[FuriousGeorge]

I need to machine a prototype heat sink and am wondering the best way to do it. The back (not really show) has a bunch of features that are milled in a first operation so I don't have to worry about crushing fins. I plan on using a slitting saw to machine the fins in a second or third operation, but am wondering the best way to hold it. Fins are 1/16" with 1/8" spacing between them in aluminum. The fin height is 0.3". I was thinking of simply using super glue to attach the heat sink to a flat backing plate and throwing the plate in a vice, but have never really tried this method. Would it work? I have almost no experience with slitting saws, so I'm not totally sure what kind of forces I'll be dealing with. My saw is 2.5" diameter, 1/8" thick and has 32 teeth. I could probably make a fixture to do this, but it may be a one off so I'd like to spend as little time as possible.

Attachment 291214

[CadRhino]

I would try using Talongrips if you can mount them vertically.
Or machine an aluminum blank that Is the same width as you part am clamp them in your vise with the part edge overhanging where you will be slitting the fins. The blank will act as a spacer to get good clamping.

I need to machine a prototype heat sink and am wondering the best way to do it. The back (not really show) has a bunch of features that are milled in a first operation so I don't have to worry about crushing fins. I plan on using a slitting saw to machine the fins in a second or third operation, but am wondering the best way to hold it. Fins are 1/16" with 1/8" spacing between them in aluminum. The fin height is 0.3". I was thinking of simply using super glue to attach the heat sink to a flat backing plate and throwing the plate in a vice, but have never really tried this method. Would it work? I have almost no experience with slitting saws, so I'm not totally sure what kind of forces I'll be dealing with. My saw is 2.5" diameter, 1/8" thick and has 32 teeth. I could probably make a fixture to do this, but it may be a one off so I'd like to spend as little time as possible.

Attachment 291214

[SCzEngrgGroup]

Mitee-Bite Pitbull clamps are hard to beat, not crazy expensive, and will hold very securely with a very small "bite".

Regards,
Ray L.

[Hirudin]

If there's enough stock remaining on the back a small toolmaker's vice might be a solution as well. It looks like the shape of your part is basically a "T" shape. If you clamped the toolmaker's vise onto the part of your heatsink that corrisponds to the vertical line of the "T", you could then probably clamp the toolmaker's vise into your milling vise.

Here's a bad drawing of what I mean. The heatsink is black, the base of the toolmaker's vise is red, the jaws are blue, and the tightening bolt is green. The jaws of the milling vise are magenta.

I think leaving the back for the last operation would be a better way to go than cutting the fins last. I think you could get adequate holding in a milling vise by aligning the fins parallel with the Y axis.

Fixturing1 - cut the fins with a slitting saw
Fixturing2 - fins up, cut away the stock over the areas that don't have fins, you could also debur the fins in this op. Take away as much stock as possible.
Fixturing3 - fins down, clamp the fins into a vise and cut out the features on the back. I'm assuming the majority of the stock is being left intact so the cuts should be pretty light.

[mountaindew]

Machinists vise that can be positioned on its side would be my first thought for holding material during arbor saw ops..
Super glue, loc tight, or epoxy to back plate is also a good idea. I was going to suggest this on another thread cadrhino had started for thin material.
I read about this method now and then although I have never used it myself yet.
Your cam setup can control the forces for the arbor operations. If production is no big concern yet then shallow cuts can be programmed to possible reduce forces.
I also find climb cuts sound better when using my arbor saw. Don't know what is best or provides less force on part. I have researched this and find little info on this type of tool.

[FuriousGeorge]

I ended up being lame and slotted them with an 1/8" end mill for a few reasons. I needed to get ONE of these done as fast as I possibly could. I don't have much experience with slitting saws and didn't have time to fail/start over, so I went with what I 100% know how to do. If I need to make more of these in the future, I think I'll go the route of a simple fixture with some pitbull clamps. Thanks for the advice!

[brian257]

I have done heat sinks with a slitting saw like that and it is not really a good way to do it. The fins vibrate and chatter and the slitting saw wants to grab the piece and throw it out of the vice. I am now using heat sink extrusions and cutting them to length. You can find a ton of different sized heat sink extrusions out there. Let me know if you want some sources.

[FuriousGeorge]

I have done heat sinks with a slitting saw like that and it is not really a good way to do it. The fins vibrate and chatter and the slitting saw wants to grab the piece and throw it out of the vice. I am now using heat sink extrusions and cutting them to length. You can find a ton of different sized heat sink extrusions out there. Let me know if you want some sources.

That would be the best solution by far and I would love some sources. I looked a little and the only one I really found was C&H technologies (Extruded Heat Sinks | Heat Sink Extrusions).

[Steve Seebold]

Mitee-Bite Pitbull clamps are hard to beat, not crazy expensive, and will hold very securely with a very small "bite".

Regards,
Ray L.

Ray is right. Mitee Bite Pitbull clamps are amazing.

I would cut the outside profile first, then make a simple fixture to hold your part on end and cut the fins with a 1/8 inch slitting saw that has side chip clearance.

Then after you finish the fins, flip the part over and make another Mitee Bite fixture and finish the work on the bottom.

I make a LOT of special fixtures using Mitee Bites. Sometimes they can seem a little on the expensive side, but once you start using them they soon become indespensible.

[brian257]

Here are some other sources to try. I have about 50' of Wakefield 2015 which is 5" wide with 1.6" tall fins and I could sell you some of that.

Thermal Extrusions
Extruded Heat Sink Solutions - heat sink design
Aluminum Extruded Heat Sinks
Extruded Aluminum Heatsinks from HeatSinkUSA
Extruded Heat Sink- Richardson RFPD