On another front... I'm having a bit of a fab & repair problem with my BBQ grill. I have a couple of the valves which have suffered impact damage; after two days of searching, it appears this valve is manufactured of weapons-grade unobtanium. 🤣 This little iron casting supports the knob shaft, which is separate from the brass casting which houses the cone valve. It would be a simple thing to whip out a replacement on a lathe...
....until you look at the business end. This interlock is what turns the cone valve slug in the brass casting still on the grill. Replicating that turns this project exponentially more complicated. I am seriously considering this as my first actual Lost PLA 3DP project... 🙀
That's definitely not a job for PLA. I assume the area gets quite hot too? McBryce.
Lost PLA. You make a model of PLA and use it to make a sand-casting mold, into which you then pour molten metal that vaporizes the PLA into the casting sand. Not sure how well such a small mass would work with the process, however. ![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1412254;image)
Now that I've disassembled the spindle assembly the solution has become quite obvious, and is something I should be able to hand-fab with tools I have at hand.
1) Grind the little bit that protrudes at the break flush with surface of casting.
2) Find bit of brass or steel tube with ID that matches shaft and cut to length.
3) Find steel washer with OD large enough to cover both screw holes and ID similar to OD of tube. Grind ID of washer with Dremel if necessary.
4) Partly assemble shaft/bushing; solder washer to tube such that it makes a flanged bushing.
5) Mark for screw holes on washer; drill holes.
6) Assemble with slightly longer screws. Keep found tubing safe for when I need to do this again for other two valves. ![Roll Eyes ::)](https://www.eevblog.com/forum/Smileys/default/rolleyes.gif)
I'll update with pics as I make progress. EDIT: Added mnemCAD scribbled on back of used Hall Pass. ![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
mnem
![Tweak :-/O](https://www.eevblog.com/forum/Smileys/default/smiliey_cal.gif)
From the FINALLY GETTING ROUNDTUIT Dept...DISCLAIMER: - this is Jackleg machining/hand-fabricobbling; it is NOT high-precision, it is not the best way or even the right way to do the job... it is just intended to be CLOSE ENOUGH to work and git 'er done. I offer this process here for the same purpose as my
splice & solder a busted knob shaft process: For cases where you don't have replacement, or where the subject is rightly borked, but you cannot justify a lot of expense or time fixing it "properly", but you CAN spend a couple hours doing a little empirical engineering.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429111;image)
My searches for a convenient source of bushing material to match the oddball shaft (7/32" ~5.5mm) on this knob assembly were utterly fruitless; I found some 5.5mm bullet connectors to use for metal stock, but they were Chinesium and made just WRONG.
No good for their intended purpose, no good for mine either.
![](https://www.eevblog.com/forum/index.php?action=dlattach;topic=81471.0;attach=772392;image)
So I had to drop back & punt... I bought these 5mm x 10mm bushings, and drilled them out using Cerebus' favored manner of embiggening a hole: 1/64th (or whatever set you have) at a time up the drill index until you get to the right size. Time-consuming
![](https://filedn.com/lEDSGUXnO7mp9lWR3BbARrR/Emoticons/evilplan.gif)
, but i
t does work if you can be patient.As the bushing was small enough, I used a trick taught me by grand-dad for
jackleg machining a bushing: if you can chuck up the bushing in a drill motor, put the drill bit in the vise rather than the usual way, as it makes it
less likely to walk and bore crooked. While this technique is
usually done with a drill press, the principle still obtains here; it's not perfect, but it does
help. It took a few tries, but I got a couple finished bushings that were close enough to straight & square that they could be soldered to a backing plate.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429117;image)
Here I have the washers drilled out for the m3 screws, then screws and nuts holding that to the washer-cum-backplate. After this, I ground the plating down to bare steel in the center of the washer with a Dremel, and a 7/32" drill bit through all of it to align & index the bushing against the hole in the casting.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429123;image)
You may be wondering why I went through the hassle of making the backing plates instead of soldering directly to the iron casting; the answer is, I tried and none of the fluxes I have on hand would give satisfactory wetting, not even this highly aggressive stuff, which is essentially a small tub of plumber's flux.
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)
I know the soldering looks a bit ugly and lumpy; I've deliberately built-up around the outside with this lead-free silver-bearing solder in hopes of adding a bit of strength to these sintered-bronze bushings, which are essentially porous metal sponge intended to be supported by whatever bit of metal they're pressed into. We'll see how it holds up.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429129;image)
The backing plates required trimming to allow clearance for the knob trim rings; now that the fabricobbledy is done and the shafts dry-fitted, time to scrub everything with IPA lest that caustic flux come back to bite me in the arse.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429135;image)
And finally a quick spritz with some Dollar-Store Rustoleum to appease the booty-fab gods.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)
A wirebrush & paint to hide the welder I ain't...
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1411237;image)
Here we are at the moment of truth... mating up the completed parts to the valve body. They warn you to never oil a gas valve, as it can mess up the grease in this precision-machined cone valve. Tinkerdwagon of course doesn't listen, and puts the tiniest drop of
Supco ZOOM! Oil on the knob spindle shaft to ensure it can move smoothly. The two parts never actually come in contact; only that little pin which turns the cone slug in the valve body.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429147;image)
There's a little spring goes in there, then put it all together with slightly longer screws.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429153;image)
After that, add the trim rings and knobs...
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429159;image)
...and now we're cooking with
propane.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1429171;image)
And the money shot: 85% lean ground chuck humbugglers with a sprinkle of garlic & onion powder (and my red stuff
![Evil >:D](https://www.eevblog.com/forum/Smileys/default/evil.gif)
), some Havarti cheese for me and mild Cheddar for the wife & daughter. Added some boutique 100% beef (from cattle raised in a day-spa, if the package is to be believed
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/shocked.gif)
) Polish sausages from COSTCO, and the smell was good enough to actually bring the family all together for a sit-down meal.
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
Time and effort well-spent, says I.
mnem
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1097200;image)