Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

Miki wrote:

Is there a better way to maintain a clean cut through the heatsink
fins? Â*They are .050" thick aluminum. Â*Base plate is .250" thick. Â*I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

I assume the fins are vertical to the baseplate. ;-)
The idea with Cerrosafe (or some such like Wood's metal, Cerrobend etc.)
sounds promising to me. When casting the metal between the fins, I would
clamp some sheet on top of the fins and leave it there while drilling (even
drill into that cover a bit). Don't forget to put some oil onto the fins,
makes coming off the Cerrosave easier.

Nick
--
The lowcost-DRO:
http://www.yadro.de

Nick Mueller fired this volley in
:


I assume the fins are vertical to the baseplate. ;-)
The idea with Cerrosafe (or some such like Wood's metal, Cerrobend
etc.) sounds promising to me. When casting the metal between the fins,
I would clamp some sheet on top of the fins and leave it there while
drilling (even drill into that cover a bit). Don't forget to put some
oil onto the fins, makes coming off the Cerrosave easier.

If I were going to use this method, I think I'd completely embed the
object in the LMA. That way, it would be self-clamping, as it were.

I think I don't like this idea, at least for even small production
quantites, as you're going to end up throwing away a lot of contaminated
$30/lb. casting metal. You could re-melt and skimming all the chips, but
I've had bad luck with contaminants affecting the surface-release
properties of Cerro-Tru ... don't know about Cerro-Safe.

LLoyd

Miki wrote:
Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

I would drill small clearance holes between fins and use a scroll saw
dabbed with kerosene to cut out the 0.6" circles, fins down.
http://www.finescrollsaw.com/hegnerreview.htm

Then I'd clean up the hole with progressively finer grades of abrasive
paper rolled into a cylinder.

--Winston

"Miki" wrote in message
...
Hi guys,

I have a project at work, it involves drilling two .600"
holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base
plate. When
the drill was through the base plate and touched the fins,
the fins
wanted to wrap around the drill and tear out of the base
plate.

The heat sinks are large surface area, but the fins are
only about an
inch high. They are joined to the base plate with
nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the
heatsink
fins? They are .050" thick aluminum. Base plate is .250"
thick. I
was thinking of filling the fins with Cerrosafe... don't
know if this
is feasible (e.g. Cerrosafe might just push out of the
fins?)

What are you using to do the drilling? If you have a
mill handy and can use power
downfeed to control the feed rate, you might try an annular
cutter. Jancy or Hougen are common brands. Crank up the
RPM, LIGHT downfeed, plenty of lube/coolant.

I use them a lot in thin and fragile material with good
results. Not as aggressive as a
drill, and much more accurate than a hole saw.

..600 is a rather odd diameter. Can you use 5/8" (.625) or
maybe 15mm (.591)????

Bill

On Dec 18, 11:35 am, Miki wrote:
Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.
...

Must be getting old. I know I found some simple way to do this but I
can't remember which idea I used out of all the ones I thought of.

Probably it was clamping the heatsink to plywood with some cardboard
in between to restrain the ends of the fins, and drilling with a sharp
new endmill.

On Tue, 18 Dec 2007 08:35:05 -0800 (PST), Miki
wrote:

Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)


2 flute endmill rather than a drill bit

Gunner

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

as you're going to end up throwing away a lot of contaminated
$30/lb. casting metal. Â*You could re-melt and skimming all the chips, but
I've had bad luck with contaminants affecting the surface-release
properties of Cerro-Tru ... don't know about Cerro-Safe.

I did that several times with embedded brass and aluminium. Used Ballistol
as oil and had no problem skimming the chips. I even didn't pay attention
when remelting to get the chips off before. I used something different as
alloy. It melts at about 96°C (cadmium free).


Nick
--
The lowcost-DRO:
http://www.yadro.de

"Miki" wrote in message
...
Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

Freeze it in a block of ice and use an end mill.

Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)


Pack the fins with modeling clay then use a two flute end mill instead of a
drill.

Mike

On Tue, 18 Dec 2007 08:35:05 -0800 (PST), Miki
wrote:

Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

Try packing the fins with brown sugar. Pack 'em good, the stuff will
tamp a lot and become quite hard. After drilling (sharp endmil as
Gunner suggests), you can dissolve the brown sugar in hot water.

How strong is tamped brown sugar? It's used to test prototype fuze
electronics in artillery shells that experience over 20,000 G's when
fired. Retreive round, soak in hot water to remove brown sugar, check
the elex.

