To achieve a precise 20° included angle (the full angle across the tip) on a tungsten electrode using a dedicated grinder, follow this step-by-step setup, verification, and grinding process. All steps focus on consistent, repeatable results for TIG/GTAW welding.
First: Clarify the Angle Definition
A 20° taper for tungsten electrodes almost always refers to the included angle (the total angle between the two opposite sides of the cone). If your grinder uses half-angle markings (angle from the centerline to one side), you set it to 10° to get a 20° included angle. Confirm this with your grinder’s manual first.
Step 1: Prepare the Grinder and Electrode
Ensure the grinder is fitted with a diamond wheel (the only wheel for a smooth, precise finish on tungsten).
Inspect the electrode collet and guide system: clean out dust and tungsten particles, and confirm the collet grips the electrode firmly without wobble. Runout will destroy angle accuracy.
Put on appropriate PPE: safety glasses, face shield, and gloves, as grinding produces fine, sharp dust and sparks.
Step 2: Set the 20° Angle on the Grinder
Dedicated tungsten electrode grinders use either a fixed-angle index plate or an adjustable protractor/scale for angle setting.
For Grinders with Pre-Set Angle Stops
Locate the angle indexing plate or selector on the tool.
Select or lock the guide into the 20° included angle position. Many professional models have a detent or marked slot for common angles like 15°, 20°, 30°, so you can simply engage the 20° setting.
Tighten the locking knob or lever to secure the guide assembly; no movement is allowed during grinding.
For Grinders with an Adjustable Protractor Scale
Loosen the adjustment screw that controls the guide arm angle.
Align the index line on the moving guide with the 20° mark on the fixed protractor scale.
For maximum precision, use a small digital protractor or angle finder placed on the guide surface to verify the angle matches 20°.
Retighten the adjustment screw firmly, then double-check the angle—over-tightening can shift the setting.
For Basic Jig-Type Grinders (No Scale)
Use a 20° angle gauge or a precision-ground 20° reference block.
Adjust the electrode guide until it sits perfectly flush against the reference angle.
Clamp the guide in place, then recheck with the angle gauge before grinding.
Step 3: Mount the Electrode Correctly
Insert the clean, cut-to-length electrode into the collet. The end to be ground should protrude just far enough to form the full cone; excessive overhang causes flex and an uneven angle.
Tighten the collet evenly so the electrode is perfectly centered and rigid. A bent or off-center electrode will produce an asymmetric, off-angle tip.
For grinders with a rotating electrode holder, ensure the rotation mechanism is engaged; uniform rotation is essential for a symmetrical cone.
Step 4: Grind the Tip to 20°
Turn on the grinder and let the diamond wheel reach full speed.
Slowly and steadily feed the electrode into the wheel, following the guide. Do not force or rock the electrode—this changes the contact angle and creates an irregular taper.
If the grinder does not auto-rotate the electrode, rotate it slowly and evenly by hand to maintain symmetry.
Grind only until the desired cone length is achieved. Stop frequently to inspect the tip; over-grinding wastes material and can introduce heat damage.
Use light, consistent passes. Heavy cuts generate heat, which can discolor, recrystallize, or crack the tungsten, ruining its performance.
Step 5: Verify the 20° Taper Accuracy
After grinding, confirm the angle to ensure it meets your precision requirement:
Visual inspection: The cone should be symmetrical, with straight, even sides and no flat spots or bulges.
Tool verification: Use a digital angle finder, optical comparator, or shadowgraph to measure the included angle. Place the electrode in a fixture and measure the angle between the two conical surfaces.
Adjustment: If the angle is too large, slightly decrease the guide setting; if too small, slightly increase it. Re-grind a test electrode until the measurement is consistently 20°.
Step 6: Critical Best Practices for Consistent Results
Always use a diamond grinding wheel: conventional wheels (Al₂O₃, SiC) cannot hold a precise angle and produce a rough, inconsistent surface.
Maintain the wheel: Dress the diamond wheel if it becomes glazed or loaded, to keep its cutting face sharp and flat. A worn wheel changes the effective grinding angle.
Avoid overheating: Let the electrode cool between passes. Discoloration (blue, purple) means thermal damage, which weakens the electrode and causes arc instability.
Keep the guide clean: Built-up tungsten dust can alter the guide angle and cause the electrode to bind or wobble.
Batch consistency: Once the 20° setting is verified, mark or lock the adjustment to ensure every electrode is ground identically.
