How to Sharpen a Step Bit
Any uni-bit (step drill bit) will eventually become dull with use.
For the best performance, the flute and the tip should be periodically sharpened.
A step drill is like a graduated drill that is used to drill holes in very thick metallic sheets. The first step on a drill makes a rather little hole, but with every subsequent step, the hole will gradually become large.
It can be a bit difficult to sharpen step drills, but if you are able to remove the bit from the drill, then there are quite a number of methods that might work.
Materials needed to sharpen a step drill:
- A chipped or dull drill bit
- A belt sander or a bench grinder
WARNING: You have to be extra careful because your hands will be quite close to the sharpening tool, and you are dangerously at risk of losing skin. Avoid wearing gloves because they can get caught by the sharpening tool and pull your hand in. Be deliberate and mindful of where you will be positioning yourself to the proximity of the sharpening tool. Safety glasses should be worn too.
Why do step Drill become dull or chip?
For you to learn the best method of sharpening your step drill, you should at least know the reason why this is important.
Chipped step drills are as a result of the landing force behind them since their weight can’t bear the forces exerted on them through the drilling procedure. The landing, should be made to have a curved shape. Curved shapes will add some support onto the lip.
Via: @montrealsparky
Dull drills are as a result of a chisel that is having some trouble smearing up the material on to the lip and requires to be re-defined at the face of the drill.
Another reason for a chopped drill is if the lip has been rolling over and requires to be re-sharpened so as to push it directly towards the work-piece.
How to practice holding the drill while sharpening it
Start with a comfortable position, by placing your hand against the support of the machine and taking the step using both of your hands. At an angle of 60 degrees, hold your step drill facing the belt sander sharpener.
Position one end of the landing in such a way that it directly faces against the belt. Ensure you use at least steps 5-7 to make some moves with the bit across the belt towards the finishing position. Steps 5-7 are simultaneous meant to get you to the finish position.
The Sharpening
Any ordinary bench grinder can be used to sharpen your step drill. Hold shank strongly in one hand to be able to rotate the drill while at the same time, you are using your other hand to support the body.
At an angle of 45-degree position the step drill facing the grinding wheel. Gently kiss the leading or cutting edge to the wheel. Maintain this light contact all the time while you are rotating the step drill clockwise, so that you finish at the end of the trailing.
Sharpen a Unibit using the Tradesman Machinist Reversing DC Variable Speed Bench Grinder:
If you have factory contours at hand, make sure you heed to them as carefully as you can. The trailing edge should be placed at a lower position compared to the leading edge by at least 1/32 inch. This will allow foe a clean precise cut without any rubbings.
If you accidentally break the tip, or if the repeated sharpening grinds the first step away, you can easily replace the tip. Read on to learn how.
How to sharpen step/uni bits:
The flutes are much easier to sharpen with the use of a proper sharpening stone. When grind cutting the edges at the sides of the flute, you will be able to to match factory contour with relation to the center of the step drill.
If you find that they are really bad from over use, you might have some luck replacing them through just regrinding the flute. It will be quite easy to manage the freehand using a coarse hand diamond lap.
Replacing one that is really beat from overuse is hard and might take you forever, but if it just appears a little worse than sharp, it will be easy to keep it functional for a little while longer through a simple but occasional lapping!
If you have been practicing a little using your step drill, and you have been able to successfully shape and roll your chisel and landing, then your step drill is quite ready to get back to drilling! You can go ahead and run a test on a hand drill or drill press.
If you find that drilling is a bit difficult, check your chisel carefully plus the landing angles to ensure that the relief on both of them is adequate.
If you notice that chips are only coming from one side of the step drill, check to ensure that the two lips are properly symmetric through to the center-line of your drill bit.
If you notice that chips are coming off of the bit from both sides of your drill bit, then you are set and ready to go!
Final Word
If your step drills are the cobalt chromium type of split drill bits, there is, unfortunately, only bad news for you.
The split you see running through the chisel is meant to make drilling a lot easier and pleasant for you, but it’s almost impossible to get a good sharpening tool that can reach to them by hand.
You should, instead, look for a machine that will go way back to cut the relief at the back side of the landing so that your chisel size can be reduced.
If you do not relieve the chisel, there will just be too much smearing of the material when the drilling is going on and it would be practically impossible to drill through any metals.
