Half Blind Dovetails - School me

[Rob Luter]

I've gotten pretty decent at through dovetails. If I take my time and really pay attention they turn out fine. This past weekend I made my first attempt at half blinds on a drawer front. I used the blue tape trick to aid in marking. Carefully transferred the lines using the tails as a template, peeled the tape covering the waste, sawed to the waste side of the line, and at the end of the day the sockets were too large. Hmm? I'm guessing a flaw in my method of transferring the cut lines. I soaked up all the YouTube I could find on the subject but had no revelations. I guess I just need lots of practice?

Suggestions?

[lowell holmes]

I would transfer the marks using a knife and just saw to the mark, not on it.

[chris carter]

I have pretty lousy vision, but after trying the blue tape thing a few times it's just not for me. I get that lots of people like it, but I'm just personally not a fan. I mark with a knife line and put a light up close to make it easier to see (headlamp works great). And/or I might fill the line with a pencil (which still preserves the knife line). With through dovetails I saw to the line and I don't pare anything unless I run into a fit problem. But with half-blinds I saw just inside the line and after I remove all the waste I stick my chisel on the line and pare it down.

[Prashun Patel]

If you can do decent through dovetails, then I suspect your marking ability is just fine.

Check that all your corners are clean and that all 3 faces of the socket are square. These things can make it appear that your socket is too large.

There's no short cut besides practice, though.

[Robert Hazelwood]

The transferring and cutting of the pins isn't any different than through dovetails, except that you have to saw the pins with the saw tilted back towards you.

If you are pretty sure that you sawed next to the tape and not into the tape (which is usually fairly obvious when it happens) then I agree there must be an error in transferring, or perhaps the tails are tapered such that the inside face of the pin socket is smaller than the outside. In that case even very accurate marking and sawing will yield a gap on the outside.

I've found that with skinny pin layouts it is fairly tricky to get an accurate transfer from the tails onto the pin board. I've had gaps that I can only explain by a transfer error. You can't see what the tip of the knife is doing, and it may not be quite up against the side of the tail. This is one argument for doing pins first. But on my current project I tried using a block plane blade to transfer and it seemed to have worked pretty well. The flat back registers against the tail and then you just press it down onto the pinboard and rock gently. Of course it takes two hands so you have to have both tail and pinboard clamped in place, a more tedious setup.

[Rob Luter]

A postmortem evaluation suggests that I didn't have the ends of the tails against the lap line when I transferred the tails to the pins and as a result it over sized the sockets. The relationship between the pins and tails is spot on otherwise. Practice practice.

[Derek Cohen]

Have you tried another blue tape trick: "The #140 trick is dead" (http://www.inthewoodshop.com/Furniture/The140TrickisDead.html) :)

http://www.inthewoodshop.com/Furniture/The140TrickisDead_html_146c950c.jpg

http://www.inthewoodshop.com/Furniture/The140TrickisDead_html_25c7a597.jpg

Regards from Perth

Derek

[Jim Koepke]

A postmortem evaluation suggests that I didn't have the ends of the tails against the lap line when I transferred the tails to the pins and as a result it over sized the sockets. The relationship between the pins and tails is spot on otherwise. Practice practice.

Derek's "The #140 Trick is Dead" helps to avoid misalignment errors.

My alignment trick is similar. It uses a small 'straight edge' and small clamps to hold the 'straight edge' to the base line of the tails:

430319

It has helped to improve my dovetails.

jtk

[Prashun Patel]

The most clever ideas are the most obvious. Thanks. I'm going to use this one.

[Rob Luter]

Have you tried another blue tape trick: "The #140 trick is dead" (http://www.inthewoodshop.com/Furniture/The140TrickisDead.html) :)

Regards from Perth

Derek


Derek's "The #140 Trick is Dead" helps to avoid misalignment errors.

My alignment trick is similar. It uses a small 'straight edge' and small clamps to hold the 'straight edge' to the base line of the tails:

It has helped to improve my dovetails.

jtk

Great suggestions both. Thanks gents. I'm also making a little alignment jig I picked up from a David Barron video. That should help with things too. Just a little more involved than Derek's wooden square, but every little bit helps

[Charles Guest]

Use a slender scratch awl and when sawing just leave the whole mark which you will have made with ONE STROKE of the awl. Do not dig a ditch. Do not use a fat awl. The point needs to be like a needle. Yes, it's a faint mark but it's dead accurate. The fit should be a little tight, but follow on with the next steps. Ease the faces of the pins by paring one thin shaving off each pin face staying away from the pins' margins. Put a slight chamfer on the edges of the tails that will enter the joint first. You should be bang on, or at least closer than you've been.

