Are these dovetails too thin?

[Afro Boy]

I marked these out using a guide but it wasn't until the second cut that I realised how narrow they get at the base. They're 10mm at the edge and 4mm at the base.

I'm wanting to turn this into a low bench/seat so it will need to support a bit of weight. The legs are Huon Pine (tails) with Red Ironbark as the seat (pins).

Do you think I should just cut them off and start again or would they be strong enough as they are? Perhaps I can support them in some other way?

Secondly, I'm having some trouble cleaning out the gap inbetween the pins. It's quite narrow at the end and I don't have a chisel narrow enough to fit in there. Any ideas?

Thanks,
Af.

[weisyboy]

you can get very narrow files to clean up the bottoms of the pins. or sharpen up a small screwdriver.

they should be strong enough as the wait is only pulling on the tails when you lift the seat

[derekcohen]

Af

Your dovetails are back-to-front/wrong way round. :o They are weaker this way. Glue may secure them, but it depends on the stresses imposed on the joint.

http://i13.photobucket.com/albums/a262/Derek50/Joints/Dovetailing/Canyourmarkingknifedothis.jpg

http://i13.photobucket.com/albums/a262/Derek50/Joints/Dovetailing/Cutboards.jpg

http://i13.photobucket.com/albums/a262/Derek50/Joints/Dovetailing/cabinetwip3.jpg

Been there, done that :U

Regards from Perth

Derek

[weisyboy]

what do u mean wrong way?

[derekcohen]

The pins point towards the base rather than outward! As a result, the base of the pin threatens to snap off. :C

Regards from Perth

Derek

[weisyboy]

no they pint up from ware im sitting.

the tails are just realy small

[Afro Boy]

Up, down, what? I'm confused here.

Thanks for the tip on using a narrow file. I never thought of that.

[Wizened of Oz]

the tails are just realy small

That's right.
Fat pins and skinny tails. As Derek tried to point out the marking out is all a-about.

[derekcohen]

Look here. In the first picture are "normal" dovetails. In the second picture are yours. These are not normal. They are going to break off.

http://i13.photobucket.com/albums/a262/Derek50/Joints/Dovetailing/Comparingdovetails.jpg

Please don't say that the boards are upside down. :doh:

Regards from Perth

Derek

[thumbsucker]

Oh - Never thought of doing it that way afro boy

What you have done is put the pin on the tails board and the tails on the pins board, OR put another way your pins should be protruding out of the dark timber and the tails should be protruding from your light colored timber. if that makes sense.

[mic-d]

The dovetails are the right way around. It's just that the pin and tail proportions should be reversed.

Cheers
Michael

[powderpost]

Whether the pins are "too" small, depends on the end use. In days long gone, a high value was placed on drawers being dovetailed. The size of the pins was a cabinet makers signature, but then the "load" on the joint was marginal in drawers. A different set of criteria was applied to "structural" cabinet work. As has been pointed out in a previous post, the pins are in fact "upside down".
Jim

[mic-d]

Whether the pins are "too" small, depends on the end use. In days long gone, a high value was placed on drawers being dovetailed. The size of the pins was a cabinet makers signature, but then the "load" on the joint was marginal in drawers. A different set of criteria was applied to "structural" cabinet work. As has been pointed out in a previous post, the pins are in fact "upside down".
Jim

The pins are the right way around. The layout IS the same as Derek's, just the tails are far too small.

[aak]

The pins are the right way around. The layout IS the same as Derek's, just the tails are far too small.

Agreed:2tsup:

Andy

[Afro Boy]

Right-o. Essentially I'm going for a look where from the top (the dark timber) you see small slivers of the lighted timber coming through.

So ... I will need to cut these off an start again ... Tails on the dark timber (top) and small pins on the light timber (legs/sides).

I think I got it right now.

Thanks for all the help guys.

Cheers,
Af.

