keep Margin shy-ing

JMN

JMN

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I'm really gonna put myself out there and let you guys have at me for a few.
Can y'all share some tips on how you do margins/ how to prevent shying up margins? I was doing fine for a long time, now i'm sometimes trashing 2-4/day and recasting. Aggravating, and makes you nervous each coping you pick up. Not to mention lost metal, time, die wear, slipping dates, boss reaction...

Biggest weirdness I can note is that my margins & fit are fine at one time, then (edit:when I'll put it back on to check reduction of sprue or think it's ready to be handed off the margin) will be turned under and/or coping is tight fitting requiring them to be redone or taken off w/ rubber wheel, sometimes it's a missed overextension that can't really be seen, at least by me, sometimes it kills the coping...
aaaaaaargggggghhhh.

Please, anything you can think of that helps you, or your process steps, or what tells you to lay off (it before it foils),or that you'd tell someone you're training even may help.
I'm losing (the rest of) my mind.
 
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Tayebdental

Tayebdental

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Jmn,
Do not lose you mind, I think we need more information. it seems inconsistency with the distilled water special liquid ratio, more water, metal coping becomes tighter as we all know.(shy margins). More special liquid loose metal coping (over extension of margin) follow the direction for investment and develop your own ratio, thick wax coping need more special liquid and thin wax coping less special liquid , I hope this helps.
 
JMN

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Unfortunatly it's my hand/eye/handpiece thats the major issue. We havent changed a thing with our wax/investment/metal/ratios. I'm the only one with the problem, so I'm the problem. Sadly.

Edit: I'd never thought of adjusting ratio based on wax thickness, intriging.
 
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desertfox384

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I found if I stray away from my technique even a little I'll have fluctuations in my fits.. best bet is to develop a good technique and do not stray away... use the same wax, the same way every time, etc.. If I let wax copings sit around for 6 hours before I invest them, and then the next day invest them just after I wax I find difference in fits. Shy margins could be caused by a few things.. really thin copings, cold torch, cold burnout, bad sprue technique. Best bet is to tell us your exact process and what you use to do it, and do you wax in a consistent way ?
 
doug

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When I did a lot of waxing I always kept them in a stable area on the bench as I worked, until time to invest. They were away from my waxer, the light(if I happened to have to use an incandescent one) and in an area where the temp was not going to fluctuate. I have warm hands so it's always been important to no handle them too much when spruing. Yes, ladies, I have warm hands. They are off the market as of 6/29
 
JMN

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Sorryy, i need to clarify that I'm grinding/wheeling it off of the coping.

I know just stop sooner right? If it's holding up on fit now and wasn't before, 2 minutes ago, what is happening.

Sorry. I'm not sure that it's not hand pressure, but, golly, you'd think metal wouldn't bend that easy.
 
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JMN

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When I did a lot of waxing I always kept them in a stable area on the bench as I worked, until time to invest. They were away from my waxer, the light(if I happened to have to use an incandescent one) and in an area where the temp was not going to fluctuate. I have warm hands so it's always been important to no handle them too much when spruing. Yes, ladies, I have warm hands. They are off the market as of 6/29

Warm hands?!? Now that is making sense. The margin in wax is taken by placing a roach carver at the land area and gently dragging, cutting away the wax below the margin. I'd wondered how they got overextended, showing the bend of the margin in metal, when they were showing the red line clearly with no shiny wax over the line.

This may help. My hands are usually warm enough I dry my wife's watches out by wearing them for a while if they get wet.
Thanks.
 
2thm8kr

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In my experience, successful casting takes a lot of discipline in your techniques. This is the last place you want to cut corners. From one of your other posts you mentioned a 20 minute burn out on 150gm ovoid ring. If you check the instructions for Fujivest II nowhere does it mention such a short burnout time for a ring that size. You may get away with it plenty of times, but it will bite you in the arse. Try not to let yourself get into a position where you have to rush your burnout or quench your castings, you are introducing uncontrollable variables to your technique. That can sink anyone.

Even though your liquid is new and doesn't appear to have crystals at the bottom it may have frozen at one time making it pretty much useless. I've used Fujivest II since it
came out and have had spot on consistent results. I've had similar problems and the solution was as simple as a different bottle of investment liquid. Order it directly from GC and not your regular supplier, its a cheap and easy way to eliminate an unknown variable. Not to mention keeping you out of the hair club for men.

Good luck, I know how frustrating that can be.
 
2thm8kr

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Edit: I'd never thought of adjusting ratio based on wax thickness, intriging.

Adjust ratio according to density of alloy (specific gravity) not thickness of wax pattern.
 
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Marcusthegladiator CDT

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Some pictures of these margins would help. But are you saying that you have a margin but by the time you finish it it's gone?
Maybe all you need is more practice and more problem solving under your belt...

Either way, pictures of your wax up, sprue technique, and coping would assist you better here..
 
JMN

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I found if I stray away from my technique even a little I'll have fluctuations in my fits.. best bet is to develop a good technique and do not stray away... use the same wax, the same way every time, etc.. If I let wax copings sit around for 6 hours before I invest them, and then the next day invest them just after I wax I find difference in fits. Shy margins could be caused by a few things.. really thin copings, cold torch, cold burnout, bad sprue technique. Best bet is to tell us your exact process and what you use to do it, and do you wax in a consistent way ?

