Cut rifling, yes, it makes one cut per groove at . Button barrels the twist is mostly controlled by the shape of the button and the twist rate can vary depending on many variables. Cutting metal from the bore produces rifling with fewer lands and grooves than pushing a tungsten carbide die through the bore which produces “button rifling. Cut rifling is a single point rifling system in which the cutter is pulled through the barrel and rotated at. They use a wooden rifling bench,with about a 3" diameter maple cylinder with the rifling grooves cut into it with hand tools. It is more of a matter of finding the machines necessary to cut, as the zenith of cut rifling machine technology was in the late '40's early '50's. Our barrels are gundrilled with counter rotating gundrilling system. The button is pushed or pulled through the barrel to press. Button rifling can produce a very smooth interior finish, and the majority of winning 6PPC barrels are buttoned. It is sometimes called "hook rifling" after the fishhook-shaped cutter used. might be some minor differences in fouling or velocities but I think a quality job and lots of lapping is what really makes the difference. Rifling Buttons are Precision Carbide Tools for forming the rifling grooves and resizing the bore in gun barrels. groove deeper on one side than the other, thus giving the illusion of "ratchet" rifling. To make a rifled barrel, normally a hole is deep-drilled in a steel bar. 1. What is the twist rate of the Remington 700? The twist rate of a Remington 700 depends on the specific model and caliber, as they are available in various configurations. This was done either with a rod with a hard piece of steel. Screw the two parts together and start sharpening the cutter. They are owned and operated by shooters who have been involved in barrel making for many years. Button-swaged rifling. Button rifling injects more as the 'button' pulled through the bore swaging the rilfing into a previously smooth surface. Also I do believe in the 5R rifling does help fight bullet failure. The bullet you want to shoot will determine your required barrel twist rate. A rifling broach is a long rod with a series of cutter discs perpendicular to the axis of the rod. 45 to . A single cutter is passed through the barrel with cutting oil being injected from inside the cutter tube. About 1550, Gaspard Zeller or Zollner, of Nuremberg, Germany, cut spiral grooves in the barrels of guns; but rifling in its perfected state is almost entirely an American development, a highly important step in the generation of the rifle which was designed. Precihole's Button Rifling machines incorporate the latest features to form precision grooves in small caliber weapon systems. The work hardening of the barrel steel caused by the button results in a bore surface that is denser than a cut surface. Barrels are rifled using a left or right twist. BarSto at one time ran "floating" cutters, and sometimes had alignment problems with latter passes (seen as steps in the rifling). RIFLING CUTTER (SCRAPE TYPE) TO DEEPEN EXISTING GROOVES IN BARREL USING EXISTING RIFLING IS GUIDE. #10. We use a HAAS T-L 2 Lathe for the ent. JES Reboring converted a Remington 760 slide action from -30-06 Whelen to 35 Whelen Whelen. There are two main rifling types, standard and polygonal. For large caliber solutions we use UNISIG B-Series deep hole drilling machines for drilling and bore finishing and a R100 or R200 CNC rifling machine. This process takes significantly longer than. This widly held belief was one of thep principal reasons Marlin switched to the Ballard style. 1 deep. com. The same practice applies to rifling, buttoned or cut. IMHO the real difficult part would be mastering how to. It also work hardens the rifling. 0001-inch per pass. Fig. Broaching uses multiple cutting surfaces (cutters) mounted on the same axis to progressively remove metal. Rifling can be achieved as either a metal cutting, or cold forming process. The top shooters in Benchrest are the ones who can really 'see' the minute differences in barrel accuracy. There are four ways to produce the grooves: Cut rifling. 004″ per size of material to insure a precision clean bore which sets up the style of rifling tool to. Conventional lands and grooves are replaced by “hills and valleys”. Couple 2x4s, some screws, a small stick of round bar, some clamps, and a cutter head that I'll machine. Double scrap cutter tooling was being used/made back even when the cut rifling was done manually by a human pulling the cutter thru the barrel by hand! Places have converted/modified the Pratt’s for pulling broaches and even pulling buttons. There are four ways to produce the grooves: Cut rifling. 45 / 70 as a close support Scout rifle. Are you meaning to say that they use a button to form their rifling? Because a button doesnt cut and your claim they they use a button to cut is objectively incorrect. By the nature of the manufacturing process, cut-rifling puts fewer stresses in the steel and twist rate is more likely to be uniform. Rifling in a . 