When used with a power drill to counter sink an existing hole, the bit tends to 'chatter', leaving a rough surface. These bits tend to be designed for use on soft materials such as timber and plastics, not metals. Sharpening - cannot be carried out satisfactorily.Īlthough not a true 'drill', it is used in a power or hand drill to form the conical recess for the heads of countersunk screws. They cut a clean hole and cause little damage when they break through the back of the workpiece. Unlike normal twist drills, the twisted flutes are ground away making a truer, more accurate bit than normal twist bits. With their central point and two spurs, Bullet drills resemble spur point bits, but can be used in metal, wood and plastics. Sharpen the point and spurs with a fine file or edge of a fine grindstone the angle between the point and spurs should be 90°. Sharpening - a bit fiddly as it has to be done by hand. Spur point bits should only be used for drilling wood or some plastics. They are ideal for drilling holes for dowels as the sides of the holes are clean and parallel. The bit cuts timber very fast when used in a power drill and leaves a clean sided hole. Sharpening - use a drill sharpener or grindstone to sharpen the tungsten carbide tip.Īlso known as a wood or dowel bit, they have a central point and two raised spurs that help keep the bit drilling straight. Long Masonry bits (300 to 400mm) are available for drilling through masonry walls. Always use a slow rotational speed for drilling into harder materials to avoid overheating the tip, and frequently withdraw the bit to remove dust. Most masonry bits can be used with a hammer action power drill, but always check as the action is quite punishing on the bit and cheaper bits have been known to shatter when subjected to the pounding. Masonry drills are usually used in a power drill although they can be used with a lot of effort in a hand brace. Some masonry drills are described as 'durium tipped', this term refers to a highly durable silicon bronze alloy used instead of tungsten as the cutting point. The cutting tip is often made from tungsten carbide bonded to a spiralled steel shaft. Forming the correct angle at the tip is important for efficient cutting.Īs the name suggests, these are designed for drilling into brick, block, stone, quarry tiles or concrete. Titanium nitride bits cannot be sharpened without destroying the coating (although if the drill needs sharpening, the coating will probably have already been destroyed). Sharpening - use a drill sharpener, a grindstone jig or an oilstone. Always hold the drill square to the work and apply only light pressure when drilling. Special care is required when using the smallest sizes since these bits are thin and brittle. They are designed for drilling relatively small holes, they sometimes tend to clog quickly especially when the wood is 'green' so when drilling deep holes (especially in hardwood) the bits should be withdrawn regularly to remove the waste. Twist drills are usually available in sizes 0.8-12 mm plus. The coating is only really effective when metal is being drilled, it has little effect when working with other materials. This coating increases the hardness of the bit and adds a self-lubricating property. Twist bits are also available coated with Titanium nitride (TiN), these are easily identified by the gold like colour.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |