The only customizable machinable expanding mandrel

The Xpandrel Advantage

Not only can you machine thin wall parts with no distortion and hold workpieces with internal features, the Xpandrel allows you to move your workpiece through a series of different machining and inspection operations without removing it from the mandrel, giving you a precise, repeatable location every time. The Xpandrel can be held between centers, in a chuck or collet, or via mounting plate.

All Xpandrels can be machined to any configuration within its diameter limits.

  • Change the way each end actuates
  • Combine design series properties
  • Add undercuts, turn down ends for tooling clearance

We can modify one for you or you can do it yourself depending on your needs.

Xpandrel Models

All of our Xpandrels are custom made and one-of-kind for your application

1000 Series - Small Precision Parts

Diameters from 5/16” – 1.00” Working lengths from 2.00” – 8.00”

2000 Series - Blind Hole Precision Parts

Diameters from 1/2”- 3” Working lengths from 2”- 8”

3000 Series - Standard Precision Parts

Diameters from 7/8” – 3.50” Working lengths from 4.00” – 20.00”

5000 Series - Large Precision Parts

No more limitations

Ready to get started?

Contact us today. 

How it Works

Using principals of classic mechanics the Xpandrel body is deformed to conform to the internal features of your work piece. This allows you to exert equally distributed forces inside your work piece regardless of features. Thus providing unparalleled holding power without damaging or deforming your work piece.

No more press fitting

No more slippage

No more limitations

Deflection, Elastic Deformation & Classic Mechanical Principals

The Xpandrel uses the fundamentals of Hooke’s law to deform the body of the mandrel within its elastic limit and below the limit of proportionality of the material. This elastic deformation allows you to repeatedly apply high holding forces without damaging or deforming your parts in the process. Working within these limits reduces the possibility of material fatigue, allowing you to repeat the process in a production setting without failure.

How it’s Done

Using various methods of expansion, the Xpandrel body is loaded, finish turned to the nominal limits of your work piece, and then relaxed. The Xpandrel is now slightly undersized and ready to be loaded with your work piece. The deformation profile on the Xpandrel can now distribute radial forces evenly to your work piece throughout the working length of the Xpandrel.



Aluminum 6061

Aluminum 7075

Aluminum Body 4140-HT End Caps (5000 series)

4140 HT

Custom –  Call with special applications

Meet the Xpandrel

Developed by machinists in 1993 and patented in 2004, the Xpandrel was truly an invention born from necessity. Originally designed to hold thin-walled high precision parts to prevent part distortion, it was quickly recognized that this new design was so much more.

We look forward to continuing the innovation and development of the Xpandrel to better meet the needs of modern manufacturing. We are looking ahead to further our work on the development of hydraulic and draw bar actuation options, as well as developing a Micro series for production of tiny precision parts for the medical industry.

Mountain Machine Works

2589 Hotel Road
Auburn, Maine 04210

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