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Making a Cylindrical on a by John Huth, Lucas Pemberton and Greg Beckwith

Sometimes our work quality and speed increases when thee lath bed true, it is possible to make a serviceable we have a mandrel that is precision-sized to the part we cylindrical mandrel by adding a follower rest to your are trying to repair. lathe carriage. The follower rest supports the stock as it is being cut, the contact point being quite close Shorter lengths of precision cylindrical (1/2” to the bit contact point. Since the follower rest is to 4 inch lengths) are easy to produce on a metal lathe. attached to the carriage, it naturally follows the Your set up is dependent upon the mandrel length: Our up the stock, ensuring a good, dimensionally consistent rule of thumb on set up is: if the stock you are finished product. extends from the less than 3X the diameter, no end support is required; when the stock extension from Here are some tips: the chuck exceeds three times the stock diameter, a live center is required. Without live center support two things can happen: 1. your stock will flex excessively resulting in an inconsistent dimension and finish, or 2. If spinning fast enough, your stock will become a serious danger as centrifugal force whips it into a right angled weapon that could tear flesh and/or break off as a

• Make certain your are sharp. Dull tools greatly increase the forces causing deflection • For mandrels, we often cut soft standard such as 12L14 or 303 stainless • The follower rest needs to contact the stock only very. lightly Too much pressure will result in missile-like projectile. inconsistent dimensions • Turn your mandrels with cutting oil. The same When the work piece extension from the chuck exceeds oil will lube the contact points of the follower five or six times the diameter, even with live center rest support, it becomes even more difficult to achieve an • Do not expect a mirror finish off your . acceptable finish/dimension. Often the stock will chatter Turn the mandrel 0.001” oversize and sand to as it flexes under the pressure of the tool bit cutting finish across its surface resulting in inconsistent dimensions o We like to use 320 aluminum oxide followed and an unacceptably rough finish in the middle section by 400 grit wet/dry with cutting oil of your mandrel. Special thanks to Brian Russell for his contributions to this article. If your lathe is level, the head and aligned and z 27