DIY Case Trimmer Power Adapter

DIY Case Trimmer Power Adapter

Case prep is one of the most boring and tedious parts of the reloading process. It takes a lot of time and can be hard on your hands, especially if you are doing everything manually. One of the most important parts of case prep is trimming cases. This process usually requires the user to turn a hand crank to perform the cutting action. Even if you only have to trim 50 cases, this can become very tiring, especially if you have arthritis. To make this process easier and faster, I made a DIY Case Trimmer Power Adapter. It will allow you to use your corded or cordless drill to trim your cases, saving time and reducing the strain on your hands.

Making a DIY Case Trimmer Power Adapter is very inexpensive. I was able to get everything I needed to build it from Lowe’s for around $3.50. Unlike many store-bought power adapters, mine allows you to easily remove the drill from your case trimmer if needed. This will reduce strain on your drill and the trimmer itself. 

Step 1: Remove the Handle Screw

The first thing you need to do is remove the screw that attaches the handle to the case trimmer. This should be fairly easy to do. I was able to remove mine with an Allen wrench. Don’t lose this screw. You will need it later.

Step 2: Determine the Original Screw’s Thread Pitch

Next, you need to determine the original screw’s thread pitch. If you don’t do this before you buy a new screw, it probably won’t fit. Reloading equipment and firearm accessories, in general, tend to use uncommon screw sizes.

Take the original screw with you to the hardware store and find the thread checker. It is usually located in the part of the store with the screws, nuts, and bolts. Find the hole that the case trimmer’s original screw will go into. It should turn easily but not be wobbly. The hole will have a label below it. The thread pitch for my RCBS case trimmer’s screw was 10-32, although your’s may be different.

Step 3: Find a New Screw

After you have determined the original screw’s thread pitch, search for screws with the same thread pitch with a length of 1 1/2 to 2 inches. You will probably have to search for it in the “uncommon size” drawers. This is where I found mine at Lowe’s.

Step 4: Find Nuts for the New Screw

Next, find a package that has 4 or 5 nuts that match the screw’s thread pitch. They will probably be close to where you found the new screw.

Step 5: Add One Oversized Nut

Next, find one nut that is slightly oversized. You want it large enough to slide onto the screw without having to thread it but not so large that it slips over the head of the screw. The oversized nut that I chose for my DIY case trimmer power adapter had a 1/4 inch inner diameter. This will be what the nut driver on your drill will attach to when in use.

Step 6: Slide the Oversized Nut on the Screw

After you get all of the necessary pieces, start by sliding the oversized nut on the new screw. It will not thread, but that is okay. The oversize nut will be held on by the smaller nuts in the next step. It should be held in place on the end by the screw’s head.

DIY Case Trimmer Power Adapter
Slide the oversized nut onto the screw.


Step 7: Secure the Oversized Nut

Next, secure the oversize nut into place using two nuts that have matching threads with the new screw. Use the first nut to tighten the oversized nut against the screw’s head. Use a wrench to ensure a tight fit. Then tighten the second nut against the other one. This should lock the oversize nut in place so that it won’t move while in use. If it does move, add some Loctite.

The oversized nut is held in place by two nuts threaded onto the screw.


Step 8: Install 2 More Nuts on the Screw

Next, thread two more nuts onto the screw. Put them far enough onto the screw that you will be able to thread the end of the screw all the way into the case trimmer.

DIY Case Trimmer Power Adapter
Thread two more nuts onto the screw. Give yourself enough room on the end to fully thread the screw into the case trimmer.


Step 9: Insert Screw into Case Trimmer

Now, insert the new screw into the case trimmer and tighten it. There will be a little bit of wobble, but you will eliminate this in the next step. Now tighten the two nuts from Step 9 against the case trimmer. This will eliminate any slop that may exist between the new screw and the case trimmer.

DIY Case Trimmer Power Adapter
Insert the screw into the case trimmer and tighten the two nuts against it.


Step 10: Test Your DIY Case Trimmer Power Adapter

After your new DIY Case Trimmer Power Adapter is assembled and installed, find a nut driver that fits the oversize nut at the end of the adapter. Tighten the nut driver into the chuck and test it out. Keep the drill on the low setting and make sure the case trimmer’s shaft and any other metal on metal contact point is well-lubricated. If any nuts slip, add Loctite or an optional spacer shaft which I will detail in Step 12.

Step 11 (Optional): Create and Install a Spacer Shaft

I added a spacer shaft to my DIY Case Trimmer Power Adapter to help prevent any of the nuts from coming loose while in use. To do this, I scavenged a length of aluminum pipe from my garage. It was actually the shaft from an old 1970’s lawn dart that I found in my grandparents’ basement. You could also use an appropriately-sized wooden dowel rod for the same purpose.

Measure the distance between the two sets of nuts (while installed on the trimmer) and cut a length of metal pipe or wooden dowel rod to that length.

I measured the distance between the oversize nut retaining nuts and the nuts near the base of the adapter that removes the slop between it and the case trimmer. I used a hacksaw to cut the pipe to the correct length and then used a 3/16 inch drill bit to open up the inside of the pipe enough to fit over the screw’s threads. It doesn’t need to thread onto the screw, it just needs to provide a physical barrier between the sets of nuts at each end of the adapter.

DIY Case Trimmer Power Adapter
A spacer between the two sets of nuts will prevent them from moving while you are using the power adapter.

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