Why Do Some Pads Have Holes and Others Don't?

Why Our Rotary Polishing Pads Don't Have a Hole (And Orbital Pads Do)

Line up a rotary cutting pad next to a dual-action pad and one difference jumps out straight away: 

The orbital pad has a hole punched clean through its centre, and the rotary pad doesn't.

It's tempting to write that off as a styling quirk, or a way of saving a bit of foam. It isn't. It's a direct engineering answer to the way each machine moves, and it's built into every relevant pad in our Thermo Pro range for exactly that reason.

Two machines, two completely different motions

A rotary polisher only does one thing: it spins. The backing plate is fixed to the machine's spindle and rotates around a single, unchanging axis, in one direction, for as long as the trigger is pulled. Every point on the pad's face travels in a perfect circle around that centre. It's a steady, predictable, purely rotational force, with nothing pulling the pad off-axis.

An orbital, or dual-action, polisher does two things at once. The pad still rotates, but the whole backing plate is also driven around a small orbit - commonly somewhere in the 15-21mm range, depending on the machine - so the centre of the pad is constantly being pulled through a tight circular path while it spins. That combination is what gives DA machines their forgiving, low-risk action on paintwork, but it also means the point where the pad is fixed to the backing plate is being flexed cyclically, in a changing direction, thousands of times a minute.

Why the orbital motion needs the hole

That lateral, cyclical load has to go somewhere. On a solid foam disc, it funnels into the small area directly behind the backing plate's fixing point, because that's the one part of the pad forced to follow the orbit exactly, rather than trailing slightly behind it like the rest of the face does. Put that area through enough cycles and you get the kind of fatigue that ends a pad's working life early - tearing at the hub or pulling away from the hook-and-loop backing, long before the rest of the foam is worn out.

Remove the centre and the geometry changes completely. Instead of one solid plug of foam taking every cycle of that flex on its own, the load is carried around the full ring of foam surrounding the hole. It's spread across a continuous loop rather than concentrated on a single point, and that ring has somewhere to flex into instead of fighting the motion on every orbit.

That's why every pad we build specifically for orbital machines - our Thermo Trapez range and Allrounder Thermo - is made with that open centre as standard, across every size we produce. You can use them on rotary still without issues, but the foam won't shed heat as well.

Why rotary pads are left solid

Ask the same question of a rotary machine and the answer changes, because the problem it's solving simply isn't there.

The centre of a rotary pad isn't being asked to follow an orbit - it sits on the spindle and spins with the rest of the pad, on the same fixed axis. There's no lateral component and no repeated change of direction to relieve.

Cutting a hole into a rotary pad wouldn't relieve a stress that actually exists on it; it would just remove usable cutting and buffing surface for no engineering benefit. That's exactly why our Thermo Rotary pads, built specifically for rotary machines, keep a full, solid face.

It's a fair question to ask about heat, too, since the centre of any pad - rotary or orbital - runs at the lowest relative surface speed and is naturally the area most prone to holding onto it.

On an orbital pad, the open centre helps here as a side benefit, letting air reach a part of the pad that would otherwise stay sealed flat against the backing plate. On a rotary pad, where there's no hole to do that job, we handle heat a different way: through the open-cell, thermostable foam built into every Thermo pad, which is what keeps a pad's hardness and cutting power consistent, instead of the face softening as it warms up through a long correction stage.

Matching the pad to the machine

Once you know what the hole is actually there to do, choosing correctly across the Thermo Pro range is straightforward:

• Thermo Professional Rotary – solid face, built for rotary machines.
• Thermo Trapez – centre hole as standard, built for orbital/DA machines, graded from Blue (ultra hard) through Red, Orange and Yellow, down to Green (ultra soft).
• Thermo Allrounder & Thermo Mini – rated for both rotary and orbital work, engineered to cope with whichever motion you put them through.
• Thermo Nano Wool – our heavy-cutting wool pad, built for rotary.
• Thermo Velour, Hybrid & Microfibre – specialist finishing textiles, built for orbital machines.

None of it is arbitrary. Every pad in the range is built around how its intended machine actually moves, not simply sized to fit a backing plate. 

Match the pad to the machine, and you're not just protecting the finish you're working on - you're getting the full working life the pad was engineered to give you.