Might have blown this part, can I safely use it?

WobblyHand said:
Think the stock part with the 2.5mm hole is a lost cause unless I basically plug the hole again. Since I don't know the material, it's hard to know how to proceed, save for plugging perhaps.

The part I made with 1144 and the 2mm hole, I think is ok. I'd feel a lot better if I could sim it. I may take my model, make a copy of it, and cut off the right hand side. Basically just simulate the first 10mm of left hand side, while under appropriate pressure.

Below are some pictures and description of the 1144 probe I made.

Yes, the blind hole is simply to allow for a taper tool to register to the part, to install o-rings. Without the taper tool, it's a 5 ring circus trying to install the small, hard, lubricated o-rings. Stretching a lubed 1.5x4 NBR90 o-ring from 4mm to 7mm and getting it over the probe without the tool is not possible for me. I spent a day trying. With the tool, the o-rings were installed in about a minute. I could make the pin shorter, say 2-3mm, or thinner. I have some 1.6x8mm pins available.

Here's the taper tool. 4mm section, tapering to 7mm over 25mm, with 15mm ends. The ends were so I could grab it in a chuck at either end. I hadn't pressed in the 2mm pin yet.
View attachment 503009
Butted up to the probe, with the o-rings successfully installed. I put an o-ring on the 4mm end, then pushed it to the taper. Then I installed the drill chuck to hold the taper and press it against the probe, which is being held by an 8mm collet. Getting the o-rings up the taper was not that easy to do even with the tool, the taper was about 6.9 degrees, and those NBR90's fought me nearly all the way. Once at the grooves they just jumped in.
View attachment 503010
Registration pin picture with the blind hole in the probe.
View attachment 503011
That pin in the taper tool looks big in this picture. It's only 2mm, or 0.079" in diameter, and 4mm (0.1575") long. It could be smaller in diameter and shorter, but I feel something like it is necessary. I suppose one could install the pin in the probe, but having a pin stick out seems like it's waiting to be damaged. The taper tool would only be used for installation of o-rings. Plus installing the pin would require a weep hole to allow the compressed air to escape. I did drill that weep hole on the taper tool, but it's not visible in the picture. I wouldn't want to install a weep hole in the probe.
Click to expand...
The original part has a radius on the end. Can you make a shallow tapered bore in the end of your taper tool that will register on the radiused end of the probe? Tailstock pressure would keep it in place while you slide the o-ring, and no blind hole in the probe is needed. (Also no pesky pin in the end of the taper tool.)
 
jmkasunich said:
The original part has a radius on the end. Can you make a shallow tapered bore in the end of your taper tool that will register on the radiused end of the probe? Tailstock pressure would keep it in place while you slide the o-ring, and no blind hole in the probe is needed. (Also no pesky pin in the end of the taper tool.)
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An interesting idea. Theoretically very possible. However, not sure how to do that. Kind of a beginner hobby machinist, really. Biggest thing that is missing is adequate magnification to see the features I'd need to machine. As the parts get smaller, it's harder to hold, and errors get magnified. Just being on center, for instance is much tougher for a small diameter part than say for for a 100mm part.

Having played with tapers, they are hard to get right, as they are quite sensitive to error. Maybe I could do something simpler like a truncated 60 degree cone. 60 is nice since you can use center drill for one end.
 
WobblyHand said:
An interesting idea. Theoretically very possible. However, not sure how to do that. Kind of a beginner hobby machinist, really. Biggest thing that is missing is adequate magnification to see the features I'd need to machine. As the parts get smaller, it's harder to hold, and errors get magnified. Just being on center, for instance is much tougher for a small diameter part than say for for a 100mm part.

Having played with tapers, they are hard to get right, as they are quite sensitive to error. Maybe I could do something simpler like a truncated 60 degree cone. 60 is nice since you can use center drill for one end.
Click to expand...
You could chamfer the part and drill a hole in the end of the tool. Then it’s just a matter of lightly chamfering the ID of the tool until it fits your part. When you make more parts in the future the taper tool can be used as a chamfer gauge !
 
I was kind of having this same idea as soon as I saw your actual part in the lathe. Is that "always" an option or does this need to be "field servicable?

Using the chamfer on the original part (doesn't take much), you could take the center out (just a little, no deeper than the chamfer, and the angle need not be critical, just so long as it registers on the outside of the taper, which is the large diameter of the taper. The O-ring doesn't care what happens in that empty space that it can't get to.The lathe would keep anything from being way out, and if it were out by a few thousandths (or probably much more) the tapers, even sloppy ones, would guide everything right into position.

I dunno... If it were me (and that's a big if....), but if it were me, your 1144 with a 2mm or smaller hole in it, that's a number that can be worked with. It "might" be less than the original, (or maybe better), but it's in a known commodity. That, to me, would take it from red alert status to "don't point it at your eyeballs status anyhow. If you could get that "cup" cut in the installer tool (and again, only the absolute outside most part of it really matters), that'd relieve a lot of doubt for me.
 
