You lot need to take an ICE COLD SHOWER
I'll now try to explain the method I used, I must admit that I had a lot of coaching from friend Pete on this which I would like to thank him for.
So making the cones:-
I'll post this in instalments as the method is rather long winded.
First Job is to make some tooling.
D Bits you will need two tapered D bit whilst you set up make a few spares to allow for breakages.
9 deg and 13 deg made from 3/16" dia silver steel (drill rod) to turn the taper you will need a razor sharp tool set perfectly on centre, to set you compound at the exact angle turn up a test length and run a DTI over a set length and not the deflection of the pointer for the 13 deg over a 10mm length the deflection will be 1.132mm
With the compound set gently turn the bar down until you have a sharp point, and give it a polish.
Part it off and centre drill the back and whilst your at it put a groove into it.
Then on the milling machine using a sharp milling cutter to reduce deflection of the point setion the D bit so that it is 0.003" 0.1mm above the centre line.
Use the groove to hang the D bit from a bit of wire , this is so you have something to hold onto, heat to cherry red and quench vertically into water, so that it stays straight.
When you make the 9 deg bit with the compound set make the assembly tool for the combination cones, this has to be made as accurately as you can.
To get the 0.101"(2.565) run out correct first turn a parallel diameter to this size, then with the compound gently turn the point down until it just runs out at the shoulder this shoule give you the correct size. then accurately turn the 0.431" (10.95mm) length.
You will also need to make a 0.037" (0.94mm) thick washer and a setting ring drilled with a No 38 drill, and some stop sleeves for the D bits
The cones have to be made in the correct sequence as you use one to make the other.
Start first with the combination cones:- turn the dia down to be a push fit into the body and part off two slugs one 0.162" (4.11mm) long the other 0.213" (5.4mm) long.
These little slugs are not easy to hold true, I solved this by using soft jaws bored out to a step to grip the slugs
You will also have to set depth a stop on the 9 deg D bit using the setting ring.
Start with the shorter of the two slugs 0.162" check that it is running true, and centre drill and drill through No 56 then its best that use use the D bit floating so with ut held in a carrier and pushing with the tail stop cut the taper , position the d Bit flat side is underneath or on its side if you have it on top the swarf will build up and probably break it.
Then using a triangular scraper radius the mouth of the cone.
Remove the cone from the chuck, now your going to use it along with the washer to cut the next cone
Put the thicker slug in the chuck checj that its running true centre drill and drill No56 and using the D bit with the first cone and washer to cut the taper to the correct depth, with the triangular scraper radius the mouth of the cone, its important you do this things won't work without it.
With the tapers correctly cut in the cones all that required now is to finish off the stepped diameters
To assembly the cones into the body you know use the assembly tool to get them to the correct depth check that you have a gap between the two cones of 0.037" (0.94mm) by using a No 63 drill as a gauge through the over flow chamber. As a belt and brasses action secure with a tiny drop of High temp loctite 640.
That took some explaining.