Using a Tap and Die set for the first time can be a fiddly process and it’s easy to make mistakes, so we’ve put together this handy guide to help you get started!
What is a tap and die set?
A tap and die set is a set of tools that is used to create new screw threads. The tap is used to cut the female part of the mating pair (such as a nut) and the die is used to cut the matching male part of the pair (for example a bolt). Cutting threads using a tap is referred to as tapping, while using the die is called threading. If these tools are used to clean up existing threads, then the process is called chasing.
There are several different sizes of tap drill and die, and it is important that the correct size for the job is used. Some companies use metric sizes, while others use imperial sizes. See the following conversion chart for a list of common sizes.
Using a Tap and Die Set
- To use a tap and die set, firstly confirm the size and depth of thread that you need, and use a chart to determine the correct size of drill it and tap.
- Drill a hole that is the correct diameter and depth. Note that most taps cannot create a thread that goes all the way to the bottom of a blind hole, so if you need to thread a blind hole make that hole slightly deeper than the desired screw length.
- Next, secure the object you are working on firmly.
- Apply a generous amount of lubricant to the surface being tapped.
- Insert the handle into the tap so that it is secure.
- Hold the tap so that it is perfectly in line with the hole and turn it clockwise. Make sure that you keep the tap straight, so that the threads run straight. You can expect to feel strong resistance as you turn.
- Rotate the tap clockwise a few times, then reverse the process to bring the tap back out. Clear the tap of chips of loose materials. Do this every couple of turns, particularly if you are working in a blind hole.
- Once the tap has reached the correct depth, back it out of the hole, clear out the chips again (use compressed air if necessary), and wipe away any excess lubricant. Test the screw to make sure it fits.
The most common causes of problems when working with taps and die sets are caused by using a worn out drill or a dull drill bit, or by choosing the wrong lubricant. A dull drill bit will make your work a lot harder, and could even result in damaging the material you are working with, or the tap itself, because you have to use so much more torque when tapping.
When you are selecting a lubricant, make sure you choose the right type for the material you are working with. As a general rule, WD-40 is good for aluminium, but it is not usually suitable for wood. If you are working with other materials you should select a lubricant that will not be absorbed by that material.
Another common mistake is failure to secure the material being tapped or threaded. If the item that you are working with slips while you are threading it, there is the risk of it being damaged or the angle of the threading being off. Take an extra moment to secure the material to reduce the risk of this happening.
Dos and Don’ts of Using a Tap and Die
DON’T: Open a split die too far, or use too much pressure when closing them, because this increases the risk of breakage.
DON’T: Continue to use a tap or die if the cutting edge appears worn.
DON’T: Force the tap or die if you encounter a lot of resistance. Instead, twist it back and forth to loosen it up, then restart the process once it moves freely.
DO: Start slowly and gradually increase the speed if you are using a tap or die with a machine.
DO: Use a lot of lubricant. Direct the flow of lubricant into the bolt that is being threaded for best results.
DO: Choose the right rake angle for the material. As a rule of thumb, long chipping materials have greater tensile strength and require a bigger rake angle. Shorter chipping materials are not as strong, and can be worked with a smaller rake angle.
Take your time when working with a tap and die set. Measure the hole that you want to make carefully, and think carefully about your choice of tap and die. Remember that if you make a mistake it may be impossible to correct. You can always make a hole bigger, but it is very difficult to rectify a mistake if the hole that you make is too big!