Advantages of Horizontal Milling

Traditional machining, CNC or otherwise, is done with the cutting tool rotating vertically. Many skilled machinists have never done milling any other way. But things are different at Strom Manufacturing, Compass Precision’s shop in the Pacific Northwest. Strom’s forte is horizontal milling, with chips flying away from cutting surfaces oriented vertically.

To better understand why Strom seeks to be different, we sat down and spoke with the Three Amigos, also known as Co-General Managers Brian Kedroske (pictured second from right, above), Paul Sonderen (far right, above), and Mike Strom (far left, above).

Why Is Strom So Focused on Horizontal Machining?

Brian – Strom has always been long-term oriented – it was a hallmark of former owner Bill Strom’s (second from left, above) business philosophy. Many years ago, our experiences caused us to realize that horizontal machining centers (HMC’s) were a better investment choice for our type of work. Initial capital costs can be considerably higher, but the larger investment is easily justified by lower operating costs and higher quality.

Paul – By their nature, horizontal mills are built much differently than their vertical cousins. Most verticals have a “C-shape” construction, with the spindle being located at the upper end of the C and the work piece at the opposite, lower end. The machine’s rigidity is limited due to this type of machine design. High speed operation can cause the cutting tool to vibrate when making chips. The natural rigidity of a horizontal mill is considerably higher – it is simply a much beefier type of machine.

Mike – More robust machine construction means we can operate at high speeds and feeds. And because our machines’ work piece axis of rotation is vertical, our cutting tools can access three faces of the work piece in one setup. This ability can reduce the number of setups required versus running the job on a vertical. This reduces cost and improves quality.

Are There Any Other Advantages of Horizontal Machining Centers?

Brian – As a quality guy by nature, one of the things I really like about HMC’s is something called “natural chip evacuation”. With horizontal milling, chips fall away from the cutting surface. Gravity is a horizontal milling machinist friend – there’s no accumulation of chips where the cutting tool is in contact with the workpiece. This can be a big problem with traditional vertical milling.

Are There Any Disadvantages To Horizontal Milling?

Paul – Hiring experienced machinist is always challenging, but finding ones with horizontal experience is even more difficult. At Strom, we overcome this by hiring lesser experienced personnel and doing our own training. But in general, I think this is a big reason why more shops don’t have HMC’s.

Does Strom Specifically Seek Jobs That Are Best Served by Milling Horizontally?

Mike – Yes, of course. We machine many so-called heat spreaders used by semiconductor companies to convey heat away from high power, light emitting diodes. These components are flat, rectangular parts, with numerous holes, notches, and other surface details. This geometric configuration is particularly well suited to horizontal milling. We also make parts with similar geometries for other industries.

How Do Customers Benefit from Strom’s Use of Horizontal Machining Centers

Paul – Lower costs and better quality. Our cycle times are usually shorter than competitors with traditional vertical mills. And often we can make parts with fewer set-ups. Both of these improve our productivity and result in lower prices. And by reducing the number of operations, we decrease potential process variability. This inherently improves quality.

Is There Anything Else Customers Should Know About Strom’s HMC’s?

Mike – Most of our horizontal machining centers are highly automated machines with multiple pallets. One pallet can be swapped out for another without operator intervention. Different parts can be machined from one pallet to another, or even within an individual pallet holding multiple workpieces. This gives us tremendous flexibility to meet varying customer needs for both low and high volume requirements.

Brian – And all of these advantages apply without sacrificing quality. Greater equipment rigidity and potential for fewer set-ups naturally reduce part-to-part variability. And natural chip evacuation keeps cutting surfaces free from debris. This helps quality, too.

For more information about Strom Manufacturing and its horizontal machining capabilities, please feel free to contact Brian Kedroske at, Paul Sonderen at, or Mike Strom at For information about Compass Precision, please contact CEO Gary Holcomb at