Hemingway Radius Grinding Attachment Ref: HK 1312

[Rod AshtonParticipant @rodashton53132]

Has anyone made the Hemingway Radius Grinding Attachment Ref: HK 1312 for the Wordon cutter grinder please? I am curious to know how the radius is measured and how accurately radii can be ground, for CNC lathe tools, Your experience gratefully received.

[Rod AshtonParticipant @rodashton53132]

[Another JohnSParticipant @anotherjohns]

Hi Rod;

I've made it, but not used it much.

I think that you'll find that the accuracy is in the setup; all it really does is hold a toolbit and allow you to move it in a circle of about 180 degrees. Fine feed is by the screw on the back of the tool holder.

I should use it more; work and family stuff has got between me and my workshop recently – so the lack of use is not a black mark on the tool design.

I made my semi-circular table on my smaller CNC mill, out of brass, 1/8" thick. Also made the tool holder slider (that slides on the semi-circular table) out of brass on my CNC mill, also.

[Rod AshtonParticipant @rodashton53132]

John thank you. – I think I can see how it works. But cannot see how to set up, if it is possible for a specific radius.

Perhaps I am seeking a method as opposed to the unit recommendation. – If the angle was set and a flat ground on the tool one side then swung round to grind the same angle on the other side. It seems this would give a reference edge and then `incrementing in` by the desired radius and carefully swinging between the two angles manually (or to pre-set stops of some kind) You could generate the radius. But it presupposes that you could register the centre of the pivot point in some way. – Not getting my head around that part. – Though I believe I have seen a setting post method with an accurate half flat milled on, to index with slips or vernier. So with a mushroom head pin of a known dia. located on the jigs pivot centre it seems it could be possible to register the position by touching off on the flat? – Have a cutter grinder with X & Y calibration to facilitate the settings.

My head is hurting now. Any input appreciated

[Martin ConnellyParticipant @martinconnelly55370]

With a 6mm diameter button insert and CNC you can do any radius over 3mm. With a 0.2mm radius insert and CNC you can form radii from 0.2mm upwards. If you make your own round cutter you only need to know the radius to be able to use it for its size and any larger radius.

If you use a wizard for basic CNC operations then to get a given radius set the radius in the wizard to the required value minus the tool's radius. So for a 6mm radius with a 0.2mm radius insert set he radius in the wizard to 5.8mm.

Martin C

[Rod AshtonParticipant @rodashton53132]

Martin – Could you elaborate a little please. Afraid I do not understand what you are telling me.

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