Dovetail Calculator

[Rob Luter]

When I started doing hand cut dovetails I always seemed to lay out the tails such that the pin sockets were not a very good match to the chisel widths I had. When I sized the socket bases to match the chisels I wasn't always happy with the size of the pin ends. Looking for a solution that didn't involve repeated layout and erasure on the workpieces, I formatted a little spreadsheet (attached) that makes a nice little reference chart for my toolbox. It's helped with planning.

Just enter the slope of the dovetail in the yellow box and the dimensional matrix below will update. Print out the chart for reference.

I hope some will find this useful.

- Rob

[Michael Gibbons]

When I started doing hand cut dovetails I always seemed to lay out the tails such that the pin sockets were not a very good match to the chisel widths I had. When I sized the socket bases to match the chisels I wasn't always happy with the size of the pin ends. Looking for a solution that didn't involve repeated layout and erasure on the workpieces, I formatted a little spreadsheet (attached) that makes a nice little reference chart for my toolbox. It's helped with planning.

Just enter the slope of the dovetail in the yellow box and the dimensional matrix below will update. Print out the chart for reference.

I hope some will find this useful.

- Rob If I'm reading this right, are you getting too carried away? You'd have to have 30 different chisels, maybe more, to fit all those combinations. Learn to get close and move the chisel. If your doing it by hand, follow Rob Cosmans system by using the two divider method. It's in his Handcut Dovetail video.

[jerry nazard]

Rob,

That is cool. Thanks!

-Jerry

[John Keeton]

Rob, that is a neat calculator, but I am with Michael on this one. Cosman's divider method is fast and failproof. As I am new to handcut dovetails, I have recently worked through some of these issues - particularly getting clearance on the pin sockets with my existing chisels. I use the Veritas 1:8 marker, and have learned, by sight, the minimum size of the pin in which I can use the 1/4" chisel I have. I just use the dividers to get the pin width, and go with it - no calculations or measurements at all.

Hopefully, I will soon be able to use my 1/8" Blue Spruce chisel that has been ordered to get even smaller pins!

I do appreciate the work you put into this and it will be very helpful to those not using the divider method.

[Jim Koepke]

Too much thinking can lead to mistakes.

One method I have seen in FWW is to make a simple tool like a bevel gauge. The tongue is marked out for even spacing and is longer than the widest board one plans on using for a dovetail joint. There would be a mark for the edges and the dovetails in between. The out side edges are aligned with the board, then the bevel is slid up to the end of the board and the marks are transferred one at a time. Kind of transfer the first mark, slide, mark the second mark and so on. I think this was made for a pins first cutter, but it can be used to mark the end for the tail kerfs, then with a bevel gauge or dovetail gauge the rest of the marks could be made.

Very little thinking involved, less mistakes and no measuring except to make the little tool. One can make different tongues for different sizes.

If this sounds confusing, let me know and I will try to make one and take a few pictures. It shouldn't take more than a few minutes to make. For me the hardest part will be deciding which pieces of scrap to use.

Personally, I usually space them out by eye, tails first. Then mark with a gauge.

jim

[Mark Singer]

I make a sketch of the pattern to scale. Transfer to a wood template with pencil markings and then mark all the tail boards.

[Al Navas]

Mark,

I believe that Frank Klausz does the exact same thing - I knew that brilliant minds worked alike, and this is another example! :D :cool:


.

[Jerome Hanby]

I ran across a program once (may have been an online application) that let you input the particulars, then gave you a printable template for the pins and tails. For me, unless it also came with a woodworker to apply the template and chisel out the waste, it wouldn't do much good :D

[David Keller NC]

Rob - Not sure I'll use this all that much in the shop (I try to avoid measuring things as much as possible), but being an engineer, I have a soft spot for cool spreadsheet examples, and this is a pretty elegant one. If nothing else, your calculator will give me a way to visualize approximately what the final result will look like.

One thought - On "period" furniture, one almost never finds thicknesses in quarters of an inch, they're almost always combinations of 1/8, and for case sides, for example, they almost always measure 7/8" in thickness, so adding a line for that might be helpful.

[Mark Roderick]

It's a great little spreadsheet, but aren't there two missing variables, the width of the wood and the number of tails you want?

[Rob Luter]

It's a great little spreadsheet, but aren't there two missing variables, the width of the wood and the number of tails you want?

Mark - I have another spreadsheet for that. I'll post it tomorrow from work.

Michael - While I aspire to someday have 30 different chisels (yet another slope after planes and saws :D) I really just use the chart to "gut check" the plan. It's nothing more than a quick reference.

As an Engineer I'm a sucker for little tools like this. I'm working on a method to feed the tabular dimensional results into an AutoCAD or Solidworks drawing so it will edit the image "real time" as thickness and/or angle variables are changed. I may get some shop projects done first though :rolleyes:

[Jim Koepke]

As an Engineer I'm a sucker for little tools like this. I'm working on a method to feed the tabular dimensional results into an AutoCAD or Solidworks drawing so it will edit the image "real time" as thickness and/or angle variables are changed. I may get some shop projects dome first though

Too bad the spread sheet's graphing abilities couldn't be used to make a dovetail graph instead of pie charts.

jim

[Tom Henderson2]

Well I'll be dipped.

I've used Excel daily for over ten years. And I never noticed the ability to use fractions as a numeric format.

Live and learn!

-TH

[Rob Luter]

It's a great little spreadsheet, but aren't there two missing variables, the width of the wood and the number of tails you want?

Here's the other spreadsheet I mentioned. I am not the author, but I can't recall where I got it.

[chet jamio]

In the Format Cells box in the Number tab, select Custom as the Category. In the input line under Type, enter "# ??/128" without the quotation marks. This will force all the fractions to round to the neareast 128th.

[Rob Luter]

In the Format Cells box in the Number tab, select Custom as the Category. In the input line under Type, enter "# ??/128" without the quotation marks. This will force all the fractions to round to the neareast 128th.

While I'd like to think I can work to the nearest .0078", I feel fortunate to hit 1/64" (.0156") regularly :o