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Member postings for Rod Renshaw

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

Thread: Small drill bits, <<1mm
06/07/2020 19:05:20

Baz, I had not realised that spotting drills were so recently developed. I have not worked in industry and imagined spotting drills being used for years without MEs getting the message.

Rod

06/07/2020 16:05:52

Spotting drills are available in small sizes and have much more robust points than centre drills. They are made for the job of "starting" drills and have better geometry for the purpose than centre drills; which are really made for drilling centres for turning work "between centres". Use of centre drills for starting twist drills is traditional amongst model engineers but they are not ideal for this purpose.

Rod

06/07/2020 13:10:13

it's possible to make small drills using methods used by watchmakers. "Swiss" or pivot drills can be made using a simple jig to put a point on what is effectively a "D" bit. Raw material can be hardened silver steel or "musical" strings intended for banjos, which are already hard. See articles by D G Gordon in ME 2 .1.1975, ME 16.1.75 and ME 15.2.1980. They don't need high speeds but do need backing out and clearing frequently. Gordon describes sizes down to about 10 thou and if you can make it once, you can sharpen it again when needed. Not much use for those needing a lot of holes but for the odd few for injectors etc.

Rod

Thread: Coronavirus, advice from ME
04/07/2020 17:44:12

I have looked in my bound volumes of ME for 1918 and not found any mention of the 1918-20 flu pandemic. There is no entry in the indexes and I can't see anything in the editorials or club news and nothing is apparent in the adverts. (I can't claim to have read every word, ME came out once a week in those days) There is a mention of the end of the war in an editorial at the end of November, but no mention of flu.

There may have been a special reason for this. The pandemic was often called "Spanish Flu" despite it having first become a known issue in the US at an army camp in Kansas, and then becoming a huge problem almost everywhere around the world. This was because Spain was neutral and it's press was relatively free to report the problems caused by the pandemic. The warring nations had powerful wartime censorship which prevented mention of anything which may have caused morale issues and this censorship may have prevented Percival Marshall saying anything.

Rod

Thread: Cutting brass with saw questions
03/07/2020 20:49:35

Hi all

I don't use a piercing saw very often, but when I do I use it on a plywood saw table, turning the saw to get around shapes and I can see the advantages of Martin's "standing" method of working.

Watching the 2 Ron Rose videos has been a bit of a revelation, as Ron keeps his saw pointing in one direction and turns the work to get around shapes, and this method clearly works well for him, and he gets to sit down!

I have a saw like Ron's, which I have always called a fret saw and have only used on wood, and I am going to try Ron's method as he seems able to develop a steady rhythym and direction, which is more than I can usually manage with my own method ( not really my own, I think jewellers have been doing it like me for a long time, but with more expertise)

Ron's method seems to depend on being able to slide the work easily on the table, so that a metal table seems preferable, does anyone know if metal tables are still available? If not I will try lubricating the plywood table or rmake my own metal one.

Regards

Rod

Thread: whats this socket used for?
29/06/2020 15:58:45

Just in case anyone is puzzled, a "Brimister" is a resistor with a high negative thermal coefficient of resistance. The resistance is high when it is cold and reduces as its temperature rises. So, by placing a Brimister in series with a load, its high cold resistance limits the current surge at switch-on, and as its temperature rises, (due to the current passing through it) its resistance reduces allowing the current to rise to the normal operating condition. This low starting current limits any thermal shock to the load. This operation is normally regarded as automatic which makes me wonder if the OPs equipment was modified in the past and that there was originally an ordinary resister which had to be switched in and out of use.

Rod

Thread: Brush motor repair
14/06/2020 20:02:23

Numatic HENRY ( or is there a Harry?)

Thread: Myford ML4 leadscrew dials
10/06/2020 14:52:13

Hi all

I can't remember where I got the idea but I have always understood that the reasons the ML1-4 were rejected for war time work was that they were regarded as too insubstantial for factory production work, and they lacked power cross- feed which made them unsuitable for use on smaller warships and submarines which bounce about too much to allow steady hand feeding. Hence Drummond were told to give Type M production over to Myford and further told to concentrate on producing Maximat ( not exactely sure of type or spelling) production lathes. In those days the Government could just tell everyone what to do and they got on with it!

Rod

Thread: Knob required
04/06/2020 11:41:09

Similar knobs are used in electronic equipment for potentiometers and rotary switches, most are for 1/4 inch diameter shafts, and these are readily available as spares and for home constructors of electronic equipment. Other sizes are less common. Try googling "potentiometer knob" or "RS components"

Rod

Thread: Low cost forge blower
02/06/2020 20:27:13

Amazing video.

The old ME books and magazines often used to say that really good work could be done with quite simple equipment, well now we can all believe it!

Rod

Thread: Lathe Way Felt
24/05/2020 09:49:28

Felt as used by chiropodists can also be used, available from the web -or even from a friendly chiropodist when they get back to work..

Rod

Thread: Removing nylon plug from carbon fibre tube
22/05/2020 18:53:36

Sam

Gentle heat ideas?

