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Ball bearings have three primary functions. With a rolling or sliding motion, they can reduce the amount of friction between moving parts, allow for precise positioning of those parts, or help distribute and carry heavy loads.
They are also attractive, smooth, and perfectly spherical, and come in many different sizes and materials. Ambitious or experienced DIYers may want to drill holes through ball bearings for a variety of projects, including shift knobs for manual transmission gear shift levers.
Drilling Holes in Ball Bearings
In this article, you will learn how to create perfectly centered holes in ball bearings. You’ll need to have a drill press designed for metal to drill safely.
- Choose an appropriate bit. The material of the drill bit you choose depends on the material of the ball bearing. For brass, choose a steel bit. Steel bearings require a bit of extra preparation before they can be drilled, but once the hard outer layer is removed, a cobalt or HSS bit should work well.
- Attach a bit to the chuck of your drill press. Open the jaws of the chuck and insert the bit. Make sure the shank of the bit is compatible with your drill press chuck. Tighten the chuck by hand and finish tightening it using the chuck key. Remove the chuck key and put it in a safe place. This prevents the chuck key from becoming a projectile when the drill is rotating.
- Put on personal protective equipment. The main concerns when drilling are metal shavings and broken bits. Either can become a dangerous projectile and cause serious injury. When drilling ball bearings, you should wear safety glasses or a full-face shield to protect yourself. Gloves are also a good idea.
- Set the speed of your drill press. In general, lower speeds are better for drilling metal. The goal is to move steadily through the ball bearing without overheating it. Drilling at high speeds causes excess friction, which can actually harden the metal and make it more difficult to drill through.
- Adjust the drill press table to a comfortable height using the crank or release lever. If you don’t want to drill all the way through the bearing, you will also need to set the depth guard. Lower the guard to your chosen height and secure it in place using the nuts.
- Place the ball bearing in a drilling jig and tighten the fasteners. Pearl jigs are used by jewelers to accurately drill holes in beads; these are ideal for holding ball bearings secure during the drilling process. A hole at the top of the jig guides the drill bit through the middle of the bearing, producing a perfectly centered hole.
- Fasten the jig to the table of your drill press. Using clamps or a vise, make sure the jig is firmly in place before drilling. Insert a center punch through the guide at the top of the jig and make a dimple in the surface of the bearing. This will make it easier for the drill to bore through the metal without slipping.
- To use the drill press, turn it on and start it spinning at your chosen speed. When the bit is rotating at full speed, swing the rotating lever to lower the bit. Drill through the bearing to your desired depth, then release the lever to lift the bit. Turn off the drill press. Remove the ball bearing from the jig and inspect the hole.
How to Drill Holes in Different Types of Ball Bearings
Ball bearings are made with a variety of materials, and each has some specific instructions to pay attention to.
Steel Ball Bearings
A steel ball bearing is harder on the outside than it is on the inside. Carbon or nitrogen is added to the top layer as part of a process called ‘case-hardening’ or ‘surface hardening’.
The hardened exterior is resistant to damage. It also allows the bearing to slip and slide easily past other hard metals and abrasive material.
Surface hardening only affects the outer layer of the bearing. The center is still soft metal. Because soft metal is less brittle than hard metal, a case-hardened ball bearing can absorb stress without fracturing.
To remove the hard outer layer from a steel ball bearing, you will need a grinding vise and a v-block.
- Insert the ball bearing into the v-block and tighten the clamp.
- Then, secure the v-block to your work surface using the grinding vise.
- Use a surface grinder to grind a flat surface of about the same diameter as the hole you want to bore.
- If you can’t use a surface grinder, a metal file should also work, but will take longer and be less precise.
Once you’re through the case-hardened layer, you can drill into the bearing using a cobalt or HSS bit. Bits treated with black oxide, titanium nitride, or titanium carbide nitride will last longer than untreated bits.
Brass Ball Bearings
Twist drill bits have a tendency to grab or ‘dig in’ to brass. To drill brass ball bearings, use a straight fluted drill bit. Alternatively, you can file down the sharp tip of a twist drill. Draw the bit across a honing stone. Do not move it back and forth; rather each stroke should be in the same direction.
A few passes should be sufficient to dull the edge sufficiently for drilling into brass. Once you have modified a bit in this way, it is no longer suitable for drilling steel, so you may want to keep a separate set of drill bits just for brass.
Drilling a hole in a ball bearing can be done easily and quickly, provided you have the right equipment. A jig is necessary to hold ball bearings of any material. You will also need a drill press and an appropriate bit. The bit should match the material of the ball bearing.
Steel ball bearings have a hard outer layer; this should be removed before you begin drilling. Always wear protective gear when drilling.