Replacement backflow valve piston

I didn't like the piece that was machined, it didn't fit well in the mating assembly. Decided to measure things again and found an error. Too much taper length and not quite the correct angles. I thought this would be a learning experience, and so far it is. Modified the drawings to reflect the new measurements. Cut a new piece of aluminum and started again. This time I bought the float piston and the bonnet down to the shop. This is what I have so far. To get the critical outer angle, I put the float piston in the chuck and set the compound angle with a DTI running along the ears. It was very close to what I had calculated. The taper fit correctly in the bonnet part of the valve. Much better than the first attempt.
PXL_20220420_202521002.jpgPXL_20220420_202533655.jpg
Used the bushing I made yesterday to hold the boring bar.
PXL_20220420_202556006.jpg

I am at the point where I need to make an o-ring groove tool. Found a piece of HSS and wanted to cut it off. Of course the 4-1/2" grinder had a grinding disk rather than a cut-off wheel. This lead to going into the garage to find the pin spanner tool to pull the special nut. Got that done and noticed that I needed a large thick flat washer to get the cut-off disk away from the guard. Don't even remember seeing a washer like that. Well I can make one! Found a piece of 1.5" 12L14 and cut off a chunk. Did the work in the mini-lathe, as I didn't want to disturb the piston. Long story short, didn't make the washer thick enough. Eventually made another one, and finally cut off a piece of the HSS. Made a mess on both lathes and the mill today. Too tired to deal with it tonight.

Cleanup will be the first order of business tomorrow. Then will grind a radiused o-ring tool.
 
Goodness, in my cleanup of the other day, I used some mineral spirits to clean up some of the lathe. What an awful mistake. Not because it didn't work, but because I was exposed to a lot of fumes in a relatively closed area. These fumes gave me incredible headaches and made the area around my eyes hurt. I had a migraine like headache for 8 hours post exposure. I'm kind of surprised, because I didn't use very much mineral spirits. I just briefly wet a paper towel in a single spot and used that to wipe down the carriage and some of the paint. I did open a window in the basement to improve ventilation, but it was not enough.

While cleaning, I managed to knock over some lathe tool holders with the vacuum cleaner hose. My parting tool fell onto the concrete floor, just missing the rubber floor mat, and snapped off the parting blade. Was an 1/8" thick blade, and was surprised it snapped. Got me mad enough to figure out how to make some tool holders for the backsplash. Designed something up and bought some material. Hope the stuff will get delivered today. My tool holders were all over the place. Hopefully the tool rack will help that a lot. Yet another project, but this one should make my machining life better.

Managed to get the HSS cut with with cut-off wheel on the grinder. So something useful got done the other day.

Last night was a poor night sleep, which is typical for me if I am exposed to chemicals. This morning I felt out of sorts and a little sick to my stomach. You know that feeling where you want to do something, but somehow can't make yourself move to do it, because you start feeling sick again... Fortunately, feeling a bit better this afternoon. I moved the mineral spirits out of the basement back into the garage. Not ever going to use mineral spirits indoors again. No thanks, don't need to get ill like that again.

Spent an hour outside today weeding the garden - good to get some fresh air for a change. Loads better than breathing chemical fumes.
 
WobblyHand said:
Goodness, in my cleanup of the other day, I used some mineral spirits to clean up some of the lathe. What an awful mistake. Not because it didn't work, but because I was exposed to a lot of fumes in a relatively closed area. These fumes gave me incredible headaches and made the area around my eyes hurt. I had a migraine like headache for 8 hours post exposure. I'm kind of surprised, because I didn't use very much mineral spirits. I just briefly wet a paper towel in a single spot and used that to wipe down the carriage and some of the paint. I did open a window in the basement to improve ventilation, but it was not enough.

While cleaning, I managed to knock over some lathe tool holders with the vacuum cleaner hose. My parting tool fell onto the concrete floor, just missing the rubber floor mat, and snapped off the parting blade. Was an 1/8" thick blade, and was surprised it snapped. Got me mad enough to figure out how to make some tool holders for the backsplash. Designed something up and bought some material. Hope the stuff will get delivered today. My tool holders were all over the place. Hopefully the tool rack will help that a lot. Yet another project, but this one should make my machining life better.

