Making a lathe tool

[cropwell]

Hi,

I have a job to do on my lathe, which involves making (for a start) 10 mild steel cones with a shaped side.The end product is like a laboratory stand, but much better looking, being finished in dark chrome.
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Anyway, the base has an 8mm vertical rod and the ones that were made before (not by me) have the rod welded into a hole in the base. This makes preparation for chroming a nightmare where the rod is inserted. So my design has a cone brazed onto the rod and then tapped M6 to screw the two pieces together from underneath.
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I wish to turn a curve into the cone and so I am thinking of grinding a tool from a 3/4 sq HSS blank
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My query is - will I get away with a zero degree rake on the cutter ?

Cheers,

Rob

[JohnHaine]

I wouldn't try that if I were you - that's an awful lot of grinding! 3/4 sq HSS is tough stuff - and do you have the height to accomodate it?

Better would be to use a bit of thinner gauge plate or an old file - in the latter case get it red hot and keep it there for several minutes to soften. Then you could form the profile and harden. You might get away without to rake if you take it slow and use lots of coolant. Of improvise a kind of "inverse ball turning fixture" so you can use an ordinary turning tool and move through an arc.

Easiest if you have only one to do would be to form the curve by a series of small steps then smooth out with a half-round file.

[cropwell]

You are right about the piece of HSS, it is too thick to go in the tool holder, maybe only by a mm or 2, but that would mean a time on the surface grinder. It might be easier to get a smaller piece (1/2 x 3/4) or nearest metric equivalent.

I have an initial batch of 10 to make, and probably another 10 after that. I would like to get them all the same, so I thought a profile tool would be the easiest. The grinding facility I have is a wet linisher with 100mm x 3 metre belts. That is at a friends workshop, and he is retiring this year, so he isn't worried about the belts.

I have been meaning to make a ball turner for a couple of years now, I have the stock to do it, but not the impetus.

[JohnHaine]

Of course, on a CNC lathe it would be a doddle.....

What are the dimensions?

[cropwell]

The cone has a base cylinder 25mm diameter 5mm high with a shaped cone atop it 20mm high tapering to 8mm. The whole thing has a 7.873 mm hole down the middle to take the 8mm rod turned down to a tight fit. (I have a 7.873mm rotary broach - found in a drawer in a vacated industrial unit).

The fun, however, is to make them myself. As well as my Amadeal 290VFF, I have a Clarke CL300 which would be an interesting base for a CNC conversion (Ummmm!) - there's another project I will never get round to.