Budget Motorized Upgrade for the Lyman Universal Case Trimmer
Reloading can easily become an expensive extension of the firearms hobby, and how costly it gets largely depends on how far down the rabbit hole one chooses to go.
At the entry level, it is entirely possible to keep costs down by using a single stage press and basic hand tools. At the opposite end of the spectrum, one can invest in virtually every premium product the reloading market has to offer—assuming independent wealth. I fall somewhere in between. I am not destitute, but I approached reloading conservatively when I first got started.
There were several reasons I decided to get into reloading. As my firearms collection grew, so did the number of calibers I needed to support—unfortunately drifting into the realm of expensive cartridges such as .45-70 Government, .338 Lapua Magnum, and .50 Action Express. At the same time, the volume of my target shooting increased, and factory ammunition was becoming an increasingly expensive habit.
From the outset, I opted for a progressive press and other mid-range reloading equipment. I knew that starting with a single stage press and hand tools would be too time-consuming for the quantities I intended to load. At the same time, I was not interested in spending top-tier money on equipment before knowing whether reloading would remain a long-term pursuit.
One area where I deliberately kept costs down was case trimming. I was not prepared to spend significant money on a high-end trimmer, and the Lyman Case Trimmer Xpress was not available at the time—it would not be released until January 2019. The motor module for the Lyman Universal Case Trimmer was also difficult to source, so I ultimately settled on the Lyman Universal Case Trimmer with the power pack combo.
The Lyman trimmer offered several advantages. It supports a wide range of pilots, and the universal shell holder eliminates the need to constantly change case holders. However, as the years passed and tens of thousands of cases were processed, the repetitive nature of manual trimming became increasingly monotonous.
A few weeks ago, I began exploring ways to motorize the trimmer without relying on a handheld power drill. While the included power adapter shaft makes drill use possible, the solution never sat well with me. The constant need to pick up the drill, hold the trigger while trimming, and deal with the drill occupying valuable bench space all detracted from efficiency. I ultimately decided that adding a dedicated motor would be a far cleaner and more ergonomic solution.
After researching several options, I settled on a sewing machine motor with foot-pedal control. It turned out to be exactly what I was looking for and was very budget-friendly, typically priced between $33 and $43 depending on brand and model. The unit I selected cost $42.95. Torque was not a major concern, as case trimming does not require much of it, and the motor’s 100-watt output was more than sufficient for the task.
The first step was removing the belt wheel from the motor. Fortunately, it was secured with a simple set screw. Once loosened, the wheel slid off without issue.
I also removed the motor mounting bracket and flipped it around, so the power cables faced away from the case trimmer. This simply required removing the two Phillips screws on either side of the belt wheel, carefully rotating the mount and power connector, and reinstalling the screws.
To connect the trimmer to the motor, I used a 6 mm to 6.35 mm shaft coupler. The power adapter uses a 1/4-inch hex shaft, which measures approximately 6.35 mm in diameter. I initially searched for a 6 mm smooth-to-1/4-inch hex coupler but was unable to find one readily available, which is why I chose this option.
Next, I replaced the hand-crank trimming shaft on the Lyman with the power adapter shaft. This involved removing the pilot and cutter head, sliding out the original shaft, and installing the power adapter shaft in its place.
Even though one side of the coupler was nominally 6.35 mm, it was not a perfect fit for the hex shaft. To correct this, I removed the retaining screws and carefully opened the bore slightly using a flat-head screwdriver and a hammer. Two firm taps were sufficient to expand the opening by approximately 2 mm.
Once modified, the 1/4-inch hex shaft fit securely. I reinstalled the retaining screw on that side, slid the opposite end of the coupler onto the motor’s 6 mm shaft, and tightened the second retaining screw. I applied blue thread locker and torqued both screws to approximately 8 Nm to ensure everything stayed secure during operation.
With the installation complete, the trimmer now operates smoothly and consistently. Foot-pedal control allows both hands to remain on the case and cutter, improving consistency while significantly reducing fatigue. The motor delivers steady speed and torque without the abrupt on-off behavior common when using a handheld drill.
Overall, this is a straightforward modification. Anyone with basic mechanical skills and common tools should be able to complete it without difficulty, and most of the required components can be sourced inexpensively. For the time and cost invested, the improvement in workflow and ergonomics is well worth it.
I also uploaded a YouTube video for anyone interested in seeing the setup in action. Fair warning, however—my video production skills are nonexistent. There is no editing, no narration polish, and no cinematic flair of any kind.
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