I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
will be set into a 3/4" piece of plywood that I routed out, and stained and
varnished.
I have never had much luck drilling plexi without having it split. Is there
a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
of plywood? All the above?
Steve
Negative raked plexi drills, a dime a dozen at WL fuller.
Taps x the millions, any metal working supply or Fuller. Use through,
3 or 4 fluted HSS. As cheap as the drills.
Expect to pay <5$/tap x ~5/16" or less. No rocket or other science
needed.
*******************************************
> Hum.
>
> Ok - where are the plastic drills you use.
> Plastic taps also ?
>
> Martin
>
> On 6/6/2012 5:17 PM, routerman wrote:
>>
> > Wow, a real BM storm, a strain @ a gnat, a complication where none
> > exists.
> > I drill PC& =A0AC& =A0a lot of other materials; I'm a driller. With a
> > plexi drill, and the work immobilized, you advance the spinning drill
> > into the work and make a hole. The exit is as clean as the entry;
> > what's the deal?
> > No goo, no lube no clay dams, no diddly, see:
> >http://patwarner.com/images/machining_plastic_d.jpg
Wow, a real BM storm, a strain @ a gnat, a complication where none
exists.
I drill PC & AC & a lot of other materials; I'm a driller. With a
plexi drill, and the work immobilized, you advance the spinning drill
into the work and make a hole. The exit is as clean as the entry;
what's the deal?
No goo, no lube no clay dams, no diddly, see:
http://patwarner.com/images/machining_plastic_d.jpg
> On 5/31/2012 10:02 AM, Steve B wrote:
>> I got a 6" square 1/8" piece of plexi to mount the switches on my boat.
>> It
>> will be set into a 3/4" piece of plywood that I routed out, and stained
>> and
>> varnished.
>>
>> I have never had much luck drilling plexi without having it split. Is
>> there
>> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer
>> piece
>> of plywood? All the above?
>>
Why plexi? Lexan (polycarbonate) is much more forgiving. It is also more
flexible and will stand up to more shock and abuse. And it is much easier
to drill. For such a small piece, you can get something at the borg and cut
it to size with any kind of woodworking saw. I have built a lot of stuff
with lexan. Most of the applications I used would have broken the
Plexiglas. Plexi is not only easy to break, but it can develop cracks over
time. Lexan will change its size slightly with temperature changes, but its
increased strength and durability make it more feasible for many
applications. And if this is going on a boat, I would want something a
little stronger and easier to work with.
My advice, toss the plexi and use lexan instead.
Let's destroy his question so we can give answers he didn't ask for.
Here is his text that was conveniently removed from the OP quote.
"Steve B" wrote in message news:[email protected]...
I got a 6" square 1/8" piece of plexi to mount the switches on my boat.
It
will be set into a 3/4" piece of plywood that I routed out, and stained
and
varnished."
-------------------
"Swingman" wrote in message
news:[email protected]...
On 5/31/2012 1:47 PM, Lee Michaels wrote:
>> On 5/31/2012 10:02 AM, Steve B wrote:
>>> I have never had much luck drilling plexi without having it split.
>>> Is
>>> there a secret?
> Why plexi? Lexan (polycarbonate) is much more forgiving. It is also
> more
> flexible and will stand up to more shock and abuse. And it is much
> easier to drill. For such a small piece, you can get something at the
> borg and cut it to size with any kind of woodworking saw. I have
> built a
> lot of stuff with lexan. Most of the applications I used would have
> broken the Plexiglas. Plexi is not only easy to break, but it can
> develop cracks over time. Lexan will change its size slightly with
> temperature changes, but its increased strength and durability make
> it
> more feasible for many applications. And if this is going on a boat,
> I
> would want something a little stronger and easier to work with.
>
> My advice, toss the plexi and use lexan instead.
Bingo ... second the use of Lexan over plexiglass, although it can get
pricey.
I can cut it on the TS with my Forrest WWII, and have drilled it
(albeit
small holes for screws) with whatever was in my tool box.
Used Lexan for this "no visible means of support" backlit art glass
shelf for a client, cut to size on the table saw from a 4 x 8 sheet,
about a year ago:
https://picasaweb.google.com/111355467778981859077/EWoodShopBacklitGlassDisplayShelf#5701367237981688482
(cell phone photos, sorry)
--
www.eWoodShop.com
Last update: 4/15/2010
KarlCaillouet@ (the obvious)
http://gplus.to/eWoodShop
Plexipoint (second up from left: http://patwarner.com/drilling_tools.html
)
with negative rake (HSS) about the best for small holes in AC.