16530 posts · Joined 2000. A bullet traveling down a 12-inch barrel with a 1:14” rate of twist will still be spun at the 1:14” rate. The carbide button tool is attached to a rod of high tensile steel, and the other end of the long rod is attached to a. Drilling small, deep, straight holes is time consuming and expensive. 22 caliber barrels or pellet guns. This gives the polygonal barrels a tighter gas seal on the projectile. . You can harden the barrels before drilling, however. Rifling twist is consistent from one end to the other. 500 Mag Rifling. I hope the pics make the operation more comprehendable. 50. The cutter rests in the cutter box, a hardened steel cylinder made so it will just fit the reamed barrel blank and which also contains the. This required multiple iterative passes of a cutting head for each groove (at first this was done with a "scrape cutter", and later a "hook cutter"). It is threaded at the muzzle to 5/8 by 24 for the use of a muzzle brake or a suppressor but comes with a threaded cap. Equipping the barrel with the spiral grooves that spin-stabilize a bullet is the essential operation that defines an entire category of firearms. This process is no longer common. Full Member. It is best for barrels that do not require deep rifling grooves. That visible a pattern indicates a problem with the process. More of a setup operation. with the catch being that we were always talking about cut-rifling. Broached rifling. It should be fluffy and feel like very fine tissue paper when crushed between your fingers. Cut rifling is done by hand or with a tool that cuts one groove at a time through the barrel. and you will find a bunch of stuff but to briefly recap:Helical grooves known as rifling are cut into the bore of a barrel of a firearm during production to increase the accuracy of that firearm. It is sometimes called "hook rifling" after the fishhook-shaped cutter used. Some folks think cut rifling can wear quicker due to the sharp interior surfaces. It performed as such in the field, changing POI 1 1/4 MOA vertical and 1/2 MOA vertical between cold and 4 shots warming, consistently moving the POI low and left over the 4 shots. Really very instructive! I have used this book very much during all the years I´ve been in the ML gunsmith`s business. The lands and grooves create a unique pattern on the bullet casing that can be used to identify the gun from which the bullet was fired. Even though a button rifled barrel typically gets restressed relieved again after button rifling there are no guarantees. The grooves cut around the shank of many of today’s bullets solve the problems associated. Button-swaged rifling. J. Cut-Rifling - All the Difference in Custom Rifle Barrel Fabrication. However, single point cut rifling takes a lot of time and is, therefore, quite costly. You may be surprised to learn that cut-rifling is probably the oldest method of rifling a barrel. PTG Replacement 223 HSS Rifling Cutter. It is available in three distinct finishes, including simple Black DLC, along with Titanium Nitride and Chameleon PVD as well. 2) Button riflings are easier on bullet jackets (less likely to produce bullet failure) than cut riflings. Lands are the raised portions of the rifling that run down the inside of the gun barrel, while grooves are the cutouts in the rifling that run along the inside of the gun barrel. A button does not cut. Make sure to wipe down both the barrel and the tool with a clean rag to remove any residue. I have three rifles with three different types of rifling. There is a slightly higher bullet velocity in polygonal rifling and they are easier to clean than conventional/cut rifling. How many grooves does a hook cutter make with one swipe? 1. In 1854, Henry D. It actually cold forms the rifling into the reamed bore of the rifle. 016 deep. 005 to . Polygonal rifling . The twist is 1:12, bullet weighs 216-grains from an Accurate mould and a mv of about 1900 fps. This is the technique that puts the minimum amount of stress into a rifle barrel. I cut the shoe recess, 1-3/8 inch long about 1/2 way through the rod. Are you meaning to say that they use a button to form their rifling? Because a button doesnt cut and your claim they they use a button to cut is objectively incorrect. Sizes range from 14 caliber Rifles to 10 gauge rifled shotgun barrels and can be ground with any helical twist right or left handed. I do know that almost all precision rifles use cut rifling (with the exception of the HK PSG-1 and a few other examples), however, so there must be something to the theory. During the search for rifling cutters I have found a lot information about rifling machines ( old and modern ). . Even if you had all the correct equipment to produce a rifled barrel like a deep hole drill a rifling, machine tool and cutter grinder ect, the skill and expertise to produce a quality blank is also needed. In addition, the article describes a new (and somewhat radical) method, Cation Rifling, which employs acid to. March 8, 2017. The first rifling method to date, which is now done with modern machinery. $691. One of our local CBA shooters uses a Broughton 5C barrel. Brophy's book on Marlins. RIFLING ROD. Hammer-forged rifling is formed by. And my thought is that square edge of the lands being sharp wear faster. Single Point Cut -- This involves cutting the grooves one at a time with a machine cutting tool pulled through the barrel. The grooves were 3 or 4 times wider than the lands. The rifling process generates the grooves and lands characterizing the barrel of a rifled firearm. 