The chance of new crankshafts and rod etc

[Bob Culver]

Hi Tony

Dowells can ensure great precision. Not sure that it is all that critcal anyway. A thin shim added and subtracted does not weigh a lot.

I guess you were referring to lathe chucks which seem to usually have about .003 runout even when new.
Much of the art and intriguing challenge of lathework is accomodating such features when doing exact work.

But the comment does also apply to lathes with removable gap beds, now out of fashion.

[Tony Griffiths]

Much of the art and intriguing challenge of lathework is accommodating such features when doing exact work.

Reminds me of an American story (possibly apocryphal), circa 1900, concerning a machine shop in an old, wooden-floored mill building. An apprentice would be given a job to perform on a lightly-built Seneca Falls lathe supported on cast-iron legs. The 20-stone foreman would deliberately lean on the tailstock-end of the lathe and inspect the boy's set-up procedure and then, satisfied all was well, walk away. Of course, when the callow youth turned the job, it was wildly out, the heavy foreman having distorted both the lathe bed and floor.

[Lowespeed]

Hi Tony,
A long time ago when I had a set of 1 5/16th rods converted to shells they use Ford SV 1172 bearings I seem to remember. They "nicked" the big end bolts but that was solved by using three bearing big end bolts. Don't know if they are still in production, but might be worth looking into>

[Charles P]

Much of the art and intriguing challenge of lathework is accommodating such features when doing exact work.

Reminds me of an American story (possibly apocryphal), circa 1900, concerning a machine shop in an old, wooden-floored mill building. An apprentice would be given a job to perform on a lightly-built Seneca Falls lathe supported on cast-iron legs. The 20-stone foreman would deliberately lean on the tailstock-end of the lathe and inspect the boy's set-up procedure and then, satisfied all was well, walk away. Of course, when the callow youth turned the job, it was wildly out, the heavy foreman having distorted both the lathe bed and floor.

Tony

It's why some of us have 1 1/2 tons of CVA in the workshop.

Charles

[Colin Reed]

HI Tony,
The Pre unit Triumph 500 had a three piece crank the centre piece being the flywheel,the two shafts were bolted either side with six Ground shank bolts going right through.

Colin 
NZ

[Bob Culver]

Way off topic but in response to Tony G again I have read that in mid 19th century America top skilled lathe operators were highly paid. They had figured just when and how to apply pressure and corrections to their lathes for exact work.

[Stuart Giles]

Much of the art and intriguing challenge of lathework is accommodating such features when doing exact work.

Reminds me of an American story (possibly apocryphal), circa 1900, concerning a machine shop in an old, wooden-floored mill building. An apprentice would be given a job to perform on a lightly-built Seneca Falls lathe supported on cast-iron legs. The 20-stone foreman would deliberately lean on the tailstock-end of the lathe and inspect the boy's set-up procedure and then, satisfied all was well, walk away. Of course, when the callow youth turned the job, it was wildly out, the heavy foreman having distorted both the lathe bed and floor.

Tony

It's why some of us have 1 1/2 tons of CVA in the workshop.

Charles

or 2 1/2 tons of Dean Smith & Grace...



Whether or not the story of the foreman leaning on an early lathe is true, I can certainly believe the effect on accuracy of any incidental load on one of these machines. The "at home" workshop lathe when I was growing up was a turn of the (last) century "Britannia" gap bed lathe, these machines, being made before the invention of high speed steel for the tooling were really flimsy even by comparison with WW1 vintage lathes. I made all sorts of bits for my motorbikes and for my special on it, but what a relief to be able to use a modern machine for the occasional "Homer" when I started my apprenticeship.

[Tony Press]

The tiny Colchesters in the Tech School workshop 65 years ago were pretty flimsy and worse when your apron got caught in the lead screw !

Never liked turning and fitting since, much to the sadness of my grandfather who maintained De Dions etcetera in his younger days.

[Tony Betts]

tony.

either you didnt listen at collage or had a bad teacher.

one of the first thing you should have been told was to always have your apron bow tied behind you. AND TAKE OF THAT TIE.

and if you had a teacher with a sense of humour, he would always tell you to check your fly before operating a lathe.

tony

[Bob Culver]

Especially on the ones with exposed feedscrew gears! 
A neighbour used to tell me about a work coleague who got pulled through the bed gap of a large lathe!

Meanwhile, there remain a few other posts not fullly answered by anyone.....