Pocket hole accuracy required?

[smorgasbord]

So I have a Kreg pocket hole jig for 2X material - used it to repair some fencing and it worked well.

I happened to notice this Massca pocket hole jig has a flippable end piece - one way gives you an overhang so you can index it properly:
[attachimg=1]

If you flip it the other way, there is not overhang and you can use it to reinforce existing joints:
[attachimg=2]

What I don't get is that the spacing from the joint differs in these two situations. That is, if you cut a "new" joint using the first method the holes are like 3/16" closer than if you cut using the "old" setting.

What's going on here? Just curious.

 

[Crazyraceguy]

I have always used Kreg, which doesn't function like that. The stop is built into the fixture and you can't "override" it. They do offer a smaller, single-hole unit that does register off the end, but you have to do it by feel.
That off-set is going to cause you 2 issues, though neither is a huge deal. First is the exit point. The settings (at least on Kreg) are designed to have the screw exit the board in the center of the thickness. Moving the jig closer/farther will move that point slightly. (I don't see it as a big deal, until you get fairly thin material)
The other problem is depth. Again, not a huge problem, but you might need to move the stop collar of the drill bit. You could go through or not have enough engagement.

 

[Packard]

So I have a Kreg pocket hole jig for 2X material - used it to repair some fencing and it worked well.

I happened to notice this Massca pocket hole jig has a flippable end piece - one way gives you an overhang so you can index it properly:
[attachimg=1]

If you flip it the other way, there is not overhang and you can use it to reinforce existing joints:
[attachimg=2]

What I don't get is that the spacing from the joint differs in these two situations. That is, if you cut a "new" joint using the first method the holes are like 3/16" closer than if you cut using the "old" setting.

What's going on here? Just curious.

It is not clear to me what exactly the second photo represents.

I have a big beefy all metal jig, as well as the original all aluminum Kreg jig, and both register off the end of the stock.

This video shows it being used both ways.  It makes no sense to me.

 

[squall_line]

I'm assuming that since you have a different face for the outside and inside corner (or face-registered vs flush-registered) setups, the indexing on each face would match the ideal indexing for the correct thickness of material and account for the offset, rather than matching each other.

 

[smorgasbord]

It is not clear to me what exactly the second photo represents.

It's the difference between the two photos. The gray hook piece is flippable. In the first photo (shown again with a red arrow), the hook is down so you hook it over the board to be drilled to set the distance from the joint.
[attachimg=1]

In the second photo, the gray hook piece is flipped so that it's not in the way of an existing joint that you're trying to strengthen via the pocket hole:
[attachimg=2]

Because of the way this works, the jig is the thickness of the gray piece further away on the second photo than it is on the first. But, it's essentially the same joint. Instead, the gray piece should just be removed completely for the second photo, although there's the issue of the sliding dovetail to consider.

 

[smorgasbord]

OK, just figured out what's going on. If you look at the first photo, there's a little arrow/triangle on the side of the gray hook piece that points to a scale on the black body. That scale is how you set the thickness of the board you're drilling. When you flip the gray hook piece around, the arrow/triangle is on the other side of the black body, and there the depth markings are different to account for the thickness of the hook piece.

So, a bit convoluted, but if you pay attention it'll work out properly.

BTW, one thing I don't often see discussed is joining woods of different thickness via pocket holes. I believe your jig settings need to be for the thickness of the board being drilled. That said, if the board being joined to is thinner (assuming a right angle joint), you may get a screw protruding out the "back."

 

[Packard]

OK, just figured out what's going on. If you look at the first photo, there's a little arrow/triangle on the side of the gray hook piece that points to a scale on the black body. That scale is how you set the thickness of the board you're drilling. When you flip the gray hook piece around, the arrow/triangle is on the other side of the black body, and there the depth markings are different to account for the thickness of the hook piece.

So, a bit convoluted, but if you pay attention it'll work out properly.

BTW, one thing I don't often see discussed is joining woods of different thickness via pocket holes. I believe your jig settings need to be for the thickness of the board being drilled. That said, if the board being joined to is thinner (assuming a right angle joint), you may get a screw protruding out the "back."

My P-C pocket hole jig has and adjustment for the thickness of the board.  But also, you need to select the correct size screw.  This, from the Kreg site:

The thinnest material I’ve used with the Kreg, is 3/4”.  Has anyone tried 1/2”?

I’ve built an entire wall of shop benches using 2” x 4” framing lumber and pocket screws.  The cheap clamp-on jigs (like the one pictured in this thread) is ideal for working with those long pieces.  It took some time, but it was an exceedingly easy build, perfect for the pocket hole joinery.  It would have taken some expensive 4-1/2” screws to avoid the pocket hole build.  This, definitely was in the pocket hole corral.

As long as my cuts were all at 90 degrees, it went up square and true.

 

[MikeGE]

The thinnest material I’ve used with the Kreg, is 3/4”. Has anyone tried 1/2”?