22 to 50 BMG. As the hammers compress the outer surface, the blank is reduced in diameter and lengthened, simultaneously creating the bore and rifling. This required multiple iterative passes of a cutting head for each groove (at first this was done with a "scrape cutter", and later a "hook cutter"). 0001 inch on each pass, thus taking several hundred passes to rifle a barrel. Very few hammer forged. These methods are the „ scrape cutter " method and the „ hook cutter " method. Tooling – gundrills, reamers, rifle buttons. We do single point cut rifling. impressed into the metal as the negatives of minute imperfections found on the rifling cutter’s surface ; these markings will be unique to each gun made - thus the marking will be individualizing characteristics to a single gun. This video shows the process of cut-rifled barrel-making by one of the world's best barrel manufacturers. 008" and in a 30 bore (. 001) per pass, so it is by and far the slowest (but most accurate) form of rifling. Rifling begins by mounting the barrel in the machine and setting the desired direction and rate of twist. The grooves are usually parallel in barrels while the sides of the lands are not. The barreled action comes with a black Cerakote® finish or natural stainless finish using a clear coat and nickel finish. Lawton did cut rifling, and also produced the worst barrel regardless of rifling method my gunsmith ever had in his shop with 33 years gunsmithing experience. Each has its own advantages and may be preferred based on specific requirements. Kolbe (past owner of Border Barrels) covers all the important processes: steel selection, hole drilling, hole reaming, and rifling (by various means). Join Date: February 20, 1999. There are 5 different rifling methods, cut, button, broach, cold hammer forged and ECM. Conventional rifling, while effective, can be improved upon in two ways. Randy Gregory of Medford, Wi. He recently purchased a Pratt & Whitney Sine Bar Cut-Rifling barrel machine. For background, current thought is to build a 600 yard f classer, right now looking at a 260 AI or variant thereof. Rifling refers to the spiral (helical) grooves that are cut or swagged on the internal surface (bore) of a gun barrel, which helps impart the spinning motion to a bullet when it’s fired. #2. Straighter, more precise. Also from just some recent testing by a bullet maker/ammo maker a few months ago is they do believe that they found that the 5R rifling helps the flight of the bullet in the transonic range vs a 4 groove barrel that was also being tested the bullet had a disturbance in the. Correct me if I'm wrong, but what made 5R famous was its enhancement over other geometries of cut-rifling . Didn't copper foul at all. How does button rifling compare to cut rifling? Button rifling is generally considered more cost-effective than cut rifling as it requires less time and labor. Although our machines are state-of-the-art, the process itself is the oldest and slowest method of rifling a barrel. A sine-bar scrape- or hook-rifling setup is far more suited to one-offs. The results of rifling gives a barrel its _____ Class characteristics . It is chambered in 30 BR and it is accurate. “A single-point cutter imposes little stress on the blank,” John Krieger says. The cutter cuts in both directions while traveling through the barrel. A 3-inch barrel with 1:14” twist spins its bullets the same as. e. Rice uses a proprietary, infinitely-variable CNC rifling machine, which has a traditional Springfield type rifling head to single hook CUT each groove. That young man "converted" one side of the rifling machine to turn out a . With this high-tech method, strips of desired shape are placed inside the bore while the whole assembly is submerged in a salt solution. Using a small 1/8" chisel, carefully remove the wood from the inside the mortise to a depth of about 1/32" to 1/16". Button rifling can be done a couple of different ways but basically it is a cold swagging process. S. It’s highly unlikely you find barrels like this being sold unless they’re some kind of premium barrel. To button rifle a barrel a carbide plug, or button, with a reverse image of the grooves and raised lands of the rifling, is pulled down the bore. Rifling consists of spiral grooves cut into the inside of a barrel of a gun. The others were unnamed gunsmiths in Augsburg, Germany in 1498. The pressure exerted by