Everything here was shop made (even the nuts), except square head bolts and insert & insert screw
Tool holders (for the lathe) gotta be the metal equivalent of wood working clamps: you can’t have enough and when you do have enough, it still isn’t.
I wanted to make a holder for 3/4″ boring bars as the one I have (bought) is 1″ with a reducer sleeve (sorta ick but works well) and doesn’t index bars with a flat. While digging through the stock piles, I found a plate that would make several regular holders.
The first order of business (after squaring the stock – see the previous posts on the fly cutters) was to cut the dovetails. This involves cutting a slot, to depth, then plowing a groove down the center to provide a relief for the dovetail cutter as it really doesn’t like center cutting. I cut this 15 to 20 thou deeper. Ideally I would use a keyway cutter to waste out most of the dovetail but I don’t have one so I went 
straight to the dovetail cutter. The regular posts were cut as one (and sawn apart after). I think this dovetail cutter isn’t ideal and needs some radial and axial rake, it makes quite a racket and gave me a headache even though I was wearing hearing protection. Notice the different colored chips (and shapes); dark blue and curly when I was really hogging out the slot, silver slivers from the dovetail cutter.
To measure dovetail width, it is best to use dowels/pins in the dovetails and measure between them. Here, I’m using an adjustable parallel to do that (1.080″ with 1/4″ pins for my BXA tool post).
My existing holders are all metric, mine will be all imperial – 3/8″-16 and 3/8″-24. I didn’t have any 3/8″-24 nuts so I just made some (from hex rod) as that was quicker than making a store run. The discs were cut from some rod I knurled.
Next up was the threaded holes. 24 tpi (NF) for height adjustment, 16 tpi (NC) for the set screws
. One of the holes is blind and some didn’t have much run out room so I used a spiral flute bottoming tap. These taps eject the chip back (spiral point eject the chip forward) and I was able to power tap everything (started the blind hole under power and then finished with a tap handle).
The bolts in the photo are interesting; I single pointed them from hex stock. Notice the thread goes pretty close to the shoulder and there isn’t a thread relief groove. I did this by running the lathe in reverse so the threading tool moves left to right, allowing me to position it close to the shoulder without worrying about a crash. I used an internal threading bar on the outer back side of the stock.
I threaded some stainless steel rod cut offs for the posts and locktited them in place.
Here is one of the tool holders with a shop made left hand cutter:
And the boring bar holder:
ZK Project Notebook 