Surface finish help

[MIKE_B]

Hi all

 

I have this extruded heatsink that I need to skim the bottom flat within .001 with a 32 finish. Anyone have any tooling suggestions? I will be holding it with a wedgeclamp pushing against a fixed stop. I can only cut between .005-.010 off the part. So far I have tried a 2.00 45° face with not much luck. Some parts cut nice but others chattered

 

Thanks

Mike

 

[Thee Dragracer1951]

I've had luck putting a little modeling clay in the fins of stuff like that to get the harmoics in a different place. Stops it from vibrating as much.

[MIKE_B]

Jim

 

Sorry I didn't mention this is a production run. Clay would not be an option. Thanks for the suggestion

[Tim Simmermon]

A fly cutter would work wll in this situation.

[MIKE_B]

Tim

 

I don't have much fly cutting experience. With something like this am I correct to want a small radius tool so not to push on the material? Do you have any tool bit suggestions to use in the flycutter? And also maybe some starting speed and feed parameters.

[Kevangel]

I would use a flycutter with a 45 degree angle (for cutting face edge) and lots of positive rake to reduce cutting pressure.sharp sharp sharp

[Guest]

clay is awesome but your right doesnt lend itself to production. could you mill nest fixture of rubber or soft plastic to help support and reduce harmonics?

also fly cutters are great but sometimes you can achieve similar effect by removeing all but one insert from face mill?

just some ideas.

 

doug

[Tim Simmermon]

quote:

---

With something like this am I correct to want a small radius tool so not to push on the material?

---

You are correct, although a larger radius will stay sharper longer. We use the style of fly cutter that uses a brazed carbide turning tool. We also use a style that has a single insert. Check out J&L or MSC.

[BernieT]

Can you send them out for blanchard grinding?? Very hard to hold .001 flatness when clamping. Probably do 50-100 at a time on a Blanchard.

How long are they? Can you clamp them 'longways' so the fins help to avoid distortion?

 

Just some thoughts.....

[David from FN MFG.]

well material is a key factor in deciding what method to use.

 

We maintain a 32 finish on 416SS material using a sandvik 1-1/2" 45 degree face mill. The key was/is the insert selection. Talk with your insert rep. about using a "wiper" insert. It was the the solution to feed lines and a "wavey" finish. I could get you the info if you are interested.

 

 

JM2C

[90rsgnuguy42]

What direction are you clamping the extrusions on? You're clamping with the clamps perpendicular to the ribs right?

[mcpgmr]

Always had good success with single point HSS fly cutter with a hand honed edge to about .005 -.010 rad and positve clearance. You should be able to take 1 pass and get a 63 fin no problem. Good luck!

[MIKE_B]

Thanks for the suggestions gang!...

 

I'm just finishing up an order now. I was not having any issues with the flatness just chatter. (Have some flatsanding to do...grrr)

I will try some flycutting on my next run and let you know how I make out.

[heavychevy2155]

If you have a facemill with four inserts could you take 2 out and try that. I have done that with good results.

[MIKE_B]

Heavy thats how I ran my first order I just finished up. The only thing I didn't look into that might help is a wiper insert. I have not had an application for one before. Anyone have experience with them?

[New Job]

I have used them in the past on cast iron and had great results. very smooth flat surface.

 

HTH

[David from FN MFG.]

We use them on 416SS and 4140 alloy with excellent results. We even use the same grade and style for both materials.

Here is the specs we use:

 

SANVIK CUTTER: RA245-051R19-12M

SANVIK INSERT: R245-12T3E-ML QUANTITY:3

SANVIK WIPER: R245-12T3E-W QUANTITY:1

 

Sanvik's website is not the best for research but most insert manufacturers make this style of insert.

[Guest SAIPEM]

What you may want to try is using a something like molten lead to fill in the gaps.

Let it set and reach ambient temperature then cut the part.

 

I've done this frequently with aircraft production work.

 

Once your'e done cutting, you simply heat up the part and just melt away the lead.

[kennebec]

This face mill is very positive and free cutting we use it to cut castings .01 deep holding with 35 in/lbs on 3 points with bump stops, the more SFM the better

 

3.00 Kennemetal Facemill

Body: 80A05RP90BG15C1WUPM

Insert: BGHX15L5PCFRG K110M

 

Good Luck

[Müřlıń®]

Lay down some double back tape in your vice and use a HSS fly cutter...

Might have to use some masking tape to keep the chips from entering from the sides and keep the tape clean.