Leave out in the sun during the day, pack around with pre dried silica gel at night?

Or, pierce a hole for the end of the mast in a tin can. Add another hole for an incandescent lamp holder and leave the lamp on 24 / 7.

Or, wind the end of the mast in gardeners' soil warming cable, (borrow from a keen gardner who will not need it now it's nearly summer.)

Or, see if anyone you know still has an old electric blanket in the loft.

Others might have other ideas!

Or, cut off the last 40 mm, as suggested above, and make a new plug, with 2 diameters, and which is 40mm longer than the old one to make up the lost lenght .

Regards

Rod

22/05/2020 17:46:32

Hi Sam

I noticed that the plug is thought to be stuck because it has absorbed water and swelled. Might very gentle heat over an extended period, perhaps several days, or even more, dry out the nylon, so that it shrinks, and thus loosens it? Perhaps use in conjunction with other methods of pulling it out. I am fairly sure this would help if the plug was wood but I have no experience of nylon.

Rod

Edited By Rod Renshaw on 22/05/2020 17:48:21

Edited By Rod Renshaw on 22/05/2020 17:49:06

Thread: The sneering detractors
21/05/2020 21:10:22

Hi all

I like this forum for the range of threads, questions and discussions which come up. There seem to be less idiots, personal detractors and ego trippers on here than most forums, and most users seem to be trying to learn or trying to assist or inform.

I am sometimes amused or amazed by the specialist expertise of some of the contributors. I can't think of an example at the moment but sometimes there is a question or situation which is a little unusual and various contributors have a go at answering or guessing from general engineering knowledge - and then someone comes along and really spells it out from what is clearly a deep and expert knowledge of just that particular field. It's like a sporting event where a "dark horse" just appears and laps the field. And we all learn a lot more about the subject.

And the ego trippers and general grousers, the thin-skinned and the (think they) know-it-alls just have to be ignored. If we don't rise to them perhaps thay will go away and play elsewhere.

Rod

Thread: Macro rust spots.
21/05/2020 12:51:46

Hi all

I am a biologist rather than a chemist but I have always understood that "stainless steel" is resistant to corrosion because a very thin layer of chromium oxide forms "instantly" on the surface of an object - when in the presence of oxygen. This layer is impervious to water and it prevents any water around the object contacting the iron in the steel, so no corrosion can occur.

This layer is normally self-repairing if the object is rubbed, but the repair process requires oxygen, so without oxygen it stops, and corrosion starts if there is water around. In the sea and sometimes in fresh water or underground there is normally at least some dissolved oxygen but this can get used up by, for example, plankton or bacteria - so, no oxygen, but some water = corrosion.

So stainless steel is not at all reliable in marine environments, and can prove unreliable in some other places , including the bottom of chemists' sinks!

I notice the mention of the earlier name of "rustless iron" I think that stainless steel was developed in Sheffield to make cutlery, especially knife blades, which did not rust as the usual knive blades did. So perhaps the original name of the new metal was "rust less iron" ie metal which did not rust as much ( or as often) as the metal previously used?

Rod

Edited By Rod Renshaw on 21/05/2020 12:52:28

Thread: SANOU 6 JAW CHUCK
13/05/2020 20:35:42

Hi Dave

I have always understood that 6 jaw chucks are specialist , and rather delicate, equipment intended for light work on round things that are thin and would be easily distorted by the 3 point pressure of a 3 jaw chuck. Eg the bezel of a clock.They are not, I think, intended as a general purpose replacement for a 3 or 4 jaw chuck.

So a lot depends on what kind of work you are intending to do.

Rod

Thread: What is it ?
13/05/2020 18:40:27

John

I think the metal clamps are intended to hold the "press" , called a "lying press" I think, to a bench or table top (This is assuming it is a bookbinder's tool) So, in use, the metal clamps are underneath the wooden part and are holding the whole thing in position, the block of paper goes in the wooden part, there are plenty of illustrations of lying presses on the web. I think "lying" in this context means "Laying" or similar, (as opposed to "upright."

Rod

Edited By Rod Renshaw on 13/05/2020 18:41:24

13/05/2020 15:34:37

It looks rather like the clamps and presses that bookbinders use to hold a block of pages to trim the edges. The groove looks like one that guides the "plough" that holds the knife that does the actual trimming.

Just a thought,

Rod

Thread: Needle File Recommendations?
13/05/2020 15:23:36

Hi

Some good advice re Vallorbe and Tome Feteira above.

But just to emphasise what Martin said, the traditional watchmakers' advice is that one should keep a set of files for use on brass and never let them anywhere near steel. Apparently any use on steel will take the sharp edge off the teeth and from then on they will only be useful on steel.

Whereas, if kept for use only on brass then one set of decent quality can last a lifetime. So perhaps a buy a good set and a cheap set, and remember which is which?

Rod

Thread: Ceramic boring on Inconel a must see
09/05/2020 16:41:18

Impressive videos, I don't aspire to do anything like that in my shed!

I wonder what the workpieces are used for/ destined to be part of.

Rod

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