View Full Version : How to Cut Shim Stock

Paul Alciatore
08-23-2010, 12:42 AM
I want to cut some steel shim stock into strips for a special feeler gauge. I plan to stack several sizes with different lengths to make a step gauge, probably starting at a few thousanths and working up to perhaps 0.050" or more. So I need to cut them with little or no burrs on the edges. Or clean them up after cutting. The thicker stock will probably be easier as it can be easily deburred after cutting. But what about a 0.002" piece? How would you cut it clean or clean it up after cutting?

Any suggestions?

And no, I do not have water jet or laser or EDM.

doctor demo
08-23-2010, 12:49 AM
My way is probably not the best way but I use a good pair of kitchen shears and then (for lack of a better word) burnish the edge on a hard flat surface with a piece of round stock and or stone the edge .


08-23-2010, 12:51 AM
A sheet metal shear would work nicely. Do you know anyone at a sheet metal or heating and ventilation shop?

08-23-2010, 01:00 AM
do you have a shear? probably not if you're asking, use a snips without serrations, scissors as suggested for thin stuff. As for cleaning up the edges, a file. Keep the file stationary and drag the work over it, with the work not quit flat on the file but sort of turned up a bit so the action is toward the edge. use a small smooth file with a bit of force on the back side of the work along edge, most material removal will be along there and burs will be gone. A deflection style roller also very hand for cleaning up sheet metal, pass the work through over and over at different orientations

08-23-2010, 01:03 AM
Shear them proud and press them between sheets of MDF and belt sand the edges lengthwise to size.

08-23-2010, 01:46 AM
I just use a big pair of steel scissors.

08-23-2010, 01:49 AM
I use a large upholstery shear. They are heavier and give a better cut than regular shears.

08-23-2010, 01:59 AM
Paper cutter (the swing arm type) works -- and often better than a regular metal shear for thin stock. The slight burr can be burnished out with a small steel roller on a flat steel plate (e.g. table saw top).

08-23-2010, 08:17 AM
Well, you are already one step ahead of the game as you realize the impact the burrs will have.

Your problem is similar to the one encountered in making transformer/motor laminations. Cores for such things, rather than being made solid, are made out of a stack of laminations separated by a layer of varnish to cut down on eddy currents. If you cut the edges with an end mill, they are mushroomed and will short out. If they are punched or sheared, the edges will be curled but will stack ok, but since you are concerned about the total thickness being accurate the curve will interfere, though not as badly as if you had milled as the added thickness from the burrs won't accumulate. Laser cutting and hydrocutting are used for prototyping laminations. I believe EDM will also work. However, you don't have those.

Grinding off the edges will probably take care of the burrs. Along the same lines, an abrasive chop saw, dremel cutoff wheel, or tile saw might work. Keep it cool though or warpage would be an issue.

However, if you are concerned about thickness accuracy, a stack is susceptible to oil, dust, grit, etc. getting between the laminations and warpage. Errors accumulate. You might be able to surface grind or machine (with good surface finish) you steps in a solid piece. Magnetic chucks and vaccum would not be able to hold the thin sections. Glue them down to a flat substrate with cyanoacrylite and be sure to keep it very cool when machining the thinest sections as heat could cause the glue to break down (you use heat to separate from the substrate when you are done). You need to take into account the thickness of the glue (do some tests). Grind the substrate flat in place before gluing the work down (with the bottom side of the work already skimmed flat). Since you want a thin film, avoid gel type adhesives. The heat spreading ability of 2 mil shim stock will be abysmal, so there is a danger of overheating they adhesive even at glacial cutting speeds. Epoxies used on circuit boards also melt at relatively low temperatures but they have the peculiar property of taking a long time to do so which is why you can solder a pcb without delaminating; it would be trick to get a predictable film thickness, though. And the resolution of your machine axes and/or measuring instruments could add a significant percentage of error to 2mils.

Prelaminating between substrates with cyano before machining might also prevent or minimize the bur.

Probably the easiest way to do this is to take apart one or more feeler gage sets, assemble the leaves into the shape you want and cut the back end so any burr is away from the measuring area. Arrange for any burr to be on the back side so the stack lays flat. Sand/grind away what you can. The edges in the measuring area should allready be clean. You still have the problem of how to hold the leaves together without affecting the thickness.

Depending on the application, a long piece of material could be ground to a taper on a sine plate and then marked along its length as to thickness. Circular wedge pieces can also be used with radial markings corresponding to thickness.

As mcgyver was suggesting, delicate use of a file flat on the bottom side of the work will remove very thin burrs without removing significants amount of thickness. Do not hold the file by the handle or you will cut an an angle. Routine part of the hand scraping process.

08-23-2010, 08:23 AM
Scotchbrite deburring wheel on your pedestal grinder works well to soften the edges on thin stock.

I keep a nice sharp pair of shears for this stuff. Aviation snips won't cut it (pun intended). Also use a Whitney punch for holes and inside corners but it has to much clearance so I have to clean up the holes afterward with a trim hammer, file, etc. I suppose a larger punch for reduced clearance could be made if needed.

08-23-2010, 12:14 PM
For thin tin, try surgical scissors.

Your Old Dog
08-23-2010, 01:33 PM
I don't think it's possible to cut feeler guages at home and not have an imperfect edge.

Do more flea marketing and buy a set for $1.00. My guess yours will be worth a couple of hundred bucks by the time you get them completed to satisfaction :D

08-23-2010, 03:37 PM
Not sure what tools/equipment you have available but
Before we had Water jet, I would piggyback the sheet of shim stock using tape to a thicker "carrier" sheet appropriate to the clearances of our punching dies. Put the thin stock on top. May not work with scissors unless you can keep the sheets from shifting.

08-23-2010, 03:44 PM
Another thought - can you mask both sides of the foil with tape (what type not sure) , trim close say 1/16" but not up to the tape around the periphery, then submerge in a cup of acid (again not sure what type) to eat away the exposed edges back to the tape mask?? It may take some trial and error to time it so the acid eats the edges but doesn't make it through the tape.

Paul Alciatore
08-23-2010, 04:28 PM
Great suggestions, thanks to all.

As for purchased feeler gauges, I have some and at least one of them came with burrs on the edges. It took me some time to get them off with fine sandpaper.

I am not overly concerned with the exact thickness. What I want is a single, stepped gauge that I can quickly stick between the work and a tool on the mill or lathe and get a ballpark idea of how far apart they are. That way I can approach rapidly for all but the last few thousanths and then slow down to find the exact point of contact. If I can make it electrically conductive, I can also use it with one of the electric edge gauges. And, yes I have a "click" type too, but the electric type is very valuable in some cases. Anyway, an approximate measure is quite valuable. I know it will be off by a few tenths on the smaller steps and probably by thousanths on the larger ones. But it should still work just fine. I am hoping to (super?) glue the working ends together and make a clamp/handle for the other, unglued end to provide electrical contact throughout the stack.

Where can you get that "large upholstery shear"? I am in a small town in Iowa and our local shopping is limited.