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Yes, you should put the corner radii on the o ring grooves 
you want them!
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you want them!Sent from my SM-S911U using Tapatalk
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Making an HPA probe
- Thread starter WobblyHand
- Start date
- Joined
- Dec 18, 2019
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- 7,495
Finally back to here again. Made a sensitive drill for my lathe. There's a separate thread for that in my projects area. Took me two days to make. Tried it out today. Drilled a 12mm deep 1.5mm diameter hole in the bottom of a 13mm deep 2.5mm diameter hole. It takes a while to drill, but it was successful. It looks a little ungainly, but hey, it worked. It consists of an Albrecht 0-3mm chuck mounted on a JT0 to 1/2 arbor. This is slid into a sleeve with a 0.5000" ID. The sleeve has a 13mm diameter tail to it, which is held by a chuck. If the micro drill bit packs with chips, it wants to rotate in you finger tips. This is a safety. It's your signal to extract the bit from the work piece and to clear the chips.
Now where was I?
Now where was I?
- Joined
- Dec 18, 2019
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Well, life has a funny way of messing up machining plans. But today, got a chance to work on it again.
Took the pre-drilled 3/8" rod and turned it to diameter, at 6.95mm and 7.86mm. Used a piece of MoMax HSS, that I had found in my father's desk (about a year ago) to turn the 1144. Very satisfying to use one of his tools. I think the MoMax dates from when he worked in the Radiation Laboratory, around and after WWII. He was a technician there, and was a jack of all trades, working on synchrotrons, magnetrons, and all sorts of interesting projects. He had to learn on the fly, learning how to fabricate and use vaccum furnaces, make magnetrons and klystrons, and whatever was asked of him. Anyways, back to machining.
Used a 3/8" collet, and a 7mm collet to hold the probe. First I turned the long 24mm section to just under 7mm. Then I changed collets to 7mm and flipped the piece and turned the remaining 3/8 stock to 7.86mm. Well, almost 7.86, I got 7.862mm, not wishing to muff it, I'm leaving that alone! For the 7.86 section, I took 2 0.25mm passes, a 0.15mm pass, a 0.1mm pass, an 0.05mm pass and a 0.038 pass. I was checking for deflection, but fortunately, there was very little. Love that HSS.
Now I'm wondering if now's the time to cross drill it, as I haven't put in the rest of the features. The hole is only 1mm in diameter, and I have to drill it on the mill. Think that will be the next step. I don't know how straight the previously drilled 1.5mm hole is, hope I'll intercept it, because that's how the air gets to the airgun!
Oh, I already have a spare probe. This work is for me to learn how to make things outside of my comfort zone. It's been a learning experience in design and in implementation. Slowly building skills.
Anyways, this is the print so far. Really ought to have another page, the dimensions are a bit cluttered for me. And incomplete. I try to fix them as I find them - usually when trying to machine it! Oh, I didn't dimension that. Stop. Go fix that, make new print, back to the shop...
Took the pre-drilled 3/8" rod and turned it to diameter, at 6.95mm and 7.86mm. Used a piece of MoMax HSS, that I had found in my father's desk (about a year ago) to turn the 1144. Very satisfying to use one of his tools. I think the MoMax dates from when he worked in the Radiation Laboratory, around and after WWII. He was a technician there, and was a jack of all trades, working on synchrotrons, magnetrons, and all sorts of interesting projects. He had to learn on the fly, learning how to fabricate and use vaccum furnaces, make magnetrons and klystrons, and whatever was asked of him. Anyways, back to machining.
Used a 3/8" collet, and a 7mm collet to hold the probe. First I turned the long 24mm section to just under 7mm. Then I changed collets to 7mm and flipped the piece and turned the remaining 3/8 stock to 7.86mm. Well, almost 7.86, I got 7.862mm, not wishing to muff it, I'm leaving that alone! For the 7.86 section, I took 2 0.25mm passes, a 0.15mm pass, a 0.1mm pass, an 0.05mm pass and a 0.038 pass. I was checking for deflection, but fortunately, there was very little. Love that HSS.
Now I'm wondering if now's the time to cross drill it, as I haven't put in the rest of the features. The hole is only 1mm in diameter, and I have to drill it on the mill. Think that will be the next step. I don't know how straight the previously drilled 1.5mm hole is, hope I'll intercept it, because that's how the air gets to the airgun!
Oh, I already have a spare probe. This work is for me to learn how to make things outside of my comfort zone. It's been a learning experience in design and in implementation. Slowly building skills.
Anyways, this is the print so far. Really ought to have another page, the dimensions are a bit cluttered for me. And incomplete. I try to fix them as I find them - usually when trying to machine it! Oh, I didn't dimension that. Stop. Go fix that, make new print, back to the shop...
- Joined
- Dec 18, 2019
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Up to Rev E on the drawing, go figure.
But, I was able to cross-drill the 1mm hole through the 6.95mm body! I was sweating that. Put it in the dividing head, indicated it, used a 3mm spotting drill to make a tiny dimple, installed the 1mm drill into my mill drill chuck, turned up the mill speed to 2500 RPM and slowly peck drilled that tiny little hole. The hole came out nice. Better yet, (after I cleaned everything out) I could see light at the bottom of the probe, light that was coming in the sides of the 1mm cross hole! That makes me feel so much better.
Might get a chance to work on this tomorrow. I'm encouraged, as I was dreading that hole. Even bought three 1mm drill bits, since I was petrified I'd break it.
