Apprentice Piece - Turning

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A plumb bob.

Make it as simple :-

Or as fancy as you like :-

Nick

That's a big ask for a beginner to get across in 1-2 hours. The trouble with trying to make one standalone piece encompassing all those is that an error in one step, say halfway through, ruins the whole piece and they have to start all over again. Hence the common use of sample pieces for beginning work. Master one skill, with the usual errors and restarts along the way, move on to a new piece and master another etc.

You may be able to break it down into a few separate useable items, such as the simple plumb bob already posted. Another I remember at high school was making a centre punch, it uses plain turning, taper turning, knurling and parting, then the heat treatment with the oxy torch and a bucket of old engine oil. Drilling and boring could be take a piece of say 3/4" round and part it off into two pieces, drill and bore a hole 7/8ths of the way through each piece, bore a step inside one piece and reduce the OD of the other so the two pieces fit together as a small container in which to store the centre punch, or the plumb bob..

But at trade school as an apprentice, I remember starting on test pieces of 1" bar turned to various diameters at various steps to match a drawing, then grooving, then screwcutting one end. Graduated then to stuff like making a C clamp from solid plate and turning, knurling and screwcutting the clamping screw and the foot to go on it. Then a crankshaft made from 1" bar turned between centres using offset centre holes. Later came a socket ratchet handle turned and milled and finally a 3" machine vice milled and the screw turned.

Six diferent operations in an hour? They would be quick if there was to be any cutting to size involved! QCTP? Tools already set to centre height? Etc, etc? The simple plumb bob shows all but boring, so doable in an hour or so, for a novice. As long as they don't have to manually hacksaw a piece of hard steel, maybe.....

Unless the pupils have had a day or two basic training on use of the lathe, they will not achieve much in an hour or two.

Ideally they should already have experience fitting/measuring and reading drawings before they try the machines, so hacksaws, files, scribes and punches, drills. You get the point. First lesson should be showing them how the lathe works,H&S and what exactly turning is, as well as the speed calculation and then you could try a basic step turning exercise.

I'm afraid you might have to explain to whoever is in charge that this is going to take more than a couple of hours. These kind of skills(turning,boring,facing,knurling,threading, tapers) are normally spread out over a number of projects rather than just one. 

Michael W

Edited By Michael Walters on 13/10/2016 08:06:29

A scriber? measure/cut/turn/knurl/drill/part off/bond hard tip?

It's a good point john, but there wouldn't be any drilling unless you wanted to make a scriber with replaceable tips, would be a better design i have to admit. You'd even have a bit of threading to do with the grub screw! 

It's probably just too much to take in one session for people who don't know what they are. Leave some decent tolerances on it then you wont make them feel like a complete failure. Although that seemed to be the point of my college course!

Michael W

Edited By Michael Walters on 13/10/2016 09:01:24

+1 for Michael & others. Having spent 9 years as Mech.Eng. instructor in a training centre ( covering NVQ L2 / BTEC ) & some months in my local college what your asking is a big ask; the groups were made of up to 12 apprentices who firstly learned the art of filing, inc. types of files & uses, filing square to Eng. squares, learning measuring using engineering rules/verniers/ micrometres /height gauges etc. Reading eng. assembly & parts drawings & safe use of drilling machines & all they encompassed; then producing a test piece...usually after 8 -12 weeks; depending on the capabilities of the apprentice.

On to machining... at least 2 days learning about the machinery / operation / feeds / speeds, H & S, only then on to calculations for RPM / surface speeds for material in use, which tool for which job, reading machining drawings 1st / 3rd angle etc.... & then practicing on the lathe, machining to shoulders, stepped diameters, drilling to depth, using callipers, micrometres, depth gauges, hand tapping / ext.threading etc. Parting off was left until the apprentice had gained more experience. As previous comments the first test piece was the plumb bob which encompasses all the points you are asking for, but to cover all that & produce a test piece in 1 - 2 hrs... highly unlikely, not surprised you / your volunteers ( albeit craftsmen ) are stumped.

George.

A simple thick washer?

I would set the topslide to 45 Deg at the start (to save time later) and use a 45 deg approach tool, then :-

1) Turn O.D.

2) Face

3) Form a small chamfer on the outside edge

(All the above done with the same tool. Hence the 45 Deg approach tool)

4) C.Drill & Drill

5) Bore

6) Generate rather than form a chamfer on the bore using topslide and boring tool

7) Part off (probably best with the rear toolpost if available)

Edited By Nick Hughes on 13/10/2016 10:18:29

Height gauge

Useful, easy to incorporate all the skills if you have the right design (even hardening and tempering) & relatively small.

I'm inclined to agree with George. Also 40 people ? All in one go ? I suspect not.

I think lots of people will be rather cautious the first time they are stood in front of a lathe and told to use it. Seeing some one doing a hands on demonstration with a bit of a chat might help with that and not consume too much of what sounds to be a rather short time. Throw in too much information and some will get a sort of glazed look and what is said will go in one ear and straight out of the other and don't I know it. Best kept casual and simple, sort of look how simple it is approach.

Boring seems to have stumped all suggestions. Maybe a brass or al egg cup ? It wont have a curved interior but could have a tapered internal bottom and eggs generally don't fit egg cups that well anyway.

I'm pretty sure that my first piece of lathe work was a centre punch. No boring and needs some simple heat treatment. There may be H&S worries if the end is polished up in a lathe for tempering but it could be done in a vice. Worth while too really as it wont be made of air hardening steel. Same with low diameter punches. I made a couple having got fed up with what can be bought. One's around 0.110 dia and used to knock out anything larger than that.

