Working With Boron-Alloyed Steel - Removal (Drilling)
To drill or not to drill, that is the question or more appropriately "how do I drill boron-alloyed steel so I don't keep going through drill bits?" Many of us have asked ourselves this when working with boron-alloyed steel or ultra-high-strength steel (UHSS).
The first thing you need to understand is that you need a special drill bit that is hard enough to go through the UHSS. That's right, the sheet metal steel is actual harder than the steel that is used for most drill bits. Also, when using these specialty drill bits made for UHSS, some companies actually recommend using a lubricant to help keep the bit cool during drilling.
It may be hard to do this for most structural technicians but when drilling you have to slow down to go faster. All of the specialty drill bit makers recommend drilling at a low speed, around 500 rpm.
How do I know what RPM my drill is spinning at? An indicator of correct speed is being able to almost see the drill bit turn. It is important to hold the bit at 90º to the part and use constant pressure. You will know that everything is just right when you start to see the metal curl off the panel instead of flake off. Low-speed drills are also helpful in maintaining the low rpm requirement of the drill bits.
Caution should also be used when drilling all the way through the part for plug weld removal. When the drill is going through the backside of the part, the drill bit can catch on the edge of the hole and damage the tip of the drill bit. To avoid damaging the bit, just before the bit breaks through the backside slow down even more and lighten the pressure that is being applied.
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