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Form Tool Sharpening

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Buffer09/05/2019 22:22:06
343 forum posts
155 photos


I have just used a bench grinder and ground my first form tool in HSS for making some brass bits. The cutting edge is about half an inch in length.

Can anyone tell me what is the best way of smoothing out the edge and sharpening this? As its a curve its not obvious.





Howard Lewis09/05/2019 22:25:24
6316 forum posts
15 photos

A round fine stone, or a round diamond hone?


Hopper09/05/2019 23:46:22
6706 forum posts
347 photos


ronan walsh09/05/2019 23:46:43
546 forum posts
32 photos

Howard has it, i always smooth out cutting edges on ground tools with a stone.

Buffer10/05/2019 08:33:48
343 forum posts
155 photos

Ok thanks. The dremel wheels I have had in the past have always just worn themselves away more than the metal!

I will look for a rounded stone

Thanks for the advice


Baz10/05/2019 08:57:33
757 forum posts
2 photos

Bit of brass or Ali held in pillar drill chuck and run slowly with a finger full of valve grinding paste and then present the tool at a slight angle. In a couple of minutes you will have a narrow band finely ground, a quick stone on the top and the jobs done.

Mick B110/05/2019 11:31:09
2226 forum posts
125 photos

Once you're happy with the shape, finish and clearance angle of the curve, grind the top face to produce the edge. If you put a few degrees of side rake on it, it'll work well enough for most other common materials as well as brass.

Andrew Johnston10/05/2019 11:42:39
6678 forum posts
701 photos

For free form shapes I hand grind, possibly against a template, and finish with diamond hones. If the profile is important I'll machine it and finish with diamond hones.


Ian S C10/05/2019 12:25:56
7468 forum posts
230 photos

For a similar shape to your's Rich I grind out the bulk of the metal on the bench grinder (now I would start with the angle grinder), then get the shape near right with the Dremel, and use a slip stone to sharpen (as used to sharper wood gouges).

Ian S C

Buffer10/05/2019 15:23:23
343 forum posts
155 photos

Thanks for the advice, lots of techniques here.

I like the idea of grinding paste on a spinning bar might give that a go first.

Ian what bits do you use in the dremel? The little grinding wheels that came with it just wear themselves away.



Derek Lane10/05/2019 19:31:23
792 forum posts
175 photos

For sharpening my HSS turning tools I use a diamond card with a little window cleaner as a lubricant, so I would go with a round diamond file and do the same Once you have it very close to shape

Jon10/05/2019 20:48:45
1001 forum posts
49 photos

Its a pain but got to be done, grind the relief if your very good can double it up for cutting edge.

Ian S C11/05/2019 12:58:24
7468 forum posts
230 photos

Rich, in the Dremel I use a stone just smaller radius than the the shape to be ground out, get as near a you can on the bench grinder first, Baz's method would then be good to finish the tool.

Ian S C

Nick Hulme12/05/2019 17:29:22
750 forum posts
37 photos

You should grind your form tools such that they have the angles required, and not "Sharpen" them afterwards.

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