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Forum topic by JerryinCreek posted 02-07-2016 11:11 PM 530 views 0 times favorited 6 replies Add to Favorites Watch
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JerryinCreek

155 posts in 1309 days


02-07-2016 11:11 PM

Haven’t turned a thing yet but have a midi lathe and Nova G3 chuck ordered. My desire is to make small bowls. The on-line manual for the chuck says I need to make a bevel in the base of the bowl for the chuck to grab. It’s supposed to be 15º.

I looked at some Sorby skews and they’re available in widths of 1/2, 3/4, 1 and 1 1/4”. Which do I want? And, is 15º the normal bevel from the manufacturer?

Any help would be greatly appreciated!

-- Jerry, Johnson Creek, WI "If it was meant to be different it would be."


6 replies so far

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toddbeaulieu

781 posts in 2472 days


#1 posted 02-07-2016 11:42 PM

I mostly use a bedan for this. I really don’t think you need to get caught up angles,trying to be precise. Dedicated dovetail chisels exist but I think that a gimmick. You can do the final mortise edge with a skew. Again,it’s not scientific. You’ll eventually have multiple sizes. Watch CL for used sets.mi got a giant set of sorbey.

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Nubsnstubs

826 posts in 1198 days


#2 posted 02-08-2016 12:31 AM

If you’re getting the standard 50 mm jaws on the G3, you can use it in the compression mode also. Then all you need is a 90° tenon which is a piece of cake to make. All you need is to know is not bottom out the tenon in the jaw bottom. The bowl bottom should rest on the jaw face. Also, there has been a lot of discussion about the size tenon to use. Nova states to make your tenon about the size of the jaw opening when it is most round. With the 50 MM jaws, that put the tenon towards 1 13/16”-1 7/8”. I did that early on, but after losing about 4-5 pieces at the tenon, I went to making all my tenons at 2 1/4”. Only lost one out of 300+ forms…. Tenons I make are 1/4” deep or long.

It sounds like you are going to be using the expansion mode, or a recess attachment. I’ve only used a recess once, and only because I made my tenon too small on the 100 mm jaws on a SN 2 chuck. I had to use the tenon, and it started breaking as I was turning, but stayed together until I cleaned it up after getting done with it. ............ Jerry (in Tucson)

-- Jerry (in Tucson)

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JerryinCreek

155 posts in 1309 days


#3 posted 02-08-2016 02:08 AM

Jerry- thanks for the advice! No, wasn’t really planning on using the expansion mode – had no idea what mode I’d be using! Just looked at the on-line manual and saw the information about a dado I needed. Didn’t know I would be able to make a bowl without it. Thanks – and I will hang onto the rest of the valuable info you gave me!

-- Jerry, Johnson Creek, WI "If it was meant to be different it would be."

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Nubsnstubs

826 posts in 1198 days


#4 posted 02-08-2016 03:11 AM

I’m editing my post above. Fell asleep again, and lost my 60 minute edit window. Below in bold is what I changed.

I had to use a recess, and it started breaking as I was turning, but stayed together until I cleaned it up after getting done with it.

Jerry, The tenon will let you have a bunch of options on what to do to the bottom of your form. When using recesses, you are pretty much stuck with a recess on the bottom of your piece.. My personal choice is use a tenon and when removing it, I always decorate the bottoms with some type of decoration. . ............ Jerry (in Tucson)

-- Jerry (in Tucson)

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LeeMills

273 posts in 769 days


#5 posted 02-08-2016 03:25 AM

I use a recess most of the time.
Nova suggest 1” of wood surrounding a recess. If you work through the math, the amount of wood surrounding a recess is three time the amount of wood in a tenon for the 50mm jaws.
Stuart Batty presents excellent instructions on tenons and recesses.
If you use a recess you can make most of the area with a parting tool. An old screwdriver (flat tip) ground with the 15* works well for cleaning out the little dovetail area.
https://vimeo.com/woodturning/videos/sort:alphabetical/format:thumbnail
There are three
One on Jaws and Chucks, one titled Recess Tenons and Preparing Recesses In A Bowl Blank, and one titled Tenons Part2.

As Jerry stated, with the Nova 50mm jaws you do not cut a dovetail for a tenon, only for a recess.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

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JerryinCreek

155 posts in 1309 days


#6 posted 02-08-2016 03:54 AM

Thanks Lee! You have both been very helpful! Just gave a quick peek at these videos and they are outstanding!!

-- Jerry, Johnson Creek, WI "If it was meant to be different it would be."

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