Stuart-Turner marine

Yes I shall certainly be adding that one to 'hot fog' and 'gypsy's breath' as official NG speak ;-)

Repair to pump drive nearly complete, damaged wheel reduced to a flange (why do I still feel a twinge of guilt cutting away original metal even when it is for a repair?) and matching register turned in replacement. The 'proper' engineers amongst you will probably be horrified that I relied in the dubious accuracy of a three jaw chuck for this work, but I only seem to have ended up with a couple of thou run-out when the assy is rotated on its shaft.

A 'proper' engineer would do very nicely with a 3-jaw and a bit of judicious adjustment with a hide mallet on setting it up, and a dial-gauge would enable a really good job as well. No shame in that at all!

We have a decent 4-jaw on the Raglan at the factory, but 9 out of 10 it's the 3 jaw and a quick 'adjustment' to get it running true.

One exception was the stub axles we made up for the trolleys, they were 40mm square MS, and they had to be set up with a dial gauge to start them off running true.

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

I toyed with the idea of turning up a mandrel, but I do so hate making up fixtures for one-off jobs and laziness got the better of me. So I put one end in chuck, hoping that S-T had cleaned up the OD on the same setting as the bore, and supported other end with a centre just nudged up into the bore (no, I don't have a live centre but I kept it well greased). Runout measured with DTI looked acceptable so I proceeded from there.

I chucked the new gear on the outer edge with a strip of shim between teeth and jaws.

How much tweakage can you get with the hide hammer? I thought the accuracy of SC chuck was dependant on the scroll and that was that.

I do regret my lack of metalworking training, but I guess I get by.

I must admit to some scratching of the forelocks trying to understand Peter's setting up technique in a 3 jaw chuck. My only thought is that he had a lot of overhang (not personally you understand). No doubt he will explain all in due course. I am also trying to figure out how he uses a DTI to set square stock up in a 4 jaw chuck. I am fortunate that when I bought my lathe, it came with a SC 4 jaw as well as the other more usual chucks. I had heard of SC 4 jaw chucks before but had never seen one. I have chucked items in the lathe using shim as you describe. It has the advantage that you can accommodate 3 jaw chucking errors by shimming unequally under the jaws. Fiddly but effective. I wouldn't worry too much about a few thou runnout on gears such as yours, the error is more than likely to be taken up by the gears moving in and out of mesh slightly. Do the gears "work" in use or do the same individual teeth always mesh together?

John

Yes, I should have thought to elucidate on that, but I assumed (wrongly) that it would be understood.

As above

I was brought up on independent 4-Jaw chucks, especially at school where there were no independent chucks other than 3-jaw.

I usually find that chucking a piece of bar for the first time will always be a little out on alignment, so I usually rotate the piece of metal as I gently tighten the (3-Jaw) chuck. A tap on the outside of the jaws will 'settle' the grip better than just leaving it tight, and I have always found that you can adjust the truth by small amounts by this method. Probably not so much for new chucks/lathes, but works for me on our old banger!

Might set up a repetitive whine, but agree it should not be too much of a problem.

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Not sure I would have had a drive dog to suit, but in principle I do believe you are right, this is where my lack of proper training shows. Sad to think that I studied mech eng at university and the last thing one was expected to do was actually make something! The late lamented traditional apprenticeship was really a far better grounding in the practical side of things.

Wrong! Get my brain in gear:

There were no self-centering chucks other than 3-jaw.

Been to Newcastle on Tyne and back so a little bit road-lagged!

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Nick,

If I have understood correctly you could have machined a center in the three jaw, put between centres the job and used a drive dog :-))

What lazy person is using a scrolled 4 jaw, I dunno Peter these people who look for the easy way out :-))

Back from Scotland chaps.

Martin P

This road lagged thing, must be related to age one thinks as I have just motored from Edinburgh and feel fine ................zzzzzzzzzzzzzzzzzzzzzzz

Martin P

Large gear it 52T and small 21T. The one not being a multiple of the other, I presume all they will "work" (not a term I have come across before so I hope I am interpreting it correctly).

But, you didn't have 3/4 ton of chargers on board, four drops and a midday meeting did you?? :-))

And, motoring one-way doesn't count!

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Nah nah na nah nah,

Maybe not but does working on two Rack washers and starting at 7:00am count for anything. :-)) Oh and driving up yesterday and working when I got there :-))

Martin P

As long as the tooth form is correct you will get a ratio of 2.47

I was also taught to "address" the workpiece and jaw end with a lead hammer when closing the jaws of a 3-jaw onto brightstock. It was pretty effective on the old 1899 Herbert No4 I was running first off, but I must admit that it would not have occurred to me to do that when using an air chuck on a Ward 2c!

Horses for courses.

I thought the term for a pair of gears that were not in a ratio where they constantly ran the same teeth together was called hunting, but it's probably one of those terms that's different in different parts of the country.

Travelling. I put 750 odd miles into a day in America last year, thus gaining an extra day in San Fransisco at the end of our trip. I wasn't fitting machinery or going to meetings, but I felt like I had done!

In the UK, I've quite frequently driven from Bristol to York and back in the day for a two hour meeting, damn fool that I was! I won't do it anymore and insist on an overnight .

Regards,

Kim Siddorn, Regia Anglorum

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apprenticeship

One of the things we learnt at school was offset turning for eccentrics and cams, and obviously the 4-jaw had to be independent for that sort of work.

I cannot recall seeing a self-centering 4-jaw until the 1980's, mainly as I was in electronics not mechanical engineering.

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Do I detect a note of envy?

I'm not sure that's it so I tried to explain using the closest word I could. I do know that designers will try to avoid having the same teeth always meeting each other. If a ratio doesn't have to be exact, they will introduce an extra tooth to avoid it happening. That is known as the hunting tooth. From that I assume that hunting means that teeth don't develop partners. At the risk of teaching about egg sucking, the problem with the same teeth always meeting is that they wear together. Should the machine be dismantled, the gears will most likely end up in different positions. Then teeth that have worn differently become meshed and that is at best noisy, at worst, weak.

John

Probably :-))

...but I think on balance I would still prefer an independent 4-jaw as long as I had a decent 3-jaw chuck to use as well.

The drill and reamer sharpening fixture on the Clarkson Tool & Cutter grinder we have has a very nice 6-jaw chuck, that is even nicer for round or hexagon work.

Peter

-- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk