could you start with a SS cutting disk and then add the boss
eg as part of a parcel of bits I wanted I have maybe 8 or so 80mm dia 1mm thick sharpened to a cutting edge as used for meat slicing of those lumps of cooked mince seen in many takeaway establishments

Edited By Frances IoM on 18/02/2021 11:44:39

Take the blank out of the lathe and using the angle grinder knock off the corners so it's 'rounder'

That will make your choice of lathe tool less critical because it doesn't have so much to do.

Have you tried setting the tool angle for face cutting and then advance it like a boring tool. If that doesn't work a carbide milling cutter tip will withstand the interrupted cut.

This is one of those times when the £80 Lidl Parkside plasma pays for it's self.

I don't see why the commercial rope cutters are just plain blades if notched was better? You may end up with a rope catcher cum propshaft bender.

That's why I didn't say machine part of the OD in the 4-jaw chuck.

A disc supported only at the centre is a ………. cymbal! Good in a drum kit but not so useful on a lathe. For the spigot I'd make the diameter of the backing surface about half the OD of the part, say around 50mm barstock. Same for the washer at the front, and I'd use a SHCS instead of a nut. Making the diameter of the driving surfaces a good proportion of the part OD means that the part is less likely to slip when taking proper cuts to avoid work hardening.

Andrew

SHCS Socket head counter sunk perhaps

Roy

Tightly trapping an intermediate plate of reasonably thick "improved wood" (Mdf, osb, flooring board or whatever you have) firmly between the plate and ends of the chuck jaws will give better support and help dap out any ringing. Hafta accept a bit of dust if you cut into the face of the plate but generally its not going to be silly messy.

Most of the improved woods are remarkably flat too so contact is good. Waterproof chippbard underfloor is my favourite as the surface is slightly rough for a better grip.

As my lathe takes 5C collets direct in the spindle I'd fix the backing plate to the faceplate and grab the work holding spigot in a collet using the tailstock to push job and backing plate into really intimate contact.

Maybe consider a bit of threaded rod as a drawbar to pull the job hard against the backing plate before finally tightening the chuck.

Clive

I suppose it helps running a Bridgeport and a choice of 10" and 14" rotary tables. The big rotary only gets used about once a year but I could not part with it.

Sam may be guilty of cruelty to machine tools if this job is typical!

Stainless 316 is on my avoid list because it work hardens. That roughly shaped octagon causes difficult interrupted cuts likely to break carbide, which is otherwise a better bet than HSS. 316 conducts heat poorly causing HSS to overheat and blunt quickly. The web recommends flood cooling HSS and 316 and also making sure the HSS stays sharp throughout the cutting. About 60 RPM for 85mm diameter.

Before turning it, I'd round the blank more with an angle grinder and remove the hangers on. Then very light cuts with carbide at about 200 rpm until the circle is formed, at which point go in a bit harder. I'd expect the disc to work harden as the tool rubs either side of the peaks, but carbide should cope without breaking provided it's not asked to chop metal too quickly.

Holding the blank is tricky too: it needs to be rigid with no chance of coming loose. Not sure what to suggest. I would try super-gluing to a fat mandrel as well as bolting. A problem with bolting as shown is shock loads tend to loosen the nut.

Dave

Would it matter if there were some extra holes in the plate?

As far I can make out it won't affect the function and not really spoil the appearance on a purely functional item if you were to drill a neat ring of 4 or 8 holes to bolt it to the faceplate, with a intervening piece of thick plywood or similar.

It's certainly the approach I'd use, where extraneous holes don't affect form or function.

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I am not convinced by your remarks about your milling-machine… I owned a Warco mill-drill, one of the round-column machines, for a few years and found no problems with it other than the inconvenience of having to recover the centering by moving the head up or down.