Every annular cutter has two dimensions: the diameter, which is the hole you want, and the depth of cut, which is the thickest plate it will go through. The second one is the one people get wrong.
What depth of cut actually means
It is the usable length of the cutting edge. A 35 mm cutter will clear plate up to 35 mm thick. Put it on 40 mm plate and it will stop before it comes out the other side.
The standard ladder is 25, 30, 35, 50, 75 and 100 mm. Most fabrication work in Singapore lives in the first three.
The rule
Measure your thickest plate. Take the next depth up. Stop there.
If everything you drill is 20 mm and under, a 25 mm cutter covers it. If you occasionally hit 30 mm, go to 35. There is no reason to buy 50 mm depth for 25 mm plate.
What a deeper cutter actually costs you
- More money. Depth is one of the two things that set the price. A 50 mm cutter costs meaningfully more than a 35 mm in the same diameter.
- A slower cut. More cutting edge in contact means more load, and the same machine has to work harder for the same hole.
- More machine. Deeper cutters want more stroke and more power. A small mag drill may not have either.
- Nothing in return. The hole is the same hole. Depth of cut does not make it rounder, cleaner or faster.
Where the over-buying comes from
Usually it is not anybody being dishonest. It is a quote written from a part number rather than from the job, and nobody upstream ever asked how thick the steel was.
It also compounds. Once a deeper cutter is on the order history, it gets reordered for years without anyone revisiting the reason.
The three questions to answer before you order
- What is the thickest plate this cutter will see? Not the average – the thickest.
- Is that a regular job or a one-off? If it is one job a year, buy the deeper cutter for that job and keep the shallow one for everything else.
- Does my machine have the stroke for it? Check the machine spec, not just the cutter.
When the deeper cutter is right
There are real cases. Stacked plate. Structural sections where you are going through two flanges. Anything where you genuinely cannot predict the thickness in advance and you would rather carry one cutter than two.
Those are decisions, not defaults. The problem is only when 50 mm gets ordered because it was on the last quote.
One thing to check on your own order history
Pull your last year of cutter purchases and put the depths next to the plate thicknesses you actually drill. If the depths are consistently two steps above the steel, you have found money.
Tell us the job, not the part number
Hole diameter, your thickest plate, and the machine you are running. We will tell you which depth fits – and we will say so when the shallower one is the right answer.
Email info@neweratools.com or call +65 6241 0908.