No breakage, clean entry & exits. Don't drill at 10000, however.
They stop working @~1/2" diameter, so if you need a bigger hole then
you need another drill.
118 degree tools will work but demand a backup, slow speed (<250) and
sharpness.
Hi feed rate will bust the plastic. Brad point, Forstner, hole saw?
Rediculous.
(That should start a BM storm)
*********************************************
On May 31, 10:02=A0am, "Steve B" <[email protected]> wrote:
> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. =
=A0It
> will be set into a 3/4" piece of plywood that I routed out, and stained a=
nd
> varnished.
>
> I have never had much luck drilling plexi without having it split. =A0Is =
there
> a secret? =A0Sharp blade? =A0High rpm? =A0Very easy pressure? =A0Use a ba=
cker piece
> of plywood? =A0All the above?
>
> Steve
On 5/31/2012 12:02 PM, Steve B wrote:
> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
> will be set into a 3/4" piece of plywood that I routed out, and stained and
> varnished.
>
> I have never had much luck drilling plexi without having it split. Is there
> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
> of plywood? All the above?
>
> Steve
>
>
Start with a small hole and work up.
"Twayne" wrote in message news:[email protected]...
In news:[email protected],
Morgans <[email protected]> typed:
> "Steve B" wrote in message
> news:[email protected]...
> I got a 6" square 1/8" piece of plexi to mount the
> switches on my boat. It will be set into a 3/4" piece of
> plywood that I routed out, and stained and varnished.
>
> I have never had much luck drilling plexi without having
> it split. Is there a secret? Sharp blade? High rpm? Very easy pressure?
> Use a backer piece of plywood? All
> the above?
> **********************
> Modify a regular twist bit. The leading edge of the
> cutting surface of a normal bit is several degrees, and
> helps lift the chips away from the cut and also pulls the
> bit into the material. That is what you do not want.
> Take a cutoff wheel on a dremel tool, and cut that
> leading edge so it is at 89 or 90 degrees to the material
> you are cutting. Then, take a little paint, like white
> or orange, and paint down in the flutes, so it will be
> easy to identify later, and not used for cutting other
> stuff, and getting thrown away. Works well, every time.
>
> -- Jim in NC
I tried that for grins; and it fails miserably.
=====================================================================================
Then you ground it wrong.
"CW" <[email protected]> wrote in
news:[email protected]:
>
>
> "Morgans" wrote in message
> news:[email protected]...
>
> "Steve B" wrote in message
> news:[email protected]...
>
> I got a 6" square 1/8" piece of plexi to mount the switches
> on my boat. It will be set into a 3/4" piece of plywood
> that I routed out, and stained and varnished.
>
> I have never had much luck drilling plexi without having it
> split. Is there a secret? Sharp blade? High rpm? Very
> easy pressure? Use a backer piece of plywood? All the
> above?
>
> **********************
> Modify a regular twist bit. The leading edge of the
> cutting surface of a normal bit is several degrees, and
> helps lift the chips away from the cut and also pulls the
> bit into the material. That is what you do not want. Take
> a cutoff wheel on a dremel tool, and cut that leading edge
> so it is at 89 or 90 degrees to the material you are
> cutting. Then, take a little paint, like white or orange,
> and paint down in the flutes, so it will be easy to
> identify later, and not used for cutting other stuff, and
> getting thrown away.
> Works well, every time.
> ===========================================================
=
> ====================== I agree. I have done production
> drilling on plexi. A neutral rake on a twist drill works
> great.
>
That's how I've done it...especially if I want to tap the
hole. The bits sold by the plastics vendors come in only a
few fractional sizes. I have a set of number bits (tap and
clearence sizes) that I've ground a small flat on the lip,
parallel to the bit axis, so it produces a "scraping" action,
rather than the "shearing" action of normal twist drill bits.
Backing, slow speed, and gentle feed...especially on
breakout. These are also great for drilling brass.
I do have a set of commercial plastics bits (1/8"-1/2"), and
the point angle on them is smaller than twist drills. But
mine work great.
Ken
Martin Eastburn <[email protected]> wrote in
news:[email protected]:
> While not a pro way, a circular dam that holds a small amout
> of water over the hole site as the drill pecks a hole into
> the glass.
