What is reccomended gap in thousandths of inch for dovetails?

[Sean Rainaldi]

What is the acceptable gap between pins and tails in half blind dovetails (I’m doing hard maple)?

I am able to get my gaps so close that I can barely slip .0015” feeler stock in – is this too tight? I love the way it looks though - but would it cause the stock to split in time after gluing?

[Heather Thompson]

If you are cutting these by hand, leave the room and shut up!!!!!!!!!!!!

Heather

[Sean Rainaldi]

If you are cutting these by hand, leave the room and shut up!!!!!!!!!!!!

Heather

Oh no - I was getting that on a router table using the Route-R-Joint jig from Woodline and a woodpeckers lift.

[Lee Schierer]

The joint halves should slip together with minimal effort or force. Remember the wood will swell slightly when the glue is applied. If the joint falls apart when dry fitted the joint is too loose. The parts should stay together without glue. If your parts have .0015 clearance per side or less you are probably perfect.

[Jason Beam]

If it goes together without forcing it, you're good. That's it. No worries about the glue.

[Chris Padilla]

Personally, I like to see the gap be no greater than 381,000 Å but that is me....

Sometimes I try to get it under 2 x 10^(-5) fathoms....

[Sean Rainaldi]

Personally, I like to see the gap be no greater than 381,000 Å but that is me....

Sometimes I try to get it under 2 x 10^(-5) fathoms....

Cool! Do you also use laser diffraction spectrography to determine the gap width?

[Alan DuBoff]

What is the acceptable gap between pins and tails in half blind dovetails (I’m doing hard maple)?
.0000" would be the perfect fit, and what I shoot for.

OTOH, I do them by hand. :p

I thought machines were more accurate though...do you mean to tell me you can't get a perfect fit?

[Karl Brogger]

I like mine just tight enough that you have to tap them together with a mallet. Not wailing on it, but just tapping.

[David DeCristoforo]

I shoot for fifteen queblors.

Seriously, do you want to know why you are getting so many smartass answers? It's because this is really a silly question (no offense intended). The thing is, this is not metal work. It's wood. I answered a similar question once when a carpenter asked me "what the tolerances were" for the fit of the joints on mitered door casings. "Zero". It either fits or it doesn't. Your dovetails are the same. They either fit or not. There are no "tolerances" or "acceptable gap". We are not talking about spark plugs. If you can tap your joints together with light hammer blows, you got em just right. If you have to beat on them, they are too tight. If they have gaps between the mating surfaces they are too loose.

[Frank Drew]

Another way to measure, if you've seen good work before and are happy with your own dovetails, you've got them right. If they look sloppy you'll know it (or your friends will tell you :D).

[Bob Genovesi]

I shoot for fifteen queblors.

Seriously, do you want to know why you are getting so many smartass answers? It's because this is really a silly question (no offense intended). The thing is, this is not metal work. It's wood. I answered a similar question once when a carpenter asked me "what the tolerances were" for the fit of the joints on mitered door casings. "Zero". It either fits or it doesn't. Your dovetails are the same. They either fit or not. There are no "tolerances" or "acceptable gap". We are not talking about spark plugs. If you can tap your joints together with light hammer blows, you got em just right. If you have to beat on them, they are too tight. If they have gaps between the mating surfaces they are too loose.

I've got to agree with Dave on this one...

Much too often we loose perspective on what we're really trying to accomplish. We are working with wood, not tool steel or precision machinery. The sawdust itself is larger than .0015 and the relative humidity will cause the wood to expand and contract more than this.

If a dovetail joint just slips together without resistance then it's too loose. These joints when assembled should require what I call a tap fit. The glue applied with be absorbed into the wood and when dry will be nearly impossible to separate.

Leave the precision to the machine shop and enjoy woodworking....

[john lawson]

I don't believe this is a silly question, it's a good one.

I posed a similar question when I attended a woodworking school some years ago. The answer I got from a very well recognized "expert" was about .003" Anything over that and the dovetails are too loose. Anything less than the perfect .000" and they are too tight.

The problem with this answer, and any others, is that we normally look at only one dovetail at a time, so if all of them fit perfectly except for one, then none of them fit; which is why we cut all the tails, or pins, first, then mark the the corresponding pins. It follows that the tails, again cut first, can be virtually any size and as long as the pins fit in relation the the tails then everything is fine.

There is of course, error in every single one cut. If the error is small, say .003" and you do a good job of cutting the pins you have a reasonable chance of everything going together. If you look very closely though, even in good fitting dovetails you will usually see some gaps and some that are very tight.

