So a customer walks into the shop and has a Remington 700 with a stainless steel barrel. They have a specific muzzle break they would like installed and have requested that we cut the threads for the muzzle break and install the part. To achieve this, you will need to Locate the threads, center the lathe and make your cuts. Tools needed for this may include Calipers, rulers, squares, protractors, scribes and layout dye. Also, I think it goes without saying that this is best done on a metal turning lathe.
One of the most important steps you can take during this whole process is when you plan the location of your threads. Check out the muzzle break and determine if you need a shoulder, shims or a crush washer to attach it and consider this in your measurements. Please remember that you really only get one shot at doing this correctly so check your measurements and equipment multiple times throughout the process. Cover the muzzle in a thin coating of marking dye and allow it time to dry. This will be how you make your measurements directly on the muzzle end of the barrel. Use the scribes rulers and protractors to begin marking the layout to include the length of the threaded area, thread relief and the shoulder. Again be sure to double check every mark and measurement you make for accuracy.
If you decide to center the lathe, you will need a bar of heat-treated steel. First chuck the steel bar into the lathe jaws and be sure it is turned true. Once you have the bar mounted in the lathe you will set your compound rest to 60 degrees with the spindle moving in reverse. After that you will check the height of the cutting edge. This will need to be centered to ensure a true cut when milling.
And now we can begin the thread cutting work. You will want to move the cutter into a position where it is just barely touching the barrel. Be sure all measurements are correct one more time before you start cutting to avoid any mistakes. Once the cutter is touching the barrel you will need to reset your compound dial to zero. Move the carriage until the cutter is just past the barrels muzzle. Using the compound wheel, advance the cutter to the depth you want to cut. The next part should be done in multiple passes. turn the lathe on and use the apron wheel to move the cutter through the cuts stopping only at the shoulder you marked earlier. Set the compound to zero again, move the cutter back, check your measurements one more time and make your final pass. I have intentionally left out the measurements of the cuts you will need to make because this can change depending on the type of threads on the new muzzle brake, the size of the barrel you are working with and the caliber of the firearm.
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