Thanks Michael - a lot going on in life unfortunately, too many distractions from what I want to do but such is the way of things. Gradually getting those distractions out of the way.
Those off center features don't affect anything other than slight appearance - but I'm glad I did the clean up.
So, the fun bit is getting the angled face on it at the right height and clocked correctly to the bolt pattern. Not all that hard - and as mentioned, if one were to eyeball it and mark the height front and back, paint some blue on, scribe a line etc it would all work out.
But I decided to make a holding fixture out of a piece of scraptonium, including a mating dowel pin hole at the center, the bolt pattern in the head / ring and another dowel pin for a tooling ball. The tooling ball acts as an easy to establish reference, the holding fixture is then angled making use of a sine bar.
I’m changing all the BA threads over to UNC or UNF threads which are easier to deal with stateside. There are close enough sizes. Not equivalent – they won’t play together – just similar physical sizes. I tabulated the whole arrangement. I was surprised I couldn’t find anything already done, figured that must surely have been done and shared before.
Anyway – the fixture block was all squared up and the center hole drilled and reamed, and bolt pattern added. Here it is tapped with my home-made small tap holder.
The idea of using a tooling ball to establish location actually came to me after making the fixture to that point. My original plan had been to use a dowel pin, but it would have been difficult to keep perpendicular to the vise jaws. The tooling ball is easy – here is a reamed hole being added. I’m using a kool mist mainly to blow chips away so nothing gets jammed in the reamer to make the hole go oversize.
Tooling ball fitted – a nice close, slip fit.
So, this drawing helps to explain the point of the ball.
The drawing has the dimension from the top of the ball to the finished wedge surface – so now you can see that it is possible to set up the fixture in a vise on a sine plate, touch off an end mill on top of the ball (by way of a feeler gauge so as to not damage either end mill or ball), and then bring the tool down (actually the mill knee up) until dimension from top of the ball to finished surface is reached. Now the wedge is very accurately created.
Although I have CAD and it’s easy to measure the dimension needed, I like to do the trigonometry. I’ll show the triangles here and how that works for the fun of it. I feel like making the effort to do the maths increases overall understanding of geometry – and it’s just a bit of trigonometry. I drew this up to show the relevant calculations and geometry.
Hopefully that’s self-explanatory. For anyone interested in the details I will go through the calcs on the video I am putting together for this, but basically the numerical dimensions are the known values – dimensions desired on the final part etc, and the dimensions in letters are what have to be calculated to get the vertical dimension that references from the top of the tooling ball to the finished angled face, when the part is set up in the milling machine.
So OK – with that known here is the set up – using a sine bar to get the angle as accurate as possible. Yes – more trigonometry! I expect you all know this. The center distance of the pins on the sine bar are 5” apart, so to set the angle calculate the height of a stack of gauge blocks to put under the rear pin. Sin (5.572) X 5.0” is the calculation.
Enough waffle – pitchers here.
So then after touching the face of the end mill off on the top of the tooling ball (using a feeler gauge) it’s just a matter of raising the knee gradually and carving away the material.
Simple enough and quite satisfying.
2 parts down, lots more to go.