A small tap wrench is easy to make. 2 piece with tapered handles one of which screws in. The tap is held in a round hole that has had a V hand filed to one side. Ideally the screw in part needs a hardened insert in the end - say a short length of 3mm silver steel locktited in. In my case the centre part was hand filed flat on both sides but it could be turned or milled, 2 hrs though and it needs some precise turning and the use of taps and dies and a needle file.

A number of things I made in training followed me around on various sections. Part of the work done on one and more done on the next etc. In some cases that meant that they went away for hardening and were waiting for me when I finally got to grinding. Some started with hand work. One item that might suite and include milling is a certain style of tap wrench. I'll try and describe it.

Toolmakers clamps are opened and closed by holding the usually knurled screw heads and twirling the whole thing one way or the other to open or close it. The tap wrench is opened and closed coarsely exactly the same way. The "handles" are easy to make but need to be a decent fit where they pass through the side of the jaws to the one that has the screw thread in it. The jaws are just a square block split down the middle with V's added to grip the tap. The only complication I can think of is milling the V's so that they line up. My father and many others made these during their training and they stood many years of real toolroom use. The handles were a bit fancy, flanged at the end so that the diameter there was a touch less than the thickness of the jaws. Then reduced and came out again tapered to meet the knurled ends. 2 handles in 2 hrs - just about on I would have thought. Milling - easily.

John

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John, re-read my post about a thick washer. It covers all the original posters requirements, also introduces the difference between Forming and Generating as a bonus and the big plus is it's all possible within the time frame.

My interpretation of the original posting is that this is a "one off" hour or two and so anything other than very basic or simple would not be possible.

Nick

There are several problems with what you're proposing. Firstly, and as others have said, 1-2 hours is not long enough to make anything useful.

Secondly you say "a Myford". Do you really mean just one lathe, or did you mean one lathe per person? If just the one lathe per group, that could mean 12 minutes per person actual lathe time (actually much less in practice).

Thirdly, given your numbers, that is 7 to 10 students per instructor - that is definitely too many if you're talking about complete novices who have never been in a workshop before, and especially so if they each have a lathe to themselves.

Fourthly, what are you actually trying to achieve, and what will these students do with this knowledge? You have to decide whether it's a safety training course or a practical lesson. If these students will be going on to do some proper machinery training then they should have more time in the future for a practical project. If it's safety training they don't need to make anything.

I would strongly recommend a re-think on the time allowed, and probably on the numbers (of both students and lathes). 1 to 2 days is a bit more realistic for just the basic safety training, double that if you actually want them to produce something.

Sorry to sound so negative, but it really annoys me when I see these sorts of courses proposed (and I saw lots in my past life) - there is no way you can teach a complete novice anything useful on machining in an hour or two and then expect him/her to have any real fundamental understanding of anything.

Edited By Steve Pavey on 13/10/2016 11:31:31

In my experience, college/classroom training would take up no more than 40 min; after that any student/ apprentice would be off into lala land ... closely followed by the instructor/lecturer ( I have on more than one occasion ) much better to have them out on the shop floor 'doing stuff '. Going back to my previous post; a group of 12 was pushing it, & that was one lathe ea. ... H & S factors where machinery is concerned, there was usually my self & another instructor covering a group of 12, much more manageable & practical.

G.

I can't remember how it long it took but in metalwork class at school we made a Toolmaker's clamp, involving:

- Marking out with ref' to a drawing.
- Cutting / Filing
- Drilling through and blind holes.
- Turning / threading / knurling / parting off.
- Heating to cherry red with oxy/acetylene and "blackedising"? in oil. I think the teacher did this part.

I still have the clamp somewhere in the shed.

Ed.

when I was at school ( early 1970's ), one of the first things we made in the metalwork class was a very useful screwdriver,

Handle was turned from a piece of 3/4" dia, aluminium about 5" long, knurled for the grip, tapered slightly towards the blade end, & drilled for the blade,

The blade was forged to form the screw end, then hardened and tempered, then pressed or loctited into the handle,

The handle could be as ornate as you like, grooves , knurling etc.

Richard.

The clamps could also include milling again I think that is achievable and a useful end product. The screws would be easier to make than handles for a tap wrench. Mild steel should be fine too - free cutting so relatively easy to get a decent finish.

Like the tap wrench this can take care of the milling aspect as well. Every time I use some of my bought tap wrenches I think about making one.

There is another simple type as well. It starts with say 2 150mm lengths of square bar. Turn a short handle on the end of each. The remaining square parts overlap and are fastened with opposing socket screws suitably spaced apart. V's cut central to locate the tap. The knurl on the sockets screw is fine for tightening. I do use one of these for what might be called model engineering sizes apart from the small stuff. Definitely apprentice made. It came with one of my lathes. The screws are spaced some way apart - to gain a bit more leverage from them I suspect.

My Dad's rusted past redemption but would be using those if they could be resurrected. I used them as kid.

John

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Curious. Thought there might be. Here is a video describing making all 3 types I mentioned.

On the last one I mentioned I would personally space the screw further apart. It also makes it easier to set the jaws parallel.

May need to edit this to correct the video link. Free pre tuition.

John

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Looking at the video on the last type there is no need to centre that accurately or turn the handles that long - it just weakens them. He looks to centre drill too deep to me as well.

Dad;s type should have a square centre too - imho. Looks like he doesn't know about twirling to open and close them keeping the jaws square. Some don't know that can be done with tool makers clamps either,

Knurling is pointless too really. I find it often turns out too sharp. I was taught and do knurl in one go and don't worry too much about how square the knurl is to the work. In fact with a heavy knurl I'm pretty sure I have angled it slightly to cut it gradually.

Tut Tut oh dear, he doesn't reverse his taps to break the chips.

John

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Edited By Ajohnw on 13/10/2016 13:24:15