On 2007-12-18, Miki wrote:
Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

Drill bits are a bit too aggressive for the task.

I have had good luck with a milling machine, milling from the
top of the fins downward -- slowly, and with the heatskink firmly
gripped end on in the milling vise, which offers some extra support for
the fins at the ends. This needs to be a center-cutting end mill,
obviously.

Of course -- a 0.600" end mill may be difficult to find. How
accurate does this need to be? Or could you use the end mill somewhat
oversized, say 0.750", and switch to a drill once you have started
facing the horizontal surface?

Or a 5/8" end mill is only 0.025" oversized. Perhaps you could
live with that?

Or -- you could set up a horzontal mill with cutters spaced the
same as the fins to make something which would hold the top 1/4" of the
fins clamped down onto the heatsink. Make it a fixture which will hold
the sinks in the same place (assuming more than one heatsink to drill),
and make it of a material which you can drill into with the endmill so
you can get the full length of the fins -- or through the fixture from
the top.

For one only, you might be able to get away with clamping it
firmly to a soft wood or plastic so the fins embed on their own and get
sufficient lateral support from that.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Don Foreman wrote:

Try packing the fins with brown sugar.

LOL! Worth remembering!


Nick
--
The lowcost-DRO:
http://www.yadro.de

If you are limited to materials that are available and acceptable at
work, hot melt glue blobs between the fins might work. It doesn't
stick to aluminum very well and you should be able to pry it out
afterwards.

Jim Wilkins

Try packing the fins with brown sugar. Pack 'em good, the stuff will
tamp a lot and become quite hard. After drilling (sharp endmil as
Gunner suggests), you can dissolve the brown sugar in hot water.

How strong is tamped brown sugar? It's used to test prototype fuze
electronics in artillery shells that experience over 20,000 G's when
fired. Retreive round, soak in hot water to remove brown sugar, check
the elex.


!!!! Interesting !!!!

Miki,
Unless you have Cerroxxx laying around, it's probably going to be
cheaper in the long run to just wire EDM the part.
DJ



On Dec 18, 8:35 am, Miki wrote:
Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

On Tue, 18 Dec 2007 08:35:05 -0800 (PST), Miki wrote:

Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

If the fins happen to be the same thickness as the space between them,
clamp two heatsinks fin-side-to-fin-side. This assumes you can live with a
fin-width variation in hole location.

If they are not, perhaps you could find some sheets of thin sacrificial
stuff (plastic, wood, soft aluminium) to take up the gap.

Thanks guys for all the suggestions and advice. I really appreciate
it.

In the end I tried the brown sugar method, because we have plenty of
it at the office coffee station. Long story short, it worked
excellently well. ZERO distortion of the heatsink fins. We went with
high speed and gentle feed.

I taped a cardboard form around the heatsink and tamped the brown
sugar down with 1/4" parallels. After the sugar was packed in, I
taped another cardboard piece to keep the sugar in the fins in case I
thumped it between my office and the machine shop.

We don't have a lathe at work, but I have one at home, so I ground
down a two-flute 5/8" endmill (based on Gunner's suggestion; improved
by others' suggestions) on the home lathe to get the precise O.D. we
need.

BTW, my company manufactures radio amps... the amp components all
mount to the heatsink, and the 'sink mounts into a rackmount chassis.
So our machine shop is somewhat limited. The 0.600" holes are for
coax end connectors, this is a very tight build so the holes had to be
relatively precise.

The purchasing department is going to wonder where all the brown sugar
went...

Miki wrote:

In the end I tried the brown sugar method, because we have plenty of
it at the office coffee station. Â*Long story short, it worked
excellently well.

That really is **such** a funny trick! Good to hear it worked so well.

Makes me smile! Thanks Don!


Nick
--
The lowcost-DRO:
http://www.yadro.de

On Thu, 20 Dec 2007 21:36:28 +0100, Nick Mueller
wrote:

Miki wrote:

In the end I tried the brown sugar method, because we have plenty of
it at the office coffee station. *Long story short, it worked
excellently well.

That really is **such** a funny trick! Good to hear it worked so well.

Makes me smile! Thanks Don!


Nick

Bitte!

Miki wrote:
Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

Given the gear here, I would use a new, sharp end mill, and
careful feed to the right depth. Machining heat sinks without
folding the fins is pretty tricky, one of the places I know not
to use a climb-mill cut.

If you need to bore all the way through the fins, too, this may
not be possible. You may have to machine away the fins first
with a separate operation.

Jon

How many do you have to do?
Can you place wood spacers between the fines?