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How to check part dimensions for automotive restorers

A plain guide for automotive restorers on checking part dimensions step by step, with what to have ready and which tools to consider.

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TexHouse is published by the makers of LunarWerx 3D Print, Vector3D and MeshyDL, which are compared here alongside other tools.

To check part dimensions, clean the part, measure it at the same marked points as a trusted reference, repeat each reading, and compare the differences against the fit you need.

OptionWhat it doesFee
LunarWerx 3D PrintBrowser tools, including turning backwards STL faces right side out [1]All of its browser tools, including this one, are free to use [1]
Digital calipersCheck the maker's own specifications for range and resolution before you buyNot published
Your CAD or model viewerCheck with its maker which dimensions it can report, and in which unitsNot published

What you need before you start

Before you measure a restored part, gather a few things. Clean the part thoroughly, because grease, rust scale and paint can hide the true edge of a flange or hole.

Have digital or dial calipers ready, along with a steel rule for longer lengths. A reference is essential. It can be the original part if it is still in good shape, a factory drawing, a service manual specification, or the mating part it has to fit.

Keep a flat, well-lit surface to work on, and a notebook or spreadsheet to record each reading against the point it came from. Photos taken with a ruler in the frame help you return to the same points later. If the part has been repaired or reworked before, note that too, since earlier repairs can shift the dimensions you measure.

Step by step

Work through these steps in order, and record every reading as you go.

  1. Clean and inspect. Remove dirt, scale and loose coating from the measuring points, then look for cracks, bends and wear before you measure anything.
  1. Choose the reference points. Mark each feature you need to check, such as hole centers, mounting faces, flange thickness and overall length. Note which points matter most for fit.
  1. Measure the reference. Measure the reference part or specification at each marked point, and record each figure with its unit.
  1. Measure the restored part at the same points. Use the same tool and the same grip each time, and take each reading from the same spot.
  1. Repeat each measurement. Take more than one reading per point and check that they agree. If they do not, clean the tool and the point, then measure again.
  1. Check both sides. Where the design should be symmetrical, measure the left and right sides and compare them. A difference can point to distortion or to a measuring error.
  1. Compare and note the difference. Subtract the reference reading from the restored reading at each point, and mark any difference that is outside the fit you need.
  1. Decide what to do with each difference. Adjust, rework or replace the part, then measure again after any change.
  1. Keep the record. Save the readings, the reference source and the date, so the check can be repeated or shared with someone else.

Tools that can do it

Several kinds of tool can help with this job, and the right choice depends on whether you measure a physical part, a drawing or a digital model. The options below are described only as far as the sources for this page allow.

LunarWerx 3D Print provides browser tools for printing and moulding work. [1] It runs in a web browser [1] and you use it on its website, which is hosted on Cloudflare. [1]

If you already have a digital model of a part, one of its tools works on model files. When you open an STL file with faces turned backwards, it turns them right side out and says how many it fixed. [1] The code package is marked private, not public. [1]

For measuring a physical part, the steps above depend on calipers and a trusted reference. For the other options in the table, check each maker's own documentation before you rely on it for this job.

Common mistakes to avoid

Measuring a worn original and treating it as the reference is a common mistake. Wear can make an old part look like the standard it should match. Check the reference against a drawing or a second source where you can.

Trusting a single reading is another mistake. Small changes in grip, angle or cleaning change results, so repeat each measurement.

Assuming symmetry without checking can hide distortion. Measure both sides before deciding that a part is correct.

Measuring over paint, rust or grease adds thickness that is not part of the metal. Clean each point first.

Skipping the zero check on your tool causes the same offset in every reading. Check the zero before each session.

Relying on a digital model without measuring the physical part is a mistake too. A model may be drawn to a different standard from the part you have, so verify it against the part.

Frequently asked questions

How do you check part dimensions on an old car part?

Clean the part, mark the points that matter for fit, and measure the restored part against a trusted reference at each point. Repeat every reading, check both sides where the design is symmetrical, and write each result down with its source. Compare the differences to the fit you need before you decide to rework, adjust or replace the part.

Can LunarWerx 3D Print check the dimensions of a physical car part?

The claims for LunarWerx 3D Print describe browser tools that work out ironing settings, check parts for injection moulding and design 3D-printable foam inserts. [1] For measuring a physical part, the calipers and reference steps earlier on this page are what the job needs. For a digital model, such as an STL file with faces turned backwards, the tool turns the faces right side out and reports how many it fixed. [1]

Is LunarWerx 3D Print free to use?

Yes, the tools are free to use. [1] You use them on the website in a web browser, and the site is hosted on Cloudflare. [1] [1] If you sign in to your account, your settings, recent test plates and print results follow you to every computer. [1]

Where does LunarWerx 3D Print keep settings and files?

It runs only in your browser. [1] If you sign in with Connections, your settings, recent test plates and print results follow you to every computer. [1] Keep your own copy of any measurement records you need, because the steps on this page depend on your notes.

What should a restorer check before trusting a digital model's dimensions?

Compare the model against the physical part at the points that matter for fit. Check the scale and the units the model was drawn in, and confirm that it follows the same standard as your part. Measure the restored part directly, because a digital model can differ from the part you are working on.

The tools are free to use. [1]

Try LunarWerx 3D Print

Sources

  1. LunarWerx 3D Print's own description of itself (the product of this site's publisher)

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