a burning charge of powder in the chamber of a gun. Conventional rifling has lands and grooves. Oct 31, 2023 #23 ; Frank Green said:By: Glen E. Single point cuts the rifling one groove at a time. Barrels: Cut Rifling vs. Cut rifling and broach rifling both involve removing metal from the inside of the barrel, which produces “grooves” that lie in between uncut areas know as “lands. The broach is fed down the barrel with a rotation that matches the twisting ground in the tool, with each progressive tooth increasing the depth of the cut. Broach cut rifling cuts all the grooves at the same time as the broach is pulled through the barrel. Don't know about Chanlyn's backlog. The oldest (and the slowest) is the use of a single steel scraper attached to a long rod to cut each groove individually. They are available in rifle only, bore only, or combination style. grooving. Cut and button rifled processes can be altered to accommodate varied twist rates, other than in extremes, whereas cold-hammer forging needs the mandrel within to be the exact shape of the bore, including the twist rate. It performed as such in the field, changing POI 1 1/4 MOA vertical and 1/2 MOA vertical between cold and 4 shots warming, consistently moving the POI low and left over the 4. The upper is a place in the chamber where the shoulder is . A button puller is another 1 axis machine with highly custom tooling. In fact, we discussed this type of cutter way back when we studied cut rifling techniques almost four years ago. The cutter rests in. Even if scrape cutter rifling requires less time to produce grooves, both processes are time-consuming and incompatible with large-scale manufacture since the cutter may require several sharpening or even replacement (Biasotti, 1981; Bonfanti, 1997). The cutter makes a full length pass in the direction the bullet travels and the machine indexes to the next point to cut the next groove. My understanding is that broach cut rifling has the potential to be better than a button barrel if the setup and QC is correct. Shape, number, and depth of grooves can be changed easily. [2] The first muskets to use this technology were called. Instead of being smaller than the radius of the bore, the radius of the cutter should be at least twice as large as the bore radius. Marlin likes to call this process "Ballard rifling" because this was how theRe: Rifling cutter shape. Here's a breakdown of the 3 main types of rifling, Cut rifling, button rifling, and cold hammer forged, and what we believe are the benefits. It takes far longer to cut-rifle than to button- or broach-rifle a barrel. Forged rifling. Cutter is made to SAAMI specs. Most button rifling mftrs will flute BEFORE final lapping and not after. May require live pilot with appropriate sized. Equipping the barrel with the spiral grooves that spin-stabilize a bullet is the essential operation that defines an entire category of firearms. 35 Remington microgroove rifled barrel. Origin action hawk hill 6. The bullet was quite tight and twisted as it came out. It is mostly all automatic with a long shaft with a ground cutter made from TanTung or Cobalt. Conventional rifling, while effective, can be improved upon in two ways. Although our machines are state-of-the-art, the process itself is the oldest and slowest method of rifling a barrel. The only cut rifled 1911 barrels I am aware of are Lissners. Then the bar is placed in the drilling machine. precise exact twist rates and 6 groove rifling . Sep 5, 2013. Rifling. Cut rifling is more precise and makes a difference for those. 104. . The actual hammer-forging is illustrated starting at 1:15 in this video. The twist is exact, where as other forms of rifling can have variances due to the process they use. If needed, hammer forging can form the chamber and throat as well as a fully profiled outer surface. Also, a high level of skill is required to maintain the tooling. Hi all, yep I`m making a sharps rifle on my lathe, what is the best rifling twist for the 45-70 cartridge with black powder, I can get 1 in 24" and a max barrel length of 25". This lube was claimed to be the critical part of the process. Their barrels are cut-rifled and. Oct 19, 2023. Cut rifling is the oldest method that is still being used. "Round bottom CUT rifling . See the figure below. For a pistol, broach or button does an equally fine job. * Cut-rifled barrels are drilled, then reamed to bore diameter. This may be changing with the advent of contoured (5R) cut riflings. Electron discharge machining (EDM) The following types of rifling use similar processes as the ones aforementioned. The traditional method is called single-point cut rifling. Now, fold or cut the patch for a snug, not tight, fit. What is Button Rifling? In button rifling, the “button” is actually a tool made of tungsten carbide. To make a rifled barrel, normally a hole is deep-drilled in a steel bar. This is why I always go back to a cut barrel being better than a button barrel. Sako, Steyr and others have proved