Milling sheet metal, can it be done ?

[maxime.levesque]

I would like to cut shapes into sheet metal (stainless steel), thickness aprox 0.8mm.

I'm thinking of screwing the sheet to plywood, or MDF, but I'd like to hear ideas, kinds of end mills, that work best, etc.

 

[Ulma Doctor]

It may help to sandwich the sheet metal between 2 pieces of sacrificial material to prevent the sheet metal from lifting.
Or
Super glue the sheet metal to a suitable sacrificial base, machine to desired result and use a heat gun or small torch to remove the part after machining

You may wish to use carbide endmills if you are going to expect any longevity of tooling due to the abrasive nature of stainless steel .
Work hardening is a problem for some grades of stainless.

HSS tools may wear out very quickly and should be run at reduced rates

I would recommend the use of cutting fluid or anchor lube for machining most grades of stainless

 

[Iceberg86300]

Absolutely.

As already mentioned, there are a variety of adhesive options that should do the trick.

Then for tooling you'd use a down cutting end mill that has a reverse helix angle that drives the part into the fixture instead of trying to rip it off to give you a very very very bad day. (Also great for finish work in materials like wood/laminates prone to tearing/chipping on the top edge)

Check out NYC CNC on YouTube. He's done a ton of this kind of work & recorded all of the trial & error.

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[mmcmdl]

Could you sub this out ? Not knowing the size it may be cost effective . SS is a SOAGun to machine depending on the grade . Mike and IC summed it up . The cost of materials , tools and your time vs a lazer cutter , water jet , wire EDM , or Strippit PP may be worth looking into .

 

[Iceberg86300]

Could you sub this out ? Not knowing the size it may be cost effective . SS is a SOAGun to machine depending on the grade . Mike and IC summed it up . The cost of materials , tools and your time vs a lazer cutter , water jet , wire EDM , or Strippit PP may be worth looking into .

That's a good point.

If it is (or can be) 304 or 316, I've heard good things about sendcutsend dot com.

Prices were pretty reasonable (for multiples anyway) when I was looking at them for routing a charge case deck for my RC helicopters. Think it was a fellow RC guy that turned me onto them.

And it's an instant quote if you have a CAD file so it's worth the time even if just for education.

There are a few other large sheet shops with the same business model as well.

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[cathead]

I have done that with aluminum and steel using a smallish end mill to cut with. I did a lot with
the rotary feature on a 6 inch vise making a centering pin to rotate the work.

Another thing one can do is mount a piece of plywood on the mill or in a vise and use wood screws to
attach thin material to the wood. Small end mills work pretty well for cutting any shape but need to run
at proper speed being careful with the travel rate. A 4 flute 3/16 end well worked well for me. I would
expect stainless would be somewhat more of a challenge.

 

[pdentrem]

Laser water jet will be most cost effective. The cost of your time, consumed end mills, making a backer and etc.
Pierre

 

[homebrewed]

I have cut sheet metal with a slitting saw. I clamped the piece to some sacrificial plywood. It was to clean up some bad edges left by some metal snips.

The saw must approach the work so it forces it into the backer plate. That should go without saying but.....I said it . I found that, while fine-tooth blades produce a nice finish on sheet aluminum, it's necessary to use a lot of lube and a brush to keep that soft aluminum from gumming up the teeth.

 

[ggbutcher]

+1 on the online-submit laser cut service. I used OSHCut to make HO scale steam locomotive parts, CAD-ed .dxf files with LibreCAD, submitted online, and had the parts in about a week and a half. Here's a pic:



side and connecting rods, frame sides are between the ruler and the wheels. 0.02" nickel-silver material, you can see sharpie marking on the parts but that can be easily cleaned off. On one of the frame sides you can see brass-milled hornblock bearings inserted, their vendor specified a 1/4" width for the accepting slot, I drew the slots to exactly that width in the CAD drawing and they slid in nicely after a bit of cleanup filing. Note the siderod bearings do not line up with the driver center lines, that was my noob error - pays to double check your drawings before submitting.

Long story omitted, I'm now milling these parts myself, not because of any shortcoming in the laser-cut service option. I'm doing the glue attachment thing to sacrificial aluminum, started with 3M 77 spray adhesive but that doesn't hold the part well as you cut away support, so super-glue would be in order. That said, my particular parts have bearing holes drilled prior to milling, and those can be used with screws to hold the part for the milling, so, think through your order of operations. I also made some task-specific tooling to assist, a couple of pre-sized clamps and a fence that has a shallow key cut in the bottom to square-up to the T-slot, to assist working with a rotary table to cut radii. Here's a shot of the setup:



The one clamp does push up the other side a bit, so a second clamp or a finger clamp into the central region of the part is in order. I originally tried mounting the vise on top of the rotary table, but that makes re-centering the table on the spindle tough. With this setup I can slide the part along the fence from bearing to bearing, remove the part for rotary table centering and put it back on the same Y axis without any fuss. That screw on top the fence is a little too tall to lower the Sherline spindle down to the table for centering, YMMV.

Anyway, with all the hoo-hah required for milling, laser cutting service is a way more expedient operation, just make sure your drawing is correct. Still, I'm going to perfect this milling thing even if it drives me to the memory-care home....

 

[ggbutcher]

I have cut sheet metal with a slitting saw. I clamped the piece to some sacrificial plywood. It was to clean up some bad edges left by some metal snips.

The saw must approach the work so it forces it into the backer plate. That should go without saying but.....I said it . I found that, while fine-tooth blades produce a nice finish on sheet aluminum, it's necessary to use a lot of lube and a brush to keep that soft aluminum from gumming up the teeth.

I have to cut a lot of 0.02" strips from 0.02" brass sheet, thinking of making a "table-saw" style plate of 1/4" aluminum to mount on the lathe cross-slide with a slot for the slitting saw, cut freehand with a fence - any shortcomings in such a setup?