Skimming flywheel

I must have mixed that G&T stronger than usual as I forgot to mention that I also skimmed the S-T's flywheel on Monday. It's only 7 or 8 inches in diameter, but still something of a challenge to my machining facilities (or perhaps skills).

My 'machine shop' consists of a Chester lathe/mill

formatting link
This will no doubt produce howls of derision from those of you with proper (ie old heavyweight British or American) machine tools, but it was the only way I could fit the capabilities I wanted into the space (and budget) available and over that last twelve years or so it has enabled me to tackle a good few jobs which would otherwise have been impossible. But there are a few things I don't understand for instance; what is the point of a 16" swing when the cross slide will only just come back far enough to clear 8" or so and, how is one supposed to screw cut with a minimum spindle speed of about

120 rpm and no 'quick stop' ?

Anyway, it just about did the job though the tool (one of those with the little trangular insert) seemed to lose its edge after only a couple of passes.

Reply to
Nick H
Loading thread data ...

Amongst my various machines, I also have a Chester Model B. With the VFD I can get it down to about 50 rpm which is useful but the levels of torque available make anything bigger than 8" a PITA. I managed to skim an MGA brake disk the other day which was about 11" diameter by changing the orientation of the quick change tool-post. I agree, quite how you ever manage 16" I don't know. You'd presumably have to build an extension to the tool post with all of the trials and tribulations that would entail.

Overall, not a match for the original British or American stuff but then you don't have to pay even knackered second hand British or American machine money for them. Mine is on its way out as soon as I can muster the energy to drag a decent sized Colchester (or similar) up to the workshop!

Mark

Posted Via Usenet.com Premium Usenet Newsgroup Services

---------------------------------------------------------- ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY **

----------------------------------------------------------

formatting link

Reply to
mark.howard10

wrote (snip):-

I guess that is one of those cunning electronic motor controls - do they only work on three phase?

Glad I'm not missing the b******g obvious, having such a huge centre height does nothing for the machine's rigidity which seems a bit dim if it can't be used.

As I said, it was space as much as money that made the decision for me - older large machine tools can be had for pretty sensible money.

Eric Brain has suggested that taking a deeper cut would be better for tool wear, but belt slip and fear rather mitigate against that. I also wondere if the rust pitted surface was rather abrasive. Curiously it did not cut like cast iron with grey almost powdery swarf, but threw off little curls just right to burn the back of your hand while advancing the cross slide. Having tidied up the flywheel (though not to the extent of removing all the pitting) it now looks far too fresh - I'll have to leave it in the garden to mature!

Reply to
Nick H

Nick,

I have an almost Identical Machine Mart lathe which does me nicely, and I get a resonable finish from it. With a bit of tinkering it is fairly accurate.

Mart> I must have mixed that G&T stronger than usual as I forgot to mention

Reply to
Campingstoveman

"Campingstoveman" wrote

Any hints gratefully received, I'm sure us dilettante hackers of metal could learn plenty from a professional machine tool fitter such as yourself.

Reply to
Nick H

For a start my lathe has grub screws to hold the gib strips in place, careful adjustment of these will improve the rigidity if only the makers had fitted locknuts once they are adjusted so I have bought longer grub screws with nuts. Never assume that the tailstock is centered to the chuck spindle, get a sine bar between centres, not a running centre in the tailstock either and turn a centre in the chuck, and see how far out the tailstock is and adjust it. You may find as I did on a mates lathe that his tailstock was .8 mm to high. Lubrication is sparing so I oil mine every time I use it even for a small job also dony forget the saddlenut, half nut in your case, keep it adjusted up and oiled so no backlash when cutting threads. Is the lathe bolted rigidly to something, if not the bed could twist when being used. When machining keep the bed ways clean as oil and cast iron will form a good grinding paste as our ways are unlikely to be hardened. One other job I have not done yet is to remove the dials on the axis and through away the bits of metal that stop them from slipping, they dont work well and will be replaced with small grub screws.

Mart> "Campingstoveman" wrote

Reply to
Campingstoveman

Yours makes my first lathe look horrible. Anything approaching a .020" cut set everything chattering. When I bought it, the headstock had flat belt pulleys on it. 3 to vary the speed. That would have been better if the previous owner hadn't fitted link belting. That stuff doesn't grip flat pulleys when it's only the rivets that are touching. An upgrade to a piece of old British iron made me realise just how bad the old one was. I can now wind on .100" cut and let the auto feed make swarf. The downside is that it weighs about 3/4 ton. You can look at your lathe as Martin suggested. It looks as though the motor drives by belts. Could you change the pulleys to slow it down? Bolting it down to a really substantial piece of metal, preferably cast iron may help. Make sure you don't twist the bed though. Has yours got the milling head? Are they any use? The replaceable tipped tools are excellent things. There are a variety of inserts available for differing materials. It could be that you have the wrong sort. When I blunt a tip, I always tap it with a hammer to snap the very end off. That way I can see that it's U/S instead of trying to re-use it and confusing myself (not too difficult these days).

