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Inner shapes and contours of mouthpieces

Postby kingrob76 » Tue Feb 18, 2020 2:40 pm

Recently I have become interested (re-interested?) in updating some testing I did 30-35 years ago to visually quantify the inside shape of a mouthpiece in order to help determine and understand better what characteristics worked for me. The pre-dialup internet solution I came up with was to soak paper towels and jam them into the cup. Once dry they could be carefully removed (usually) and give me some idea of the shape. While extremely crude this was useful in making A to B to C comparisons.

I'm at a point now where I'd like to revisit that idea make "casts" of mouthpieces for the same reasons. Cutting a mouthpiece in half would work, but, there are some no-longer-available pieces I'd like to examine, so a casting of some sort seems ideal. Since backbores usually widen as they approach the end of the receiver this will have to be a cup / throat effort I expect.

The question I put to the TNFJ is this: What's the best way to create a casting using the mouthpiece itself as a mold that is a) removable and b) not going to ruin the mouthpiece?
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Re: Inner shapes and contours of mouthpieces

Postby Worth » Tue Feb 18, 2020 4:45 pm

As a retired dentist, I would offer the idea of a polyvinylsiloxane elastomeric putty. Excellent dimensional stability over time, easy to mix the two components (kneaded together with your fingers) and sets in under 5 minutes. They are available on Amazon to the general public and although not all that cheap, this could be a decent option. You can also make really good custom earplugs with it.
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Re: Inner shapes and contours of mouthpieces

Postby marccromme » Tue Feb 18, 2020 5:47 pm

Yes, Dentist PuTTY works really well. And can be cut with sharp scalpel into two halves, thus showing the internal cup profile nicely
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Re: Inner shapes and contours of mouthpieces

Postby timothy42b » Wed Feb 19, 2020 8:27 am

Bench rest rifle competitors use something called Cerrosafe to cast chambers.

https://www.midwayusa.com/product/1007021082
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Re: Inner shapes and contours of mouthpieces

Postby tadawson » Wed Feb 19, 2020 4:04 pm

Note that rifle chambers, unlike a mouthpiece, never rewiden and narrow again . . . IE solid metal will be removable, unlike a mouthpiece, where something with enough elasticity to be removable would be mandatory. I agree with a medical type putty or gel - the stuff used to take ear canal impressions would likely be ideal, since they have numerous twists, turns, narrowings, etc. to deal with.
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Re: Inner shapes and contours of mouthpieces

Postby Tom » Wed Feb 19, 2020 4:13 pm

tadawson wrote:Note that rifle chambers, unlike a mouthpiece, never rewiden and narrow again . . . IE solid metal will be removable, unlike a mouthpiece, where something with enough elasticity to be removable would be mandatory. I agree with a medical type putty or gel - the stuff used to take ear canal impressions would likely be ideal, since they have numerous twists, turns, narrowings, etc. to deal with.


I was thinking about that. Even with dental putty or wax or something of that sort, how do you get it out of the backbore/shank intact considering you have to deal with there being a choke point? If the material has to remain flexible enough to be forced through the choke point from one side or the other, then the casting will be destroyed in the process and render the whole thing useless, yes?
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Re: Inner shapes and contours of mouthpieces

Postby marccromme » Wed Feb 19, 2020 4:56 pm

Nope. You make two casts, one for the bowl side, another from the backboard side. Since you know the length of the mouthpiece, you know where they should meet. Easy
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Re: Inner shapes and contours of mouthpieces

Postby Worth » Wed Feb 19, 2020 5:04 pm

Ideally, a cartridge system with a heavy body injectable material would be best. Something like this, plus with cartridges you need the dispensing gun as well. Examples below
https://smile.amazon.com/Defend-Impress ... 413&sr=8-1
https://smile.amazon.com/CNBTR-Dispense ... 586&sr=8-6
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Re: Inner shapes and contours of mouthpieces

Postby bort » Wed Feb 19, 2020 5:08 pm

How do people make exact copies of mouthpieces? Maybe there's something in that...?

Otherwise...

Computers...

https://youtu.be/lE1bS-Mn2Mk" target="_blank
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Re: Inner shapes and contours of mouthpieces

Postby Tom » Wed Feb 19, 2020 6:13 pm

marccromme wrote:Nope. You make two casts, one for the bowl side, another from the backboard side. Since you know the length of the mouthpiece, you know where they should meet. Easy

Well, okay...I had been thinking about it being done as a one piece casting which seems impossible.

