Need custom shim stock ~1/32 thick
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  1. #1
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    Default Need custom shim stock ~1/32 thick

    I'm trying to source 2 different custom thicknesses of corrosion resistant steel shim stock. .065" +/-.001" and .071" +/-.001".

    I've called several suppliers of "custom ground stock", "custom shims", etc. So far as soon as I mention my thickness they say it can't be done. It's too thick to be considered "shim" and too thin to be "custom ground sheet".

    I currently have a RFQ in to a shim stock supplier that says they can provide custom thicknesses but they outsource their custom work and it will be 3 days to get a quote. The lady I spoke with didn't seem very knowledgeable so I have doubts that they can actually provide what I'm asking for. I have a sinking feeling that their custom shop is going to come back and say it can't be done.

    Is it possible? I only need an 8X24 (or two 8X12) piece of one, and a single 8X12 piece of the other. I realize I may have to order a minimum quantity larger than that.

    We are currently machining from AL but want something that will hold up better and machining them is labor intensive and I suspect the tolerance isn't actually being met.

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    Sheetmetal is really accurate for thickness across a given sheet. Why don't you just buy the next thinner size of stainless sheet and then laminate shim material to get the thickness you need?

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    McMaster offers .063 and .075 if you can use that.

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    Are those sheets making multiple parts? or are they just one part...

    How about buying some 17-4 sheet, McMaster has .080 thick.

    17-4 is almost as corrosion resistant as 304,

    BUT!!!! unlike most stainless shim stock its magnetic,
    then get some yahoo with a surface grinder to knock them down to size.

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    Sheetmetal is really accurate for thickness across a given sheet. Why don't you just buy the next thinner size of stainless sheet and then laminate shim material to get the thickness you need?

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    Quote Originally Posted by Booze Daily View Post
    McMaster offers .063 and .075 if you can use that.
    It's for setting a sensor on sensitive equipment. I'm not sure of the implications of changing the shim thickness but I'm certain it will lead to sensor errors. And it's in the aerospace industry so getting a variance to change sensor calibrations is probably more trouble than it's worth.
    Quote Originally Posted by Bobw View Post
    Are those sheets making multiple parts? or are they just one part...

    How about buying some 17-4 sheet, McMaster has .080 thick.

    17-4 is almost as corrosion resistant as 304,

    BUT!!!! unlike most stainless shim stock its magnetic,
    then get some yahoo with a surface grinder to knock them down to size.
    Making multiple parts. The .065 stock makes a 3.5 x 1.6 part and the .071 makes a 3.5 x 3.5 part that gets riveted to another part that holds it in-place during use.

    It doesn't matter if it's magnetic or not. Prefer non-magnetic but it's not a big deal. Hardness really isn't critical either. Estimated use is about 300 uses for the life of each part with no sliding etc, just a pinching force of a couple hundred lbs to squeeze the shim tight. We currently have prototypes made from AL, but we're trying to solve corrosion problems. Alternative option is machined and anodized/coated AL, but we need a coating that can be deposited uniformly in a precise fashion so we can hit our target thickness without too many failed parts. I just assumed stainless shim stock would be easily acquired, even in custom thicknesses so I suggested we switch material to SS to stop the corrosion and now I can't find any SS in the thickness we need.

    I was told by not 1, but 2 different shops that they can't grind that thin as there is no way to hold.

    Also, I would think trying to grab a thin sheet like that on a vacuum table/fixture could cause problems unless you're already starting with 1 side perfectly flat. My understanding of grinding is limited though.
    Quote Originally Posted by Garwood View Post
    Sheetmetal is really accurate for thickness across a given sheet. Why don't you just buy the next thinner size of stainless sheet and then laminate shim material to get the thickness you need?
    Laminate as-in hold it together by hand or by some gluing operation? Gluing isn't entirely out of the question but we would really like to stay away from it because of the environment these are actually used in. The shims could become delaminated unless the glue is VERY good.

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    Perhaps buy the next-thinner stainless shim and find a plater to deposit electroless nickel to the required final thickness. ELN has good corrosion resistance (variable depending on "recipe", confirm best choice with plater). ELN can be heat treated at low temperature to improve strength without damaging hardness of the base metal.

    More information here: https://www.nickelinstitute.org/medi...kel_10081_.pdf or from an applications person at the plater.

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    I seem to recall from my machine building days using pre-laminated shim stock, with each lamination having a thickness of 0.002" and starting somewhere north of your target thickness. Since it looks like you don't need much, it wouldn't be too much of an issue to peel them down to the proper sizes. Tolerance of ±0.001" should be achievable by peeling away the correct number of 0.002" layers, you should end up somewhere in the range as you remove the last one.

    A quick search turned up aluminum, brass, stainless steel, and carbon steel as options on McMaster, here it is. Comes in 20x24" sheets and you can cut it to shape if you're careful. Stainless pricing is a bit steep, but might be better than a MOQ for custom?