When I built my router table, I was going to use the Kreg 1-inch screws for the 12mm drawer panels. However, it was taking more time than I wanted to spend on a shop project, so I abandoned the pocket hole screws and used an air nailer and glue for the rest of the drawers.

I didn't have any problems with the screws in the top drawer, and there wasn't any over penetration on the 12mm side panels.

 

[Crazyraceguy]

BTW, one thing I don't often see discussed is joining woods of different thickness via pocket holes. I believe your jig settings need to be for the thickness of the board being drilled. That said, if the board being joined to is thinner (assuming a right angle joint), you may get a screw protruding out the "back."

That is kind of a thing. The limitation in thickness is a factor, since the screw can only go in "so far". First of all, the sharp point is not holding anything, but it needs to be there. (it's adding to the length, without adding holding power) With 1/2" material, so little of the screw is doing anything. If you can get some glue in there or it's a very low stress situation, maybe. It's similar to a couple of brad nails. They are just holding the assembly in place, while the glue sets. The glue is actually holding it.

 

[Packard]

The thinnest material I’ve used with the Kreg, is 3/4”.  Has anyone tried 1/2”?

 

When I built my router table, I was going to use the Kreg 1-inch screws for the 12mm drawer panels.  However, it was taking more time than I wanted to spend on a shop project, so I abandoned the pocket hole screws and used an air nailer and glue for the rest of the drawers.

I didn't have any problems with the screws in the top drawer, and there wasn't any over penetration on the 12mm side panels. 

[attachimg=1]

The drawer is a situation where I would first pin nail and glue.  And after the glue dries, I would through drill and add small dowels.  For 1/2” thick stock, I would probably use 3/16” diameter dowels about 1” long.  I usually would not add a fastener for the 2” on either edge, but that would mean one or two dowels only.  I would probably come in about 1-1/4” from both edges.

These dowels can be added at any time.  With modern drawer slides, the need for extremely strong joints on drawer fronts has largely been made obsolete.

 

[Michael Kellough]

[member=74278]Packard[/member] said, “With modern drawer slides, the need for extremely strong joints on drawer fronts has largely been made obsolete.”

Excellent point! I don’t recall anyone pointing this out before.

 

[smorgasbord]

My P-C pocket hole jig has and adjustment for the thickness of the board.  But also, you need to select the correct size screw.

Right. What I'm getting at here is that when joining boards of different thicknesses, I believe the correct procedure is to use the jig's thickness setting for the board being drilled and then the screw length may need to be shorter if the other board is thinner (and maybe could be a bit longer if that board is thicker).

I haven't see any guides, for instance, for attaching a ⅝" board to a 1" board.

 

[smorgasbord]

"Pocket Holes Overexplained"

Interesting. His short tests show that the glue is still the most important part for strength.

I also liked his "pocket holes are like mortise and tenon joints bought at Harbor Freight."

 

[Packard]

[member=74278]Packard[/member] said, “With modern drawer slides, the need for extremely strong joints on drawer fronts has largely been made obsolete.”

Excellent point! I don’t recall anyone pointing this out before.

The “need” for fine joinery is perpetuated by the big companies that still use dovetail joints.  The only reason they do that, is that there are sophisticated automated dovetail machines that can build them as fast as the crown stapled versions.  The only reason the stapled versions exist is that they are using 5/8” thick vinyl-clad particle board which cannot be made with dovetails.  So they advertise “premium dovetailed drawers”. 

The other hoax that is production driven is “Durable UV finish”.  These finishes are not necessarily UV resistant.  They are UV cured.  A UV cured finish can be ready to handle in a minute or less.  Other finishes take hours to cure.  Again, production driven techniques, not fine craftsman driven techniques.

 

[Packard]

My P-C pocket hole jig has and adjustment for the thickness of the board.  But also, you need to select the correct size screw.

Right. What I'm getting at here is that when joining boards of different thicknesses, I believe the correct procedure is to use the jig's thickness setting for the board being drilled and then the screw length may need to be shorter if the other board is thinner (and maybe could be a bit longer if that board is thicker).

I haven't see any guides, for instance, for attaching a ⅝" board to a 1" board.

I think you are correct.  But I would make a test sample to be sure.  In fact, I would skip the logic and go right to the sample making.  [big grin]

 

[smorgasbord]

It's an interesting thought about how drawer slides affect the need for strong corner joints. I admit I haven't thought about it.

Do we know the failure mechanisms/causes in old drawer joint failure? The ones I can recall are on wide drawers, like bottom drawers on a chest or the big bottom drawers in some old kitchen cabinets.

I do have to admit that I built some small drawers with ½" hardwood using biscuits and Blum Tandem soft close slides, and they've held up perfectly over a couple of decades. And some 15" wide drawers that are more than 30" deep in ⅝" stock that also, with biscuits, have held up perfectly, again with soft close slides.