I try to cut mine, by hand, as tight as I can get them. When I test fit and I can see that it will assemble then I pound them home!!!!. If there is a little glue in the joint the small gaps disappear. If you have cleaned out the the "little crumblies that are between the tails and pins you will have a nice tight dovetail. I have seen many dovetails that were well cut with the saw but were not cleaned out and it will hold them apart from seating properly or can cause them to crack.

Practically speaking I would not quibble with any ones method, every one that has expressed and opinion is probably correct, but to get all those piece of wood to fit together requires a little gap or space, in my opinion it about .003"

[Peter Quinn]

Well, most glue makers are looking for around a .003 to .005" glue film, so if you are getting .0015", there is not really enough room for glue. I like the .003" answer for most glue joints.

If these are for drawers, and made by machine, make a test box from scrap trying to achieve your .0015" gap, let the wood sit several days after cutting the dovetails, then rub glue all over those suckers and see if you can bang them together. Maple gets real chippy when you start banging it hard, I learned this the hard way. Seriously, bang out a quick sample and do a live glue test, and look at your results. This is a visual art more than a science. This will give you more information than I can or a set of feeler gauges can, unless you are making the dovetails as a birthday present FOR your feeler gauges, then by all means let them be your judge.:cool:

PS: I use feeler gauges to set up machines but it honestly never even occurred to me to use them for any other tests. At least one of us may need therapy.:D

[Sean Rainaldi]

Well, most glue makers are looking for around a .003 to .005" glue film, so if you are getting .0015", there is not really enough room for glue. I like the .003" answer for most glue joints...PS: I use feeler gauges to set up machines but it honestly never even occurred to me to use them for any other tests. At least one of us may need therapy.:D

Probably I need the therapy!


On the .003 - .005 glue film gap, would that also apply to hot hide glue?

[Joe Chritz]

However much a solid smack with a palm is to seat them. I figure if I can pick up four sides of a box without them falling apart (before glue) it is just right.

Interesting phenomenon is that if you have a .500 hole and .500 dowel they won't go together without help. You are about as good as it can get.

Joe

[Steve Schoene]

I think that number is the spread thickness. The clamped glue line would want to be more like 1 or 2 thousandths thick. And it is the fit of dovetail joints that provides the clamping. Snug is right. Tap tight for sure.

[Dan Friedrichs]

If you're trying to get a gap of 0.003", you're trying to get a space of less than a human hair's width. Good luck.

[Steve Schoene]

Gaps of less than that are common for dovetails cut in drawers with poplar drawer sides. The fit is close enough that there is just a bit of compression in the poplar as it is tapped or clamped into place. The gap is essentially zero. I'm not advocating any measurement of dovetail tolerances. They should be snug. I end up making one or two of them snug with a sliver of wood glued in place after they have been glued up. In maple, there has to be more room since it doesn't compress very easily.

[Alan DuBoff]

Much too often we loose perspective on what we're really trying to accomplish. We are working with wood, not tool steel or precision machinery. The sawdust itself is larger than .0015 and the relative humidity will cause the wood to expand and contract more than this.
...
Leave the precision to the machine shop and enjoy woodworking....
Then prey tell, why do so many folks use a tailed router to accomplish what has been done with wood by hand for years?

To me, using a tailed router is like trying to work wood like metal.:o

Why does it need to be exactly the same? Why do they need to be perfect?

Sure, I'll never get them perfect by hand, but I will always shoot for those results. And I have learned that I will be happy with my results even if there is a gap...nothing a ball pein hammer can't fix. Closes the gap right up...

[Roger Jensen]

OK, I'm not saying this is right or wrong, but I just happened to be looking at the Sommerfeld web site at their Katie jig. On their tool description they have the following quote:

"The perfect glue gap of .006"-010"-between pins & tails"

I have no idea if this is correct, other than I have seen Marc Sommerfeld at a woodworking show and he seems like a pretty sharp guy.

[John Keeton]

...nothing a ball pein hammer can't fix. Closes the gap right up...
Alan, does this mean that if I am using an 8# sledge, I need to work a little harder on my accuracy?? Just curious.

Actually, I am really enjoying this thread as I just finished acquiring the various "implements" with which to embark on this handcut thing - and I shudder to think what my first gaps will be. But, whatever they are, it will be fun and you guys give me hope that I can accomplish this!

