Dovetail joint ? Any HELP!! for a rookie

[bogydave]

I've never made a dovetail. The picture i'm working of of to build the workbench has blind dovetails. I found 3 ways to make them off the "how to" sites but how to & doing aren't equal. ( all by hand saw & chisel)
The picture shows 4 dovetails (2 sizes) in each joint. I'd be happy with 3 the same size. The dovetail jigs I looked at don't go to 1- 3/4" thick. Since I'm learning as I build the bench, "Time to learn dovetails".
How do I make the blind tails in a 1 -3/4" X 6" board, about 1-1/2' into the board ?
Do I need to buy a router, bits & Dovetail jig? :)
Then : mark the pins (Band saw for the pins?) (waste removal ?)
Hardwood 1 : 8 ? what does this mean.
Now my rookie status really shows. I played with a wood chisel on the maple & WOW that's hard wood.
glueless & clueless Dave.
http://i274.photobucket.com/albums/jj269/bogydave/dovetailjoints-1.jpg[/IMG]

[Don]

Dear Glueless and Clueless in Alaska

We've got to stop meeting like this. Since no one has come to your rescue I'll chime in.

Time to become one with the wood. Unfortunatley, if you had your workbench done you'd be in a better position to do this. Routers and jigs are not necessary on these four corners. Take your time and learn to do it by hand--once. And then never do it again.

The mystery of the 1 : 8 is this. It is the angle of the dovetails and can be set on your sliding T-bevel as such. (you have one, right?) Very simply, on a right angle corner of a board, mark 1" over and 8" up. Connect those points with your sliding T-bevel and you will have the proper (or asked for) angle for marking the tails. Note: When I was in school the angle was 1 : 6, but that's not that crucial. Whatever angle looks good to you will work. The shallower angle of 1 : 8 will make the mortises a little easier.

Accurately layout your tails on the ends of your side rails. This is where the old fashioned dovetail saw comes into play. Make the angled cuts then the two cuts top and bottom. This will leave you to come up with a way to remove the center pieces any way you can, coping saw, bandsaw, chisel.

The mortises are laid out on the ends of your end rails using what you have actually cut on the side rails. There will some slight variation between what you laid out and what you ended up with. You will be better off to use a sharp layout knife to mark your mortises. Here is where your dovetail saw comes into play again. I'm sure you saw this on the other sites. The saw is used on an angle to cut the face and draft of the mortise at the same time. The rest of the work is accomplished with a chisel, sorry. This is how it was done 200 years ago, you'll feel good about it when it's done. The work really pays off if you have contrasting wood to show off your skill.

Tip, when cutting the tails, make a slight draft on the sides, this will compensate for a little error in chiseling the mortises. Wood filler makes errors in your cutting look like a million. Keep in mind you are actually going for strength in this design, cosmetics second. The resin glue you have ordered will fill all gaps and make it solid as a rock.

Here is a pic of the only "hand" cut dovetails I've ever made, thirty-five years ago.

http://www.internetcp.com/gallery/data/503/dovetail_2.jpg

All the best, Don

[bogydave]

Thanks. I ordered a dovetail saw & bought some stanley chisels. Here is an idea I came up with. Use a router to remove most of the tail. Then use a chisel to cut out the rest. OR is it a sin to make round cornered dovetail? I shot a dove once tha ha a slightly rounded tail. I was going to cut the dovetail a little deeper than the 1-3/4" ( if I can get the bit in deep enough) for the pins to fit into. I figured I could clamp this jig to the end of the board. I would draw the dovetail lines on the board & sit the jig over the lines, rout out what I can & then chisel. (sure would be nice to have a heavy workbench with a vise to work on) Is 3 dovetails enough in 1-3/4" X 6"?
Don't LOL at the router bit, it wouldn't even rout the plywood. It's in a snow bank.
1/2" router bit just goes in the beginning of the dovetail then V's out to 1" in the back of the dovetail.
http://i274.photobucket.com/albums/jj269/bogydave/blinddovetailjig.jpg[/IMG]
http://i274.photobucket.com/albums/jj269/bogydave/dovtljigrtr.jpg[/IMG]
I was going to cut the pins close with a band saw.
I know a guy should make at least one project with hand cut dovetails but this is in 1-3/4" Maple & 1/2 blind.
If my idea won't work or has some flaw, PLEASE let me know, I don't have alot of wood left to make throwaway mistakes. I'll be making the 1-3/4" aprons the same way I'm making the top, 3/4" boards & glue (which still hasn't arrived).
Thanks Don & guys for all your help. I'm sure I'll have ?s after the glue gets here.

[bogydave]

Found an 8 degree dovetail bit that has 1-1/4" depth. Eagle & infinity
Whiteside had one 1-1/2 deep but 8mm only
infinity # 18-706.
18-706 1/2" 13/16 wide 1-1/4"deep 8deg $26.90
Would this work? could I make the joint wider than 13/16 by setting up a parallel jig to make 2 passes. Would have to buy a new 1/2" router though :) :) :)
Was hoping to find a 12 to 14 deg bit 1-1/2 deep, but this has potential.
lazy dave

[Don]

Hey, Bogy. Make any kind of "dovetail" you want, I've seen all sorts of different shapes. Anything goes here.

Sometimes we get caught up thinking that a dovetail is the strongest joint out there because it is so rarely used. Not true, a dovetail does have it's advantages but it originated from a need to assemble joints sans glue.

The joint that I use when failure is not an option is a finger joint, the more fingers you have the stronger the joint. Think of it as a laminated joint in a corner. They are relatively simple to make, don't look bad, and you will have complete project failure before the joint comes loose.

dawjr

[bogydave]

No glue in this joint may be the deciding factor. I think I need to let the joint move, due to the top size & severe moisture changes Alaska has. Maybe just glue the 2 front corner joints & let the top move/flex to the back. The directions do say to just glue the end apron , only on the tounge of the slab the first 4" or so of the front , to allow for movement to the back. I think the dovetails are to hold the end caps on & allow movement. ??
It will be a while before I'm mounting the aprons so I have time to decide. Got a call that thet sent the glue to a store in Seattle, I've got a long drive to make. :(
Thanks

[Don]

I can see the logic of the floating end rails. If you are going to follow that method and allow the pins to "float" in the mortises, you'll need to allow for some shrinkage, should that occur as well. If you don't and the top shrinks across the width, then your siderails could be pushed off at the corners. As far as gluing the rail to the tongue of the slab the first four inches or so, consider this. You really only need to fasten it in the center. The wood will then move left and right of the fastened area, unless of course you are going to have one corner hard glued and the other corner float like you wrote above.

The bench that I built has similar end rails that are keyed in place as well. I simply lag bolted them in place at the one third marks. It's worked well. But then again, my bench is an old Chevy truck compared to your Rolls Royce. I'll post some pictures. It's worth a laugh.

dawjr

[bogydave]

I'm thinking about a sliding bolt mount. I had to do it for some synthetic decking for thermal movement. (did it after a piece broke the screws off, Alaska -40 to 100 deg, thats expansion)
A paperclip shaped hole in the apron to allow for some movement, tightened snug enough to hold them, then if it shrinks a little I can tighten the lag bolt.
One near the ends & on in the middle. Can always plug the bolt access if it's in the vise area.
I'm curious what the bench is going to look like when done. Looking for Lexus hope for Toyota (last long time)
I'll keep yuns posted.