Diablo 10-Inch Blades, Type 27 Discs, and Router Bits: 7 Quick Answers for Contractors

I coordinate the accessory wall at a tool supply house. When a contractor calls at 7:00 AM because the crew is standing on a job site with the wrong blade, I don't have time to ease into an essay. Last quarter alone, we processed 47 rush orders with 95% on-time delivery, so I've gotten pretty good at answering the same questions without wasting anyone's time. Here's the version I give when someone is standing at the counter. If you're in a rush, jump to the question that matches the tool in your hand; they don't have to be read in order.

• Which 10-inch Diablo saw blade should I order?
• What does Type 27 mean on a Diablo masonry grinding disc?
• What is the shank on a router bit?
• What is the 42-106 bearing flush trim router bit used for?
• Do you actually need an electricians hammer?
• Can one 10-inch Diablo blade handle wood and metal?
• What should a crew buy first?

Which 10-inch Diablo saw blade should I order?

Most people ask this while staring at the saw blade rack. The answer starts with tooth count. It took me about four years and a lot of returns to understand that more teeth doesn't mean better; it means different. A 40-tooth blade is a safe all-around choice for a 10 inch Diablo saw blade, but only if the job is general carpentry. Here's the shorthand I use:

• 24-tooth: framing, ripping, rough lumber. Fast removal, coarse surface.
• 40-tooth: the generalist. Crosscuts, plywood, most miter saw work.
• 60-tooth: plywood, melamine, laminated panels. Noticeably less chip-out.
• 80-tooth: finish trim and fine crosscuts. The blade you want when the cut will be visible.

Don't ask which one is 'best.' Ask which one matches the next hour of work. If you're building one starter kit, a 40-tooth combo blade is the safest way to go.

What does Type 27 mean on a Diablo masonry grinding disc?

When the label says 'diablo masonry grinding disc type 27,' the 'type' refers to shape, not material. Type 27 is a depressed-center wheel: the center is recessed, so you can hold an angle grinder at a comfortable angle and get more surface contact without the edge digging in. This is the configuration most people want for masonry grinding. A Type 1 wheel is flat and is usually a cut-off wheel, not a grinding wheel. The 'masonry' part means the abrasive blend is made for concrete, block, or brick. I'm not a materials engineer, so I can't take you through the bond chemistry. What I can tell you from a supply standpoint is that a masonry disc is meant for masonry. Running it on steel will wear it out fast and the cut will feel wrong. Check the stamped label before you mount it.

What is the shank on a router bit?

The shank is the smooth, straight section of the bit that gets clamped inside the router collet. It's not the cutting part; the flutes do the cutting. Put another way, the shank is the part that keeps the bit attached to the motor. Shank size is one of those details new router owners ignore until a bit slips. A 1/2-inch shank is much stiffer than a 1/4-inch shank, and stiffness means less chatter. Less chatter means cleaner edges and fewer burn marks. Most full-size routers accept a 1/2-inch collet; trim routers typically accept a 1/4-inch shank. Check your router's collet capacity before ordering any bit, including a Diablo flush trim bit. If the shank doesn't seat fully in the collet, don't run it. It's a safety issue, not an inconvenience.

What is the 42-106 bearing flush trim router bit used for?

The 42-106 bearing flush trim router bit is a bearing-guided bit. The small bearing at the tip rides along a template, and the carbide cutters trim the workpiece until it's level with that template. That makes it a practical choice for pattern-routed parts, laminate edge trimming, veneer work, and any job where you need a lot of identical pieces. I've used it to clean up edge banding and to copy shapes from a plywood template. Before you use it in a rush, spin the bearing with your finger. It should turn freely. If it's stiff or packed with pitch, clean it or replace it. A stuck bearing can ruin the workpiece and cost you the whole day. Also check the shank size on the shaft: flush trim bits come in both 1/4-inch and 1/2-inch versions. The 42-106 is a flush trim bit; the shank marked on the bit tells you which one you're holding.

Do you actually need an electricians hammer?

I'll start with a boundary: I'm not an electrician, and I don't have to swing a hammer all day. So I won't tell you which hammer handle angle to buy. What I can tell you from selling tools to electrical contractors is that the name 'electricians hammer' gets searched more than it gets seriously used. Most rough-in work is about making holes and driving fasteners, not hammering. If that search phrase brought you here because you're assembling a new kit, I'd put a specialty hammer at the bottom of the list. A regular hammer is fine for the occasional staple. What burns up your time is drilling through studs and boxes without a bit that can handle it. A good carbide-tipped hole saw or a sharp spade bit set will do more for your schedule than a dedicated hammer. If you already have a favorite hammer, use it. But don't buy a specialty hammer before you own a decent set of bits.

Can one 10-inch Diablo blade handle wood and metal?

It's tempting to think that one blade can handle everything. That idea ignores the physics. Wood-cutting tooth geometry will grab in aluminum, and a metal-cutting blade will tear wood and load up fast. So no, I don't recommend a single 10 inch Diablo saw blade for both. The right move is to keep a wood blade and a dedicated non-ferrous or ferrous metal blade and swap them when the material changes. It feels like a hassle—or rather, it is a hassle—until the wrong blade kicks back or destroys the workpiece. Trust me on that one—I've seen a bad match turn a quick cut into a two-hour redo. Diablo makes specific blades for different materials; the label on the blade will tell you what it's for. Read it before you mount it.

What should a crew buy first?

Start with a 40-tooth 10 inch Diablo saw blade for the miter saw or circular saw, a Type 27 masonry grinding disc for the grinder, and a flush trim router bit with a shank that fits your router. That covers a surprising number of job-site setbacks. Add a 24-tooth framing blade when rough carpentry is the bulk of your work, and an 80-tooth finish blade when you start doing visible trim. The goal isn't to own every accessory Diablo makes; it's to have the right one for the next job. I've learned that the hard way, when a $30 blade choice turned into a $300 rush delivery. Keep the basics predictable, and order specialty bits before you're standing on the job site staring at a pile of parts and a deadline.