John

Reply to
John Manders

Yes, the VFD is an electronic device (cunning or otherwise) that drives a

3-phase motor. Overall, it's a wonderful device to reduce the belt changing activities but it has it's limitations! It cannot properly replicate a decent back-gear!

Eric is right in that running a carbide tool hard and fast is a better bet than treating it like an HSS tool. That assumes, of course, that your lathe can drive it - and there's the rub!

The normal rules would indicate that if it produced swarf instead of dust, then it wasn't cast iron. Not being familiar with the flywheel I assume it is it a solid (i.e. not spoked) device. If that's the case it would seem to be a grade of steel rather than cast iron.

Mark

Reply to
mark.howard10

John, Mine has the milling head but so far I have not used it for no other reason the whole thing came second hand but hardly if ever used because of a HSE problem and secondly I also have a mill/drill which does all my milling work. I can see uses for it like cross drilling shafts etc and it does seem quite a rigid unit.

Martin P

Reply to
Campingstoveman

"John Manders" wrote (snip):-

Yes, though I haven't used it with anything larger than a 1/4" slot drill in tufnol, brass and ally, but again it enabled me to tackle jobs which I would otherwise have had to 'sub out'

Reply to
Nick H

Thanks for that Martin.

Gib strips on the Chester are held by short grub screws then locked by another in the same hole, which of course alters the adjustment you have just set. So trying to get it just so is something of a process of trail and error, longer grub screws and nuts is a good idea as at least you can hold the screw still while you tighten the nut.

Being an early machine, tail stock on mine has no set over so any correction would probably mean moving the dowel pins which locate it. I take it a 'sine bar' is simply an accurately centred and parallel bar to be used in conjunction with a DTI on the saddle?

Not sure how to adjust half nut, I will have to investigate. Mind you, I have never attempted screw cutting on the thing - that needs a visit to my father and a Myford ML7 with back gear and clutch.

The machine and drip tray are bolted to a steel tool cabinet topped with a sheet of 1/2" mdf - probably not the last word in rigidity.

All dials are rigidly fixed to their respective handwheels, so nothing to do there.

Thanks again

Reply to
Nick H

I take it a 'sine bar' is simply an accurately centred and parallel

You are correct in your assumption.

I have never attempted screw cutting on the thing - that needs a

I have cut threads with mine with no problem, just take it steady and have a sharp tool.

Martin P

Reply to
Campingstoveman

"Campingstoveman" wrote (snip):-

How do you stop in the right place over several cuts at 120rpm and with no clutch?

Nick H

Reply to
Nick H

carefully :-)) plus a rapid wind out of the cross slide as I hit the stop button and remembering where the dial is.

Mart> "Campingstoveman" wrote (snip):-

Reply to
Campingstoveman

"Campingstoveman" wrote

You're braver than me!

Reply to
Nick H

It just proves that mass is essential to good turning :-) ttfn Roland

Reply to
Roland Craven

Have I upset you recently, I dont think so you old bugger :-))

Mart> It just proves that mass is essential to good turning :-)

Reply to
Campingstoveman

No - a sine bar is quite different.

formatting link
It's a gadget for setting up angles - any angles, and very accurate. Often found in pairs, it's an accurately ground flat bar with a pair of small cylinders fastened to the bottom edge. These cylinders are accurately parallel, parallel to the top surface of the bar, and an accurate and simple distance apart. You use them in conjunction with a surface plate and a set of gauge blocks.

If you put the bar on the surface plate, then put a gauge block under the cylinder at one end, you tilt the bar and make an angle with the surface plate. This angle is such that its sine is the ratio of opposite/hypotenuse, or the gauge block height divided by the bar's cylinder spacing. By the clever use of two cylinders, not a sharp edge, the "hypotenuse" measurement remains constant, even as the bar is tilted through varying angles.

So with a set of Johansen blocks and a book of log tables, you can set up whatever angle you want.

By similar geometry, you can calculate the tailstock offset needed to turn a particular angle of taper. However gauging an accurate cylindrical bar to ensure tailstock parallelism to the bed is just using a gauge bar, not a sine bar.

Reply to
Andy Dingley

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.