But, I was able to cross-drill the 1mm hole through the 6.95mm body! I was sweating that. Put it in the dividing head, indicated it, used a 3mm spotting drill to make a tiny dimple, installed the 1mm drill into my mill drill chuck, turned up the mill speed to 2500 RPM and slowly peck drilled that tiny little hole. The hole came out nice. Better yet, (after I cleaned everything out) I could see light at the bottom of the probe, light that was coming in the sides of the 1mm cross hole! That makes me feel so much better.
Might get a chance to work on this tomorrow. I'm encouraged, as I was dreading that hole. Even bought three 1mm drill bits, since I was petrified I'd break it.
- Joined
- Dec 18, 2019
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Ground a HSS tool to form the 120 included angle. Well, it's about 120 degrees, within a 1/2 degree maybe. Nothing fancy, didn't even hone it. About 15 degree side rake, 0 degree on the top, like a threading tool. Was thinking about Mikey when I ground it, RIP.
And then I slowly plunged 0.7mm. When that was done, I moved it slowly over by 1.5mm. QD/Foster groove done. It's a relatively snug fit to my female Foster pump whip fitting, so that's good. A little more progress
Now I need to do the other end, with all the o-rings. I'll slightly radius the tips of the parting blade, for the HPA o-rings. Then I need to make a rounded groove tool, that will be from HSS as well, might just use a parting blade and radius it even more. I can either save the blade, or grind it square again if I need it.
And then I slowly plunged 0.7mm. When that was done, I moved it slowly over by 1.5mm. QD/Foster groove done. It's a relatively snug fit to my female Foster pump whip fitting, so that's good. A little more progress
Now I need to do the other end, with all the o-rings. I'll slightly radius the tips of the parting blade, for the HPA o-rings. Then I need to make a rounded groove tool, that will be from HSS as well, might just use a parting blade and radius it even more. I can either save the blade, or grind it square again if I need it.
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- Dec 18, 2019
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The HPA o-ring grooves are in, or at near depth. Print called for 1.4 depth, I did 1.375mm. I gently radiused the corners, have no idea what the radius is, but it's not sharp. Just a small area of ground surface that you can see reflected in the light. Afterwards, grabbed a piece of 1/16 parting blade and rounded it off. Needed some hand work to fix up the radius. Need to move the work piece a little, as the groove would be next to the chuck surface. Might flip it around since there isn't much to grab onto any more. Basically, to look like the picture in the previous post.
Well, that wasn't too hard. Now I have to coax the NBR90 o-rings onto this. Strangely all the same size, 1.5 CS x 7 OD. I might use NBR70 for the bumper, to make it easier on me. I heard you boil the o-rings to get them pliable enough?
Yes, the probe fits in the airgun, just checked! Gee, just noticed, the cross-hole in the original is bigger. Don't know why I thought it was 1mm. I made mine with 1mm - it will help me tell mine from the original...
Well, that wasn't too hard. Now I have to coax the NBR90 o-rings onto this. Strangely all the same size, 1.5 CS x 7 OD. I might use NBR70 for the bumper, to make it easier on me. I heard you boil the o-rings to get them pliable enough?
Yes, the probe fits in the airgun, just checked! Gee, just noticed, the cross-hole in the original is bigger. Don't know why I thought it was 1mm. I made mine with 1mm - it will help me tell mine from the original...
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- Dec 18, 2019
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So I had a little diversion, had to make a taper gizmo so I could get the NBR90 o-rings onto the probe. I couldn't get the last o-ring on. So I made this:
Then I drilled it with a 1.95mm drill 5mm deep. Took it to the mill and cross drilled a 1mm hole half way through as a weep hole.
Then I pressed in a 2mm diameter pin, 4mm deep. Then I drilled the probe with a 2mm drill (actually an oversized 1.95mm drill bit) as a receptacle. This allowed me to push the taper flush to the probe. The taper was lubricated with silicone oil. Then I installed an o-ring on the taper small end and wiggled it up onto the taper and eventually onto the probe.
Finally it is complete.
I never anticipated that installing the o-rings would prove to be so difficult. I'm going to modify the other probes so when the o-rings need replacement, I can re-use this tool to make it easier.
Then I drilled it with a 1.95mm drill 5mm deep. Took it to the mill and cross drilled a 1mm hole half way through as a weep hole.
Then I pressed in a 2mm diameter pin, 4mm deep. Then I drilled the probe with a 2mm drill (actually an oversized 1.95mm drill bit) as a receptacle. This allowed me to push the taper flush to the probe. The taper was lubricated with silicone oil. Then I installed an o-ring on the taper small end and wiggled it up onto the taper and eventually onto the probe.
Finally it is complete.
I never anticipated that installing the o-rings would prove to be so difficult. I'm going to modify the other probes so when the o-rings need replacement, I can re-use this tool to make it easier.
- Joined
- Dec 18, 2019
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Nothing. I only had one of them. At 7mm in diameter, and 38mm long, they are too easy to lose. To buy another one is maybe $20. By the way, I did buy another, but I still made one. Was hedging my bets. I didn't need to.
To make my own, I learn new and valuable skills. It means that my skill level goes up and I'll be able to make replacements well into the future, long after the company ceases production. It's simply an exercise for me to improve my abilities by making stuff that was impossible for me to do in the past.
I live in an old house. There's stuff here that was last made a hundred years ago. Or stuff that was made two years ago, that's ridiculous to buy new. So I make it, or repair it using my new skills.
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