[derekcohen]

Originally Posted by mic-d
The pins are the right way around. The layout IS the same as Derek's, just the tails are far too small.]
Agreed:2tsup:

Andy

Andy, you're either spatially challenged or dreaming :U:U:U

Regards from Perth

Derek

[mic-d]

Andy, you're either spatially challenged or dreaming :U:U:U

Regards from Perth

Derek

Sorry Derek,

Grow his tails and shrink his pins and you'll see the layout is the same as yours.
Cheers
Michael

[Woodwould]

Yes, the only difference between Afro's and Derek's dovetails is proportion. Nothing's upside down.

[derekcohen]

OK. OK. I'm wrong about the orientation. :U But not about the fragility of the construction. It seems that, after marking, the wrong areas have been removed.

Regards from Perth

Derek

[aak]

OK. OK. I'm wrong about the orientation. :U But not about the fragility of the construction. It seems that, after marking, the wrong areas have been removed.

Regards from Perth

Derek

Hi Derek,

Agreed:2tsup:

You said abit earlier: "Andy, you're either spatially challenged or dreaming"

I am actually neither Derek.

I have high regard for your woodworking skills and read most of your comments and published articles with interest. However, making comments like this are unnecessary and uncalled for and they will not make you any better woodworker or any more respected!

Regards
Andy

[mat]

Not sure if Derek is eluding to this but the pins are cut so the grain runs across the pins not longitudinally in picture 1 - a big no no and weak as.

[Peter36]

Hi Afro Boy
It looks as though the direction of the tails is at right angles to the direction of the grain which would make them weak.Maybe you could confirm that for me . The leg panel needs to be turned 90deg so the tails run with the grain and then the proportions would be fine .

Regards
Peter

[derekcohen]

making comments like this are unnecessary and uncalled for and they will not make you any better woodworker or any more respected!

Hi Andy

It looks like you mis-read my tone. I was teasing you (been there and done that type of dovetail when not concentrating). Obviously that did not come across. I apologise if I have hurt your feelings. Last thing I would want to do.

We learn from our mistakes. This experience will hopefully bring a smile to your face in future. I know mine did.

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Wrongdovetails2.jpg

Regards from Perth

Derek

[Peter36]

Andy, you're either spatially challenged or dreaming :U:U:U

Regards from Perth

Derek

The interpretations which can be placed on this statement are
1. Andy is spatially challenged
or
2. Andy is dreaming
:D:D

[46150]

.............would someone please clarify this situation,,,,,,think I'll have a Bex powder and a lie down.......AL

[aak]

Hi Andy

It looks like you mis-read my tone. I was teasing you (been there and done that type of dovetail when not concentrating). Obviously that did not come across. I apologise if I have hurt your feelings. Last thing I would want to do.

We learn from our mistakes. This experience will hopefully bring a smile to your face in future. I know mine did.

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Wrongdovetails2.jpg

Regards from Perth

Derek


Hi Derek,

No problems. Sorry for mis-reading your tone. I suppose, people like me who's first language is not English will not always get the subtleties of jokes like this.

Regards
Andy

[silentC]

1) It is difficult to tell from the photos but it looks very much as if the tails (on the light-coloured board) have been cut into the edge of the board, rather than the end. If so, the tails will snap off. It also creates a movement problem if the mating pieces do not have their grain parallel.

2) The tails are much too narrow and even if the grain is running the correct way, they will not be strong enough to carry any weight. For maximum strength, I believe the pins and tails should be of the same width. So you either need more tails, with much smaller gaps between, or the tails should be as wide as the gaps between currently are.

Yes, you need to saw them off and start again. If someone sits on it, it will probably break.

[Afro Boy]

Thanks again for the tips everyone. I'll be sawing off and starting again this evening.

I want the look of smaller light coloured tails when looking down from the top of the dark board (the seat). So if I put larger tails on the dark board and the pins on the lighter board (pointing in the correct direction) then I think I'll be right.

Cheers,
Af

[silentC]

I want the look of smaller light coloured tails when looking down from the top of the dark boardIf you put the tails on the seat board, then when you look down from above, you will see the ends of the pins protruding through between the tails. I think that's what you mean. They are a trapezium shape (triangular with the pointy bit cut off).