Also, rest assured, that if my first one is tight - you will hear about it! If not, it is winter, and we need wood for the fireplace.

[Sean Rainaldi]

...Actually, I am really enjoying this thread as I just finished acquiring the various "implements" with which to embark on this handcut thing.

Speaking of handcut dovetails, can anyone suggest a hand cut "dovetail kit", with a saw, chisels, maybe templates and such? Or do these items need to be purchased separately?

[John Keeton]

Sean, I am sure this will invoke responses from others, but I have really enjoyed the Rob Cosman DVDs and book. They are informative, and provide a good list of needed tools. You can even watch his 3.5 minute dovetail video and get a good idea of what you need. He sells some of the items, although they are probably cheaper elsewhere. Keep in mind that he is sponsored (it appears) by Lie Nielsen. Not that such a sponsorship is a bad thing, but I think there are other quality tools out there.

There are also other sources for the fret saw, etc. PM me if you want my list - and others may offer theirs as well. Keep in mind that I have yet to cut my first dovetail, so my "list" may not be particularly reliable!!

[Marcus Ward]

Ahhh you silly wood machinists. Frank Klausz can cut better looking dovetails than your router in his sleep and he hammers his together. Are you guys all sure the OP isn't just pulling our legs?

[Marcus Ward]

Sean, you don't use a template or a kit. You eyeball it based on scribed lines. Seriously, it's easier than you think. A nice sharp dovetail saw, a chisel, and a mallet are all you need. Maybe a marking gauge, if you're really anal retentive. ;)

Can I say anal on here?

[Clifford Mescher]

OK, I'm not saying this is right or wrong, but I just happened to be looking at the Sommerfeld web site at their Katie jig. On their tool description they have the following quote:

"The perfect glue gap of .006"-010"-between pins & tails"

I have no idea if this is correct, other than I have seen Marc Sommerfeld at a woodworking show and he seems like a pretty sharp guy.
I'm guessing that glue manufacturers recommend about .003-.005 gap between wood for the glue. Two sides for each dovetail. Double the .003-.006 gap and you have the .006-.010 gap.Clifford.

[Sean Rainaldi]

Thanks John I’ll check it out. I could imagine that after investing in top quality hand tools for hand cut dovetails that the price could be pretty close to a good dovetail jig but I’ll sure look into it.

Marcus,

If you mean I am pulling your leg about the .0015 gap between pin-tail I can get with a Route-R-Joint, I swear on my mothers grave that I am able to do that.

I want to do wider than 14 inch boards which is why I am thinking about getting Leigh jig to replace it – I hear it’s possible to index the template over with my current jig for wider boards, but that will introduce error in the joint fit and probably take a lot more time and aggravation for me to set up. Plus I want a new toy!

[Sean Rainaldi]

Sean, you don't use a template or a kit. You eyeball it based on scribed lines. Seriously, it's easier than you think. A nice sharp dovetail saw, a chisel, and a mallet are all you need. Maybe a marking gauge, if you're really anal retentive. ;)

Can I say anal on here?

Cool thanks!

With what instrument do hand dovetail crafters mark the dovetail angle with?

[Frank Drew]

Sean

Machine cut dovetails are perfectly appropriate for wide boards, such as for casework. Especially if you're doing a run of them (more than one box).

I prefer hand cut for drawer sides and other work that shows, for cosmetic rather than structural reasons. As Marcus notes, hand cutting is pretty low tech and is done, and the results are judged, by eye. A bevel gauge and a small square for layout are the only measuring instruments I'd use. I can't imagine checking my fit with a feeler gauge.

[Just saw your last question: The adjustable bevel gauge is for the angles; you set it by eye, by what angle looks good to you, within reason. You can also buy or make dovetail gauges, with preset angles, but IMO they're superfluous if you've already got a bevel gauge, which is a useful tool for lots of other layout needs.]