Firstram said:
You could chamfer the part and drill a hole in the end of the tool. Then it’s just a matter of lightly chamfering the ID of the tool until it fits your part. When you make more parts in the future the taper tool can be used as a chamfer gauge !
Click to expand...
That sounds practical. Good idea. Think that's very doable.

It does mean back to the drawing board. Not complaining, but I need to do some head scratching to make it all work.

When I design stuff, I sit there and think, how could I make that in the shop? If I can't figure out a way, I stop. At that point, I may change the design to something I believe I can actually machine. For the case of machining, it has to be an operation with tools I own, or are inexpensive to acquire.

verbotenwhisky said:
Cool.... I do very heavy weight stuff on this machine with extreme file sizes but it is a beast, its a laptop that is bigger than most desk tops.
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My laptop is pretty svelte. It's not a powerhouse, but it's ok for small work. 36GB RAM and 1TB SSD. I've simulated using 10 out of 12 cores on some of my CFD work. (Supersonic rocket model.) Had to quarter my model using cylindrical symmetry on an FEA sim as I was running out of memory. It's very easy to use up a lot of memory.
 
Jake M said:
I was kind of having this same idea as soon as I saw your actual part in the lathe. Is that "always" an option or does this need to be "field servicable?

Using the chamfer on the original part (doesn't take much), you could take the center out (just a little, no deeper than the chamfer, and the angle need not be critical, just so long as it registers on the outside of the taper, which is the large diameter of the taper. The O-ring doesn't care what happens in that empty space that it can't get to.The lathe would keep anything from being way out, and if it were out by a few thousandths (or probably much more) the tapers, even sloppy ones, would guide everything right into position.

I dunno... If it were me (and that's a big if....), but if it were me, your 1144 with a 2mm or smaller hole in it, that's a number that can be worked with. It "might" be less than the original, (or maybe better), but it's in a known commodity. That, to me, would take it from red alert status to "don't point it at your eyeballs status anyhow. If you could get that "cup" cut in the installer tool (and again, only the absolute outside most part of it really matters), that'd relieve a lot of doubt for me.
Click to expand...
Real pictures, rather than drawings always help. :). That's why I posted them.

Prior to making the tool it was impossible for me to stretch that tiny hard o-ring over the probe. It really was a struggle. Then I came up with the taper and I was really worried about maintaining alignment, or me knocking the taper out of alignment. I had wanted alignment on both ends, at the probe end, and the skinny 0.157" diameter end, since I was really exerting a bit of force on those itty bitty o-rings. I was afraid I'd knock the big end off and bend the small end. That taper took far longer than it should have, probably since I chose the less favorable way of doing it (out of ignorance), so I didn't want to damage it.

I'm up for another go at it. It would be good to safely alter my stock probe as well. That appears to be a chamfer at the LHS, rather than a radius. Then I could make a new taper tool to match it. Making the probe was an interesting exercise - because it exposed that the o-rings are really hard to put on, especially if they are NBR90's. So I did learn about the need to make the taper tool.

Stock probes seem to cost about $18. I can assure you that I put in far more than $18 of labor in making mine. It was fun, because it was a challenge in several ways. But if I drop the stock probe into the dirt, (and stuff like that happens in the real world) I will want to be changing out the o-rings. Getting them out is easy, you can just partially cut them and pull them apart. Putting new o-rings in isn't easy, at least without some kind of fixture.
 
When I design stuff, I use Elon Musk’s approach. Make one, ruin it and try to make a better one. Eventually I nail it!
 
Extend the end of the probe to get your pin hole out from under the o ring...

Collapse calculations are complex and sensitive to minor out of roundness. Very fuzzy results...

Sent from my SM-S911U using Tapatalk
 
WobblyHand said:
That sounds practical. Good idea. Think that's very doable.

It does mean back to the drawing board. Not complaining, but I need to do some head scratching to make it all work.

When I design stuff, I sit there and think, how could I make that in the shop? If I can't figure out a way, I stop. At that point, I may change the design to something I believe I can actually machine. For the case of machining, it has to be an operation with tools I own, or are inexpensive to acquire.


My laptop is pretty svelte. It's not a powerhouse, but it's ok for small work. 36GB RAM and 1TB SSD. I've simulated using 10 out of 12 cores on some of my CFD work. (Supersonic rocket model.) Had to quarter my model using cylindrical symmetry on an FEA sim as I was running out of memory. It's very easy to use up a lot of memory.
Click to expand...
I do a great deal of Laser scan work and CAD design, Brownfield work where I scan a facility and asbuilt what is required to modify existing facility or add new equipment. Many of my point clouds are between 50 and several hundred GB before I start adding to the model so the machine I have has 64GB RAM 12th gen, i9, 12th gen and 8TB SSD. We also do FEA and CFD but I am not typically involved in that.
 
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