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REAMERS
Reamers are used to finish a bored or drilled hole to a specific size or tolerance (often H7 tolerance), leaving a better finish in the bore. Reamers can be used by hand or machining depending upon the type of reamer selected, several types of reamers are available depending on the application. Generally reamers are made of High Speed Toolsteel; Miller’s Tooling can also provide carbide tipped reamers and solid carbide reamers, in addition re-sharpening of reamers.
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Adjustable Hand Reamers
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 blades slide along a tapered groove. Blades can be replaced as sets. 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.
Hand Reamers
Hand reamers are held in a tapping wrench to manually finish a hole to a neater finish.
They are similar to a chucking reamer however the hand reamer has a greater lead to start the hole & a square drive on the shank.
Chucking Reamers
Chucking reamers are to be used in a drill chuck or collet for a machining application usually to secure dowel pins or create a sliding fit, etc. The chuck reamer has only a short lead at the start. German, “Walter – Titex” has chucking reamers are avail in 0.01mm increments up to 10mm. Chucking reamers are preferred by toolmaking, the shank is parallel.
A machine reamer only has a very slight lead in to start. Because the machine 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 the machine reamer starts cutting immediately. Spiral flutes are essential on a machine reamer to clear the swarf automatically. Machine reamers have a Morse Taper shank.
Taper Pin Reamers
The taper pin reamer is ideally used for securing tapered pins as its name suggests. Tapered pins are used to secure steel plates & blocks together. The taper is ¼” in 1 foot, and are used by hand in a tap wrench.
Reamers
Bridge reamers are used to enlarge or to align two holes. Generally bridge reamers are designed for use in structural steel, in the building industry, bridge erection, and ship construction. The cutting end of the flutes is tapered therefore allowing the reamer not only to enter overlapping holes but also permits insertion into very badly misaligned holes. Bridge Reamers are commonly used in portable electric or pneumatic machines.
Taper Pipe Reamers
Taper Pipe Reamers are used before tapping with a variety of different types of pipe taps those includes BSPT, NPTF, Dryseal, and ANPT.
Morse Taper Socket Reamers
A Morse taper reamer is used manually to finish & reclaim Morse taper spindles & 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 Morse Taper reamer is a finishing reamer, or a roughing reamer. The roughing reamer would have serrations along the flutes to break up the thicker chips produced by the heavier cutting action used for it.
TECHNICAL INFORMATION – REAMERS
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 generalize, 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. 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 0.003 inch to 0.005 inch.
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 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. SPEEDS MUST NOT BE SO HIGH AS TO PERMIT CHATTER.
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.
Bevel and Taper Lead Sharpening
(a) Machine reamers usually have bevel leads of 45°, but for particular applications and after suitable trails in the work piece material it may be as great as 50° or as small as 30° – relief on the bevel varies with the job, an angle of 7° to 10° is normal practice.
(b) Hand reamers have a taper lead immediately behind the bevel lead. The taper lead is usually about 1° per side and must be sharpened in such a manner as to bring it to a sharp cutting edge, the relief angle is normally 5° to 10°. The taper lead functions to effect a scraping cut that helps to size and smooth the walls of the hole.