Managed to get the HSS cut with with cut-off wheel on the grinder. So something useful got done the other day.

Last night was a poor night sleep, which is typical for me if I am exposed to chemicals. This morning I felt out of sorts and a little sick to my stomach. You know that feeling where you want to do something, but somehow can't make yourself move to do it, because you start feeling sick again... Fortunately, feeling a bit better this afternoon. I moved the mineral spirits out of the basement back into the garage. Not ever going to use mineral spirits indoors again. No thanks, don't need to get ill like that again.

Spent an hour outside today weeding the garden - good to get some fresh air for a change. Loads better than breathing chemical fumes.
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Ugh, yeah chemicals in a small shop are not fun. I think I've gotten more sensitive over the years. My preference is isopropyl alchohol for general purpose cleaning. It does evaporate much faster than mineral spirits. Before the pandemic you could get a gallon pretty cheap, still a little pricier these days, but isn't everything?
 
rabler said:
Ugh, yeah chemicals in a small shop are not fun. I think I've gotten more sensitive over the years. My preference is isopropyl alchohol for general purpose cleaning. It does evaporate much faster than mineral spirits. Before the pandemic you could get a gallon pretty cheap, still a little pricier these days, but isn't everything?
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Seems like I also have become more sensitized to chemical exposure. Remember working with radar absorbing materials and eventually getting collosal headaches from the exposure even after a short time. I'll try isopropyl alcohol again as I don't recall a similar reaction.
 
I was around a painter that had to quit because he became sensitized to the hardener in Imron paint.
 
Today I made a HSS grooving tool. Not the best tool, but it cuts 6061, and I expect it will cut brass just fine. I'm pondering whether the tool is too narrow - or my o-rings are too fat. My o-rings measure about 0.101 - 0.102? Maybe the tip of the tool is slightly undersized. Here is a test cut with the tool. My first cut was on the right, it chattered. Attempted to clean it up, but you can still see the marks. Cut on the left also chattered but I hand turned the chuck to remove the last 0.010" in 0.001" steps. Think it came out nicer. This was done on my mini-lathe, just as a test of the tool.
PXL_20220425_200247928.jpg
Tomorrow, back to the G0752Z and cut the real o-ring groove on the prototype.
 
You don’t need the groove to be full radius, you can move the tool a bit to widen the groove. Typical groove design should be substantially wider than the uncompressed o-ring.
 
jwmelvin said:
You don’t need the groove to be full radius, you can move the tool a bit to widen the groove. Typical groove design should be substantially wider than the uncompressed o-ring.
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Definitely. Was planning to move the tool a little.

Rightly or wrongly, I'm duplicating the float piston I found in the valve. On that piece, the groove is an exact fit to the o-ring. I don't understand the valve enough to make too many changes. The o-ring seats into a taper in the bonnet. Not motivated enough to model the assembly to figure it all out. I'm having enough fun just trying to capture the float piston's essence.
 
The oring groove has a lot to do with how it seals pressures involved and application. In this application in needs to be tight to hold the oring in place And while under pressure and flow.
If your cutting the groove on a taper than your groove should be perpendicular to the taper.
 
Cadillac said:
The oring groove has a lot to do with how it seals pressures involved and application. In this application in needs to be tight to hold the oring in place And while under pressure and flow.
If your cutting the groove on a taper than your groove should be perpendicular to the taper.
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The real o-ring goes in the part this way. The photo was just a test piece to try out the HSS tool I ground.
pistonworing.jpg
The o-ring seals against a conical piece, kind of like this rendering.
valve_n_seat.jpg
Water pressure forces the piston up and the o-ring seals against the conical section. Not shown is a spring which pushes the piston down to break the seal when there is a loss of water pressure. The ears that stick up are guides for the spring. The hollow base of the piston also has guides (not shown) that come up from below to keep the piston in place.
 
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