Drilling and tapping
21 May 2008
Simple enough tasks, or complex science?
Well a bit of both really, if we use the right tool for the job and use it according to the recommendations then all should be fine. Always make sure the tool is suited to the material being drilled or tapped, (we don’t use a cheese knife to cut the bread or a bread knife to cut the cheese) ensure the machine is capable of doing what it is required do, check alignment and accuracy of the machine and always ensure the coolant is going to where it is needed most – the front of the tool where the cutting is being done. This is particularly important where the holes to be drilled or tapped are deep.
Drilling deep holes with through coolant drills can be very effective in cooling and assisting with swarf removal. Swarf not clearing from the flutes is probably the biggest cause of breakages and other problems, if the swarf is clogged in the flutes on drills without through coolant this will stop the coolant getting to the front of the tool and prevent the tip of the tool being cooled, the resulting heat build up causes premature failure in the tool.
It is imperative to run a tap at the recommended speed, this is particularly true of the application taps (normally colour coded or named). The geometry, material and in some cases coating on these tools is specifically adapted to the type of material which normally fall into 4 or 5 basic groups. Running the tap too slowly can cause oversized threads.
The core hole prior to tapping must be within the tolerances allowed, the hole must he counter sunk before tapping to assist the lead in of the tap (this also reduces the risk of chipping a tap considerably and creates a neater hole than chamfering afterwards).
On materials which have a tendency to work harden it is advisable to use a drill and drilling method to keep this to a minimum (avoid using tungsten carbide drills at high speeds); this will allow the tap to cut a material that is not harder than the material it is designed for.
Using a quality coolant will also extend the life of the tool, it is vitally important that the tool does not cut without coolant or lubrication, this often happens during the setup stage of the process or after a tool change when the operator turns the coolant off to visually check the positioning of the tap.
During this first “dry” cut it is possible to get edge build up on the tap, this is when the material to be tapped sticks to the tap surfaces and prevents proper chip flow and results in poor surface finish and oversized threads.
Simple enough……….
Other Press Releases By This Company
- 21/05/2008 - Miniature Carbide cutting tools from Toolex
- 14/11/2007 - New Presses fron Maeder
