Lathe turns convex

Professor Chaddock CBE was teaching those and myself at Loughborough, and was highly respected. I knew him slightly as I was in residence at Quorn Hall. He lived in Quorn, hence the name of his tool grinder.

"Attending a lecture by Frank Whittle (later, Sir Frank Whittle—developer of the first British jet engines), Chaddock became highly interested in the challenges involved is high speed turbines. Working with flash steam as the power source, he developed bearings and turbines gearing systems............his home made turbines and bearings eventually achieved speeds of 120,000 rpm. ...................with speeds in excess of 400,000 rpm."

I think that he could quite manage in the average Jig and tool office, at least in any I have worked in.

Best regards

Terry

Edited By Terryd on 26/10/2012 16:21:44

Reference is ME4026 page 396+ "Cross Slide at right angles to spindle (to face flat or concave only)

Schlesingeer Limit lathes to 16" 0.001"/ft

31/2"model engineers lathe 0.002"/ft allowance, actual 0.0015"/ft

65mm instrument lathe 0.0008"/ft allowance, actual 0. 0002"/ft

These are lathe inspection limits

Lorch precision lathes actual 0.005mm/300mm, 0.02mm/300mm allowance

Kwil is spot on, the Schlesinger limits have historically been applied to lathes and are still appropriate for any hobby lathe.

The only material fault on my Clarke mini-lathe is facing convex and it's a right pain sometimes. this was a known fault on some of the earlier batches (the 3-jaw that came with mine is dated 1998).

I have considered milling the slideways true, there's only 2-3 thou to come off. I won't be able to get it perfect, but the Schlesinger limits show me which way to let the error be.

Neil

Who is building a jet engine on a hobby machine?

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There's a bundle of pulse jet stuff out there

It's a wee bitty noisy and they run white hot pretty quickly, not good when you live cheek by jowl with hundreds of neighbours

Intruiging stuff though

There are model gas turbine engines being built too, they don't run quite as hot as pulse jets, but they make a good amount of noise, some of the little turboprop engines would go well in a boat. Ian S C

If the mating faces on the flanges of successive sections of a jet engine are not flat to the same sort of accuracy as (1) then they both don't seal and they can fret themselves to pieces .

All well and good, but the mating surfaces of the flanges of various sections of jet engines are only a couple of inches wide on sections that are 4 feet or more in diameter - the sections tend to have a big hole through the middle !

And the sections are almost always turned on vertical borers with upwards of 54" diameter tables - add "borer" to the title of a machine tool & the accuracy requirements become much tighter. The rebuilt machines that I used to commission & install for my previous employer sold for £180-200,000 depending on spec & options - new machines are £400,000 plus, so it would be not unreasonable to expect them to be a bit more accurate than a small hobby lathe.

And the same work on the Myford would be within 0.0005" flat - if it could turn a 12" diameter job. Not too bad for a hobby lathe then.

Best Regards

Terry

I'm struggling here... either the boy Terry has aged overnight or got even younger!

Neil