GTX Academy: Wood drills – spiral, shovel, auger
2026-01-28
GTX Academy: Wire and nylon brushes – how to choose them
2026-01-28Bi-metal holesaws are the fastest and also the cleanest method of making large holes in steel, stainless steel, aluminum, wood and plastics. But what should you keep in mind when using them? The key is the right adapter, a well-chosen pilot drill bit, variable 4/6 TPI tooth pitch, cooling and proper technique. Below you'll find a complete, practical guide to bi-metal hole saws - from diameter selection to solutions to common problems.
How bi-metal works and when to choose it
- HSS M3 teeth + steel body: ensures high hardness of cutting edges and resistance of the bearing part of the crown.
- Variable pitch 4/6 TPI: alternating tooth density reduces vibration and "bites" well into both thinner sheet metal and thicker profiles.
- Standard depth of cut: 38 mm; for most jobs, this is enough to cut through the material at one time; for thicker walls, it is worth using the "two-sided" method.
Diameter selection and depth planning
- Diameter - measure what actually has to go through the hole (can, choke, pipe) and choose a hole saw specifically for this dimension. Remember to leave a small clearance so that the item will go in without forcing it in.
- Wall thickness - if the material is thicker than 38 mm, be sure to drill on both sides. First enter the pilot and start cutting halfway through the thickness, then mark the center on the other side, finish the cut. With this approach to the material, the edges will be cleaner.
- Tolerance - for installations (EL/HS/IT), the crown closest to the nominal dimension of the component will usually be better; for general transitions, you may want to take a little more clearance to make installation easier.
Adapter and pilot drill - the key to stability
What do you need the adapter for? It connects the hole saw to the device's handle, transmits torque, and allows quick replacement of the crown and remote control.
How to select an adapter:
- Due to the diameter range of the hole saw:
- 14-30 mm → "small" adapter.
- >30 mm → "large" adapter with a stronger pin.
- Type of grip for the device:
- HEX → quick coupler in the screwdriver, quick accessory changes.
- Crown locking: for larger diameters, choose an adapter with locking pins/bolts/locking nuts - they prevent loosening.
Pilot (guide) drill:
- Material: HSS (universal); for stainless steel, it's worth using high-quality HSS and coolant.
- Length: choose the accessory so that the pilot fixes the axis before the crown teeth touch the material.
Interchangeability: the adapter should allow for quick replacement of the remote control (wear/breakage/material change).
Take-off and guidance technique - step by step
Settings for specific materials: speed, lubrication, control
Metals (steel, stainless steel, aluminum):
Wood/plastics:
Most common problems → quick solutions
- Overheating and dulling → RPM too high or lack of coolant. Reduce RPM, use oil/spray, take breaks.
- Caked "plug" of excavated material in the crown → too long operation without interruption. Enter pulsating technique, use slots to remove the plug, clean the crown.
- "Jerking" and vibration → too fast RPM, under-tightened adapter/pilot, poorly stabilized component. Tighten connections, choose 4/6 TPI (better vibration dampening), reduce pressure and RPM.
- Pulling edges in wood → remember to underlay from underneath and release on the exit.
Occupational health and safety and quality of work
- Stabilize the workpiece: use clamps/vise grips; avoid holding the workpiece in your hands.
- Personal protection: goggles, gloves (against sharp chips), hearing protection for large diameters.
- Maintenance: after work, remove the excavated material, wipe the crown and adapter, check the pilot drill (dull necessarily replace).
Quick selection download
|
Task |
What to choose/do |
|
Stainless steel, thin sheet |
Bi-metal 4/6 TPI, low RPM, coolant, even feed rate |
|
Structural steel 3-4 mm |
4/6 TPI, pumping and breaks, drilling oil |
|
Thick wall / plate |
Cut on both sides with remote control for a clean exit |
|
Large diameters (60-83 mm) |
Adapter "large" with crown lock, secure attachment |
|
Rips in the wood |
Primer + release on exit |
Where to buy
Go to categories on fixero.com: bi-metal 4/6 TPI holesaws, 14-30 mm / >30 mm adapters, pilot drills, drilling oils. Match the diameter to the grommet, and the adapter to the diameter range and chuck of your power tool. For more advice and accessory tips, visit our GTX Academy.