>
> Must keep the speed down as the plastic melts. The linear
> movement of the circumference is what gets you. The outside
> really whips around. But in water it will keep the drill
> and plastic cool. Just keep adding drips of water to keep
> it full. When the hole is drilled, the water drops through.
>
> Remember it is inches per minute that is important, not RPM.
> Slow down the large drills even more than the small ones.
>
> Martin
>
> On 6/3/2012 1:10 PM, CW wrote:
>>
>>
>> "Twayne" wrote in message news:[email protected]...
>>
>> In news:[email protected],
>> Morgans <[email protected]> typed:
>>> "Steve B" wrote in message
>>> news:[email protected]...
>>> I got a 6" square 1/8" piece of plexi to mount the
>>> switches on my boat. It will be set into a 3/4" piece of
>>> plywood that I routed out, and stained and varnished.
>>>
>>> I have never had much luck drilling plexi without having
>>> it split. Is there a secret? Sharp blade? High rpm? Very easy
>>> pressure? Use a backer piece of plywood? All
>>> the above?
>>> **********************
>>> Modify a regular twist bit. The leading edge of the
>>> cutting surface of a normal bit is several degrees, and
>>> helps lift the chips away from the cut and also pulls the
>>> bit into the material. That is what you do not want.
>>> Take a cutoff wheel on a dremel tool, and cut that
>>> leading edge so it is at 89 or 90 degrees to the material
>>> you are cutting. Then, take a little paint, like white
>>> or orange, and paint down in the flutes, so it will be
>>> easy to identify later, and not used for cutting other
>>> stuff, and getting thrown away. Works well, every time.
A touch of soap in the water also helps.
The problem with drilling most plastics is that they have a nasty
combination of poor thermal conductivity, and high thermal expansion.
That means that once the material starts getting hot, it wants to expand,
but the only place it can go is towards the drill. If the thermal
conductivity was higher, the hole would actually get bigger as the whole
piece expanded. The inward expansion creates more friction, which begats
more expansion, and you can rapidly get a runaway condition leading to
the drill grabbing. You have to keep the plastic & the drill cool enough
that it nevers gets into the runaway condition. Slows speeds, pecking,
and coolant all help.
Doug White
On Thu, 31 May 2012 15:38:00 -0500, Leon <lcb11211@swbelldotnet>
wrote:
>On 5/31/2012 12:02 PM, Steve B wrote:
>> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
>> will be set into a 3/4" piece of plywood that I routed out, and stained and
>> varnished.
>>
>> I have never had much luck drilling plexi without having it split. Is there
>> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
>> of plywood? All the above?
>>
>> Steve
>
>Start with a small hole and work up.
That's the _opposite_ of what she said. <domg>
LJ, humming "Lay 'er down, roll 'er over, and do it again."
--
Self-development is a higher duty than self-sacrifice.
-- Elizabeth Cady Stanton
There is help below - but Dad and I always used a ring of clay -
modeling type - oil base - and water inside. It keeps the plastic
cool - and pec drill. Keep the tips slow. RPM's slow. A fast
turning tip of a drill - the outer cutting edge - can melt plastic
and then it cracks it.
Martin
On 5/31/2012 12:02 PM, Steve B wrote:
> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
> will be set into a 3/4" piece of plywood that I routed out, and stained and
> varnished.
>
> I have never had much luck drilling plexi without having it split. Is there
> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
> of plywood? All the above?
>
> Steve
>
>
On Thu, 31 May 2012 10:02:51 -0700, "Steve B" <[email protected]>
wrote:
>I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
>will be set into a 3/4" piece of plywood that I routed out, and stained and
>varnished.
>
>I have never had much luck drilling plexi without having it split. Is there
>a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
>of plywood? All the above?
>
>Steve
>
A drill bit with the right grind?
http://www.rplastics.com/plasticdrill.html
http://www.amazon.com/s?ie=UTF8&tag=mozilla-20&index=blended&link_code=qs&field-keywords=plexiglass%20drill%20bit&sourceid=Mozilla-search
On 5/31/2012 10:02 AM, Steve B wrote:
> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
> will be set into a 3/4" piece of plywood that I routed out, and stained and
> varnished.
>
> I have never had much luck drilling plexi without having it split. Is there
> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
> of plywood? All the above?
