Hi FD,

Wow, that is a very kind offer; it looks like a very nice stainless part.
For the moment, I can't see a specific need that would warrant the outrageous cost of USA-Canada shipping but I will certainly bear this in mind.
Many thanks,

bidoowee

(Btw - nice shop in the background. I particularly like the combination of "ground coffee" with the sanding station and I covet your table saw!)

Ok - boiler build time!

The second attempt at the boiler bolt ring using 304 stainless M10 set screws. The previous attempt (no picture at the moment) involved brazing socket head cap screws in place. This proved problematic: I ran out of gas (not once, but twice) while attempting to braze them in place with a toy oxy-acetylene torch from the hardware store. I then attempted to finish the brazing using my TIG torch as heat source - which, while technically possible, was, in the hands of this welder, not a good idea. Lot of swearing that day. Since then, I have finally succumbed and added a real oxy-acetylene setup to the shop.



The biggest problem with cutting the holes in the boiler was holding the 6" diameter pipe in the mill. I finally decided to tack weld the ends in place to give the pipe itself enough rigidity during machining.



Even having done this, I couldn't get enough clamping pressure and holding force (without spending a day or two on building a jig) to prevent the whole part from lifting when cutting the holes with an end mill. So dumb drilling it had to be. First a centre-drill.



Then I work my way up through drill bits by about a 1/16" at a time...



...till I get to 3/4". I would have built a jig, but I think that I may well be able to have the boiler tube precut with on a laser tube cutter, so I will hold off until I have a better understanding of the requirements.



Image of the holding setup. It was enough to keep the assembly from moving laterally, but didn't generate enough friction from stopping the boiler from lifting when using the end mill...



First row of holes complete and I use a pointed brass spud for a visual alignment of the next bunch. The lead-free fittings that I cut on the lathe are dry-fit for now. I like to mark out the placement with a Sharpie by hand before drilling to avoid the painful forehead slap on the discovery that the part was placed backwards in the vice and consequently the holes are in the wrong place.



A little cleanup with a deburring tool and we are done!

Welding time!

First thing that is required is a stand; made from a couple of scraps of 1x1 mild steel tubing and a piece of L section.



The tube rotates easily in the stand which makes it simple to keep the torch and filler material alignment correct.



I experimented a bit beforehand using some scraps of the same materials and decided that a fairly agressive butt-weld seemed to offer the best weld consistency. Close-up of the finished weld.



Lead-free brass parts brazed in place.



A view of the open end. I should probably have fluxed the inside of the tube more than I did to prevent the oxidation.



The lone fitting in the centre of the boiler tube is the brass thermal bridge that will sit inside the brew reservoir to facilitate the heat-transfer.



Last bit of welding it the most tricky as space it tight and the pipe wall thicknesses differ: connecting the brew reservoir to the boiler tube. The boiler is now done except for cleanup with pickling paste. This last task was significantly less fun as handling hydrofluoric acid is not exactly like playing with a bundle of puppies.

Before I can pressure test the boiler I need to plug all of the holes!
I ordered a couple of cheapee G-thread dies a couple of months ago, but didn't consider the problem of holding them. They are, very conveniently, different diameters. So I decided that it was finally time to build a die holding system for the lathe. A mild steel handle, some 2" OD aluminum tubing, an acetal hub with a stainless shank and, in the case of the larger diameter die, a 6061 aluminum adaptor.



Once done, cranking out the 1/4 and 3/8 plugs in acetal was a snap. Then I dropped them into the milling machine to cut some shoulders for wrenching. I love working with acetal - you can almost form it by staring at it hard.

Pressure test day!

All of the plugs are cut and fit to the boiler with a little Teflon tape.



The pickling paste cleaned the stainless welds nicely by removing the surface layer of metal that was oxidized during the welding and brazing.



The 1/4" ply wood blank end started leaking at about 10 psi. I must not have had enough coffee - don't know what I was thinking.



Same blank plate, this time made from a scrap of unidentified aluminum (from Nortel!).



Using a regulator, a manual valve and a check-valve I can up the pressure gradually and keep it there for a bubble test in the sink. 54 psi on the dial - which is 3.75 times the working pressure and more than twice the maximum pressure (the safety valve opens at 1.5 bar). I will not be pressure testing all the way to failure

The boiler is done!

Yeah, Canada to USA is not just a walk across the border, sadly.

That boiler work is beautiful!! It looks seriously stout and something that would probably pass any boiler certification. Heck, you could get a model steam engine and run a grinder off the steam toggle

This is all so fascinating to watch develop. Than you again for sharing. Is there any sort of passivation that must be/should be carried out?

This is all coming out very nicely - nice stainless boiler! Can't wait to see it come alive!

Thanks all for the kind words.

FotonDrv wrote:...you could get a model steam engine and run a grinder off the steam toggle

Haha! Great idea - I can convert my entire shop to steam power and revert completely to the 19th century!

TomC wrote:Is there any sort of passivation that must be/should be carried out?

All the welds and parts of the areas around the brazed connections needed to be passivated. I did this with the hydrofluoric pickling paste. Next time I will try displacing the air inside the boiler tube with argon from the TIG machine to avoid the significant oxidation I got on the inside as I really want to limit the use of the pickling paste.

I may also go back to brazing the bolt ring as the process induces far less distortion in the part. The downside is that the bolt heads are almost flush with the 6" pipe and any spill of the braze material will contaminate the weld (very bad) and must be removed prior to the TIG welding.

Awesome post! Thanks for taking the time to share as it's really great to see what you're doing over there. Keep up the great work!!