Reverse Engineering Services: How to Recreate an Obsolete Part When the Drawings Are Gone

You have one part left. The manufacturer is gone. The drawings? Probably in a filing cabinet that got tossed in 1998. And now you need fifty more.

This is the situation reverse engineering services were built for — and it happens more often than most people realize. Pumps, gearboxes, agricultural equipment, medical devices from the 1980s, custom industrial fixtures, military spares. Anytime the original supplier disappears, the design lives only in the part itself.

At PartSnap, we recreate these parts every month. Here’s how the process actually works, what it costs, and when it’s worth doing.

What Reverse Engineering Really Means

Reverse engineering is the process of producing a complete, manufacturable design package from a physical part — without access to the original drawings, CAD files, or specifications.

It’s not just “measure it and copy it.” A proper reverse engineering job produces:

• A fully dimensioned 3D CAD model (usually a STEP or Parasolid file)
• 2D engineering drawings with GD&T callouts
• Material identification (often via spectroscopy or destructive testing)
• Surface finish, heat treatment, and coating specifications
• Critical-to-function tolerance analysis

Without that full package, you have a model — not a manufacturable part. The difference matters when your part has to fit, seal, or carry load in a real assembly.

The Three Methods We Use

1. Hand Measurement (Calipers, Micrometers, CMM)

The oldest method, and still the best for simple geometry. A skilled machinist with a granite surface plate, height gauges, and a coordinate measuring machine (CMM) can capture a prismatic part — a bracket, a pulley, a shaft — to ±0.0005″ tolerances in a few hours.

This is the right approach when:

• The geometry is mostly flat surfaces, holes, and basic curves
• You need traceable measurements for ITAR or AS9100 documentation
• The part is small enough to fit on a CMM bed

2. 3D Scanning

For complex, freeform, or organic geometry — turbine blades, automotive body panels, sculpted housings — structured-light or laser scanning captures millions of points in minutes. The resulting point cloud is then converted into a CAD model through a process called parametric reconstruction.

Scanning excels at sculpted surfaces but produces a “dumb solid” without engineering features. You still need a CAD engineer to convert that mesh into a feature-based, manufacturable model. Anyone who tells you scanning alone gives you a ready-to-machine file is selling something.

3. Hybrid (Scan + Hand Measurement)

This is what we use most often. Scan the freeform surfaces, hand-measure the critical features (bearing bores, mating faces, threaded holes), and combine both data sets in CAD. You get the speed of scanning with the precision of hand measurement on the features that matter.

When Reverse Engineering Is Worth It

The cases where it’s almost always worth doing:

• Production-critical spares — A $400 part shutting down a $40,000/day line is a no-brainer.
• Discontinued OEM parts — Once the supplier is gone, your options are: recreate it, or replace the whole assembly. The whole-assembly cost is usually 10–100× the recreation cost.
• Legal/regulatory continuity — Some medical devices and aviation components require an exact part for FAA/FDA compliance. You can’t substitute.
• Improving on the original — Reverse engineering is also the starting point for redesign work. We’ve taken cast iron parts and reworked them as machined aluminum, dropping weight 60% and lead time 80%.

What to Send Us (And What Not To)

To get a fast, accurate quote, send:

• Photos of the part from multiple angles, with a ruler or known reference in frame
• Approximate overall dimensions (length, width, height, weight)
• What the part does, and what it mates to or interfaces with
• Quantity needed and target lead time
• Any known material — even “it’s some kind of bronze” helps

Don’t send the part itself until we’ve agreed on scope and pricing. Shipping a 40-pound gearbox housing across the country before we know if we can help is a waste of everyone’s time.

Common Mistakes (And How to Avoid Them)

Mistake 1: Copying Wear Into the New Part

If the original part is worn — and almost every part needing replacement is — measuring it as-is bakes that wear into the new design. A bearing bore that’s worn 0.003″ oversize will be reproduced 0.003″ oversize unless someone catches it. Good reverse engineers identify worn features and reconstruct nominal dimensions from the surrounding geometry.

Mistake 2: Skipping Material Testing

“It looks like steel” is not a material spec. A part that originally was 4140 heat-treated to 30 HRC will fail in service if you make it from 1018. Material identification via X-ray fluorescence (XRF), spark testing, or hardness mapping is cheap insurance.

Mistake 3: No Functional Validation

The first part off the machine should be inspected against the original — fit-checked, function-tested, and ideally run on a test stand before you authorize a full production run. Skipping this step is how you end up with 500 useless parts in a box.

What This Costs

Real numbers, not marketing fluff:

• Simple prismatic part (bracket, plate, simple housing): $400–$1,200 for the full CAD + drawing package
• Moderate complexity (pump impeller, gearbox housing, custom fitting): $1,500–$4,500
• Complex assembly (full gearbox, multi-part valve, scanned organic geometry): $5,000–$25,000+

Manufacturing the actual replacement parts is separate and depends on quantity, material, and tolerances. We typically quote both in the same package so you see the all-in cost.

Why Use a P.E. for Reverse Engineering

Most reverse engineering shops are good draftsmen. Few are licensed engineers. The difference matters when:

• The part carries structural load (a P.E. stamp may be required by the end user)
• The part is for a public-safety application (elevator components, pressure vessels, lifting equipment)
• You need a written engineering analysis of the redesigned part, not just dimensions

PartSnap is a licensed P.E. firm. When we reverse-engineer a part that carries load, we can stamp the drawing — which matters for liability, insurance, and procurement at most industrial customers.

Reverse engineering isn’t magic, and it isn’t cheap. But when the alternative is replacing a $200,000 piece of equipment because you can’t get one $80 part, it’s the most cost-effective engineering work you’ll ever buy.