Casting separate pieces would be a way around that problem.
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Re: Inner shapes and contours of mouthpieces

Postby Donn » Wed Feb 19, 2020 7:16 pm

Right. If the elasticity of your material is just perfect for the application, you might be able to pop the backbore through the throat, without any permanent deformation, but that seems like a long shot. The good thing about something like the dental putty is (I think) you could expect it to naturally pack into the cup without fully expanding into the backbore, and vice versa, and if you did it right you might even be able to make a mated pair of castings there. With a liquid material like melted wax, you'd just have to bung up the throat. Since the throat itself is one of the interesting features of a mouthpiece design, the approach that yields a good representation there is a winner.
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Re: Inner shapes and contours of mouthpieces

Postby tadawson » Wed Feb 19, 2020 11:16 pm

Tom wrote:
tadawson wrote:Note that rifle chambers, unlike a mouthpiece, never rewiden and narrow again . . . IE solid metal will be removable, unlike a mouthpiece, where something with enough elasticity to be removable would be mandatory. I agree with a medical type putty or gel - the stuff used to take ear canal impressions would likely be ideal, since they have numerous twists, turns, narrowings, etc. to deal with.


I was thinking about that. Even with dental putty or wax or something of that sort, how do you get it out of the backbore/shank intact considering you have to deal with there being a choke point? If the material has to remain flexible enough to be forced through the choke point from one side or the other, then the casting will be destroyed in the process and render the whole thing useless, yes?


That's why I suggested the stuff used for ear molds. No backside mold possible, but flexible so that you can stretch it (narrows it) to get it past the restriction, and have it stay intact coming out. Two molds could also work, but I would think that most mouthpieces would not require it.

Kinda of like silicone rubber - it's amazing what it can snap back from.
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Re: Inner shapes and contours of mouthpieces

Postby Donn » Thu Feb 20, 2020 12:42 am

I think in the interest of science, all of these methods will have to be employed, and the results carefully compared.
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Re: Inner shapes and contours of mouthpieces

Postby YORK-aholic » Thu Feb 20, 2020 2:58 am

bort wrote:How do people make exact copies of mouthpieces? Maybe there's something in that...?
Otherwise...
Computers...
https://youtu.be/lE1bS-Mn2Mk" target="_blank" target="_blank" target="_blank



My understanding is that Kanstul used a 3D scanner to scan and digitize mouthpieces, then cut the file using a CNC lathe.

There are semi-cheap (relative term) 3D scanners available. I have no experience with them or how they would do on interiors.

If you went that route the files should be able to be 'sliced' to give the same result (on the computer screen) as cutting a mouthpiece in half lengthwise. Then you'd be able to overlay different mouthpiece shapes to compare contours and dimensions.
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Re: Inner shapes and contours of mouthpieces

Postby Donn » Thu Feb 20, 2020 10:41 am

YORK-aholic wrote:My understanding is that Kanstul used a 3D scanner to scan and digitize mouthpieces


And that guy, James R New, still does, when he intends to copy a mouthpiece. Sends it out to be scanned, that is. No idea who does it or how much it costs. I suppose it's a particularly obvious way to go, if the object is to make CNC instructions.
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Re: Inner shapes and contours of mouthpieces

Postby kingrob76 » Thu Feb 20, 2020 12:24 pm

Great ideas here - thanks everyone!
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Re: Inner shapes and contours of mouthpieces

Postby tadawson » Thu Feb 20, 2020 6:19 pm

Frankly, since mouthpieces are circular (IE no variation in diameter around the circumference at any given depth), it would seem that something similar to a key cutter with a probe and a marker would give the profile, and from that, a duplicate can be cut, models made, etc. (If someone has one that is asymmetrical, then clearly this won't work . . . ).
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Re: Inner shapes and contours of mouthpieces

Postby Donn » Thu Feb 20, 2020 7:52 pm

I think I know what you mean, but "key cutter" doesn't call it up. Some kind of contour gauge?

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Re: Inner shapes and contours of mouthpieces

Postby timothy42b » Fri Feb 21, 2020 9:13 am

Maybe try pantograph instead.
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Re: Inner shapes and contours of mouthpieces

Postby tadawson » Fri Feb 21, 2020 4:04 pm

Pantograph is the proper term, although the key cutters pretty much accomplish the task without all the linkages in a pantograph - basically a probe and marker that is free to move left/right, but fixed about an axis such that the 'up/down' of both is the same (and somehow, that doesn't seem much clearer . . .)

'key duplicator' did have some relevant hits in a search . . .
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