I need some help with a Bowl from a Board W/ Dovetails

[Tim Boger]

Seems like every weekend my turning interests moves from one technique to another. This weekend I'd like to try a Dovetail Bowl from a Board but really know next to nothing about the Dovetail bit.

I have all the tools just feel stuck on how to get the Dovetail cut centered so that the surfaces of my pieces remain flush once the sliding joint is put together and glued but before I start cutting the rings out of the boards (Maple and Walnut).... it is assumed I'm starting with boards planed to common thickness.

I'm thinking one uses the same bit to make the pin cut on the other boards edge, how do I make it exactly the correct size to fit tight into the tail cut previously?

I've watched a handful of videos last night but never really found the answers I need, sorry about the elementary question, just never done this application before.

I seem to learn best from watching videos,so links would be much appreciated.

Thanks,
Tim

[Michael Mills]

Here is a group of videos by Bob Hamilton which may answer your questions.
http://www.youtube.com/results?search_query=bobham5+true+economy&oq=bobham5+true+economy&gs_l=youtube.3...27922.35047.0.36750.29.23.0.0.0.2 .422.3109.1j9j2j2j1.15.0...0.0...1ac.1.5sJBCyAGz3M
If the link doesn't work search on youtube for ... bobham5 true economy
It is a group of 8 or 9 that make up the entire video.

I have made dovetails with a jig (for flat work) but it is still cut and test to get the exact fit.

[Tim Boger]

Here is a group of videos by Bob Hamilton which may answer your questions.
http://www.youtube.com/results?search_query=bobham5+true+economy&oq=bobham5+true+economy&gs_l=youtube.3...27922.35047.0.36750.29.23.0.0.0.2 .422.3109.1j9j2j2j1.15.0...0.0...1ac.1.5sJBCyAGz3M
If the link doesn't work search on youtube for ... bobham5 true economy
It is a group of 8 or 9 that make up the entire video

I have made dovetails with a jig (for flat work) but it is still cut and test to get the exact fit.


Hi Michael,

I've actually been through the entire series of videos by Bob Hamilton last night. I've made several Bowls from a Board and have a good understanding of that process, it's the actual cutting of the sliding dovetail on the mating surfaces and their fit and alignment that I've not got my arms around yet.

I understand where Bob suggests cutting a (I think) 3/8" slot in the first board that gets the dovetail to allow for the waste to move, but getting the Dovetail bit perfectly centered after that slot has been cut I don't have figured out as yet.

Then on the other piece that gets a pin, I'm assuming it requires 2 passes using the same bit, one on each side to create the pin shape .... do you just keep sneaking up on the size of the pin until it fits snug into the dovetail ?

Scratching head ..... I have a feeling I'm over thinking this.

[Mike Golka]

Tim if you flip the board around and run it through the router again that centers the cut ( each side against the fence) . Do the same for the pin and as you said sneak up on it until you get a snug fit.

[Tim Boger]

Tim if you flip the board around and run it through the router again that centers the cut ( each side against the fence) . Do the same for the pin and as you said sneak up on it until you get a snug fit.

Thanks Mike,

After a few practice runs the details are becoming clear, I appreciate your feedback.

Tim

[Bob Hamilton]

Hi, Tim:
If you run a piece through and then turn it end for end and run it through again with the other face against the fence the cut will automatically be centered. I cut the dovetail groove first and then "sneak up" on the tongue width by making very small fence adjustments and running both faces and test fitting. When cutting the groove you really need to make sure that the bit is cutting on the cheek of the groove that is away from the fence on the second pass or the workpiece will self feed: http://www.youtube.com/watch?v=HV78hzkPlhI&feature=plcp

A proper fit is when the tongue slides easily into the groove with hand pressure alone but has no slop. I have found that if the joint won't slide together easily there is no room for glue. If I need to use a mallet to put the joint together then when the glue is applied the sides of the groove get wedged outwards and the joint is no longer flush.

Good Luck!
Bob

BTW, it is very important that your router table surface have no sag. If there is any sag then the board rides down one side and the bit starts cutting at full depth. As the board passes through the bit it rides back up the other side of the sag and at the midpoint of the cut it will be bridging the sag. The cut will be getting progressively shallower. During the second half of the cut the trailing end of the board comes down the sag so the bit is once again cutting at full depth as it exits the cut.