# What's the "proper" way to cut a dovetail for chuck jaws?



## Quickstep (Apr 10, 2012)

I've been cutting outside dovetails on my rounded peppermill blanks using an EZ wood square cutter. I cut the angle to match the angle of the chuck jaws and I cut the depth so that I have maximum contact, but I don't let the blank bottom out in the jaw. Sometimes though, particularly if I get a catch, the blank comes loose, gets wobbly and well, you know what happens from there. Any tips to be had for improving the grip on the wood by the chuck?


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## 9thousandfeet (Dec 28, 2014)

Quickstep said:


> Any tips to be had for improving the grip on the wood by the chuck?


 I don't think it matters what tool one uses to turn the tenon (I use a 3/8 spindle gouge usually, or a detail gouge—whichever is closest to hand), but the best hold is obtained when the tenon is a good fit to the jaws being used. 

I do pay attention enough to get the angle pretty close to the dovetail angle of the jaws (I use the smooth "Vicmarc" style jaws, not the "Oneway" profiled style) and I do focus carefully on the diameter so that the tenon is real close to the jaws "perfect circle" diameter, which is just a little bit bigger than the diameter when the jaws are closed all the way.

I rarely have a tenon more than 1/4" long though, which I've found to be plenty long enough to stop the tenon from popping out of the jaws and is nowhere near long enough to bottom out in the jaws. (I often hold work with a 1/8" long tenon for that matter, and seldom have problems so long as the timber is sound and the tenon is otherwise a good fit for the jaws).

For long workpieces (like peppermill blanks, say, or candlesticks etc) I use the same approach for the tenon, but use the tailstock as backup insurance until the last possible moment.

Getting a catch on a long workpiece with no tailstock backup is going to be a problem no matter how the workpiece mounted.
A heavy catch will exert an enormous amount of leverage if it happens 10 or 12 inches from the mounting. You can even pull screws out of a faceplate mount in a situation like that.


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## NCPaladin (Aug 7, 2010)

I have Nova's and until you get to the 100mm or larger there is no dovetail on the inside of the jaws. You cut the tenon/spigot straight.

I do cut a tenon longer than most folks, normally about 3/8" or a little more.
Like 9000, I pay pretty close attention to the diameter. Nova jaws have 2mm removed when they are split apart. For dry wood I go about 4-5 mm larger than fully closed. For green wood to return I go about 12mm larger in order to have wood to retrue when dry.

I also agree that anything hanging out 6" or more can be a problem and I use spigot jaws and make the tenon 1"+ long.


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## NCPaladin (Aug 7, 2010)

I would also add that one of the main problems is the area which the top of the jaws seat against is not flat. This flat area provides a lot of the support. If the area is curved then the item can rock fairly easily.
Stuart Batty has three excellent video. Just look for spigot/tenons, recesses, and chucks & jaws. Each video is 12-15 minutes. I admit I do not fuss over them as much as Stuart but the explanation is clear.
https://vimeo.com/woodturning/videos/sort:alphabetical/format:thumbnail


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## Bill Boehme (Feb 9, 2014)

If you are turning green wood, you will need to frequently stop and tighten the chuck because green wood will compress under load and this means that the grip on the tenon won't be quite as tight as it was when you started. The other thing is to not get catches ... seriously, if you are getting catches then you are doing something wrong. If you live near another turner, getting help is the best way to figure out why you are getting catches. Otherwise, finding the answer will be a lot harder. When you get a catch, stop and figure out the reason.


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## firehawkmph (Apr 26, 2008)

I have a Vicmarc chuck also. I cut my dovetails using a skue with a peeling cut. The angle on the skue matches up with the dovetail on the jaws pretty well. Like Bill said, there must be a true shoulder for the jaws to register against when you tighten up the blank. I turn peppermills 12-16" with no problems coming loose. 
Mike Hawkins


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## Bill Boehme (Feb 9, 2014)

I think that you can buy a special scraper to cut dovetails at the right angle to match the chuck jaws, but I don't have one. I normally use either a bedan or a skew chisel. With the skew, I just lay it flat and use it as a scraper like mike does. With the bedan, I cut a square tenon or mortise and then tilt the tool on edge and swing the handle to get the desired angle cut.


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## NCPaladin (Aug 7, 2010)

If you want to make one you can use an old flathead screwdriver.
Quick to grind the angle on the tip to match you chuck jaws.
You can just push straight in like a parting tool or bedan and then pull/push to the side to form the dovetail.


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