the first time, and pressurised the room just enough for the people in there to be trapped until the reciever emptied.

Thread: Back plate
03/06/2022 20:21:51

Take the jaws out of your chuck, assuming that you have some external ones and place one at the radius required by the workpiece. You can assess the number of teeth on the jaws which would be engaged by the scroll, it may be enough for safety. I would not be happy with less than 3 teeth engaged. You need not tighten the jaws much to allow facing cuts and maybe reduce the diameter carefully and then turn the work around. Three flats would certainly be a safe way although the work would probably run eccentrically at first.

Thread: My Faith in Human Kindness is Reinforced
03/06/2022 17:45:09

You people from the other side of the pond often look down on their lowly relatives from the UK, but at least we never have to think about getting shot, ever.

Thread: Review prejudice - who do you trust?
03/06/2022 15:56:36

You have to allow for a reviewer comparing a budget item with a top quality expensive one. Value for money can take a rear seat at times. Also, the occasional bad review can be caused by certain people not reading or understanding the instructions properly.

Thread: Back plate
03/06/2022 15:15:01

The aluminium will make perfectly good backplates for smaller lathes. You can try a test cut in the metal to ensure it is nice to work with or not. I doubt if the aluminium would be a nasty soft type to machine grade seeing where it came from.

Thread: Metallurgy of Copper
03/06/2022 13:48:17

I plumbed in a 5000psi air system in my old firm using tungham tube. This looks like brass, but stronger. The joints were made mostly using a setting tool in a vise to set the olives which had a small sharp edged step in the bore which cut into the tungham. This allowed better repeatability of joint strength than forming in situ. I seem to remember that the fail pressure for that size, about 9/16" od was about 20000psi. The pipe fittings and olives were made of steel.

Edited By old mart on 03/06/2022 13:50:10

Thread: Finally able to get good finish on mild steel
03/06/2022 13:38:26

That is how carbide should be used, however, you need to be absolutely sure that the last pass will be exactly to final size. That is why creeping up on the finished size is popular. There is a great deal of difference between steel alloys in their machining qualities. Same with aluminium, the pure metal is horrible to machine, the stronger alloys are much better mostly. You can google metal alloy properties and some sites give relative machinability.

By experimentation, you will soon find the best ways to machine metals.

Edited By old mart on 03/06/2022 13:39:39

Thread: Now What Have I Done? (Odd Display Effect)
31/05/2022 20:41:05

Not too clever to have a browser setting like that on by default, not many people would ever need it.

Thread: Bearings or bushed
31/05/2022 20:36:43

Plain bearings would be best, and if you are concerned with temperature, you can get a tube of ceramic bearing grease which will be more than adequate, and plenty left over for other jobs.

Thread: Now What Have I Done? (Odd Display Effect)
31/05/2022 17:52:12

Looks like you have stumbled on an obscure Windows shortcut key combination.

Thread: facing mill insert - what radius ?
31/05/2022 17:45:24

The sharp inserts intended for aluminium will work very well with lighter cuts in steel, both for mills and lathes. The cheap ones have got far better in recent years and if you are happy to use them instead of the steel grades, then go for it. Small cuts will take more time, but will extend the tip life greatly The radius differences are only significant if you want a sharp corner, and the tiny bit left could be removed using an ordinary end mill.

Edited By old mart on 31/05/2022 17:48:41

Thread: Riser blocks
31/05/2022 17:35:49

The Atlas 12 x 24 which we have been getting ready to sell at the museum has been raised about 40mm with a solid aluminium block at the headstock end to allow the fitting of adjustable screws at the tailstock end for "leveling". Rod ran some tests and found that the lathe was true even without the tailstock end being tightened up. So "leveling" should be easy. I posted this photo some time back when the subject was last brought up. The principal is like ega's photo in this thread.

A very good reason for riser blocks is to get the working height comfortable for older backs.




Edited By old mart on 31/05/2022 17:39:06

Thread: fixing loose valve guide
30/05/2022 21:22:28

The main difference is that bronze must be lubricated and iron not, that is why most iron guides on more modern vehicles have seals to keep oil from getting into the cylinders and coking up.

The last bronze guides I had were on Royal Enfield twins.

Edited By old mart on 30/05/2022 21:23:34

Thread: Mis-described item?
30/05/2022 21:17:19

A bit posh for a roofer, I think. laugh

Thread: Scaping bearings
30/05/2022 21:12:32

I had never heard of M-Machine, but have now downloaded their pdf, thanks IVY. Most of the metal on p48 would do if the sizes you want are there. The Smart & Brown model A gets fed a plentiful supply of 5W30fully synthetic motor oil and seems to like it, after all, modern oils are light years ahead of what was available in the 1940's.

 You should see about getting the spindle reground first, let the grinding shop see if they think it is ok to do.

Edited By old mart on 30/05/2022 21:15:21

Thread: fixing loose valve guide
30/05/2022 21:01:20

You could take the valve guide to an electroplating firm and they could plate up the relative part while masking off everything else. Then the od could be carefully turned down to the correct interference fit. Turning using a very sharp tool and taking minimum depth cuts. The head would best be heated when fitting the guide.

Thread: chips from cast iron abrasive ?
30/05/2022 20:52:23

I used to have to go over the inside of the sink with wire wool to get rid of the rust spots left when deglazing the brake drums with wet and dry paper before fitting new brake shoes.

Thread: Advice on Belt Tensioners
30/05/2022 20:48:36

If the rod which provides the tension was telescopic, it could have a spring between the halves to allow more tension without overdoing it. It is difficult to see exactly how the system works, so I'm guessing.

Thread: Diary of a watch breaker
30/05/2022 14:04:17

The title made me smile, imagining a very small skip filled with tiny scrap. teeth 2

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