The pins can be quite narrow, but that doesn't give you the strongest joint. For strength, the pins themselves would be about the same width as the tails. I think the only thing you have done wrong is to make the tails so much smaller than the pins. If it was the other way around, you would be fine.

[Afro Boy]

If you put the tails on the seat board, then when you look down from above, you will see the ends of the pins protruding through between the tails. I think that's what you mean. They are a trapezium shape (triangular with the pointy bit cut off).
Absolutely. That's exactly what I was thinking. In doing this I think I just cut away the wrong parts using the opposite angles.


The pins can be quite narrow, but that doesn't give you the strongest joint. For strength, the pins themselves would be about the same width as the tails.
In the current design, any rocking back and forth will easily snap the tails from the legs. If I make large tails and place them on the seat board (with smaller but still sizable pins) there should be enough surface area in contact to prevent any snapping. The only weakness will be when lifting the seat which shouldn't be an issue.

Amazing how much you can learn from a simple mistake like this. Thanks again for your help and advice.

Cheers,
Af.

[Peter36]

Can someone tell me what is the problem with the dovetails in post No23 . Thanks:)

[silentC]

I remember when Derek did that. There's no problem per se. However what he wanted was wide tails and narrow pins but he laid them out back to front and ended up with narrow tails and wide pins. The joint still works but is not as strong as it could be, and is probably not as aesthetically pleasing as what he intended to do.

[GraemeCook]

Peter

I think Silent is correct and that Derek really intended to do something like the example below. Note the difference in the amount of end grain displayed.

I'd still be happy with Derek's result, though.

Cheers

Graeme

[robyn2839]

Can someone tell me what is the problem with the dovetails in post No23 . Thanks:)
nothing as far as i can see.bob

[silentC]

nothing as far as i can seeThe tails are too narrow and/or too far apart. Can you not see that?

[mat]

Having a different look at this particular project it is different to a drawer. The forces exerted on a drawer are straightforward but on a bench I would assume it is more of a racking force and as said previously the pins and tails should probably be of equal size.

[mic-d]

The tails are too narrow and/or too far apart. Can you not see that?

or to put it another way, "Does my pin look big in these drawers?"

Cheers
Michael

[Wongo]

This is the look most people like.

Seen that logo before? :;

[Waldo]

This is the look most people like.

Seen that logo before? :;

:no:

Looks like a few mountains in a row, with - must be a map for the Three Sisters or the Glass House Mountains. :D

[derekcohen]

...not as strong as it could be, and is probably not as aesthetically pleasing as what he intended to do.

Silent, that is what I mean about learning from one's mistakes. My son still uses the drawers with the wrong-way-round dovetails. They have held up ... but the grain is orientated correctly here (unlike in the original picture).

This is what I would have preferred .. :U

http://i13.photobucket.com/albums/a262/Derek50/Joints/Dovetailing/3.jpg

Regards from Perth

Derek

[silentC]

that is what I mean about learning from one's mistakes
And the beauty of the forum is that everyone else does too :D

(we hope :wink: )

[Peter36]

or to put it another way, "Does my pin look big in these drawers?"
:o:o

[jefferson]

Derek,

A little curious - did you pin the frame with a dowel in the pic? Seems a lot of work to me! Or were you building something to last a generation or three?

Jeff

[derekcohen]

Hi Jeff

It does not take much extra effort to pin a M&T joint. That frame is to hold a glass panel, so it needs to be strong.

Regards from Perth

Derek

[robyn2839]

The tails are too narrow and/or too far apart. Can you not see that?
in your eyes not mine,its a drawer front not a lot of stress there ...bob

[silentC]

To the contrary, drawers are subject to a lot of stress, especially if they are loaded with heavy items. How often does a kitchen drawer full of cutlery get yanked open every day? I find that opinion a bit odd actually. Don't you want to make things to last? Do you find yourself deliberately making things in an inferior way because you feel that "there's not a lot of stress there"?

However you don't have to take my word for it. You can discover the recommended approach to sizing and spacing dovetails in just about any woodworking text book and if you can find one that recommends pins be twice the size of the tails, then I will be very surprised.

