Due to request here are some more pictures and explanation of a modification I did more than 5 years ago. This tool holder is too tall for the tool post and it would also have the top surface of the tool steel way above centre. To overcome the centre height problem I welded a piece of keysteel on the side of the shank taking care to make sure that the vertical centre line of the tool steel was square to the top surface of the cross slide which is true to the lathe bed. I also welded a piece of keysteel on the front end of the holder. The tool in this holder is 3/32inch wide(at top) 1/2inch high and 4inch long.
The piece of keysteel at the front is tapped in the bottom to take an adjustable "foot". I put the tool holder in the toolpost and adjusted the foot to touch the cross-slide then gave it just a tiny bit of preload then locked it with the lock nut. Each time the tool holder is put in the tool post the setting is correct and doesn't have to be redjusted unless of course something changes. This front end support makes it a great rigidiser of the whole parting set up/compound assembly. One of the penalties of course for having the leg at the front is that the four way toolpost cannot be rotated without removing the holder from the toolpost.
All industrial keysteel I've had anything to do with is medium tensile with 1040 being pretty normal. The tool holder is possibly also medium tensile steel therefore I welded the keysteel on with an appropriate welding rod, probably a lot better rod than actually required, it was one of the u-beaut rods for dissimilar steels and spring steel etc.
Close up detail of the bottom edge of the tool steel from the back end of the holder. You can see that the holder has a tapered face where the tool steel sits in, the bottom of the toolsteel is also tapered to suit. Of course the tool must be put in the correct way around.
The top face of the tool is chamfered at an angle that matches the angle face of the clamp bolt. There is absolutely nothing wrong with this type of tool holder and this design is extremely similar to industrial parting tool holders made for years by the likes of "Armstrong" in the USA and "Lock" in Australia, both of which I am familiar with and used in industry.
Here is the front view of the tool with an engineers square sitting on the lathe so the side clearance can be seen, side clearance should be about the same on both sides. If the tool is held at an angle so there is positive clearance on one side and negative clearance on the other then the base surface(the face that sits in the tool post) of the tool holder will have to be machined or ground to correct the problem. That is assuming of course that the surface of the tool post or such isn't the problem.
Here is a small tool holder I have. When I get around to welding a packing piece on the bottom so the top of the tool is automatically on centre when I put it in the tool post I will also change the angle so the tool comes straight out. With the tool on an angle as one adjusts the tool out to cut deeper, or back in, the centre height changes and the packing has to be changed. If you have a quick change tool post then the vertical adjustment has to be fiddled with. All this stuffing around is the last thing one wants if one is just changing the distance the tool sticks out. As can be seen the tools come with a lot more front clearance on them than needed.
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