Thread: How to make a D-type reamer to chamber a barrel

Making a D reamer is a piece of cake. Start with a piece of 10 or 12mm silver steel and a good accurate drawing. Face and centre drill the rod then extend it from the chuck about 75mm to give you working space and support the centered end with a live centre. Turn a pilot about 25mm long that is a neat running fit in the bore then work your way back turning the leed, case and rim to a very high finish about 0.01mm above the desired finish diameter and bring it to size with a fine file and fine grade (400 then 1000 grit) wet & dry paper and oil. Evenly heat the entire length of the turned portion to a good cherry red and vertically quench in oil (SAE 30 is fine, swirling could cause the hardening to be more on one side and cause warping, hence the vertical plunge). With a good bench grinder a pail of cold water, neatly grind the entire length of the leed, case, and rim to exactly half of the diameter, (D shape) quenching frequently to avoid overheating. A light flick across the ground face with a fine slip stone and the reamer is good to go. I recommend boring or drill the chamber to within 0.5mm of the finished size before reaming. I prefer to grind a square on the end of the shaft and use a tap wrench supported by the live centre on the lathe rather than using power as you would with a proper reamer. Use plenty of good cutting oil and withdraw the reamer and clean the reamer and the bore frequently to avoid swarf picking up and grooving the chamber. Go to whoa in less than a hour!