Hole saw: HSS, bi-metal or carbide, which to choose?

To drill sheet metal and steel with a hand drill, choose a bi-metal or HSS hole saw; for abrasive materials such as PVC, fibre board and plasterboard, or for wood, saws with carbide inserts work better. If large holes in steel are a repeated job, the answer is an annular cutter with a Weldon shank on a magnetic drill. In the collection you will find diameters from 14 to 48 mm and cutting depths of 30 or 50 mm: before the material, check that the diameter and the depth cover your hole. And remember that the saw alone is not enough: you need the arbor with the pilot drill, and its shank must fit the chuck you use.

The types

• HSS and bi-metal hole saws: toothed cups with chip clearance, made for metals and mixed jobs. They are sold singly or in sets, like the Fervi set of 6 HSS hole saws with side chip ejection and pilot drill.
• Hole saws with carbide inserts: the teeth are carbide tips, suited to materials that wear down a normal cutting edge quickly. An example is the Fervi F019/022, part of a series with several diameters.
• HSS annular cutters with Weldon shank: cylindrical tools for magnetic drills, where the diameter is often given in inches (from 9/16 to 15/16 in the collection).
• Arbors and chucks: the part that connects the saw to the drill. They come with different threads (M10 x 1.25, M12 x 1.25, M14 x 1.5, M16 x 1.5). An example is the DeWalt DT8108-QZ hole saw arbor.
• Pilot drills: the central bit that guides the saw, to be replaced when worn.
• Sets and ranges: several diameters in one case, handy if you change hole size often.

How to choose by job

The same saw does not do everything well. Here is how to orient yourself.

The arbor: the part chosen last that causes the most trouble

The saw screws onto an arbor, and the arbor is clamped in the chuck. Three measurements must match: the saw diameter, the range the arbor accepts and the shank the chuck can grip. These are the data for the A.M.E.S. arbors in the collection:

Two practical consequences. First: the arbor for small saws (14-30 mm) and the one for medium and large saws (32 mm and up) are not interchangeable, so if you go from a junction box to a pipe opening you usually change arbor too. Second: the arbor with a 15.8 mm shank needs a chuck that opens to at least 20 mm, and an ordinary drill with a 13 mm chuck will not grip it. For the largest diameters, therefore, it is worth looking at the chuck first and the saw second.

The pilot drill is a spare part sold separately. The Fervi 0712/300 pilot drill for hole saw arbors has a 6.35 mm shank, is 75 mm long and is sold in packs of 10; the data sheet lists it for Fervi arbors 0712/700 and 0712/800, not for all of them. Before ordering, compare the code of the arbor you have.

The features to look at

• Diameter: this is the size of the hole. In the collection it runs from 14 to 48 mm; in inches you find 9/16, 5/8, 3/4, 7/8 and so on. For a hole that must take a cable gland or a pipe, choose a diameter slightly larger than the object.
• Cutting capacity: this is the useful depth of the saw, 30 or 50 mm in the data. It must be at least equal to the thickness to be drilled. For thin sheet the lowest is enough; for a section or thick wood you need the high one.
• Material: bi-metal, HSS, hardened steel. Bi-metal is tougher, HSS is the classic choice for steel. For saws with inserts, the carbide of the teeth is what counts.
• Shank and thread: the saw must have the same thread pitch as the arbor. With Weldon cutters, the type of chuck on the machine matters. For an impact driver look for an arbor with a hex shank.
• Pack size: from 1 piece to 10 per set. The set pays off if you change diameter often, the single piece if you always have the same size.
• Weight, packaging, height: these are logistics data and do not change the result of the hole.

Common mistakes

• Buying the saw without checking the arbor: if the thread does not match, it does not fit. Check it or ask our technicians.
• Choosing the arbor without looking at the chuck: a shank the chuck cannot grip, or grips only partly, wobbles and spoils the hole.
• Running too fast on large diameters: the saw overheats and loses its edge. The larger the hole, the lower the speed must be, especially on metal.
• Not lubricating on metal: a little cutting oil greatly extends the life of the teeth.
• Using hammer action with a bi-metal or HSS saw: these saws drill in rotation only.
• Using a wood saw on steel: the teeth are ruined at the first hole. And a bi-metal saw wears out at once on masonry: concrete and stone need carbide.
• Forcing and tilting: the saw must work straight, with constant feed. If it smokes, you are pushing too hard or the tool is worn.

Frequently asked questions

Is the pilot drill always needed?

Yes, the pilot drill centres the saw and keeps it on axis at the start of the hole. Pilot drills wear out and must be replaced with spares suited to the tool.

Which arbor do I need for a 40 mm saw?

One from the 32 mm and up range: in the collection these are art. 45318 (up to 100 mm), art. 45314 and art. 45315 (up to 210 mm). The choice among them depends on the shank your chuck can grip.

My drill has a 13 mm chuck: can I use the arbor with a 15.8 mm shank?

No. That arbor states a minimum chuck of 20 mm. With a 13 mm chuck you can use arbors with an 11.1 mm shank or smaller.

How do I remove the disc of material left inside?

Many saws have a side slot or an ejector that pushes it out at the end of the hole. Do not wedge it out with screwdrivers while the saw is turning: always stop first and work with the machine switched off.

Can Weldon cutters be fitted to an ordinary drill?

They are made for the Weldon chuck of magnetic drills. On a hand drill, use hole saws with an arbor.

Can I use the same saw on wood and on metal?

With a bi-metal saw, yes: it is made for wood, metal and plastic. On metal, though, lower the speed and lubricate.

Better a set or single sizes?

The set pays off if you change diameter often, single sizes if you always make the same hole in series and want the spare ready.

You will find the whole range in the hole saws and annular cutters collection: if you are not sure about diameter or shank, ask the AMES technicians for a quote or advice.