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    Quote Originally Posted by BoxcarPete View Post
    I seem to recall from my machine building days using pre-laminated shim stock, with each lamination having a thickness of 0.002" and starting somewhere north of your target thickness. Since it looks like you don't need much, it wouldn't be too much of an issue to peel them down to the proper sizes. Tolerance of ±0.001" should be achievable by peeling away the correct number of 0.002" layers, you should end up somewhere in the range as you remove the last one.
    I've used laminated shim (although not in quite a while), and if memory serves there's a thin adhesive between layers that leads to some compliance under load. That may or may not be an issue with the OP, and he should check with a vendor about stiffness if that's important.

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    Quote Originally Posted by Milland View Post
    I've used laminated shim (although not in quite a while), and if memory serves there's a thin adhesive between layers that leads to some compliance under load. That may or may not be an issue with the OP, and he should check with a vendor about stiffness if that's important.
    A fair point, though at the time I was using them I was calibrating microhole EDM heads which don't have much (any) load applied other than the clamping force from assembly screws. OP stated a squeezing force of "a couple hundred pounds" which seems in the range that is achievable with a pair of firmly tightened 4-40 screws. We never had any issues with stiffness that I know of, so I think that the modest loads indicated by OP wouldn't go out of bounds. Always helps to think ahead and check though .

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    Quote Originally Posted by BoxcarPete View Post
    I seem to recall from my machine building days using pre-laminated shim stock, with each lamination having a thickness of 0.002" and starting somewhere north of your target thickness. Since it looks like you don't need much, it wouldn't be too much of an issue to peel them down to the proper sizes. Tolerance of ±0.001" should be achievable by peeling away the correct number of 0.002" layers, you should end up somewhere in the range as you remove the last one.

    A quick search turned up aluminum, brass, stainless steel, and carbon steel as options on McMaster, here it is. Comes in 20x24" sheets and you can cut it to shape if you're careful. Stainless pricing is a bit steep, but might be better than a MOQ for custom?
    I suspect that the layers could become delaminated too easily. They won't stay within our shop and the risk of losing a layer and it going unnoticed is something I fear.

    Additionally, plan is to waterjet the shape of the shims (it's not an easy shape). Will the lamination hold up to waterjet cutting? We've had problems with other layered materials like G10 etc delaminating on the waterjet.


    One question that is still burning inside is if custom shim stock can be ground that size. Is there a reason a shop with a grinder and vacuum fixture can't get the next thickness up, slap it on the grinder, and grind it down a few thousandths? A mag chuck may not hold it, but certainly a vacuum would? Our shop doesn't have a large enough vacuum but somebody out there must have one...

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    Quote Originally Posted by Bobw View Post
    How about buying some 17-4 sheet, McMaster has .080 thick.

    17-4 is almost as corrosion resistant as 304,

    BUT!!!! unlike most stainless shim stock its magnetic,
    then get some yahoo with a surface grinder to knock them down to size.
    We did this on a project. Had the 17-4 sheet waterjet to size/shape and then slapped them on the surface grinder. Being magnetic, it was quick work.

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    Get a thick block and wire edm whatever is you need...works well

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    could moglice the baseplate, stick the base on a grinder and grind the moglice to req'd thickness? wont corrode, should last forever if handled carefully

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    Contact these guys- they can do amazing stuff. They diamond turned Teflon sheet for us to 1/4 mm thick with a very tight tolerance on thickness. We were fly cutting it on vacuum chucks and they made it look easy.

    Surface Finishes

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    Have you tried Boker's? They specialize in custom washers and shims. They must have a tremendous stock of shim materials as well as suppliers who can handle whatever they want. They can probably measure the stock they have on hand to hit your tolerance or even better.

    Boker's, Inc. | Stamping and Washer Specialists

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    Would it be possible to get some slightly thicker stock and get a jeweler to slip roll it to size?

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    Quote Originally Posted by Dan from Oakland View Post
    Contact these guys- they can do amazing stuff. They diamond turned Teflon sheet for us to 1/4 mm thick with a very tight tolerance on thickness. We were fly cutting it on vacuum chucks and they made it look easy.

    Surface Finishes
    I have a RFQ in with them right now, thanks for the suggestion. At least their website says they specialize in grinding thin parts so that gives me hope.

    Quote Originally Posted by EPAIII View Post
    Have you tried Boker's? They specialize in custom washers and shims. They must have a tremendous stock of shim materials as well as suppliers who can handle whatever they want. They can probably measure the stock they have on hand to hit your tolerance or even better.

    Boker's, Inc. | Stamping and Washer Specialists
    Bokers confirmed they can re-roll stock to precision thicknesses for custom parts and they asked for the prints. Waiting to hear back. Thanks for the lead!
    Quote Originally Posted by crossthread View Post
    Would it be possible to get some slightly thicker stock and get a jeweler to slip roll it to size?
    I was under the assumption that a jewelry roller probably wouldn't be able to handle stainless stock 4" wide (one of the parts is 3.5" wide).

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    Does it have to be 1 sheet? McMaster has rolls of thicknesses that would add up to your numbers.

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    Have never waterjet shims, but have WEDM'd them. You can stack up a whole bunch of them, clamp them tightly and wire through the entire mess. Really nice wehn you're making complicated shims from sub .010" stock.


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