drilling reces

[Brandon Speaks]

I just got my new forstner bit to drill recesses, a 50mm one for my 50 mm Nova jaws. What I am finding is that the hole is a touch too small. Are my bit or jaws out of spec or did I get the wrong size?

[Brandon Speaks]

Well looking at the thread that gave me the idea they recommended 2 1/16 which is a hair over 52mm so looks like I may have screwed up in ordering.

If I order again should I get 2 1/16 2 1/8 or 55 mm? I cant afford another incorrect size $20 bit.

[John Keeton]

Brandon, I use 2 1/16" for my Nova jaws and it works quite well.

[Len Mullin]

Brandon, I use a 2 and 1/8" forstner bit, I like the little bit of extra space.

[John K Jordan]

I just got my new forstner bit to drill recesses, a 50mm one for my 50 mm Nova jaws. What I am finding is that the hole is a touch too small. Are my bit or jaws out of spec or did I get the wrong size?

Brandon,

I don't have a 50mm bit to try but I use both 2-1/16 and a 2-1/8 carbide Forstner bits for recesses. The 2-1/8 is larger but still works ok but I prefer to use the smaller one.

The further the recess diameter is from the closed jaw diameter the less secure it can be but both of these sizes have worked OK for me (approximately 52.4mm and 54mm) in walnut and cherry. It seems like 55mm should work OK especially on softer wood but if buying another new bit you might go for the 2-1/16.

If you are turning a dovetail after drilling (which I do with harder wood) the 50mm should work fine, of course. How easy this is to do depends, of course, on the geometry of the blank and how you can hold it!

Also, did you measure your jaws with calipers? I don't remember exactly what mine measure but I could check. If a bit large, you can turn them down a little while mounted on the wood lathe with woodturning tools. Earlier I posted about turning down 25mm steel jaws to 20mm using a Thompson scraper - this was slow but worked fine. I have a bunch of Nova chucks and since all the new chucks come with the 50mm jaws I have a box of spares - send me a message if you want to experiment and don't have a spare set. It should be easy to make them smaller and keep the dovetail shape. Here is the thread about turning steel, where I wanted a non-dovetail shape: http://www.sawmillcreek.org/showthread.php?255923-Turning-steel-on-the-wood-lathe-with-woodturing-tools

BTW, I bought carbide Forstner bits in the hopes they will work for years. A HSS or carbon steel bit probably cuts a lot cleaner hole but that doesn't matter much for recesses. They will likely need to be sharpened periodically.

JKJ

[John K Jordan]

I'd be interested in knowing how the drill recess performs when turning, since there is no dovetail? Also, when do you drill as opposed to cutting in a dovetail recess.

Joe,

My experience: in softer wood like walnut, cherry, soft maple, etc. the dovetail of the chuck jaws presses into a drilled hole in the wood and forms it's own "dovetail". For me this has worked very well - I've never had one come off. If it is ever necessary to take it off the jaws and remount and hope to have it even close to registered (iffy at best, regardless) you have to make sure the jaws are in exactly the same place.

I prefer to drill when my blank is flat on both sides (cut from a plank), quicker, especially if I'm doing a bunch. I usually cut the recess on the lathe if just doing one piece, especially if the blank is held by a screw chuck.

If the wood is hard like osage orange, black locust, and lots of exotics I will cut a dovetail since there is little give to the wood. Also, the dovetail makes sense for large and heavy blanks. In addition, if the jaw diameter is not very close to the recess diameter the dovetail will help hold more securely. One more thing - I knew a turner who was horrible at tool control - I saw the same bowl come off his lathe three times. He needed a good dovetail (and to learn how to turn without catches!) That's all I can think of at the moment.

JKJ

[Joe Frank Porter]

thanks, Joe