Technical Foundation
What Is a Shim Stock?
Shim stock is thin, precisely-toleranced sheet material used to fill a gap between two mating surfaces, correcting alignment, setting a bearing preload, or leveling a machine base — the shim's job is dimensional, not structural, so tolerance on thickness matters more than raw strength for most applications. Stainless steel shim stock is the general-purpose default for its combination of corrosion resistance and durability under repeated compression; brass shim stock is chosen where a non-sparking or non-magnetic property matters, or where the shim will be soldered in place.
Laminated shim stock — thin layers bonded together with a peelable adhesive — lets a technician peel away individual layers on-site to fine-tune a gap without needing an exact pre-measured single-thickness shim on hand, which is standard practice in machine alignment and bearing preload setting. Plastic shim stock (typically polycarbonate or polyester film) is specified where electrical non-conductivity is required, or where the shim needs to resist corrosion in a chemically aggressive environment that would degrade metal shims.
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| Spec | What It Means | Why It Matters |
|---|---|---|
| Material | Stainless steel, brass, plastic/polycarbonate | Brass for non-sparking/non-magnetic needs; plastic for electrical isolation or corrosive environments |
| Thickness Range | Typically 0.001in to 0.125in (or metric equivalent) | Thickness tolerance directly determines alignment/gap precision achievable |
| Form | Flat sheet, coil, laminated (peelable), precut shapes | Laminated shims allow field fine-tuning by peeling layers without a full re-measure |
| Hardness/Temper | Full hard, half hard (affects formability) | Softer temper conforms better to slightly uneven surfaces; full hard resists deformation under load |
| Tolerance | Precision thickness tolerance, often ±10% or tighter | Critical for bearing preload and precision alignment applications, less so for rough gap-filling |
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Applications
Where Shim Stock Get Used
Shim stock is used wherever a precise, adjustable gap needs to be filled between two mating surfaces without permanently machining either part.
Machine Tool Alignment & Leveling
Setting precise machine base alignment and correcting bed-to-frame gaps during installation and maintenance.
Bearing & Coupling Preload Setting
Laminated shims fine-tuning bearing preload and shaft coupling alignment during assembly.
Automotive & Engine Assembly
Setting valve clearances, gear backlash and component alignment during engine rebuild and assembly.
Die & Mold Setup
Precision shims correcting die height and mold cavity alignment in stamping and injection molding tooling.
Electronics & Precision Assembly
Non-conductive plastic shims providing controlled spacing without risk of electrical shorting.
General Fabrication & Equipment Installation
Leveling and gap-filling shims used during machinery installation and structural equipment mounting.
FAQ
Shim Stock Questions, Answered
What's the advantage of laminated shim stock over a single fixed thickness?
Laminated shim stock is built from multiple thin layers bonded with a peelable adhesive, so a technician can peel away individual layers on-site to dial in the exact gap needed, rather than needing to have the precise thickness pre-measured and on hand. This is standard practice in bearing preload and machine alignment work where the exact required thickness isn't known until the assembly is test-fit.
Why would I use brass shim stock instead of stainless steel?
Brass is chosen where a non-sparking property matters (around flammable atmospheres), where non-magnetic properties are needed near sensitive instrumentation, or where the shim will be soldered into an assembly. Stainless steel remains the general-purpose default for most alignment and gap-filling applications due to its durability and corrosion resistance.
How tight does the thickness tolerance need to be for my application?
Precision applications like bearing preload setting or tooling alignment need tight thickness tolerance, since the shim's whole purpose is setting a specific dimensional gap — a loose tolerance defeats that purpose. Rough gap-filling or general leveling work can tolerate a looser tolerance, since the exact thickness matters less than roughly closing the gap.
When should I use plastic shim stock instead of metal?
Plastic (typically polycarbonate or polyester) shim stock is specified where electrical non-conductivity is required to prevent shorting between components, or where the shim needs to resist a chemically corrosive environment that would degrade metal shims over time. It's not typically chosen for high-load-bearing gap applications where metal's compressive strength is needed.
Does shim material temper (full hard vs. half hard) matter for my use?
Yes — full hard temper resists deformation under sustained compressive load, which matters for shims under continuous clamping force. Half hard (softer) temper conforms more readily to slightly uneven mating surfaces, which can improve contact and sealing in less demanding gap-filling applications.
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