Reamer A reamer or ream is a tool for enlarging holes and is used in metalworking . It may be used as a hand tool or may have a specialized drive end . For production machine tools the drive will usually be a standard taper . For hand tools the drive will usually be a square drive , intended for use with the same type of wrench used to turn a tap for the cutting of screw threads . A typical reamer consists of a set of parallel straight or helical cutting edges along the length of a cylindrical body . Each cutting edge is ground at a slight angle and with a slight undercut below the cutting edge . Reamers must combine both hardness in the cutting edges , for long life , and toughness , so that the tool does not fail under the normal forces of use . They should only be used to remove small amounts of material . This ensures a long life for the reamer and a superior finish to the hole . The spiral may be clockwise or counter-clockwise depending on usage . For example , a tapered hand reamer with a clockwise spiral will tend to self feed as it is used , possibly leading to a wedging action and consequent breakage . A counter-clockwise spiral is therefore preferred even though the reamer is still turned in the clockwise direction . Adjustable hand reamer Adjustable hand reamer An adjustable hand reamer can cover a small range of sizes . They are generally referenced by a letter which equates to a size range . The disposable blades slide along a tapered groove . The act of respectively tightening and loosening the restraining nuts at each end varies the size that may be cut . The absence of any spiral in the flutes restricts them to light usage ( minimal material removal per setting ) as they have a tendency to chatter . They are also restricted to usage in unbroken holes . If a hole has an axial split along it , such as a split bush or a clamping hole , each straight tooth will in turn drop into the gap causing the other teeth to retract from their cutting position . This also gives rise to chatter marks and defeats the purpose of using the reamer to size a hole . Straight reamer ( precision ) A straight reamer is used to make only a minor enlargement to a hole . The entry end of the reamer will have a slight taper , the length of which will depend on its type . This produces a self centering action as it enters the raw hole . The larger proportion of the length will be of a constant diameter . Reamed holes are used to create holes of precise circularity and size . This will allow the force fitting of locating pins , which need not be otherwise retained in the body holding them . Other holes , reamed slightly larger in other parts , will fit these pins accurately , but not so tightly as to make disassembly difficult . This type of alignment is common in the joining of split crankcase halves such as are used in motorcycle motors and boxer type engines . After joining the halves , the assembled case may then be line bored ( using what is in effect a large diameter reamer ) , and then disassembled for placement of bearings and other parts . Another use of reamed holes is to receive a specialized bolt that has an unthreaded shoulder . This type of bolt is commonly used to replace hot peened rivets during the seismic retrofit of structures . Hand reamer A hand reamer has a longer taper or lead in at the front than a machine reamer . This is to compensate for the difficulty of starting a hole by hand power alone . It also allows the reamer to start straight and reduce the risk of breakage . The flutes may be straight or spiral . Machine reamer Spiral fluted machine reamer A machine reamer only has a very slight lead in . Because the reamer and work piece are pre-aligned by the machine there is no risk of it wandering off course . In addition the constant cutting force that can be applied by the machine ensures that it starts cutting immediately . Spiral flutes are essential on a machine reamer to clear the swarf automatically . Rose reamer A rose reamer has no relief on the periphery and is offset by a back taper to prevent binding . They are primarily used as roughing reamers . Shell reamer Shell reamers are designed for reaming bearing and other similar items . They are fluted almost their whole length . Tapered reamer ( precision ) Four small tapered pin reamers A precision tapered reamer is used to make a tapered hole to later receive a tapered pin . A taper pin is a self tightening device due to the slow angle of the taper . They may be driven into the tapered hole such that removal can only be done with a hammer and punch . They are sized by a number sequence ( for example , a No.4 reamer would use No.4 taper pins ) . Such precision joins are used in aircraft assembly and are frequently used to join the two or more wing sections used in a sailplane . These may be re-reamed one or more times during the aircraft 's useful life , with an appropriately oversized pin replacing the previous pin . Morse taper reamer No. 3 morse taper reamer A morse taper reamer is used manually to finish morse taper sleeves . These sleeves are a tool used to hold machine cutting tools or holders in the spindles of machines such as a drill or milling machine . The reamer shown is a finishing reamer . A roughing reamer would have serrations along the flutes to break up the thicker chips produced by the heavier cutting action used for it . Combination Reamer This combination reamer was made for a long run , tight tolerance electronic parts . A combination reamer has two or more cutting surfaces . The combination reamer is precision ground into a pattern that resembles the part’s multiple internal diameters . The advantage of using a combination reamer is to reduce the number of turret operations , while more precisely holding depths , internal diameters and concentricity . Combination reamers are mostly used in screw machines or second-operation lathes and not with Computer Numerical Control ( CNC ) machines because G-Code can be easily generated to profile internal diameters . Combination reamers can be made out of cobalt , carbide , or high-speed tooling . When using combination reamers to ream large internal diameters made out of material with lower SFM , carbide tips can be brazed onto a configured drill blank to build the reamer . Carbide requires additional care because it is very brittle and will chip if chatter occurs . It is common to use a drill or combination drill to remove the bulk of material to reduce wear , or the risk of the part pulling off on the combination reamer . Tapered reamer ( non-precision ) A tapered reamer may be used cleaning burrs from a drilled hole , or to enlarge a hole . The body of the tool tapers to a point . This type of reamer consists of a body which , typically , is up to 1/2 inch in diameter , with a rod cross piece at the large end acting to form a handle . It is especially useful for working softer metals such as aluminum , copper , and mild steel . A similar tool can be seen on select Swiss Army knives , such as the Electrician model , to be used on conduit . See also Hone Broach ( metalwork ) Metalworking : Metalworking cutting tools : Broach | Burr | Chisel | Counterbore | Countersink | Cutting tool | End mill | Metalwork file | File | Hand scraper | High speed steel | Milling cutter | Reamer | Stellite | Tipped tool | Tool bit Metalworking topics :   Casting | CNC | Cutting tools | Drilling and threading | Fabrication | Finishing | Grinding | Jewellery | Lathe ( tool ) | Machining | Machine tooling | Measuring | Metalworking | Hand tools | Metallurgy | Milling | Occupations | Press tools | Smithing | Terminology | Welding Categories : Metalworking cutting tools In other languages : Deutsch | Español | Italiano | 日本語 | Nederlands | Polski | Slovenčina | Svenska 