Tapping is a highly efficient and easily mastered manufacturing process. It provides effective and economical threading through high cutting speeds, reduced downtime and better tool life.
Tapping involves cutting a thread in a hole so that a cap screw or bolt can be threaded through it. It can also be used to make a thread on nuts.
It can be carried out by hand or on a lathe using a power feed. Either way, the proper sized tap drill must be used to drill the hole. At the end, it must be chamferred.
Good Practice
Use a Tap Guide
These are a core element in producing a usable, straight tap if you are manually aligning a tap. A 90-degree tap guide will produce a far more accurate result than sight alone. When using a lathe or mill, the tap is naturally already aligned and centred.
Use Oil
Oil is critical when you are drilling on tapping machines. It stops the tapping machines bits from squealing, cleans out any chips, ensures that the cut is smooth and prevents the stock and drill from overheating.
Pecking
Pecking is a useful method to ensure that bits stay at a reasonable temperature and therefore don’t break when you use them to drill or tap. It involves drilling only part of the way through a part and retracting it to remove chips and allow the piece to cool.
Common practice is to rotate a handle for a full turn, then back the other way for a half turn. When the bit or tap is out, you can take out as many chips as possible, then add oil between the drill or tap and the piece you’re working on.
Hand Tapping
1. Choose a drill size.
2. Add chamfer to the hole if necessary.
3. Get a tap guide.
4. Tap the block.
5. Complete the tap.
Tapping using a lathe
1. Mount the workpiece in the chuck.
2. Face and center the drill.
3. Identify the proper tap drill for the tap you are using. For example, ¼ – 20 unc uses a #7 drill.
4. Set lathe to the right speed and drill using the tap to the required depth. Use plenty of cutting fluid.
5. Use a very slow spindle speed as the piece will rotate (40 to 60 rpm), along with plenty of cutting fluid.
6. Chamfer the hole’s edge..
Drilling and fixing basics for the workshop
Before cutting a thread, the hole itself needs to be right. Choose the drill bit to suit the surface: masonry bits for solid walls, tile bits for tiles. Always wear goggles, whatever you are drilling. For a large hole, drill a small pilot hole first to guide the bigger bit. A pilot hole is essential in hardwood or thin, brittle timber, which can otherwise split.
Screws come in three common head types: Phillips, slot and Posidrive. Use the matching screwdriver or bit, or you will wear down both the screw head and the tool. Apply firm, steady pressure with both hands.
Wall plugs give a screw something to grip. They are usually colour coded, which shows which surface they suit and which screw and drill bit size go with them. Before drilling into any wall, use a stud finder or metal detector to check for hidden electrical cables and water pipes.
