Technical Information Reamers
Hints on use Feeds
In reaming, feeds are usually much higher than those used for drilling. The amount per feed may vary with the material, but a good starting point would be between 0.038mm and 0.10mm per flute per revolution. Too low a feed may result in glazing, excessive wear, and occasionally chatter. Too high a feed tends to reduce the accuracy of the hole and may lower the quality of the finish. The basic idea is to use as high a feed as possible and still produce the required accuracy and finish.
Stock to be removed
For the same reason, insufficient stock for reaming may result in a burnishing rather than a cutting action. It is very difficult to generalise on this phase as it is closely tied with the type of material the finish required, depth of hole, and chip capacity of the reamer. For machine reaming 0.20mm for a 6mm hole, 0.30mm for a 12mm hole, and 0.50mm for a 50mm hole, would be a typical starting point guide. For hand reaming, stock allowances are much smaller, partly because of the difficulty in hand forcing the reamer through greater stock. A common allowance is 0.08mm to 0.13mm.
Speeds
The most efficient speed for machine reaming is closely tied in with the type of material being reamed, the rigidity of the set-up, and the tolerance or finish required. Quite often the best speed is found to lie around two-thirds the speed used for drilling the same material.
A lack of rigidity in the set-up may necessitate slower speeds, while occasionally a very compact, rigid operation may permit still higher speeds.
When close tolerances and fine finish are required it is usually found necessary to finish the reamer at considerably lower speeds.
In general, reamers do not work well when they chatter. Consequently, one primary consideration in selecting a speed is to stay low enough to eliminate chatter. Other ways of reducing chatter will be considered later, but this one rule holds: SPEEDS MUST NOT BE SO HIGH AS TO PERMIT CHATTER.
The following charts gives recommended surface meter per minute values which may be used as a basis from which to start. m / min Aluminium and its alloys.................................................................................. 20 – 35 Brass and Bronze, ordinary............................................................................. 20 – 35 Bronze, high tensile............................................................................................. 18 – 22 Monel Metal.............................................................................................................. 8 – 12 Cast Iron, soft........................................................................................................ 22 – 35 Cast iron, hard....................................................................................................... 18 – 22 Cast Iron, chilled...................................................................................................... 7 – 10 Malleable Iron........................................................................................................ 18 – 20 Steel, Annealed...................................................................................................... 13 – 18 Steel, Alloy................................................................................................................ 12 – 13 Steel, Alloy 300-400 Brinell.............................................................................. 7 – 10 Stainless Steel.......................................................................................................... 5 – 12
Chatter
The presence of chatter while reaming has a very bad effect on reamer life and on the finish of the hole. Chatter may be the result of several causes, some of which are listed:
1. Excessive speed. 2. Too much clearance on reamer. 3. Lack of rigidity in jig or machine. 4. Insecure holding of work. 5. Excessive overhang of reamer in spindle. 6. Excessive looseness in floating holder. 7. Too light a feed.
Correcting the cause can materially increase both reamer life and the quality of the reamed holes.
Coolants for Reaming
In reaming, the emphasis is usually on finish and a lubricant is normally chosen for this purpose rather than for cooling. Quite often this means a straight cutting oil.
Limit of tolerance on cutting diameter
The tolerance on the cutting diameter measured immediately behind the bevel or taper lead for parallel reamers listed is M6 as specified in BS122-PT2-1964. It is not practicable to standardise reamer limits to suit each grade of hole and the limits chosen are intended to produce H7 holes.
Over
Nominal Diameter Range
Cutting Edge Diameter
Inch mm Inch mm
Up to and including
Over
Up to and including
0.0394 0.1181 1 3 0.0004 0.0001 0.009 0.002 0.1181 0.2362 3 6 0.0005 0.0002 0.012 0.004 0.2362 0.3937 6 10 0.0006 0.0002 0.015 0.006 0.3937 0.7087 10 18 0.0007 0.0003 0.018 0.007
High +
Low +
High +
Low +
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0.7087 1.1181 18 30 0.0008 0.0003 0.021 0.008 1.1811 1.9085 30 50 0.0010 0.0004 0.025 0.009 1.9085 3.1496 50 80 0.0012 0.0004 0.030 0.011
480