>
> Steve
>
>
the drill tip has a different angle on it. you can get them at the
plastics shop. i don't think i've ever seen them at a borg.
On 5/31/12 12:02 PM, Steve B wrote:
> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
> will be set into a 3/4" piece of plywood that I routed out, and stained and
> varnished.
>
> I have never had much luck drilling plexi without having it split. Is there
> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
> of plywood? All the above?
>
> Steve
>
All of the above, except high rpm. Go slow. Brad point bits helps.
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
[email protected]
---remove "DOT" ^^^^ to reply
On 5/31/12 12:13 PM, tiredofspam wrote:
> always avoid edges, you can be close, but they will crack
> over time.
For close to the edge, I've used a soldering iron to melt holes in thin
plexi.
Also, you could drill the holes in a larger piece, first, then cut to
size.
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
[email protected]
---remove "DOT" ^^^^ to reply
"Steve B" <[email protected]> wrote in message
news:[email protected]...
>I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
>will be set into a 3/4" piece of plywood that I routed out, and stained and
>varnished.
>
> I have never had much luck drilling plexi without having it split. Is
> there a secret? Sharp blade? High rpm? Very easy pressure? Use a
> backer piece of plywood? All the above?
http://www.eplastics.com/Plastic/Plexiglass_Lexan_Plastic_Drill_Bits
On Thu, 31 May 2012 10:02:51 -0700, Steve B wrote:
> I have never had much luck drilling plexi without having it split. Is
> there a secret? Sharp blade? High rpm? Very easy pressure? Use a
> backer piece of plywood? All the above?
There are special bits, but I've had pretty good luck with a plywood
sandwich.
--
Intelligence is an experiment that failed - G. B. Shaw
"Steve B" wrote in message news:[email protected]...
I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
will be set into a 3/4" piece of plywood that I routed out, and stained and
varnished.
I have never had much luck drilling plexi without having it split. Is there
a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
of plywood? All the above?
**********************
Modify a regular twist bit. The leading edge of the cutting surface of a
normal bit is several degrees, and helps lift the chips away from the cut
and also pulls the bit into the material. That is what you do not want.
Take a cutoff wheel on a dremel tool, and cut that leading edge so it is at
89 or 90 degrees to the material you are cutting. Then, take a little
paint, like white or orange, and paint down in the flutes, so it will be
easy to identify later, and not used for cutting other stuff, and getting
thrown away.
Works well, every time.
-- Jim in NC
In news:[email protected],
Morgans <[email protected]> typed:
> "Steve B" wrote in message
> news:[email protected]...
> I got a 6" square 1/8" piece of plexi to mount the
> switches on my boat. It will be set into a 3/4" piece of
> plywood that I routed out, and stained and varnished.
>
> I have never had much luck drilling plexi without having
> it split. Is there a secret? Sharp blade? High rpm? Very easy pressure?
> Use a backer piece of plywood? All
> the above?
> **********************
> Modify a regular twist bit. The leading edge of the
> cutting surface of a normal bit is several degrees, and
> helps lift the chips away from the cut and also pulls the
> bit into the material. That is what you do not want.
> Take a cutoff wheel on a dremel tool, and cut that
> leading edge so it is at 89 or 90 degrees to the material
> you are cutting. Then, take a little paint, like white
> or orange, and paint down in the flutes, so it will be
> easy to identify later, and not used for cutting other
> stuff, and getting thrown away. Works well, every time.
>
> -- Jim in NC
I tried that for grins; and it fails miserably. Std drill bit will work as
below:
Backer piece plus tape applied to the other side where the hole will be has
always worked well here. Speed slow enough to let it cut before it burns the
plastic. Need a sharp bit.
"routerman" wrote in message
news:4ce5c54a-e1d1-44d6-9051-af82e4123690@qq9g2000pbb.googlegroups.com...
Wow, a real BM storm, a strain @ a gnat, a complication where none
exists.
I drill PC & AC & a lot of other materials; I'm a driller. With a
plexi drill, and the work immobilized, you advance the spinning drill
into the work and make a hole. The exit is as clean as the entry;
what's the deal?
No goo, no lube no clay dams, no diddly, see:
http://patwarner.com/images/machining_plastic_d.jpg
=======================================================================
I agree completely.
On Thu, 31 May 2012 10:04:28 -0700, chaniarts
<[email protected]> wrote:
>On 5/31/2012 10:02 AM, Steve B wrote:
>> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
>> will be set into a 3/4" piece of plywood that I routed out, and stained and
>> varnished.
