Dovetail shoulder

[JohnnyNoName]

I have been working to improve my dovetailing skills by trying out new techniques. One thing that I have seen done a couple of times for dovetail joints is that they will cut a shoulder, as if it was a tenon, on the inside face of the boards. Can some please explain the purpose of that shoulder?

Thanks,

Jonathan

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[Darnell Hagen]

I think what you are describing is what is known as the "140 Trick", called that because a Stanley or Lie Nielsen 140 Skew Rabbet Block plane is used to make the shoulder. The shoulder is cut precisely at the tail base line, and it is used as a positive reference for registering the tail board against the pin board. It makes lining up the two pieces for tranferring layout a snap. Be sure to compensate for the slightly thinner board when you set up your marking gauge.

[JohnnyNoName]

I think what you are describing is what is known as the "140 Trick", called that because a Stanley or Lie Nielsen 140 Skew Rabbet Block plane is used to make the shoulder. The shoulder is cut precisely at the tail base line, and it is used as a positive reference for registering the tail board against the pin board. It makes lining up the two pieces for tranferring layout a snap. Be sure to compensate for the slightly thinner board when you set up your marking gauge.

Oh... OK, I can see the helping. Would you put it on both boards or just the one you cut first? Are there any dangers or "by-the-ways" that I need to be aware of using this technique? Can it be used for both tails and pins first?

Jonathan

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[Darnell Hagen]

Because of the way the joint is assembled, it's used only on the inside of the tail board. As long as you set your marking gauge for the decreased thickness everything will work out fine, whether you go tails or pins first.

[bois]

Just to clarify this is something you would only do on half blind dovetails where you don't have the option to trim long tails and the alignment that the shoulder provides is critical for a good fit. However this would add more work than benefit for through tails where you typically try to leave tails proud/long anyway to be quickly cleaned up with a block plane.

[JohnnyNoName]

Just to clarify this is something you would only do on half blind dovetails where you don't have the option to trim long tails and the alignment that the shoulder provides is critical for a good fit. However this would add more work than benefit for through tails where you typically try to leave tails proud/long anyway to be quickly cleaned up with a block plane.

Ahhhh... Thanks for the clarification.

Jonathan

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[Darnell Hagen]

Actually, proper registration at the baseline during layout is critical for a good fit, whether half-blinds or not. The 140 trick has validity in both situations.

[bois]

Sorry Darnell but I have to disagree with you there. A rabbet certainly isn't critical as through dovetails have been done just fine for centuries without one. It's an alignment aid but actually has no impact on the fit of through dovetails at all (assuming you don't move the board as you are marking). And if you do use the rabbet with through dovetails it means you have to reset your marking gauge to the new thickness when you mark the second board. There is very little benefit and several extra steps, which just slows things down. I'm not saying this technique won't work for through dovetails just that for me it just slows things down unnecessarily. Any slop in the extra length of the tails can be quickly cleaned up with a block plane after assembly.

[Darnell Hagen]

What are you talking about? You disagree with me that accurate registration is critical, then you write that it has no impact, as long as you don't move the board? That is exactly what the rabbet is for. Of course it has an impact on the fit of through dovetails, the inside face of the pins still need to align with the bottoms of the tails, regardless of how long they are. And yes, you do need to reset your marking gauge, just like I said, twice, and just like you'd have to do with half blinds. And yes, both the tails and the pins can be cut long so that they can be planed flush with the sides after assembly. Their length is set by the marking gauge and the rabbet, and is planned for and not considered slop.

[bois]

Darnell, I was just debating that a rabbet is critical for registration in through dovetails(my apologies if that is not what you were implying). My point here is that the rabbet serves a much more important purpose in half-blind dovetails where any variation in the length of the tails (due to misalignment) directly impacts the fit of the joint. In through dovetails, if you are slightly off your scribed line, the tails will still fit. I'm not saying it wouldn't help, I'm just suggesting that it's far more of a common practice with half-blinds, and rarely used in through dovetails.

[jwatson]

I say rabbet and forget the dovetail dovetails are overrated!

[kipster]

I think speed in any operation precludes the extra steps the rabbit represents for through dove tails.

.

[Darnell Hagen]

Anyway, Jonathan, that's the reason for the rabbet. Ignore opinion, try it, and decide for yourself. Good luck!