Member postings for Bill Davies 2

I left school in 1968, to start an apprenticeship. Whilst everything in the factory was Imperial units, the apprentice instructor taught us about unified, which he expected to replace Whitworth in a short while. At college, perhaps from the first year, but certainly soon after, we were initally taught Imperial and Metric units, and then later Metric only.

My "Science for Mechanical Technicians Book 1" (M G Page), revised in 1970, uses Metric units throughout, ditto the Maths book by the same author. Metrication was announced by the Government in 1966.

But back to the OP, thanks for the spacer idea, it will be useful for my old lathe.

Bill

Gary, I had 'access denied' when trying to download your chart. Should I request access, or can you make it public?

Thanks,

Bill

Another long-term Antex user. As a school technician I replaced the awful cheap irons with Antex, with silicon leads. These are more flexible in colder weather, and resistant to being burned by pupils.

I agree that you need different powers for different job, I expect a temp controlled iron allows for different jobs, but I've never used one.

Bill

It seems that it comes in two colours:

Black and green silicon carbide

The Wikipedia article mentions multiple colours, sometimes due to impurities. My recollection from long ago was that the wheels I used in industry were always green. This was for brazed carbide cutting tools, before inserts were common or perhaps available.

Bill

Hi, Tony, and welcome. I have what I think is a Britannia No. 14. There is a large ball bearing (a ball, not a ball race) which takes the axial load. I don't know whether it is an original feature. It's under a load of 'stuff' (a future project...) but I can check the details if it helps. Mine would have been a treadle lathe but someone (short?) cut the bottoms of the legs off, so it sits on wooden blocks to bring it up to a suitable height - I'm 5'10''.

Bill

Especially as there were, at that time, much better ways of measuring pitch and concentricity errors in gears.

Bill

Anthony, if you've had your irons for some time, you will need to replace them. The lead-free solder melts at 34 degrees higher temperature, and older iron may not get there. Especially a problem if you are soldering parts that conduct a significant amount of the heat away.

The lead-free solder also doesn't freeze with the nice shiny surface that suggested a good joint had been made using the lead-tin solder.

Bill

Thanks, John, I'll take a look.

Bill

Brian H, Replicet looks very useful, but definitely an improvement from what I used all those years ago. It seems to be a silicone based material, capable of reproducing fine features such as surface finish or, in this NASA document, crack detection:

Replica based crack detection

I thought, today, that my unknown material might be a dental cement (e.g., ToofyPegs - over the counter filling repair ! ) which contains zinc sulphate plus zinc oxide and sets very fast. However, it generates some heat, which I don't recall from my experience, however the metal components would have conducted heat away very readily.

Mike now has many options for reproducing the thread; does anyone have a design for a shadowgraph type projector?

Bill

Working in an inspection department in the early 70s, we used a plastic to copy internal threads. This came as a powder mixed with water, and set very quickly. The form and pich were then measured using an optical projector. We were discouraged from using it due to its expense. I haven't been able to identify what the material was. Along with other suggestions, I offer plaster.

Bill

Pete may be referring to a specific thermoplastic, polycaprolayone, otherwise polymorph, and various other names. Quite useful but it is biodegradeable, so not so useful for permanent uses.

Bill

Rod, the commercial grade on the site below shows a tolerance of +0.0013" to -0.0007" (per inch?), which is a little tighter than the two thou per inch of length difference implied by the Imperial vs Metric tapers.

Taper pin specs

The company (Stanho) is US, so the spec is not to BS36, and its name derived from "Standard Horse Nails."

But I can't judge whether it would make much difference. It's a wedging taper so friction plus some distortion would probably fold it. The site also mentioned a 'precision' grade, +0.0005" / -0.0000", so perhaps it does for some applications.

Bill

Slightly off-topic, here is a description of the Myford Tri-Lever:

Myford Tri-Lever descritption

Bill

A very interesting find, Michael; a surprising number of stages.

However, posting at this time is not doing my sleep any good!

Bill

A good point, Dave. A similar machine languishes at my former employment. I would hope it is used again.

I was responding to Nigel's comments. Machines, especially relatively slow-moving ones, can surprise users in the harm they can cause.

I don't see the school curriculum moving against its long-term trend of more simulation and automation versus practical usage. Those older manually operated machines are gradually disappearing, and I see more CAD and CNC/3D printing replacing them, as in industry, all of which I understand.

Bill

And to depress you, and cause consternation among the rest of us, see page 58 of the following H&S guidance, summarising a couple of hundred of their publications:

HSG129

Note: these apply to industrial settings. Your HoD can advise you, but you should take a look at the CLEAPPS website, which provides information on science and technology in schools. You will need to get a current password.

CLEAPPS

Bill

Hi, Tristan. I was a school technician until recently; not a D&T technician (Physics), but I am time-served mechanical engineering. I don't think the 'kids' are allowed to use such machines now, and you may find the teachers reticent to use them. They might have had training but will have had none of the experience that you might possess. I'm not making a dig at anyone; different jobs.

Whilst teaching at an FE college, years ago, a student was milling vee blocks (haven't we all...) with a half-angle cutter, was cleaning swarf witha piece of 1/4 inch plate, against instruction (we provided brushes). Inevitably, the plate caught, was pulled through the cutter, knocking the teeth off the cutter and bending the arbour. The teeth were punched through the 1/4 inch plate.

The lad was shaking, so after a while when he had settled down, we set the machine up again so he could get his confidence back. Takeway lesson: geared machines have low speed, but (surprisingly) high torque. Not a Senior, probably a Victoria or similar mill.

The machines had the criss-cross guards, but where there's a will... , so H&S are doubtless right.

Bill

Ian, I would presume that they are intended to hold a 'dead size' tool, as the morse taper relies on friction along its length to provide drive. It doesn't have a drawbar, but if driven in (well, gently tapped in) past its nominal size, it will not drive properly. I noticed that TubalCain had some resistance when pushed into the sleeve so presumably sprung to a slighly smaller diameter.

As noted on other occasions, the tang does not provide drive, but is for removing the taper.

Sorry if this is 'sucking eggs' to you.

Bill

... and by chance I fall across this:

Mr Pete on centre drill driver

Me Pete aka TubalCain (the American one). He shows a centre drill being held in a split morse taper sleeve, and he mentions that the drill locks when it is partly rotated, which I don't understand.

Bill

Michael, thank you, some interesting articles.

Unfortunately, among the 'other items', the 1915 textbook of advanced engineering has suffered from some images being removed; the current fad of copyright restriction being applied to a 100 year old book?

Bill