[Thomas McCurnin]

David Barron makes a dovetail alignment board, or you can make your own after watching his video.

http://davidbarronfurniture.blogspot.com/2013/08/dovetail-alignment-boards.html

[Andrew Hughes]

I’m also a self proclaimed dovetail expert. I say sawn the tails as straight as you can correct any crooked one before using them to Mark the pins. When marking the pins be as accurate as you can with good light so you can be sure your marking where you want. Saw a little wide and leave the line you can pare down.
No rushing.

Good Luck

[Jim Koepke]

I’m also a self proclaimed dovetail expert. I say sawn the tails as straight as you can correct any crooked one before using them to Mark the pins. When marking the pins be as accurate as you can with good light so you can be sure your marking where you want. Saw a little wide and leave the line you can pare down.
No rushing.

Good Luck

My epiphany in regards to this is how one can decide whether their dovetails should be cut tails first or pins first.

For me keeping the cut square vertically is easy. Keeping front to back square while cutting on an angle is more of a challenge. If one does what one is weak at first, it can be corrected via paring before moving on to the next step.

So if one is challenged cutting the vertical square but is good cutting front to back square, then it might be easier if you work the pins first.

Of course with half blinds it is difficult to mark the tails from the half blind pins.

Another observation, once you have the first part cut and pared to as good as they are going to get, leave it be. The only corrections after this should be to the second piece. Learning and applying this alone made a great improvement in my dovetails.

jtk

[Derek Cohen]

.....
For me keeping the cut square vertically is easy. Keeping front to back square while cutting on an angle is more of a challenge. If one does what one is weak at first, it can be corrected via paring before moving on to the next step. ..

Hi Jim

I agree with you with the importance in sawing square front-to-back. This is the heart of an accurately fitting dovetail.

I may start marking with a pencil, but then I score the lines with a knife. This gives the saw blade a "kerf" to follow ..

https://i.postimg.cc/QtFsJ0J7/11dovetail.jpg

Saw straight across to create the line ...

https://i.postimg.cc/N0fQ5gyp/12dovetail.jpg

and then saw diagonally, bisecting two lines. This will ensure all is straight.

https://i.postimg.cc/gjRWfj5k/13dovetail.jpg



It is exactly the same for the pin board. I use blue tape for the transfer. Then saw up against the tape on the horizontal ...

https://i.postimg.cc/KzgMJBwW/3.jpg

... then diagonal ...

https://i.postimg.cc/MGHRfhDq/4.jpg

.. and straighten to the base line ...

https://i.postimg.cc/1XhNT4Z3/5.jpg

We all know that these will never go together :)

https://i.postimg.cc/TYncRMks/7.jpg

Regards from Perth

Derek

[James Pallas]

This may help. Which ever you are going to mark with, pin or tail check for square. An easy way for me is to stand a rule against the sides. You should be able to see any out of square easily. Correct any error before you mark the other part. Sorry pictures rotated. My new phone has me more perplexed than dovetails ever have.

[Andrew Hughes]

Hay that’s a good one James.
I remembered another part of the process that’s important and would like to share.
Its taking the time to check both ends are square to the same side and the ends are square to the same face.
Since we use this as our reference the closer the better.
Good Luck

[Jim Koepke]

A quick thought on half blind dovetails, for me it is easier to cut an extra kerf in the middle of the waste on the pin board. It helps when chopping out the waste.

Also a kerf tool like Derek made or one like mine made by Ron Bontz:

430483

A piece of saw blade or other thin piece of metal will work. Do not bevel the end, it will work better if the edge is flat.

A clamp across the end helps to avoid splitting.

jtk

[steven c newman]

Board will still split....just won't show up, until you remove that clamp....

[Jim Koepke]

Board will still split....just won't show up, until you remove that clamp....

Beside the use of a clamp there is technique involved. It is important to 'nibble' one's way through the work. It is tempting to try to get it all done in one heavy blow.

jtk

[Andrew Pitonyak]

Board will still split....just won't show up, until you remove that clamp....

Never noticed a split when I have clamped. Done bad things when I have not. Also, I cut as far as I can before I use it.

I have not done a bunch of these, no more than 10 to 20 boards, so not that much experience.

[Rob Luter]

Never noticed a split when I have clamped. Done bad things when I have not. Also, I cut as far as I can before I use it.

I have not done a bunch of these, no more than 10 to 20 boards, so not that much experience.

I tried the kerf tool approach. I had one split on the end even though I clamped. I had sharpened the edge instead of leaving it square, and my metal piece was about .005" too thick. I'm smarter now. We live and learn.