Cutting Lexan?

If I cut Lexan on a bandsaw, what is the best way to sand out the cut marks
along the cut line? Sand paper? File? I want to make a new windshield and
the cut edge will be the top of the windshield (open cockpit).


--
Scott
http://corbenflyer.tripod.com/
Building RV-4
Gotta Fly or Gonna Die

If I cut Lexan on a bandsaw, what is the best way to sand out the cut marks
along the cut line? Sand paper? File? I want to make a new windshield and
the cut edge will be the top of the windshield (open cockpit).

You could start with a file if necessary and then go to abrasive paper.
Depending on how the file works start with say 200 grit paper and sand until
the texture of the lexan is uniform before moving on to a finer paper. Do this
till you have gone up to 1000 grit at least. Then get some crocus cloth and
use it wet. I was taught that at this point use one piece of crocus cloth and
use it up till it is gone. After that you can use toothpaste with pumice or
make a solution of chalk dust and turpentine with either apply with your finger
tips.

After the toothpaste the edges of the lexan should be as clear as the rest of
the surface. The important thing is to never move on to a finer grit until the
entire edge is uniform. We did this in A&P school and it will work. Don't
know of any mechanical techniques that will do as well.

John Dupre'

In article ,
(JDupre5762) wrote:

If I cut Lexan on a bandsaw, what is the best way to sand out the cut marks
along the cut line? Sand paper? File? I want to make a new windshield and
the cut edge will be the top of the windshield (open cockpit).

You could start with a file if necessary and then go to abrasive paper.
Depending on how the file works start with say 200 grit paper and sand until
the texture of the lexan is uniform before moving on to a finer paper. Do
this
till you have gone up to 1000 grit at least. Then get some crocus cloth and
use it wet. I was taught that at this point use one piece of crocus cloth
and
use it up till it is gone. After that you can use toothpaste with pumice or
make a solution of chalk dust and turpentine with either apply with your
finger
tips.

After the toothpaste the edges of the lexan should be as clear as the rest of
the surface. The important thing is to never move on to a finer grit until
the
entire edge is uniform. We did this in A&P school and it will work. Don't
know of any mechanical techniques that will do as well.

John Dupre'



Automotive rubbing and polishing compounds work very well, too. Also,
you can go up to at least 2000 grit wet/dry (use it wet). The technique
also works for scratches, and is a LOT cheaper than the "Plexiglass
repair kits" that you can buy.

File smooth, and then use an oxy-hydrogen torch with a soft flame. This
will give an instant flame polished edge. See your local plastic
supplier if you're not equipped to do this solo.

Rip

Scott wrote:
If I cut Lexan on a bandsaw, what is the best way to sand out the cut marks
along the cut line? Sand paper? File? I want to make a new windshield and
the cut edge will be the top of the windshield (open cockpit).


--
Scott
http://corbenflyer.tripod.com/
Building RV-4
Gotta Fly or Gonna Die

"rip" wrote in message
news
File smooth, and then use an oxy-hydrogen torch with a soft flame. This
will give an instant flame polished edge. See your local plastic
supplier if you're not equipped to do this solo.

Rip


Right on, Rip. This is the slickest, easiest, most professional way to get
clean, clear edges on Lexan and Plexiglas. If you are really quick with
the torch, you can de-burr drilled holes this way too.

Bill Daniels

In article ,
"Bill Daniels" wrote:

"rip" wrote in message
news
File smooth, and then use an oxy-hydrogen torch with a soft flame. This
will give an instant flame polished edge. See your local plastic
supplier if you're not equipped to do this solo.

Rip


Right on, Rip. This is the slickest, easiest, most professional way to get
clean, clear edges on Lexan and Plexiglas. If you are really quick with
the torch, you can de-burr drilled holes this way too.

And -- if you are NOT quick with the torch? It is safer to use the
filing/ sanding/polishing technique.

"Orval Fairbairn" wrote in message
news
In article ,
"Bill Daniels" wrote:

"rip" wrote in message
news
File smooth, and then use an oxy-hydrogen torch with a soft flame.
This
will give an instant flame polished edge. See your local plastic
supplier if you're not equipped to do this solo.

Rip


Right on, Rip. This is the slickest, easiest, most professional way to
get
clean, clear edges on Lexan and Plexiglas. If you are really quick
with
the torch, you can de-burr drilled holes this way too.

And -- if you are NOT quick with the torch? It is safer to use the
filing/ sanding/polishing technique.

Safety has nothing to do with it. Just practice on scrap plastic until you
get the hang of it just like everything else you have to learn building an
airplane. Rip is talking about little more than a match sized flame. It's
a damn useful skill to have and it virtually eliminates any stress risers
that will cause the plastic to crack later.

Bill Daniels

Bill Daniels wrote ...
... a match sized flame ... virtually eliminates any stress risers
that will cause the plastic to crack later.


Eliminate _risers_? Yes. But I can't imagine a better way to induce
latent stresses in Lexan than to use a flame.


Daniel

"Scott" wrote in message
...
If I cut Lexan on a bandsaw, what is the best way to sand out the cut
marks
along the cut line? Sand paper? File? I want to make a new windshield
and
the cut edge will be the top of the windshield (open cockpit).


--
Scott
http://corbenflyer.tripod.com/
Building RV-4
Gotta Fly or Gonna Die

Make a template out of medium density fiberboard. sanded to the exact size
you want the windshield to be, then cut the windshield a hair larger than
the template. Use a pattern tracing bit in a router (ball bearing),
variable speed, if possible, run at a fairly slow speed.

If it is a long straight line, a jointer works great. Try it on a scrap.
You will be impressed.
--
Jim in NC


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"Scott" wrote in message
...
If I cut Lexan on a bandsaw, what is the best way to sand out the cut
marks
along the cut line? Sand paper? File? I want to make a new windshield
and
the cut edge will be the top of the windshield (open cockpit).


--
Scott
http://corbenflyer.tripod.com/
Building RV-4
Gotta Fly or Gonna Die



Scott.

I manufacture lexan windshields and acrylic canopies.
If you want to work lexan, and I don't think you do, none of the methods
mentioned by other guys will work. Lexan will not flame polish with a
torch.
Sanding lexan after sawing will take an ENORMOUS amount of effort to
get back to clear, if you can. Using a router giives you a better edge if
you
are tooled to do it. Remember to tape the plastic so the router base
doesn't
mar the plastic. When we cut one-offs, we bandsaw and disc sand with 36
grit
discs and finish with a sheet metal deburring tool. Really does a nice job,
but
the edge will not be clear.

If on the other hand you are talking about ACRYLIC/PLEXIGLASS, then most
of what you have read is applicable. Flame polishing adds huge residual
stresses
to the sheet. Filing in many cases causes chipping when the teeth are too
large.
Sanding gets you real close, but SCRAPING is the best. We prefer to use
routers
on our acrylic parts, but when making one-offs, we bandsaw, disc sand 36
grit,
usa sanding boards at 80 grit and go straight to scraping with a $5 craftics
tool
or piece of tool steel. There isn't a better way to get the edge finished.
We
have to re-sand the scraped edges at 2000 grit but it doesn't buy you that
much.

Call me at the shop if you need to know more.

Scott

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