Shim Stock: Materials, Uses, and Practical Tips

Shim stock supplies the thin materials used to make shims for gap-filling, alignment, and spacing. It is available as precision commercial sheets in various metals and plastics or improvised from wood, cardboard, or paper for temporary fixes. Applications span construction, carpentry, plumbing, electronics (including CPU protection), medical imaging (passive and active shimming), software compatibility (code shims), and locksmithing. Choose materials by load, environment, and permanence; use commercial stock for lasting installations and improvised shims only temporarily.

What is shim stock?

Shim stock is the raw material used to make shims - thin pieces of material inserted to fill gaps, adjust spacing, or align parts. Shims restore alignment, level surfaces, and control tolerances in mechanical assemblies, construction, and equipment setup.

Where shim stock comes from

You can obtain shim stock in two ways. Commercial suppliers sell precision shim stock in metals (stainless steel, brass, aluminum, copper), plastics (nylon, PTFE), and specialty alloys, typically in sheets, strips, or pre-cut gauges. These are available in measured thicknesses (fractions of an inch or millimeters) for repeatable use.

The second source is improvised shims. Craftspeople commonly cut shims from wood, cardboard, thin plastic, or even paper for temporary alignment or when a quick on-site fix is needed.

Common materials and why they're chosen

• Metals (stainless steel, brass, copper, aluminum): durable, stable under load, and available in very thin, precise thicknesses.

• Plastics (nylon, PTFE): nonconductive and corrosion-resistant, useful where electrical isolation or chemical resistance matters.

• Wood and cardboard: inexpensive, compressible, and easy to trim for temporary leveling or when load and precision demands are low.

Typical applications

Shims appear across trades and industries.

• Construction and masonry: shims level windows, doors, and fill uneven gaps beneath fixtures.

• Carpentry: thin wood shims fine-tune joinery and set cabinets plumb.

• Plumbing and mechanical assembly: metal shims align shafts, flanges, and piping to maintain proper fit and reduce stress.

• Electronics and CPUs: thin protective or spacing shims have been used to protect delicate chips from uneven heatsink pressure; modern mounting systems have reduced but not eliminated this need.

• Medical imaging: in MRI and other precision systems, technicians use passive metal shims and active shimming techniques to correct magnetic field inhomogeneities and improve image quality.

• Software and compatibility: "shim" also describes small pieces of code (compatibility shims or polyfills) that adapt or intercept calls to preserve functionality across platforms.

• Security tools: in locksmithing and security testing, thin metal shims are used to bypass or test padlocks and other devices.

Practical tips

Pick a material rated for the expected load and environment. For permanent assemblies, use commercial metal or engineered plastic shims sized to the specified thickness. For temporary or one-off fixes, trimmed wood, plastic, or layered paper can work but may compress or deteriorate.

Always place shims so they distribute load evenly and do not create point stresses. When precision matters, verify final alignment with measurement tools and replace improvised shims with rated stock for long-term installations.