Magnetic chuck for holding brass sheet stock?

[pdentrem]

Here is a picture of part of a milled piece using the method I suggested. No it is not the smallest I have done, but it is one of the most elaborate to date.
Pierre

 

[SilverWorker]

Thanks Pierre!

That looks beautiful. What material is it? Do you have any recommendations for the "Good" tape?

 

[rdhem2]

Mr. pdentrem;

Very fine looking gizwichie in your last photo. How thick is the material and how did you manage such sharp inside corners if not punched?


Always curious in the great PNW. :thinking:


Russ

 

[4GSR]

Boy! You weren't kidding about your part being small.)

 

[SilverWorker]

Ken, I was thinking about what you said about the magnetic field not going through the brass, and was curious- did a little reading and a little experiment. I was able to hold a thin sheet of brass to the fridge with a kitchen magnet, which was not too powerful, so it seems maybe there is enough field getting through to be useful. My reading suggests that brass behaves like air or paper with respect to static magnetic fields, it has a low magnetic "permeability", so it shouldn't block a static magnetic field, but it is a conductor, so it will block oscillating electro/magnetic fields as they will just set up eddy currents in the brass. I'm wondering if you know if the magnetic chucks use static permanent magnets or electrically generated oscillating magnetic fields?

 

[lrsglory]

x2 for the laser cutting. I don't think milling is worth the frustration nor is the costr of a vacuum / magnetic chuck.

x 3 for laser cutting. Larry smith here

 

[churchjw]

I have a project where I need to cut some parts out of thin stock (<.030") Nothing as detailed as these parts. I tried to get some quotes for having it laser cut. But they want $2 a piece and I need 80 of them. More than I can put into the project. I tried making a die to cut them but sheet stock that thin is hard to shear to shape. Never could get my tolerances right. Does anyone know of a good source to get metal parts laser cut? I think I may try gluing some to a board and milling to see if that works for me. Thanks for that wonderful idea.

Jeff

 

[pineyfolks]

Not to sure of your shape but you might try sandwiching them between alum sheet if your end mill is long and strong enough.
dickr

2 Pieces of lexan might work to sandwich them also.

 

[pdentrem]

Re: Thanks Pierre!

That looks beautiful. What material is it? Do you have any recommendations for the "Good" tape?

It is a copper silver braze material. What I use for tape, a good new roll of quality true masking tape, not the low stick stuff. The trick is it can not be old as the glue gets to be not as sticky and dried out. Once heat or humidity gets to the tape the likelihood of movement is higher. I have not tried the new Gorilla tape as of yet.
Pierre

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Mr. pdentrem;

Very fine looking gizwichie in your last photo. How thick is the material and how did you manage such sharp inside corners if not punched?

It is .002" thick and was milled using a .012" end mill at 60k rpm. Used a CNC mill of course.
Pierre

 

[Tom Griffin]

Pierre,

You might try MEK to dissolve the 3M 77, it'll likely cut the adhesive much faster than spirits.

You are right about the RPM's for those small end mills, it amazing fast they need to spin to keep the chip load down. I had to mill a .010" square hole in a sheet of brass once with a .005" end mill and the CNC mill I had could only manage 4000 rpm. I had to do the work under a microscope and could see the mill flexing as it fed around the frame. Luck was apparently on my side because I got it on the first attempt.

Nice job on the parts.

SilverWorker: I have a lot of experience with both permanent and electromagnetic chucks and can say with certainty that you won't be able to hold a piece of brass sheet with a piece of steel sheet firmly enough to mill. They barely have enough holding power on thin steel parts for grinding. You would also need a spacer between the brass and the chuck so you don't mill the chuck which would only make matters worse. The spray adhesive is definitely your best option.

Tom