Tap and Dies

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Taps and dies are tools used for cutting threads while usually sold in sets they are in fact individual tools.
A tap is which looks like a bolt if used for making the female thread (nut) and the die which resembles a nut is used to make the male thread (bolt).
Usually made from HSS (high speed steel) alloy steel and are extremely robust and have very hard cutting edges.
This is needed as both the tap and dies have threads like those on nuts and bolts that are used to bore threads in smooth metal.
A tap screws into a hole and makes it in to a threaded hole and a die puts a thread in to smooth shafts.
These tools are most commonly used to repair threads that have been striped or crossed.
Using a Tap When using a tap care must be taken not to break the tap off mid repair.
Due to the type of steel and heat treatment used to get the hard cutting edge taps can be quite brittle.
If a piece of the tap id broken off in a hole it can be extremely hard to remove it and as the tap will probably harder that the average drill bit even drilling it out is not always an option.
However if used properly you shouldn't have any problems.
Usually they get broken by bending not twisting and in most sets a "T" handle will be supplied allowing you to easily turn the tap without bending it.
Generally most problems are caused by trying to turn a tap with an inappropriate tool like mole pliers.
When preparing to you a tap to create a thread its essential that you drill the correct size hole for the tap that you are using to small and will be very hard to cut the thread and you will likely break the tap and too large and the thread will not be cut deep enough and easily striped.
Tap Drill Chart Tap Size mm | Drill Size mm 2.
3 1.
9 2.
6 2.
1 3.
0 2.
5 3.
5 2.
9 4.
0 3.
3 4.
5 3.
8 5.
0 4.
2 6.
0 5.
0 7.
0 6.
0 8.
0 6.
8 9.
0 7.
9 10.
0 8.
5 11.
0 9.
5 12.
0 10.
2 Once you have the correct size hole using the "T" handles turn the tap in to the hole.
As the tap cuts strips of metal will be pushed out of the flutes (grooves).
To prevent the flutes becoming clogged up, this is done by turning the tap backwards and braking the metal strips up.
Ideally you should turn the tap one half turn or until you feel increased resistance then turn back a quarter turn.
On very deep holes it would be advisable to completely withdraw the tap from time to time.
It is also advisable to use some king of cutting fluid you can buy special cutting fluid but if you are using the tap but hand any general oil will do the job.
Using a Die To repair a crossed threads on a bolt simply select the die from your set that is an exact fit for the bolt.
It's advisable to apply a drop of oil to the bolt and run the die down the bolt.
If the die gets tight and you feel high resistance just run the die back up the bolt and start again.
To create threads on a smooth shaft select a die that just smaller than the size of the shaft and a couple of drops of oil on the die blades and work the die down the shaft.
As with the tap a half turn should be followed by a quarter turn back to prevent the die from becoming clogged.
For a comprehensive range of tap and die sets see Tap and Die sets.
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