These tools are basically for precisely enlarging holes. Reamers are used for round ones, while brooches are usually used for other shapes: flat square, rectangular, hexagonal etc. Normally both have tapers, some with very gradual ones. More sophisticated ones are adjustable.
In general reamers are used with a twisting motion. Some are very simple steel rods or cutters, straight or fluted, usually for hand finishing. Extremely useful to the modeller for enlarging detail mounting, side rod, grab iron and other holes with a snug fit,_ is a set of 6 from Mascot (Dixon, Maxon) ranging from almost zero up to about .096 in. Square shaped, they will cut in either direction and also double as brooches in plastics and nonferrous metals. Their only restriction is that the hole must be clear through in most cases.
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Small gradual tapered hand reamers for modelling.
Just insert in hole until reamer stops. Twist a few turns with very light pressure. The slight taper allows easier insertion, without effecting alignment. Test for fit. repeat until insertion is successful and still snug. It is much easier and quicker than redrilling. In most cases, the residue on the flats will serve as a depth guide for successive holes.
For more delicate work, dental finger reamers and files (drills) are often used. Resembling fluted drill bits with small handles, they are twisted clockwise to enlarge very small holes. In sets of six, the reamers range from .015 - .040" and the files .045 - .080".
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Small finger reamers.
Frequently truck journals have flash or rough surfaces. To improve rolling, a special tool is offered to ream them. This apprears to be a shortened counter sink with a small, soft band to improve grip. The tool should be held perpendicular to the frame and very lightly twisted to avoid enlarging hole or upsetting concentricity. With a little applied force, depth can be increased to accept longer axles, when changing wheel sets.
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Truck journal reamer.
Very often truck kingpin holes have flash or burs at the top boss, which may interfere with free turning. Cleaning with a tapered reamer will remove this and slightly chamfer the edge, without enlarging the hole. General offers a fluted reamer with a tip just under the 1/8". used on most HO trucks, to 3/8". Designed for reaming beads to eliminate cutting strings and other hard materials, a diamond set provides three tips in a storage handle. The smaller tapers up to about .064" while the larger goes to about .126". Useful for chamferring, the third is a cone with about .26" base.
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Hand fluted reamer.
Diamond bead reamer.
In some cases a small round file may be used as a reamer for rougher work. The correct turning direction must be determined to avoid dulling teeth.
A much larger reamer, with a shorter taper, can be found in better hardware stores in several sizes. It is commonly used in sheet metal work and in deburring pipes or tubing after cutting.
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MEDIUM TAPER MACHINIST'S HAND REAMER
Another type is stepped to ream successfully large holes in sheets of softer metals or materials.
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HAND REAMER/DRILL
The above types a generally used without lubricant , while those below normally require lubes such as cutting oil.
Most other hand or machine driven reamers are sized for one or a small range of diameters and due to price, most machine shops stock only a few standard sizes. With a very long taper, these are only used in a very slightly undersized drilled hole. Although they may possibly be used manually, they produce better results with a lathe. Larger sizes were once commonly used to ream replacement kingpin bushings in autos.
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1/8" CHUCKING REAMER USED TO SIZE AXLE BEARINGS
The cutting teeth of brooches resemble those of a file, which, except for very accurate work, can replace them. They are normally pushed through the hole. Only jewelers types may be useful for detailing work and these are expensive.
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