Pins and tails of equal size for strength. Pins smaller than tails for appearance where strength is less important. Pins larger than tails when someone makes a mistake marking out..

I actually can't believe I'm having to debate this point.

[silentC]

Here you go, here's one I looked up for you.

Gary Rogowski in The Complete Illustrated Guide to Joinery:



The strongest arrangement is when tails and pins are exactly the same size. When superior strength is not required and a more refined look is desired, make the tails roughly two to three times the size of the pins.

[silentC]

Ernest Joyce in Encyclopedia of Furniture Making:


It is usual to make the tails at their widest part about twice that of the pins, but for extra strong work they can be equal.

[robyn2839]

mate your a legend, thanks for that............................bob

[silentC]

Yep, in my own lunchtime :D

[Peter36]

Glad we got that sorted.:U

[silentC]

I think Bob is just subscribing to the old "never wrestle with a pig because you both get muddy and the pig enjoys it" :)

[Wongo]

mate your a legend, thanks for that............................bob

Don't encourage him. :D

[Eowyn]

After looking at this thread at various times since it started, I'm finally going to ask a really dumb question, given that I have in the past, made at least 15 drawers, and 5 boxes, all with dovetailed joins. (with router and jigs, not by hand)

What's the difference betweeen a pin and a tail? Which one is which?

[Afro Boy]

The tail has side perpendicular to the board. The pins don't.

So, if you're looking down at a flat board, the tails are the ones that look like fish tails.

Tails are the ones on the top, pins are the ones on the bottom ...

http://thecraftsmanspath.com/TCP_blog/wp-content/uploads/2008_02_16/Completed_Front_Tails_and_Pins_With_Groove.JPG

[Woodwould]

In the image below, the white section contains the dovetails (which take their name from the shape of Fantail Doves tails) and the grey section contains the pins.

http://upload.wikimedia.org/wikipedia/commons/7/73/Joinery-throughdovetail.gif

[Eowyn]

thank you

[mic-d]

So, if you're looking down at a flat board, the tails are the ones that look like fish tails.




Yes, but Eowyn's asking about dovetail joints, not fishtail joints. I'm pretty sure that is a dovetail joint in your photos tho'

:wink:

Cheers
Michael

[GraemeCook]

Pins and tails of equal size for strength. Pins smaller than tails for appearance where strength is less important. Pins larger than tails when someone makes a mistake marking out..

I actually can't believe I'm having to debate this point.


I was re-reading this thread in company of a friend who is a civil engineer - he usually builds roads and bridges - and he casually mentioned that the above is not technically true. He said it might be true if the dovetails cut in metal or plastic of the right thickness.

He said it would rarely be true in wood:


the cell and grain structure in wood meant it had different strength properties in different directions. Wood is strong in tension, but splits easily.
Pins are largely in tension, Tails have a mixture of compression, torsion and bending forces.
different species and samples of the same timber have varying strength characteristics.
the thickness of the timber in the pin and tail can be different.
In general, the tails should be bigger than the pins.

Now, my mate is an engineer, not a woodworker, but his analysis seemed cogent - much more so than my amateurish attempt to repeat what he said. Perhaps someone with an engineering background could develop this better than I can.

Cheers

Graeme

[robyn2839]

Don't encourage him. :D
trust me i,m not

[silentC]

A couple of points:

1. In the absence of a microscopic analysis of each and every bit of timber used in dovetail construction, which is the only way you could make a call on the individual strength characteristics of the timber being used, what I quoted is a rule of thumb.

2. The references from which I quoted this rule of thumb are recognised woodworkers with many years experience, built upon the collective knowledge and experience from all the years of furniture construction that have gone before.

If your mate has a theory that contradicts this, he should publish it :) Ask him to include diagrams, because as a layperson I can't see how the forces exerted on the pins are any different to the tails once the joint is glued up.

For what it's worth, my non-degree qualified opinion is that the intention in making them the same size is to maximise the size, and therefore strength, of the pins without compromising the same attributes of the tails. The volume of fibres at the root of the pins and tails would be similar if not the same and therefore of similar strength. It seems to me that this is the point at which the joint would fail.

