FlyMaster

I'm wondering if any has come up with a formula for calculating the spacing between cuts when cutting dovetails. By my calculations, it should be sometime like the following:

spacing = cutter_diameter x sin(90 - cutter_angle) x 2.
so if you had a 3/4" 7 degree cutter, your spacing should be ~1.35"

This is for those of us that DON'T have all the Incra templates.

Can anyone confirm? (I'm trying to be accurate while working on a project with a few remaining boards of 200+ year old oak)

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bobj3

Hi FlyMaster

This may help with your question...▼

http://www.canadianhomeworkshop.com/...dovetail.shtml

http://www.ukworkshop.co.uk/forums/v...a85b89bf5d2278

Bj

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PodCast videos
RWS on YouTube

http://www.routerforums.com/86898-post1.html
Besure and click on the Up Arrow key ▲ on the Youtube video, you can select other youtube videos on router tables
http://www.woodworkingonline.com/?s=dovetail
Machine Cut ▼
http://www.woodworkingonline.com/200...cut-dovetails/

http://www.woodworkingonline.com/woo...podcast-store/

http://www.woodshopdemos.com/menu2.htm

Bob J.

Mike

In one issue of The Woodworkers Journal Ian Kirby details his method for hand cutting dovetails. If you want to use a router to cut your dovetails you can buy a jig from Harbor Freight for about $30 that is virtually identical to Rockler's 1/2 blind dovetail jig but at less than half the cost. You will find that routers are too difficult to control for accurate dovetails without a jig.

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Mike

Dr.Zook

Hello FlyMaster and welcome to the RouterForums. I like the fact that you jumped right in and asked a question.

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Dave
the "Doctor"

In woodworking there is no scrap, only firewood.

FlyMaster

Dr. Zook - Love the quote - no scrap, only fire wood. Matter of fact, we've been using left over sawdust (in cups w/wax) as campfire starters.

Update on the calculation, I think there should be a factor on the depth of cut multiplied by the sin of the angle. Still playing around with in to confirm.

harrysin

FlyMaster, why on earth would you need to do any calculations, especially using higher maths. when making dovetails either hand or jig made? I'm surprised that others, especially Bobj3 and Joe haven't raised the question or has it just been beginners luck that my dovetails have turned out OK?

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Harry

bobj3

Hi Harry

I was going to BUT some woodworker look down on any one that needs to plug in a tool to cut dovetails ,,, I call them the Roy Underhill type and will only use hand tools that are made in the 1700 to 1800s ,it's true the dovetail joint has been used in wood const. for a long ,long time and most the pros.don't need to use math they just mark it and cut it out, my grandfather was like that but I'm sure it took him years to get it down right....but now days you and I can do the same thing with a router and a jig in about 1/10 of the time and they come out right every time unlike the hand cut type.

But then woodworking is about having fun in your own way...

Bj

__________________
PodCast videos
RWS on YouTube

http://www.routerforums.com/86898-post1.html
Besure and click on the Up Arrow key ▲ on the Youtube video, you can select other youtube videos on router tables
http://www.woodworkingonline.com/?s=dovetail
Machine Cut ▼
http://www.woodworkingonline.com/200...cut-dovetails/

http://www.woodworkingonline.com/woo...podcast-store/

http://www.woodshopdemos.com/menu2.htm

Bob J.

FlyMaster

Gents,
Thanks for the link to WWE (woodworkersedge). The needle pin jig on next on the list after I get a handle on this other stuff.
Harry, The reason for the calculations is for my first crack at double/inlaid dovetails using different cutter sizes & angles. I need to be dead on for the tail/pin alignment on those (or at least close as the eye can tell). Base on that, I’ve invoked the “higher math”. Not sure that I’d really call sin, cos, tangent “higher math”, more of a jr. high level math don’t ya think? I remember calc 1, 2, 3, differential equations, and linear algebra as needing a bit more gray matter than the old “opposite over hypotenuse” stuff. But hey, I’m still learning this router & wood stuff so it’s back to school for me too. Once I get the hang of getting it right on the router table, I’ll try the hard stuff – by hand.
Thanks again!
FlyMaster (aka –O.F.I.S.)

harrysin

Flymaster, you must forgive me for not remembering much about calculus but I finished school at the end of 1949 and although I spent fifty years in the consumer electronics industry, reaching the top of my profession, manipulating simple formulae was the only maths necessary. Going back to dovetails, wouldn't an Incra jig solve all of you're problems, whilst I haven't used one, I have seen several live demonstrations and was very impressed.
Finally I really would be interested in finding out how many members of the forum could still pass a calculus exam. and how many could not.

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Harry

curiousgeorge

Duh. What's calculus?
I subscribe to the Bob & Rick no math methods.

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George

PLEASE! PLEASE! Fill in your first name and location in your profile. I like to know who you are and where you are from. If you don't want me to know who you are, then I don't want to talk to you.