[Marcus Ward]

Sean: Frank Klausz appears to eyeball his, some people use a gauge that has the proper angle on it. You can make one pretty easily too. Lee Valley sells some nice stuff for marking dovetails.

http://blog.lostartpress.com/2008/03/19/Dogmatic+About+Dovetail+Angles.aspx

And the 14 deg marker:

http://www.leevalley.com/wood/page.aspx?c=2&p=32586&cat=1,42936,50298

No I meant pulling our leg about caring about a .0015 gap in your dovetails. At what humidity did you determine that? Have you plotted it at other humidities? What I'm trying to say is, "Put it together and keep going, it doesn't matter as long as it's snug." :)

[Sean Rainaldi]

Sean: Frank Klausz appears to eyeball his, some people use a gauge that has the proper angle on it. You can make one pretty easily too. Lee Valley sells some nice stuff for marking dovetails.

http://blog.lostartpress.com/2008/03/19/Dogmatic+About+Dovetail+Angles.aspx

And the 14 deg marker:

http://www.leevalley.com/wood/page.aspx?c=2&p=32586&cat=1,42936,50298

No I meant pulling our leg about caring about a .0015 gap in your dovetails. At what humidity did you determine that? Have you plotted it at other humidities? What I'm trying to say is, "Put it together and keep going, it doesn't matter as long as it's snug." :)

Never plotted humidity but I live in Michigan - we have humidity extremes here.

Thanks for all the great info!

I will probably get into hand cut dovetailing at some point seems like a lot of fun - I will prob get that DVD – maybe do it on an heirloom project like a blanket chest.

In the mean time though, if I don't get the kitchen cabinets done soon my wife will kill me so I think I better get a dovetail jig and get going on the 11 drawers I owe her. It seems I have started to turn the kitchen re model into my hobby.

I can only imaging her fury were I to tell her - honey - I want to laboriously and slowly cut each and every dovetail by hand...

[Marcus Ward]

Expediency is important. :) Good luck!

[John Keeton]

Expediency is important. :) Good luck!
Most surely when a wife's "fury" is added to the mix!! Get a jig - quickly!

[Chris Padilla]

Frank says it is SO EASY:

http://www.youtube.com/watch?v=G-o4jryTkUc

[Frank Drew]

In the mean time though, if I don't get the kitchen cabinets done soon my wife will kill me ...

Sean,

I wouldn't hand cut dovetails for normal built-it kitchen cabinets, and unless it was a freestanding unit that would go with the client when they moved, probably not machine cut ones, either. Maybe for a reproduction hutch or whatever meant for a kitchen I'd hand cut.

My basic "good" drawer for pieces like wall units, library bookcases or closet fittings, better quality kitchen non built-ins, were machine-cut using Baltic Birch for the box and applied fronts; for custom freestanding furniture, always half-blind hand cut.

[Alan DuBoff]

Alan, does this mean that if I am using an 8# sledge, I need to work a little harder on my accuracy?? Just curious.
You don't use the ball pein for force, you use the ball pein to pein the wood together. Sure, you can use an 8# sledge if you like, but I wouldn't recommend it. My $0.02.

[Alan DuBoff]

Ahhh you silly wood machinists. Frank Klausz can cut better looking dovetails than your router in his sleep and he hammers his together. Are you guys all sure the OP isn't just pulling our legs?
In fact, I have saved his quote, because I think it is one of the best quotes I have heard in a while...

"Put some glue on it and put it together. Slap-slap, If it's too tight,
don't force it, just get a bigger hammer...bam, bam,
bam-bam-bam...bam-bam-bam-bam-bam..."
Frank Klausz

That is classic! ;)

Here's the 3-minute dovetail the quote comes from (http://popularwoodworking.com/article/klausz/).

[Jim Dunn]

I've got to agree with Dave on this one...


Me too.....:D

On another note as an X tool room machinist, haven't been in a tool room for 20+ years, I find myself looking for perfection when none is possible nor necessary.

[Michael Gibbons]

Cool! Do you also use laser diffraction spectrography to determine the gap width? I'd use a tricorder if I were you...

[mike holden]

Sean said: "In the mean time though, if I don't get the kitchen cabinets done soon my wife will kill me so I think I better get a dovetail jig and get going on the 11 drawers I owe her. It seems I have started to turn the kitchen re model into my hobby.

I can only imaging her fury were I to tell her - honey - I want to laboriously and slowly cut each and every dovetail by hand... "

Eleven drawers - Piker!

Try 60! Only 55 show, there is a hidden drawer in each as well. You CAN do eleven! Go for it!

Mike

106979

106980

[joe milana]

What about glue? I find that by the time I get all the glue (titebond I) spread and everything fitted, the wood swells and I have a hard time "pounding" things together. Would a slow set epoxy or poly glue act as a lubricant?

[Harry Goodwin]

I'm with David. I wonder why rules and scales used in woodworking for former generation included 64ths at the most. If you can't see it to read the scale its a metal working term. Thousand's are probaby the rsults of people who want to sell a great array of new tools. Somethings simply have to be right other measurements can vary and never be noticed or have any negative elements. Harry