You usually orient the joint so that the tails are parallel to the usual direction of forces pulling it apart. So it seems natural that you would want to maximise the strength of the tails by keeping the roots as large as possible. Making the pins the same size as the tails would maximise the strength at the base of the pin without compromising the tails. You are dividing the available fibre volume evenly between the two.

Once the joint is glued together, the collection of pins and tails would form a solid block and so the weak point will always be the connection between these and the rest of the adjacent boards. What does he make of that?

[Skew ChiDAMN!!]

What Silent says makes sense to me. (Scary, innit? :oo:)

So long as the total cross-sectional areas of contiguous fibres - typically the base of the tails and the whole of the pins - are the same, then both have equal strength. Assuming good joints and glue-up, of course.

It's not quite 1:1 for pins:tails if you wanna be anal about it, as you need to deduct the tapers of the tails & allow for differences in board thisknesses, but pretty close. Close enough for all practical purposes (or general statements :D) anyway.

[silentC]

What Silent says makes sense to me. (Scary, innit? :oo:)
Don't worry, an engineer will be along shortly to tell us why we're wrong :D


It's not quite 1:1 for pins:tails if you wanna be anal about it
Yes I deliberately skirted that argument. If you said that the pins and tails were sized such that the width across the centre of the base of a pin was equal to the width at the base of tail, they would be the same. But that's just silly :p

[chrisp]

Don't worry, an engineer will be along shortly to tell us why we're wrong :D

You called?

Forget the dovetails - use a box joint :D

[Wongo]

Stop the nonsense. Let's see how pretty they are to look at.:D

http://www.woodworkforums.com/attachment.php?attachmentid=91572&stc=1&d=1229394264

[chrisp]

Wongo,

Beautiful workmanship (as usual) :2tsup:

Dovetails look great on draws, but aren't we talking about a stool here? :)

[GraemeCook]

Once the joint is glued together, the collection of pins and tails would form a solid block and so the weak point will always be the connection between these and the rest of the adjacent boards. What does he make of that?

Hi Silent

I pretty well agree with what you say. Those rules of thumb work well and have done so for hundreds of years. That's good enough for me.

But there is so much reserve strength in a good dovetail joint that we probably over-emphasise the need to maximise strength. Enclosed is a picture of my old pine kitchen dresser that has been in daily use since the 1870,s - as kids we certainly did not treat it with respect. It has only one full plus two half pins per side, but it is still firm. The putty dots on the tail actually hide 3mm dowells - do not know if they are original or were added later. They were there in the 1950's, at least.

Point taken on the glue-up. But part of the strength of dovetails is that the wood in the joint is also load bearing, not just the glue.

Thanks to you, Silent, and every one else who has contributed to this thread. It's made everyone think about something we all take for granted.

Merry Christmas

Graeme

[silentC]

Agreed. Joyce suggests that a narrow pin layout is suitable for drawer fronts. He says two full pins for drawers up to 6" and a third for deeper drawers is sufficient. Obviously you have living proof there that one pin is just as good in a smaller drawer.

The equal sized pins and tails layout is for carcase joinery or any situation where you want more strength, probably (although he doesn't explicitly state this) where racking might be an issue. I'd suggest this layout would be best for a stool as in the original poster's situation.

Despite all that, I think a lot of what we do is done for looks as much as anything else. For some reason, narrow pins look good to my eye.

[Waldo]

I like pins that go all the way up... :D

[silentC]

Hmm, you might be onto something there, Waldo...

[Afro Boy]

Thought I should post an update on my "small dovetails" issue. I managed to turn my oversized pins into new tails. I then trimmed off the far too thin dovetails and made new pins to match.

The result is below. Not exactly the look I was going for but I think it comes up quite nice (espec. for a very rank amatuer like me). I finished it with a couple coats of dewaxed white shellac and then some EEE. I'm quite happy with the result so thanks everyone for your help and advice.

[weisyboy]

nice