Welding hardened steel

I'm sure that members of this group will have an answer to my question below.
I have a parting off blade holder on which I want to make the shank wider.
The holder is made of steel which is hard. Whether it has been case hardened or hardened by some other process I've no idea.
Before I discovered it was hardened I intended to screw a plate to the side of the shank, which is now not possible.
What I am now considering is running some beads of weld on the side of the shank with my MIG welder and then machining the new metal make to the extra width I need.
Is this feasible, will the resultant weld be machinable or is there a flaw in the idea?
Thanks in advance.
John H
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On 09/04/16 22:43, John H wrote:

If it's nything like the tool-holders I used to have, it will be drop-forged steel, and any hardness would be imparted by surface chilling during manufacture.

Whether it is case-hardened or hardened all the way through, welding it will anneal areas. It is far better to silver-solder it, assuming that won't temper it too much.
Have you thought of adhesives?
If it is only case-hardened, a diamond-coated drill isn't terribly expensive and that would allow you to thread the drilling and attach your plate..
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Rusty Hinge
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