that they can make some incredibly accurate high volume hammer forged barrels. Texas. It is essentially a negative image of the barrel, i. It is essentially a negative image of the barrel, i. 010. Cut-rifling is also the only practical way to rebore barrels. engineering. Pull it through a plywood plate with a hole and notch guide cut in it. Many of the largest and most respected names in the firearms industry rely on us for our outstanding commitment to quality and on-time delivery for their firearm related tooling. The main focus of the article is on Cold Hammer Forging of. 32 and . The only exception to this rule is Forsyth style rifling with wide grooves, and narrow lands. The cut-rifling method removes metal from the surface of the bore to create the grooves using a single-bladed, hook-type cutter. 3642). Button rifling is done by pulling a solid carbide forming die (referred to as a button) through the drilled and reamed barrel bore. Rifling Cutters at Pacific Tool and Gauge. There. You will even find some loading books that say, cast bullets don't do well in MG barrels past about 1. Bartlein Barrels is a manufacturer of precision cut-rifled barrels used for hunting, precision tactical shooting, and benchrest competition. A broach can be used to cut rifling into the inner surface of a barrel, b. After the rifling has been cut, clean the barrel of the gun and the rifling cutter carefully. 150-gr. I wanted to use 250 grain rn and rnfp bullets. cut to provide a completely stress free barrel. Whereas it had taken an hour to cut the old Ballard-style rifling with the scrape-cutter method, a barrel could be button-rifled in less than five seconds. There is sometimes confusion about whether Krieger Barrels does button rifling, because in 1999, another barrel company was started under our roof, Criterion Barrels , which manufactures button rifled barrels for. Cut rifling is the first rifling method to date which was invented in Germany around 500 years ago. Hook and scrape rifling are no longer used by manufacturers that mass produce barrels; however, some custom barrel makers may still use these methods. I see now that manufacturers are using the "5R" label on both hammer. Hammer forging is also known as the "Appel process" or cold forming. , a receiver only. Conventional rifling has sharp 90-degree corners from the top of the land to the bottom of the groove. The rifling process is a key part of barrel manufacturing, resulting in lands (bore) and grooves that create a spiral down the length of the barrel. 3crows said: No, Remington built Marlin . A broaching tool may be pulled or pushed along a workpiece. 6 x 0. Rock Creek Barrels are made in Albany, WI. While the number of companies offering reboring has decreased considerably in the past few decades, the few remaining in the U. As a result, it is most commonly seen in . That is why . Contact us to discuss your large-scale defense projects. 0)Actually, making the rifling in a gun barrel can be done in a few ways. After. Don. Machine marks are caused by poor tooling or cutting speed causing the cutter to chatter leaving these marks. Bartlein's state-of-the-art cut rifling machines can hold uniform twist rates to the 4th. Using a small 1/8" chisel, carefully remove the wood from the inside the mortise to a depth of about 1/32" to 1/16". LaBounty worked out a method for his rifling cutter to follow the old rifling, deepening it slightly. With specialized cells dedicated to this industry, we have. To date, Criterion’s button rifled barrels have set. Which rifling technique involves the use of cold-working to harden the interior of the barrel and permits the use of. The most commonly used rifling method is called 'broach rifling'. The process of Single Point Cut Rifling is the most stress free way to rifle a barrel. Then the rerifling process involves the rifling cutter moving in and out of the barrel approximately 300 times (50 times per groove). The cut-rifling method removes metal from the surface of the bore to create the grooves using a single-bladed, hook-type cutter. Whereas it had taken an hour to cut the old Ballard-style rifling with the scrape-cutter method, a barrel could be button-rifled in less than five seconds. Equipping the barrel with the spiral grooves that spin-stabilize a bullet is the essential operation that defines an entire category of firearms. A rifling broach is a long rod with a series of cutter discs perpendicular to the axis of the rod. Button rifling is simpler and faster than cut rifling and usually less expensive. 