Fairly consistant, die lube (isolit),air-chuck blast excess, dip in renfert tauchwax(sp) at 197, scrape off excess, run bead of corning inlay wax around margin, bead around occlusal table and dots at "stretch" points, build support as needed, fill-in around mesial/buccal/distal/lingual to even out wax depth/height between margin and occlus. table, scrape with roach carver to remove wax knife add/remove points, smooth wax and then place roach carver on same angle as land area, scrape gently 'till on stone and continue scraping in direction opposite from scrape motion(scrape toward and rotate die so as to put carver farther away). Then add sprue, add ceramist's holder on lingual/distal corner. Then they sit in front of me on a small bench-shelf(ikea all over our office) until there's enough to put in a ring.

Putting them on the ring is just pick up, holding die below wax, pull wax off, change hands and hold by holder, melt gate and put onto bar. They then get treated with a brush-drop of wax-it debubblizer/wetting agent and shake off excess wax-it.
Go invest.


Same thing every time unless they want to stick from setting overnight etc., then I pull'em with a rubber dam after a few unsuccessful attempts at fingers only.

Thanks
 
JMN

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Some pictures of these margins would help. But are you saying that you have a margin but by the time you finish it it's gone?
Maybe all you need is more practice and more problem solving under your belt...

Either way, pictures of your wax up, sprue technique, and coping would assist you better here..

That sums it up. Generally I love problem solving, but can't seem to work this back out. It was a non-issue for a long time. Feel like I'm wasting everbody's time, just cannot understand why the margins fold under, that's really the crux of the problem.
 
desertfox384

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Get a microscope if you don't have one.. the waxer needs one and the metal finisher definitely needs one. Yes metal does bend that easy. To finish a margin I use an 8x scope and a small barrel stone that is smoothed out on a truing stone, then lightly go over the margin until its flush.. the microscope saves the day.. I can't believe I ever finished metal without it.
 
Marcusthegladiator CDT

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Get a microscope if you don't have one.. the waxer needs one and the metal finisher definitely needs one. Yes metal does bend that easy. To finish a margin I use an 8x scope and a small barrel stone that is smoothed out on a truing stone, then lightly go over the margin until its flush.. the microscope saves the day.. I can't believe I ever finished metal without it.

I totally agree... I trim my wax under a 8x and finish with the same scope... Even if this doesn't solve your particular problem. It will improve your margin quality overall...
 
JMN

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Get a microscope if you don't have one.. the waxer needs one and the metal finisher definitely needs one. Yes metal does bend that easy. To finish a margin I use an 8x scope and a small barrel stone that is smoothed out on a truing stone, then lightly go over the margin until its flush.. the microscope saves the day.. I can't believe I ever finished metal without it.


I'm using a maginfying lamp, but that sounds nicer for sure. Was taught this way, and was, until recently doing ok, at least looked that way w/o microscope... how do you keep from destroying the microscope's objective lens wigh metal fragments?

Edit: magnifier looks like one of those ring bulb magnifiers, but has a bilb in rear only.
 
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Marcusthegladiator CDT

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I got a giant bulky scope that mounts to the desk and has two solid mobile arms and the whole thing sucks....


I carry this from my wax bench to my finish bench and I love it...

image.jpg

Haven't had any issues scratching up the glass...

But I know it's removable and replaceable... The outside glass isn't a magnifying lense... Just a replaceable piece of glass.... But still, it's clean as a whistle...
image.jpg
 
Tayebdental

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That sums it up. Generally I love problem solving, but can't seem to work this back out. It was a non-issue for a long time. Feel like I'm wasting everbody's time, just cannot understand why the margins fold under, that's really the crux of the problem.

Do you use a stereo microscope to do your wax up?. Thicken the margin slightly and avoid touching the margin when spruing.
 
JMN

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In my experience, successful casting takes a lot of discipline in your techniques. This is the last place you want to cut corners. From one of your other posts you mentioned a 20 minute burn out on 150gm ovoid ring. If you check the instructions for Fujivest II nowhere does it mention such a short burnout time for a ring that size. You may get away with it plenty of times, but it will bite you in the arse. Try not to let yourself get into a position where you have to rush your burnout or quench your castings, you are introducing uncontrollable variables to your technique. That can sink anyone.

Even though your liquid is new and doesn't appear to have crystals at the bottom it may have frozen at one time making it pretty much useless. I've used Fujivest II since it
came out and have had spot on consistent results. I've had similar problems and the solution was as simple as a different bottle of investment liquid. Order it directly from GC and not your regular supplier, its a cheap and easy way to eliminate an unknown variable. Not to mention keeping you out of the hair club for men.

Good luck, I know how frustrating that can be.

Thanks 2thm8kr, that may be helpful too. I'm already in the hair club.

Shouldn't have given my grandfather the bald mans hairbrush...
 
Tayebdental

Tayebdental

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Adjust ratio according to density of alloy (specific gravity) not thickness of wax pattern.

Very well understood of what you're saying,
but experience thought me that if i invest a thick wall wax coping and a thin wax coping in the same ring, they won't fit the same on the die as metal coping, that is why I invest the thin wall wax up coping and the thick wall wax up coping in two separate rings and I use a slightly different distilled water special liquid ratio, ( this way i could control fit with minimum internal adjustment, works with me every time!!
I use slightly more special liquid and less distilled water for thicker wax coping and vise versa .
 
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