Case Repairs and G1/4 Tapping

posted Jan 4, 2013, 2:43 PM by Andrew Stock
Hope everyone had a nice Christmas / New Year holiday! I spent a lot of time with family over the last two weeks... so I only had bits and pieces of time to work on Prism. None the less... I made some progress! Here's what's been going on in the workshop over the past few weeks:

After the spectacular failures with bondo, I opted to address the holes in the bottom of the case with a plate and some acrylic as shown in my last post... but what I didn't address was the sad little rivet tab that broke off while messing with the case. 

Yes... what to do about him. Bondo clearly isn't working, and I've tried some of the other similar products like SteelStik and such, but they just don't have the holding strength for a piece that needs to withstand riveting. The case will be very heavy when all is said and done, too, and the last thing I need is for this to snap and fall apart post-assembly. One option left...


Unfortunately... I don't quite have the budget for a MIG or nicer TIG welder... and no friends that have one nearby (yet)... so I looked around for some solutions. What I landed on was this stuff called "Alumiweld" that you can supposedly use at lower temperatures (730F) to weld aluminum together. It also just so happened that my local hardware had a package of the stuff for only $15... so what the heck? Worth a try. 

Since this was a 2-handed operation, I didn't really take any pictures of the process... but here are the first attempts on some 'scrap' metal:

... Kinda ugly.  That's why you practice with scrap! Unfortunately... I gave it a quick tug, and it came right apart!  The guides weren't kidding when they said welding aluminum was tricky. The first problem... my propane torch takes like 15 minutes of direct heat to warm the aluminum up to the point where the Alumiweld actually starts melting. The second problem... it talks about an "abrading tool"... but I have no idea what that is, and couldn't find anything similar at the hardware store. Some online guides pointed to using the alumiweld rod as the abrading tool by pressing it through the surface of the other molten alumiweld... but every time i did that, more alumiweld on the rod would just melt off, making a bigger and bigger pool. 

Anyway, I broke that weld... but no time to complain, time to try again!  

Looks better... but...

Either I have herculean strength, or this stuff isn't holding at all. I have a feeling that I am not heating up the base aluminum enough. The smaller piece that I am welding on is getting so hot it is practically molten... but the base doesn't seem to be melting enough to mix with the alumiweld at all. I tried a few times after this without much success either... not sure what I am doing wrong.

One thing I did notice is that I was clamping down these two pieces so that they would stay in place using some steel bench clamps. These clamps were getting very hot... I think they might have been drawing heat away from the aluminum pieces. As soon as I took them off, the pieces would heat up much faster... but they were way harder to work with then, as the small pieces would just scoot around any time I tried to prod them with the Alumiweld. 

Oh well... for $15, it was worth a try! 

One last resort $5 attempt with another cold-weld adhesive that seems to have good reviews:


Fail!  Welp, I've tried everything that is within my price range to complete this little task myself... time to outsource to a local professional! 

I found a nice little mom & pop welding shop nearby, showed them my work so far and what needed to be done, and they were happy to do a one-time small job for me at a very affordable price (only $35!):

Much better... that little tab isn't going ANYWHERE now. Considering how thin the aluminum is, and the fact that its a weird angle... they did a very good job I think. Definitely be heading back there for any other small needs. The guy did a remarkably good job lining the tab up with where it needed to be, also... only a tiny bit off of perfect:

Nothing a little Dremel work can't solve. 

So... that's that for the case repairs (hopefully!) Now I can focus on other things... like the reservoir!

I bought a kit online a while ago to let me tap my own G1/4 ports for building the reservoir... but never really got to mess with it until now. As always, I don't trust myself with new tools, so I set out to practice a bit on some scraps. I started by putting the drill bit into my drill press for making the initial holes in some 5mm thick acrylic. 

First problem... the drill bit I got seems to like to 'explode' acrylic... it's clearly not really meant for it like my acrylic bits are. It's a general purpose bit, so I think it is more for wood and metal. I got it to work eventually without shattering the acrylic by slowing the press down to about 800 rpm, and using a liberal amount of spray lubricant between 3-4 second pulses of the drill press. 

Next problem... I realized I don't have any kind of tool for the actual tap... because it's huge! I have plenty of tap kits for smaller bits, but nothing would fit this monster.  I thought for a while, and looked around online for a good tool, but ended up with a fairly cheap solution:

The obvious problem with this approach was getting strait taps. This will be especially important since it needs to seal perfectly... it will be on the bottom of my reservoir! A few shots at eyeballing it revealed this was a hopeless endeavor. I needed a tool... but what? Then an idea hit me... why not make a guide that is sure to work?

First, I cut a chunk out of a scrap 2x4 piece of wood I had laying around that was about the size of the G1/4 tap bit:

Next, I took a spare 1" thick piece of acrylic I had left over from the bottom of the radiator housing and drilled a hole in it:

I set up the contraption like so:

... and then tapped the full 1" piece of acrylic. The wooden guide helped make sure I was more or less strait, and as I put the tap through the entire piece of acrylic, it gradually straitened itself out to be perfectly strait, due to the drill press drilling a perfectly strait hole. When the tap went all the way through the block, it had about 5mm sticking out the back side of it:

There we go. Now I have a guide tool! Now, when I want to tap a perfectly strait G1/4 tap, all I have to do is set this guide piece on top of the hole I want to tap, run the tap all the way through the guide piece, and the little bottom piece sticking out in the picture above will start to tap the actual piece of acrylic that I want to tap. Easy peasy, no tool necessary!

See you next time! I plan on doing a bit more work on the reservoir, maybe a little detail work on the radiator housing... and maybe if I have enough time I can get to priming my case.  Thanks for reading!