A reader wrote in, asking for advice about combination tap drills. This type of power tool accessory features a drilling tip and thread-cutting grooves all in a single too.
Usually, I associate combination tap drills with sheet metal or thinner plate stock.
I’m am looking into buying a set of drill and tap combination drill bits. Do you think this is a good idea? Would it be better to buy a thread tapping kit, and just drill with normal drill bits.
I have been thinking of how to answer Jacob’s question, but there’s no right answer.
How do Combination Tap Drills Work?
Here’s a quick video demo of the Dewalt tap drills from a past media event:
Combination Tap Drill Pros
No tool changes are needed.
No specialty-sized drill bits are needed.
No tap wrenches or other accessories are needed, just a cordless drill or impact driver (if impact-rated).
Combination Tap Drill Cons
Can only be used in thinner materials.
One-size-fits-all means you cannot cater drill size to the material or application.
I’ve seen some complaints about breakage.
Some manufacturers advise that you can use tap drills in most commonly tapped metal materials up to 2X as thick as the desired threaded hole diameter.
Combination tap drills seem convenient for portable tool kits when you might come across a quick task that would otherwise require a hefty tap and drill kit.
Personally, I don’t use these for my regular thread-tapping tasks, I use separate drill bits and hand or spiral taps.
It seems to me that combination tools are better suited for certain construction or repair tasks, but I prefer standalone tools for fabrication-type work.
This is one of those questions that I find difficult to answer without knowing more. I would rather have a tap and drill bit set first, and then pick up a combination tap and drill set later if the needed presented itself.
For that matter, I like having plug, bottoming, taper, and spiral taps in the sizes I use most often, as well as a couple of common tap drill bit sizes, plus a full set of wire gauge and lettered drill bits in case I need to deviate in certain materials. Having wire gauge and lettered drill bits also come in handy for drilling different sizes of clearance holes.
Irwin sent over a Hanson tap and die set a few years ago, and although I have used it a bit, I still have a very firm preference when it comes to drill bits and hand taps.
The thing is, good taps and drill bits can get pricey. An all-in-one repair set comes in handy for those times when I’m not sure what I’ll need, and when I run into a situation where my on-hand tooling doesn’t cover all the sizes I need.
A combination tap drill set can be an interesting first choice, but its suitability absolutely depends on user intent.
For added benefit, many combination tap drills can drill, tap, and also countersink in a single operation. If the accessories fit the workpiece dimensions, it’s hard to beat the one-step operation they allow for. Separate tools and accessories would take a lot longer to achieve similar results.
BUT, use a tap drill improperly and it could break on you. This can happen to any hand or power tap, but it seems like it might happen more with this type of accessory.
I also feel that combination tap drills might not be as precise compared to using separate tools. It of course requires different machinery or accessories, but I can drill and tap holes much closer to a perfect 90° with separate tooling than I can with a tap drill in a handheld cordless drill or impact driver.
Whether tap drills could or should be used depends on the task. If it helps, consider how individual screwdrivers might be needed for tasks where multi-bit driver tips simply don’t fit.
Here’s what I would buy if I was set on combination tap drills:
What’s your take on this type of accessory? Did I miss any pros or cons?
Update: Yes, these are available in metric sizes as well. Here’s our follow-up post on metric combination tap drills.