7 or 14 degrees for sliding dovetails? - Woodworking Talk - Woodworkers Forum
Old 03-21-2014, 11:26 AM Thread Starter
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7 or 14 degrees for sliding dovetails?

What are the advantages of 7° vs 14° dovetails used in sliding dovetail joints?

I'm building a bunch of shop cabinets and drawers using 3/4" plywood (5 ply, maple veneer) using a combination of sliding dovetails and dadoes. I've been using a 14° dovetail bit but need to get a new one. I'm wondering whether a 7° dovetail bit (like the Freud 22-114) would be better for sliding dovetails cut in plywood. The only comments I've seen so far are that the 7° joint might be stronger but the 14° cut "looks better". What does this community think?
Thanks.
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Old 03-21-2014, 01:15 PM
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7 or 14 degree dovetails

I go for 7 degrees. Unless the joint is for show I can't think of a reason not to go for strength, especially in plywood. When I have used them it has been for shelf supports and once the joint is made there is no reason to slide the joint apart,
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Old 03-21-2014, 03:56 PM
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+1 to above post

Pure mathematics is, in it's way, the poetry of logical ideas. - Albert Einstein.
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Old 03-21-2014, 04:04 PM
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I do not think, for most applications, that there is enough strength difference to be concerned.

If you are building a project for which great strength is a major consideration then use the 7 degree. Otherwise let your taste be the determining factor.

George
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Old 03-29-2014, 01:26 PM
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I'm not sure how well sliding dovetails will work in plywood. The corners of the tails or of the dovetailed dado may tent to split off?? The 7 Degree should be most resistant to breaking off.
I have only used sliding dovetails in solid stock. I would be interested in comments of anyone using them working in furniture grade plywood. I may have to go and try. I seems the cross plies would limit sliding if they did not break off the corners.
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Old 03-29-2014, 02:04 PM
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Quote:
Originally Posted by Midlandbob View Post
I'm not sure how well sliding dovetails will work in plywood. The corners of the tails or of the dovetailed dado may tent to split off?? The 7 Degree should be most resistant to breaking off.
I have only used sliding dovetails in solid stock. I would be interested in comments of anyone using them working in furniture grade plywood. I may have to go and try. I seems the cross plies would limit sliding if they did not break off the corners.
x2

I would like to hear about tearout (or lack thereof) of the plywood as well.

Mark

"Measuring is the enemy of accuracy." Chris Schwartz
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Old 03-29-2014, 11:24 PM Thread Starter
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So far, I've used sliding dovetails for a couple of 12" deep drawers to attach the drawer face to the drawer sides, and also the back wall of the drawer to the sides. Since the sliding dovetails were just 12" long, they slid together fine and seem to have glued up nicely. The dovetail groove in the face and back pieces cut fine with no tear-out. However, I did get terrible tear-out when cutting the male part of the dovetail in the ends of the side pieces. I solved that by scoring both sides with the table saw prior to cutting the tails on the router table. Probably could have scored with a sharp knife instead. I got a 7 degree dovetail bit now and for fun I will try a longer sliding dovetail instead of a dado for the next drawer's floor-to-sides joint - that will be a 23" long joint. I suspect I'll find that the joint needs to be rather loose in order to slide together, in which case it may not be very strong. If it doesn't work nicely then I'll just use a dado. No need for a tapered sliding dovetail for these shop cabinets.
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