Hot knife

D

D Yuniskis

Guest
Hi,

[Obviously, the weekend has been spent disassembling
and repairing/replacing a variety of "toys" :-/ ]

What tricks can be brought to bear disassembling
plastic items that have been solvent welded (or glued)
together IN A COSMETICALLY ACCEPTABLE MANNER?

I typically use a heated exacto knife to slice the
item on the apparent "seem/weld". But, this is
time consuming, wasteful of energy and still doesn't
leave very "clean" results.

I've looked into purchasing a *real* "hot knife" but
I suspect they don't have the thermal mass to deal
with items as massive as most plastic enclosures (?)
 
D Yuniskis <not.going.to.be@seen.com> wrote in message
news:hg56lb$h0t$1@aioe.org...
Hi,

[Obviously, the weekend has been spent disassembling
and repairing/replacing a variety of "toys" :-/ ]

What tricks can be brought to bear disassembling
plastic items that have been solvent welded (or glued)
together IN A COSMETICALLY ACCEPTABLE MANNER?

I typically use a heated exacto knife to slice the
item on the apparent "seem/weld". But, this is
time consuming, wasteful of energy and still doesn't
leave very "clean" results.

I've looked into purchasing a *real* "hot knife" but
I suspect they don't have the thermal mass to deal
with items as massive as most plastic enclosures (?)
Click to expand...

Squash, long ways first, in a carpenters vice usually splits enough in the
middle of the run, to make a start, and then blades. If nothing seems to be
happening , before you chicken out, try diagonally or short ways. Sometimes
will make a small tear into the cosmetic area but I've never had a full tear
into the fare surfaces. Somtimes distorts internal heatsink if up against
the case


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
D Yuniskis wrote:
What tricks can be brought to bear disassembling
plastic items that have been solvent welded (or glued)
together IN A COSMETICALLY ACCEPTABLE MANNER?
Click to expand...
I've had good luck with ham radio battery packs for handhelds by freezing them
and then hitting them on a stone step. The welds crack open.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the
situation. i.e possessing less facts or information than can be found in
the Wikipedia
 
On Mon, 14 Dec 2009 11:59:05 +0000 (UTC), Geoffrey S. Mendelson wrote:
D Yuniskis wrote:
What tricks can be brought to bear disassembling
plastic items that have been solvent welded (or glued)
together IN A COSMETICALLY ACCEPTABLE MANNER?

I've had good luck with ham radio battery packs for handhelds by freezing them
and then hitting them on a stone step. The welds crack open.
Click to expand...
In the same vein, I try the freezing and then use an old wood chisel and
a light mallet along the seam. Sometimes it takes several passes around
the weld. The last bit is usually done with a thin, wide knife blade.
The corners -- if any -- can be the toughest...

GL
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm
 
On Mon, 14 Dec 2009 11:59:05 +0000 (UTC), "Geoffrey S. Mendelson"
<gsm@cable.mendelson.com> wrote:

I've had good luck with ham radio battery packs for handhelds by freezing them
and then hitting them on a stone step. The welds crack open.
Geoff.
Click to expand...
That's what I do. It works best with plastic that has been glued as
the glue becomes brittle when cold. The plastic will bend somewhat
while the glue will crack. It doesn't work so well when the enclosure
has been solvent welded properly. Fortunately, few toys, battery
packs, and devices are properly solvent welded.

For real butchery, there's the ultrasonic knife. For example:
<http://www.abbeon1.com/fabric%20pages/ultrasonickn.html>
<http://www.abbeon.com/store/item.cfm?code=COMPACTULTRASONICKNIFE>
<http://www.youtube.com/watch?v=QvJJDwOocsU>
Think of it as a miniature Milwaukee Sawzall. I don't own one but
have used one to tear apart a reluctant battery pack that was filled
with RTV. It worked quite well, but I can't claim that it was
cosmetically acceptable when I was done. Like all such reciprocating
power tools, it will cut when sharp, but burn when dull. I also tried
to make one out of an electric tooth brush and a razor blade, which
didn't work.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
Geoffrey S. Mendelson wrote:
D Yuniskis wrote:
What tricks can be brought to bear disassembling
plastic items that have been solvent welded (or glued)
together IN A COSMETICALLY ACCEPTABLE MANNER?

I've had good luck with ham radio battery packs for handhelds by freezing them
and then hitting them on a stone step. The welds crack open.
Click to expand...
Hmmm.... I was just about to tackle a small UHF transceiver.
I'll try that (if it doesn't work, I can always trash the
thing :< )
 
N_Cook wrote:
D Yuniskis <not.going.to.be@seen.com> wrote in message
news:hg56lb$h0t$1@aioe.org...
Hi,

[Obviously, the weekend has been spent disassembling
and repairing/replacing a variety of "toys" :-/ ]

What tricks can be brought to bear disassembling
plastic items that have been solvent welded (or glued)
together IN A COSMETICALLY ACCEPTABLE MANNER?

I typically use a heated exacto knife to slice the
item on the apparent "seem/weld". But, this is
time consuming, wasteful of energy and still doesn't
leave very "clean" results.

I've looked into purchasing a *real* "hot knife" but
I suspect they don't have the thermal mass to deal
with items as massive as most plastic enclosures (?)

Squash, long ways first, in a carpenters vice usually splits enough in the
middle of the run, to make a start, and then blades. If nothing seems to be
happening , before you chicken out, try diagonally or short ways. Sometimes
will make a small tear into the cosmetic area but I've never had a full tear
into the fare surfaces. Somtimes distorts internal heatsink if up against
the case
Click to expand...
Ouch! This seems more likely to yield a *mess*...
 
D Yuniskis wrote:
Geoffrey S. Mendelson wrote:
D Yuniskis wrote:
What tricks can be brought to bear disassembling
plastic items that have been solvent welded (or glued)
together IN A COSMETICALLY ACCEPTABLE MANNER?

I've had good luck with ham radio battery packs for handhelds by
freezing them
and then hitting them on a stone step. The welds crack open.

Hmmm.... I was just about to tackle a small UHF transceiver.
I'll try that (if it doesn't work, I can always trash the
thing :< )
Click to expand...
I tried freezing and then wacking with a hammer (i.e., as
if trying to dislocate one side of the weld from the other).
No good.

I'll try a sharp wood chisel on the seam next.

Then, resort to the heated knife. :<
 
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