>>
>> I have never had much luck drilling plexi without having it split. Is there
>> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
>> of plywood? All the above?
With normal metalworking twistbilldrits, use low RPM, light touch,
sharp edges. Backer boards are a very good idea, too. Some forstner
bits work well (small diameter), others don't (like sawtooth styles).
>the drill tip has a different angle on it. you can get them at the
>plastics shop. i don't think i've ever seen them at a borg.
Aha! I didn't know that one.
I used to drill square holes in plastic dashboard with an air drill
and twistbilldrits, but that's not plexi. (I think it was ABS.) I
worked in Phoenix one summer (what an idiot!) installing air
conditioners in brand new trucks. One 118F day, it was only 108 in
the shop with 4 humongous swamp coolers running.
--
Self-development is a higher duty than self-sacrifice.
-- Elizabeth Cady Stanton
On 5/31/2012 1:47 PM, Lee Michaels wrote:
>> On 5/31/2012 10:02 AM, Steve B wrote:
>>> I have never had much luck drilling plexi without having it split. Is
>>> there a secret?
> Why plexi? Lexan (polycarbonate) is much more forgiving. It is also more
> flexible and will stand up to more shock and abuse. And it is much
> easier to drill. For such a small piece, you can get something at the
> borg and cut it to size with any kind of woodworking saw. I have built a
> lot of stuff with lexan. Most of the applications I used would have
> broken the Plexiglas. Plexi is not only easy to break, but it can
> develop cracks over time. Lexan will change its size slightly with
> temperature changes, but its increased strength and durability make it
> more feasible for many applications. And if this is going on a boat, I
> would want something a little stronger and easier to work with.
>
> My advice, toss the plexi and use lexan instead.
Bingo ... second the use of Lexan over plexiglass, although it can get
pricey.
I can cut it on the TS with my Forrest WWII, and have drilled it (albeit
small holes for screws) with whatever was in my tool box.
Used Lexan for this "no visible means of support" backlit art glass
shelf for a client, cut to size on the table saw from a 4 x 8 sheet,
about a year ago:
https://picasaweb.google.com/111355467778981859077/EWoodShopBacklitGlassDisplayShelf#5701367237981688482
(cell phone photos, sorry)
--
www.eWoodShop.com
Last update: 4/15/2010
KarlCaillouet@ (the obvious)
http://gplus.to/eWoodShop
While not a pro way, a circular dam that holds a small amout
of water over the hole site as the drill pecks a hole into
the glass.
Must keep the speed down as the plastic melts. The linear
movement of the circumference is what gets you. The outside
really whips around. But in water it will keep the drill
and plastic cool. Just keep adding drips of water to keep
it full. When the hole is drilled, the water drops through.
Remember it is inches per minute that is important, not RPM.
Slow down the large drills even more than the small ones.
Martin
On 6/3/2012 1:10 PM, CW wrote:
>
>
> "Twayne" wrote in message news:[email protected]...
>
> In news:[email protected],
> Morgans <[email protected]> typed:
>> "Steve B" wrote in message
>> news:[email protected]...
>> I got a 6" square 1/8" piece of plexi to mount the
>> switches on my boat. It will be set into a 3/4" piece of
>> plywood that I routed out, and stained and varnished.
>>
>> I have never had much luck drilling plexi without having
>> it split. Is there a secret? Sharp blade? High rpm? Very easy
>> pressure? Use a backer piece of plywood? All
>> the above?
>> **********************
>> Modify a regular twist bit. The leading edge of the
>> cutting surface of a normal bit is several degrees, and
>> helps lift the chips away from the cut and also pulls the
>> bit into the material. That is what you do not want.
>> Take a cutoff wheel on a dremel tool, and cut that
>> leading edge so it is at 89 or 90 degrees to the material
>> you are cutting. Then, take a little paint, like white
>> or orange, and paint down in the flutes, so it will be
>> easy to identify later, and not used for cutting other
>> stuff, and getting thrown away. Works well, every time.
>>
>> -- Jim in NC
> I tried that for grins; and it fails miserably.
> =====================================================================================
>
> Then you ground it wrong.
"Morgans" wrote in message news:[email protected]...
"Steve B" wrote in message news:[email protected]...
