Drilling pilot holes and clearance holes

[Paul F Franklin]

Does anyone make a two diameter drill bit that drills the pilot hole and clearance hole at the same time?
I know you can get the sets with countersinks, and some of them have an extended shaft from the countersink that does create a clearance hole, but all the sets I've found like this drill, at most, a 3/8 deep clearance hole. I typically need 3/4". Plus, those little wings get dull very quickly when drilling abrasive materials.

I'd like a set of bits that have a pilot diameter section an inch or so long, and then widen out to clearance hole size for at least another inch.

I've tried the tapered bits, and they work after a fashion, but they seem to break easily, and they also dull very quickly in mdf or similar materials.

This comes up all the time in remodeling, and also when I'm building jigs and fixtures out of mdf, which can split if you don't drill a pilot. I generally don't need or want a counterbore or countersink, and when I do I don't mind doing that as a separate step.

When I have a bunch to do, which seems to happen fairly often, I set up two drills with the right bits. But it's still a pain and takes way too long. I'd like a one step solution.

My searches have only turned up the pilot/counterbore/countersink combo bits, or the step bits that can drill 8 or 10 different holes sizes in thin material.

[Wayne Lomman]

Change to using chipboard screws. They have a rolled thread that is larger diameter than the shank meaning you can drill a single diameter hole. Cheers

[joseph f merz]

I get what your asking but cannot help with the stepped bit . In the remodel/constr work I do I use pretty much only construction screws .As for drilling these are my favorite . http://www.rockler.com/8-pro-tapered-countersink-bit .They stay sharp much longer then the fuller [isn't that the brand?] Mostly though the narrow profile allows me to make a steeper hole so I can pull things together better ,like a pocket screw hole .I often order screws on line from http://www.screwsolutions.com/ .I keep different sizes on hand and only in the bronze ext . I also will mention I use a lot of the 1/4" lags they carry .great for pulling stuff together .Hope that is helpful info .Joseph

[Andrew Seemann]

I haven't seen what you are looking for. It may be that a collar/sleeve for a clearance hole on a pilot bit would be too thin to easily manufacture, especially if it is an inch or more long.

Myself, I broke down years ago and began to use two cordless drills and an impact driver when I drive screws. The first drill has a pilot hole countersink combo bit, then I grab the second drill with a bit sized for a clearance hole, and after that I drive the screw in with the impact driver. It is kind of a pain, but it works and it is easy to adjust for different sized screws/lags. I keep an extra drill bit next to my index the size I use for clearance holes the most.

[Bill Dufour]

piloted drill, but the small diameter is not normally very long. only 2-3 diameters long before the big diameter. I see no reason a sharpening shop could not extend the small diameter.
I suppose you could do something with a countersink cage...use a drill instead of the pilot shank and a flat counterbore of the correct diameter. But they are normally only one inch or so of travel.
Chip removal will be an issue. Check Brown Tool for online catalog
Bill D

[andy bessette]

The very best setup is the excellent Fuller tapered bit with attached countersink/counterbore (which can be detached when not needed).
https://www.jamestowndistributors.co...waAk1GEALw_wcB

[Bill Dufour]

I use a standard drill for the main hole then a piloted countersink or counterbore, in a countersink cage, to make the recess portion. If the main hole is critical I use a threaded drill in a countersink cage. A countersink cage depth can be adjusted by 0.001 inch steps so you can line things up.
A 747 airplane has about 850,000 rivets so you can see why the aircraft industry has developed special tools for accurate drilling and countersinking. Check the auction sites for aircraft drills, aircraft count ersinks etc.
Bill D.

[Morey St. Denis]

In metalworking the technique and tool you're describing is known as an integral counter-bore or step drill. They are available for recessed shoulder screws, but mostly limited to combinations of a tap drill size for the machine screw thread and its customary precision-ground shoulder diameter. A step drill or "subland" bit such as you're describing is also made by Kreg for drilling pocket-hole screws, but limited to only two sizes and their pilot drill length seldom exceeds 12mm. The KJD drill bit might potentially serve as a convenient workpiece for your local machinist to grind down an extended pilot length and slope-grind that counter-bore cutting step. For typical woodworking use, considering the underlying compliance or small-scale yield strength of wood as compared to steel or brass screws, many of us get by with an adjustable set of countersinks that employ the long-tapering drill bit. Longitudinal positioning of the machined countersink annular step is adjustable to suit the application.

Depending on the specific diameter combinations you favor in those larger sizes, might consider an annular plug & tenon cutting bit set in conjunction with a concentric pilot drill bit of your choice.

[joseph f merz]

still not understanding your troubles .i do not have any issue using construction screws . what screws are you using ,are you having to use tapered [old fashioned] screws . though i have a large supply of 3/8 and bigger lag bolts which i may set up two sizes of bits . but for clients if i have anymore then a couple to do i buy lag screws which do not even require a predrill . but you [OP] said you were doing this when making jigs with MDF . can you post a picture of the screws your using .maybe it is reginal thing . I do not use drillwall type screws for jobs anymore .lowers work quality and use up to much time messing with them .

[Peter Christensen]

Joseph. Paul wants to screw two pieces together such that the threads pass through the first piece without biting into it and into the second piece so the screw does. That way the two parts are drawn tight together. So he wants a drill bit with the minor diameter of the screw (pilot size) and a second diameter (clearance size). That way he can drill the holes in two parts clamped together in one operation. The principle would work for deck or framing screws, drywall screws or anything else you had to use including lags. His problem is finding drill bits to do that.

[Paul F Franklin]

Peter, thanks, you explained it better than I did. I do generally only use construction screws...spax or GRK. Sometimes I can clamp the two parts tightly and then it doesn't matter as much if I skip the clearance hole. More often than not however, I need the screw to pull the parts tightly together and thus need a clearance hole in one piece.

Thanks all for suggestions and ideas! I'll do some more digging based on the ideas above. First try may be one of the higher quality tapered bits mentioned as they are readily available, but I'll look into the other suggestions as well.

[Mark Bolton]

I would be looking at using a construction style self-feed bit like a Milwaukee self-feed or dewalt 2 wing style and remove the center drive screw (they are replaceable with an Allen set screw) and replace it with a ground down twist drill. May have to fabricate a bushing for small diameter bits. Controlling the feed and depth of cut may require a stop collar.

[glenn bradley]

You can get what Peter describes by changing screws as an option. I have screws that have a section of smooth shank that is smaller than the diameter of the threads. Pocket holes are a good example of this but, they come in other head types too; pan, flat, oval. Nearly all my screws are of this type except those meant to show.

pocket screw.JPG . FHWS.JPG

[Mike Cutler]

Paul

WL Fuller, in Warwick RI. makes any type of drill bit you can think of.
All they make are drill bits and milling machine cutters. If what you're looking of is not in their online catalog, it's an odds on bet that they can make it for, if you can provide them a drawing.
I think page 32, of their current catalog, is close to what you're looking for. You might have to special order a longer pilot.
Give them a call.

http://wlfuller.com/html/catalog.html

[Robert Engel]

I would look at some machinist tool sources.

If I'm understanding you, a CS bit without a shoulder would work.

Something like this.