So, is the failure mechanism from wide drawers getting crooked as they're pulled out and people just pull harder? Or perhaps using stops registering against the back of the front face for stop position?

Separately, while my current drawers all use an added front technique, I do aesthetically dislike seeing a ¾" thick front applied to a drawer box that itself may be ¾" thick. It's just so much wood at the front. We do this, I think, because it allows us to align the applied front well within its opening, but again, with modern drawer slides I wonder if that's even necessary anymore and whether we should all be doing the equivalent of half-blind dovetails without the dovetail (rabbeted joints?).

I'm also lucky enough to have my parents' furniture built by George Nakashima in the 1960s. The chest of drawers, about 3' wide, uses what we'd consider a drawer lock joint. Here's a photo:
[attachimg=1]

Note that there is no applied drawer front and the front of the drawer slightly overhands the sides by about 2mm-3mm. I'd have to go back and measure. Anyway, these have only wooden drawer slides (groove in the drawer's sides fits into an oak runner in the cabinet side). The stop is at the back I believe. I can pull the drawers out to check if anyone's really interested

 

[Crazyraceguy]

[member=77266]smorgasbord[/member] this is a rather complicated topic. While it is true that modern roller type drawer guides do decrease friction, making the pulling strength of the front not as important, there is also a counter-point.
Although it is definitely abuse, the opposite can now happen. If someone slams the drawer shut, you have all of that force doing one of two things: knocking against the back of the drawer box or trying to rip the drawer box from the applied front.
With as many as I have seen, over the years, damage of all kinds just seems to happen.
I have replaced drawer guides from all kinds of abuse, bottoms from people trying to stand in them, hinges from people leaning on them. The abuse is endless  [blink]

I would bet that the drawer from your parents, is built in one of two common ways.
Many just slide into a fitted opening, just riding straight on the bottom edges of the sides themselves. The opening is usually fairly tight, so they don't tip down when opened. Many times, the back is set in a dado, which is significantly short of reaching the back of the cabinet. This signifies that the drawer is fully open (stop pulling) but enough of the sides are still inside, keeping the drawer stable. This also increases the total length, which decreases the tipping factor.
With inset drawer fronts, the drawer sides are usually the stops too. They make contact with the back itself. They are made long and planed to fit, so the front is flush. With the other common type at the time, "lipped overlay", the front it the stop.
The other way wood only drawers are fitted is with a wooden runner, that rides in a groove, milled into the sides. With these, the runners are usually the stops. They are tuned to hit the end of the groove, stopping the drawer in the right place, for inset anyway. With lipped overlay, the front is still the stop.

 

[smorgasbord]

... If someone slams the drawer shut, you have all of that force doing one of two things: knocking against the back of the drawer box or trying to rip the drawer box from the applied front.

Again, I think the soft close feature reduces this force considerably, and since the "stop" is built into the slide, which is attached to the drawer's sides (and maybe bottom, too), it doesn't impact the drawer joints.

I would bet that the drawer from your parents, is built in one of two common ways....
The other way wood only drawers are fitted is with a wooden runner, that rides in a groove, milled into the sides. With these, the runners are usually the stops. They are tuned to hit the end of the groove, stopping the drawer in the right place, for inset anyway. With lipped overlay, the front is still the stop.

As I said, maybe not clearly enough, the drawers have grooves in the sides riding on wooden runners on the inside of the carcase. The drawers are insert. The stops, however, I believe are the drawer sides hitting the back, but I can pull some drawers out to double-check if you want. The back of the drawer uses a similar joint to the front, except the sides of the drawers continue past the back. Note that these joints were cut by Nakashima using a tablesaw or radial arm saw as you can see the kerf has the tell-tale ATB profile. BTW, the carcase is through dovetailed at the top joints, but just a butt joint using screwed (plugged) at the bottom. The sides extend past the carcase bottom by ⅛" or so for a nice little detail.

I imagine there was quite a bit of hand work fitting the drawers in this chest. The result is a pretty simple drawer that has held up with daily use for over half a century. Note the drawer bottoms and back of the carcase are plywood - everything else is solid wood.

 

[Lincoln]

My P-C pocket hole jig has and adjustment for the thickness of the board.  But also, you need to select the correct size screw.

Right. What I'm getting at here is that when joining boards of different thicknesses, I believe the correct procedure is to use the jig's thickness setting for the board being drilled and then the screw length may need to be shorter if the other board is thinner (and maybe could be a bit longer if that board is thicker).

I haven't see any guides, for instance, for attaching a ⅝" board to a 1" board.

That's correct. I just built a kitchen load of drawers, with 16mm sides/fronts/backs and 12mm bottoms. Pocket screws through the 12mm bottoms into the 16mm sides. Everything was set to suit 12mm thickness and used 1" screws. I did a trial run into a piece of scrap 16mm and the 1.5" screws broke through the face.
This was my first time using my Kreg 720 Pro, so followed the Kreg guide/set up notes, then a practice run.