I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
will be set into a 3/4" piece of plywood that I routed out, and stained and
varnished.
I have never had much luck drilling plexi without having it split. Is there
a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
of plywood? All the above?
**********************
Modify a regular twist bit. The leading edge of the cutting surface of a
normal bit is several degrees, and helps lift the chips away from the cut
and also pulls the bit into the material. That is what you do not want.
Take a cutoff wheel on a dremel tool, and cut that leading edge so it is at
89 or 90 degrees to the material you are cutting. Then, take a little
paint, like white or orange, and paint down in the flutes, so it will be
easy to identify later, and not used for cutting other stuff, and getting
thrown away.
Works well, every time.
==================================================================================
I agree. I have done production drilling on plexi. A neutral rake on a twist
drill works great.
"Doug White" wrote in message
news:[email protected]...
Martin Eastburn <[email protected]> wrote in
news:[email protected]:
> While not a pro way, a circular dam that holds a small amout
> of water over the hole site as the drill pecks a hole into
> the glass.
>
> Must keep the speed down as the plastic melts. The linear
> movement of the circumference is what gets you. The outside
> really whips around. But in water it will keep the drill
> and plastic cool. Just keep adding drips of water to keep
> it full. When the hole is drilled, the water drops through.
>
> Remember it is inches per minute that is important, not RPM.
> Slow down the large drills even more than the small ones.
>
> Martin
>
> On 6/3/2012 1:10 PM, CW wrote:
>>
>>
>> "Twayne" wrote in message news:[email protected]...
>>
>> In news:[email protected],
>> Morgans <[email protected]> typed:
>>> "Steve B" wrote in message
>>> news:[email protected]...
>>> I got a 6" square 1/8" piece of plexi to mount the
>>> switches on my boat. It will be set into a 3/4" piece of
>>> plywood that I routed out, and stained and varnished.
>>>
>>> I have never had much luck drilling plexi without having
>>> it split. Is there a secret? Sharp blade? High rpm? Very easy
>>> pressure? Use a backer piece of plywood? All
>>> the above?
>>> **********************
>>> Modify a regular twist bit. The leading edge of the
>>> cutting surface of a normal bit is several degrees, and
>>> helps lift the chips away from the cut and also pulls the
>>> bit into the material. That is what you do not want.
>>> Take a cutoff wheel on a dremel tool, and cut that
>>> leading edge so it is at 89 or 90 degrees to the material
>>> you are cutting. Then, take a little paint, like white
>>> or orange, and paint down in the flutes, so it will be
>>> easy to identify later, and not used for cutting other
>>> stuff, and getting thrown away. Works well, every time.
A touch of soap in the water also helps.
The problem with drilling most plastics is that they have a nasty
combination of poor thermal conductivity, and high thermal expansion.
That means that once the material starts getting hot, it wants to expand,
but the only place it can go is towards the drill. If the thermal
conductivity was higher, the hole would actually get bigger as the whole
piece expanded. The inward expansion creates more friction, which begats
more expansion, and you can rapidly get a runaway condition leading to
the drill grabbing. You have to keep the plastic & the drill cool enough
that it nevers gets into the runaway condition. Slows speeds, pecking,
and coolant all help.
=========================================================================
The right speed and the right drill bit is all that is needed.
Brad point bit, very little pressure, medium rpm,
yes backer, always avoid edges, you can be close, but they will crack
over time. cleanout with a counter sink...
On 5/31/2012 1:02 PM, Steve B wrote:
> I got a 6" square 1/8" piece of plexi to mount the switches on my boat. It
> will be set into a 3/4" piece of plywood that I routed out, and stained and
> varnished.
>
> I have never had much luck drilling plexi without having it split. Is there
> a secret? Sharp blade? High rpm? Very easy pressure? Use a backer piece
> of plywood? All the above?
>
> Steve
>
>
Tap also.
Hum.
Ok - where are the plastic drills you use.
Plastic taps also ?
Martin
On 6/6/2012 5:17 PM, routerman wrote:
>
> Wow, a real BM storm, a strain @ a gnat, a complication where none
> exists.
> I drill PC& AC& a lot of other materials; I'm a driller. With a
> plexi drill, and the work immobilized, you advance the spinning drill
> into the work and make a hole. The exit is as clean as the entry;
> what's the deal?
> No goo, no lube no clay dams, no diddly, see:
> http://patwarner.com/images/machining_plastic_d.jpg