4. A real cut rifling machine is getting closer to a real 3 axis machine. At the same time, the expansion of the fired cartridge. This video shows the process of cut-rifled barrel-making by Krieger Barrels, one of the world’s best barrel manufacturers. The quality of the barrels turned out by this method was very good, but it is a time-consuming process that slowed down production (the scrape cutter rifling process took about an hour to. Now we will study a more modern technique called Broach Rifling. Rifling begins by mounting the barrel in the machine and setting the desired direction and rate of twist. Then he’d. It is used for critical operations where precise angle or depth control must be maintained. This recovered Hornady . They are used to remove metal from the surface of the barrel to create the grooves and spirals. This article describes in detail how barrels are crafted, using both cut-rifling and button-rifling methods. The Broughton 5c rifling looks alot like the rifling in a glock no sharp edges. Brux Barrels is a machine tool company located in Lodi, Wisconsin, specializing in the finest custom-made cut-rifled barrels. So, cut rifling is still favored by many manufacturers. The part that grips the patch is the edge of the rifling. S&W advertises that the smoother surface produced by EDM is an improvement over the broach cut rifling it replaced approxamently 1997 for most centerfire production revolvers. The Model 444 was introduced with a 12. I personally think the whole cut rifled vs button rifled thing is over done and the merits of cut rifling and the downfalls of button rifling are often exaggerated. We start with 4150 chrome-moly or 416R stainless steel double stress relieved bar stock, bore with the renowned Barnes gun drill, ream with an industry-standard Pratt & Whitney reamer, and then hand lap each barrel to our high-precision standards. (a) What are the weight and specific gravity of this sphere? (b) Will it float in 20°C gasoline? If so, how many cubic centimeters will be exposed? Verified answer. In addition, the article describes a new (and somewhat radical) method, Cation Rifling, which employs acid to etch. 6K fps. As previously stated it is hard to get extra deep rifling to seal, and not burn up the patch. 5R is an improvement over conventional rifling by changing the shape and configuration of the lands and grooves. The part that grips the patch is the edge of the rifling. Like all old technologies, cut rifling is slow and requires a high level of skill to make and maintain the tooling. Each is interesting in its own way. So we are only cutting one groove at a time at an approx. It's a production method for hundreds of barrels rather than being suited to a one-off. Single-point rifling. A machine pulls a sharp cutter down the bore, removing a thin layer of steel in a spiral. Rifling can be cut into the inner surface of a barrel using a broach, the rifling can be formed using a hardened steel button, or the rifling will be formed through a process called hammer forging. Logged Dave B. Minuteman. The Model 444 was introduced with a 12. Rifling begins by mounting the barrel in the machine and setting the desired direction and rate of twist. In a 50 caliber rifle, the cutter is ground to an exact radius to create a round shape that is a circle. Single point cut rifling is the most accurate method of rifling and produces low stress on the barrel during the cutting process. Why because they don’t understand the tooling for cut rifling is one. Today, four- and six-groove barrels are the most popular. Barrel Twist Rate – is the inches a bullet needs to travel in order to make a complete revolution. The traditional method is called single-point cut rifling. Rifling Cutter Body & Carbide Cutter. A rifling bench or equivalent is needed to control rate of twist and index the rifling grooves. 22 caliber barrels or pellet guns. Rifling Twist:. 1675 posts · Joined 2007. This rifling-machine post will still be here when you come back). With this type of cutter, it is possible to set the depth of cut very precisely by rotating the bolt on the left side. Building on a savage action, have an additional post in competition forum but figured I'd ask the barrel question here Guess wondering the accuracy difference one could expect out. Not sure about the cut or button detail. with the catch being that we were always talking about cut-rifling. Choose Options. This comment assumes this rig is a cut rifling machine. The originals I have examined favor 7 L/G and very narrow deep. Back in the day it was all about very deep cut rifling. The principle problem was (and is) the availability of cut rifling machines - you don't exactly trip over them at machinery auctions. The problem is that the round bottom rifling cut by most barrel makers is to small in the radius cut. This required multiple iterative passes of a cutting head for each groove (at first this was done with a "scrape cutter", and later a "hook cutter"). With cut rifling, grooves are carved into the barrel using a cutting tool, whereas with button rifling, grooves are pressed into the metal using a hardened steel button. Ballard rifling came about during the years Marlin made Ballard rifles. If the rifling grooves make a complete revolution in 9 linear inches, it is a 1:9” twist whether the actual barrel is 9 inches long, 30 inches long or just 3 inches long. This method produces almost perfect concentricity between bore and.