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jadecy
09-21-2007, 12:57 PM
I searched previous posts and have not been able to locate the answer to this. It is probably simple but with my limited experience I can't figure out how it is done.

Example:

You have a flat 3/8" thick piece of metal. Let's just say it is 6061 t6 aluminum. It has two 1/4" holes in it and they are 1/2" to 1" apart. You need to cut a slit between the two holes. The slit needs to be fairly thin lets say in the range of say .010 to .030". The holes are toward the center of the material so it would be very difficult (impossible?) to position or use a slitting saw on a milling machine.


I don't have a specific need at the moment but I've seen pictures of machined items with slits similar to what I've described.

How is this done? Is it done with a jewelers saw? Is there some amazing setup for a slitting saw on a mill?

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Note: I'm not looking for the "farmed" out answer such as EDM, waterjet, laser,...

I've seen this in home machinist projects and I'm fairly certain they didn't farm the job out.

Thanks for your help!:)

Fasttrack
09-21-2007, 01:04 PM
A horizontal mill ...?

Otherwise a small diameter slitting saw and the piece mounted on a 90* setup plate - then move the knee and table to posistion correctly.

Or maybe you can use something like a dremel with a cut-off wheel. I've seen a grinding attachment, for lack of a more descriptive term, that goes in a vertical milling machines spindle and bumps rpm way up to use small abbrasive wheels and what not. I've either read about it here or in one of the magazines.


<edit> i just realized your example material was aluminum which wouldn't work so good with the cut-off wheel idea...

Peter N
09-21-2007, 01:30 PM
Use a coping saw (or jewellers saw)

Uncouple the blade, feed it though one of the holes, re-attach it and saw away. Blades of 0.020" thickness are available.

Peter

Asquith
09-21-2007, 01:44 PM
In principle you could do it with a slitting saw if you work from both sides. You can prove this with a pencil, ruler and compasses. In practice, I think it would be a bad plan to try this with a thin saw!

dp
09-21-2007, 02:00 PM
Have a look at EDM.

Fasttrack
09-21-2007, 02:42 PM
I thought you were trying to just cut a groove without worrying about breaking a tiny endmill ... actually cutting through to the other side is a different story. My bad.

Spin Doctor
09-21-2007, 02:50 PM
Wire EDM. It actually wouldn't cost all that much. We have the plans on line for the 3D stereo lith machine. Now we need somebody to develop a good home brew wire EDM

dp
09-21-2007, 06:41 PM
Have you seen the May 1995 HSM mag's home brew EDM?

SGW
09-21-2007, 06:59 PM
A lot depends on just how difficult/impossible it is to set up on a vertical milling machine, whether extra holes are allowed in the piece for clamping, etc., and how accurate the slot needs to be. It could get to be pretty impossible.

But, a fairly wide jeweler's sawblade of appropriate thickness, if you can put some guide blocks on both sides of the to-be slot to help keep the blade on track, and IF the slot is close enough to an edge so the frame of a jeweler's saw will clear...would be one way of doing it with pretty decent accuracy.

ammcoman2
09-21-2007, 07:06 PM
The Jerry Howell plans for the "Micro-drill" has this exact scenario for mounting a post in the base plate.

When I built mine I used the slitting saw, going just deep enough to cut into the section between the holes. I then used a jeweler's saw blade as mentioned above to get through the rest of the metal. In this way the top (viewing) surface has a clean looking cut.

Geoff

mochinist
09-21-2007, 08:17 PM
Scroll saw or a coping saw for the non farmed out answer.