April 30, 2022 Custom barrel makers are honing barrels after drilling to improve bore diameter uniformity and smooth the interior finish. This also reduces barrel lapping times. Honing has been a common practice for large-scale producers of hammer-forged barrels for many years. This process is now being used by smaller, boutique barrel-makers. This article will explain how and why barrel honing works. Watch the video. This video by Sunnen Products Co. is a great resource for anyone interested in barrel-making. Honing is a time-saver for custom barrel makers and a cost-cutter. A honing machine takes only a few minutes and can cut down lapping times by half. It leaves a cross-hatched surface in single- or double-digit Ra. The same process is used to make diesel fuel injectors that have bore roundness and straightness reduced to fractions of microns. (This manufacturing process is also used for hammer-forged barrels. Custom button-rifled barrel makers are now paying attention to it. This is called precision bore-honing. Honing is essential for hammerforging. It produces a fast bore surface of high quality. Why is honing so important for hammerforging? The barrel’s surface finish cannot be controlled with hammer forging. As the blank is formed on a rifling mandrel, surface imperfections in a barrel blank are magnified. Surface imperfections are magnified if the bore has been chromed after. Honing significantly improves bore diameter uniformity, accuracy, surface finish, and roundness along the length of the barrel. It can be used in lieu of a pre-rifling lapping. The main difference between a lapped bore and a honed bore lies in the direction of the bore’s finish lines. Honing leaves fine spiraling crosshatch lines while a lap leaves lines running longitudinally through the bore. If desired, the manufacturer can remove crosshatch lines with a quick lap after rifling. Honing is fast and accurate, and can even be automated. Its surface quality and geometry can replicate lapping, with the exception of the longitudinal lines of the lapped end. Frank Green from Bartlein Barrels stated that they had worked with Sunnen to develop the prototype machine. It works great! We ordered and received… a brand new machine manufactured with the changes that we requested. We then ordered another one.
The Sunnen hone holds the barrel blank in a 3-jaw Chuck. Honing oil is pumped into one side of the tool while it works from the other. Sunnen’s Long Bore Tool is a specialized tool that uses metal-bond diamonds or CBN superabrasives. It can quickly remove reamer marks and other imperfections caused by upstream processes. Honing is an ideal alternative to hand-lapping barrel blanks prior to rifling. It removes surface waviness and reamer scratches quickly without the need for labor-intensive hand-lapping. By producing a consistent bore diameter (+-0.0001? A consistent bore diameter (+-0.0001? The ideal bore geometry reduces bullet distortion. “Computer-Controlled Bore-Honing
Computer-controlled honing machines allow for precise honing. Sunnen Products Company offers an advanced machine that can handle barrels ranging from.17 to 50 calibers (see control panel). This machine’s spindles can correct bore size imperfections that are so small that an air gauge cannot measure them. The consistency this allows improves bore uniformity, which, in turn, produces more accurate barrels for the precision market.Sunnen Products Company is the world’s largest vertically-integrated manufacturer of honing systems, tooling, abrasives, coolants, and gauging for precision bore-sizing and finishing. Sunnen’s customers include oil field equipment manufacturers, diesel and gas engine manufacturers, aerospace components, hydraulic parts, and gun/cannon barrels. Sunnen employs over 600 people around the world.
