As part of my OCD reloading process I use mandrels at the final step in case prep. Until now I have used conventional mandrels due to a readily available and economical supply. I had noticed that these mandrels are taking on some scratch's with use. I know it is not a big deal, but I thought that switching to carbide would eliminate that as well as likely require less pressure to open up the case necks (my experience is the less force used at all operations of the resizing process results in less concentric error at bullet seating, but that is just me).
After searching around on ebay, I found a China outfit that would sell me individual carbide pins in metric sizes for $8-$10 each depending on diameter. I didn't know what it would take to get a taper on the carbide mandrels, but come to find out it was rather simple.
I started by putting a double bevel on one end of the pin gage (using my Deckel clone), first one was 8 degrees, then 4 degrees up at the confluence of the 8 degree grind and the side of the pin gage. I chose 4 degrees as the transitionary bevel because it matched the 4 degrees on my K&M chamfer tool.
The polishing operation was very easy. I purchased a few different grits of diamond paste, 1K, 2K, 5K, 50k, 200K to be exact. Cheap stuff from Amazon. As you can see from the photo below, I drew a few lines on a 1"x2" piece of scrap pine board and marked them accordingly. Put a small dab of the paste in each section to charge the pine. Chucked up the mandrel in the mill, started slow to get coverage all over the ground end, then ran the speed up to 2K rpms. Held the board at an angle, rocking it gently across both the 4 degree and 8 degree grind. After a few seconds of slight pressure from the board, I simply wiped the mandrel down with a paper towel and moved on to the next finer grit on the board. I don't know if I needed 5 different grits to get from diamond grinding wheel to mirror finish, but the process for each mandrel was only around 5 minutes start to finish so I used the same steps for all 8 mandrels (I know, but that many different calibers is a whole different problem). Super easy to grind, even easier to polish. I do use lanolin as a lube. Don't have a way to actually measure the insertion force, but it is substantially easier than the steel pins. Wasn't bad before, but if the goal is less force during case prep, this is a good step to try.
After searching around on ebay, I found a China outfit that would sell me individual carbide pins in metric sizes for $8-$10 each depending on diameter. I didn't know what it would take to get a taper on the carbide mandrels, but come to find out it was rather simple.
I started by putting a double bevel on one end of the pin gage (using my Deckel clone), first one was 8 degrees, then 4 degrees up at the confluence of the 8 degree grind and the side of the pin gage. I chose 4 degrees as the transitionary bevel because it matched the 4 degrees on my K&M chamfer tool.
The polishing operation was very easy. I purchased a few different grits of diamond paste, 1K, 2K, 5K, 50k, 200K to be exact. Cheap stuff from Amazon. As you can see from the photo below, I drew a few lines on a 1"x2" piece of scrap pine board and marked them accordingly. Put a small dab of the paste in each section to charge the pine. Chucked up the mandrel in the mill, started slow to get coverage all over the ground end, then ran the speed up to 2K rpms. Held the board at an angle, rocking it gently across both the 4 degree and 8 degree grind. After a few seconds of slight pressure from the board, I simply wiped the mandrel down with a paper towel and moved on to the next finer grit on the board. I don't know if I needed 5 different grits to get from diamond grinding wheel to mirror finish, but the process for each mandrel was only around 5 minutes start to finish so I used the same steps for all 8 mandrels (I know, but that many different calibers is a whole different problem). Super easy to grind, even easier to polish. I do use lanolin as a lube. Don't have a way to actually measure the insertion force, but it is substantially easier than the steel pins. Wasn't bad before, but if the goal is less force during case prep, this is a good step to try.
