I don't know how to measure something like that. So, I just drilled down on one bore a bit, then drilled down on the second a bit, till they met. I have several 400 bodies, so if I f'up, I'll try again. I'm sure there's lots of guys who know the math. Not me, bud!
I'm 75% there. I need to make up my mind about the second stage. I'm going to do a mock-up to decide.
I've made a rough kinda to scale drawing of the reg, so I can determine fairly closely how deep I can drill and how tall the second stage has to be, etc. It is not accurate to thousandths of an inch or anything. However, this isn't rocket science and things aren't so critical as that, except for the depth of the second stage drilling.
The angle of the drilling from the IP chamber to the new second stage port is 75 degrees, so I knew roughly how deep to drill it in order to meet up with the second stage pilot hole (and how deep to drill the pilot hole to meet up with the IP drilling.) I lined it all up carefully and had a good chance of not breaking through the first stage body by going too far.
Phil, what type of brass do you use for machining the second stage body? Just wondering. I think you mentioned somewhere that the HPR is too high, what about using a stock DAAM second stage?
3/4" C360 brass. This is just standard brass rod.
The HPR isn't too high. It needs to be raised about 1/8", in order to be at the same level in the FX cans as it would be mounted in a Titan II. The levers are bent too high, but that's an easy fix. The stock DAAM body is the same height, and it requires some sort of lever retainer and fixing scheme. To use the DAAM ears would require extremely accurate drillings into the first stage body for the DAAM ear/retainer screws.
I like the simplicity of the Trieste type second stage with the slotted-ring lever retainer and a set screw to orient.
Threads on the HPR are 5/8" x 27 tpi. This is a fairly standard size, but a bit on the odd side, IMO. I guess 27 and 28 tpi in 5/8" were used for various things, but 24 is much more common. Not sure why USD chose 27tpi, but Voit used 24 tpi. Taps and dies are available.
TD, to be sure, you need a drill press in the very least to do this sort of thing.
My friend who works at U.C. Berkeley showed me how to tap something using a press. Basically you drill your hole, then, put the tap bit into the chuck. Lower the bit into the hole, this procedure never uses power BTW, keep lowering/feeding it and turn the chuck by hand. It takes practice to learn, but you can do a very nice job from doing it this way:
If you used the HPR, how would you shape the volcano orifice in the Dacor, or is there another solution for this?
Yes and no. The die will but I don't think the tap will. There are 3 types of taps- taper, plug and bottoming. The number of NON-complete threads at the end of the tap determines which it is. A taper has 5-6, plug 3-4 and a bottoming 1-2 plus the end of the tap is shorter as you go from tap to bottoming. Tapers are used for through holes or deep holes with not much thread, they are much easier to get straight and less prone to break, plugs are less so and bottoming are the hardest to get straight. Its best practice to start with a taper or plug if you can, then follow it with the bottoming tap. This helps get the hole straight and reduces wear on the bottoming tap since only the last 2 threads do all the cutting. This looks to be a plug tap at best, what it really is you won't know until you have it in hand. No telling if the photos are correct, it could easily show up a taper. What you must have for this job is a bottoming tap. The hole you are working with is pretty shallow to begin with so you need as many threads as you can get. Odds are you will not get a single complete thread with a taper tap, the plug is iffy.
I usually buy a 3 set since it's not uncommon for me to need all 3 at some point and to reduce wear on the bottoming tap. These guys usually have sets or the separate taps. A bit more expensive but you can be sure of what you are getting. drillsandcutters.com/search?q=5%2F8-27
Some progress: I got a different singlehose second stage and have modded it in a different way. The intrusion into the Dacor first stage is now minimal at 1/4" max, maybe less, and the volcano orifice is integral to the second stage. This means a 5/8" hole (it can easily be taken down to 1/2") about 1/4" deep is all that is required to install a second stage (aside from the IP tap) . Pics to follow.
More progress today. I made a Delrin second stage body that screws onto (not into) the modded single hose hard seat carrier. Don't worry if you don't quite get it, I will post pics soon! I just ordered some bottom taps to make this all happen, but it'll be a few days.
I went over to see Jim Steele yesterday and showed him my Dacor 400 conversion and a Titan II conversion. I was flattered when he said he loved what I am doing to mod, make, and refurbish.
He told me he was sitting in the kitchen with the designer of the Dacor Balanced 400-800 (can't remember his name) when he described his idea for a Titan II type Dacor first stage. Jim said he was encouraging, because his favorite reg was the Titan II.
The Titan II and the Dacor 400 have a lot in common, and I don't know of any other that looks like these two regs, which are so similar. They have to be based on one design idea.
It is such an honor to be able to talk to a man who was there when all of this happened!