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Preferred Jaw Sizes... (Read 535 times)
 
John Grace
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Preferred Jaw Sizes...
Jun 18th, 2017 at 10:18am
 
Just curious...I have about 20 blanks of spalted maple I need to start working through and most are in the 12"-15" diameter and 3"-5" thick range.  What size of jaws do you typically hold pieces this size with?  I have a size and methodology that has served me well for several years now but like many of you, I'm always curious if there's a better and safer way, etc.

thanks...
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Mike Mills
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Re: Preferred Jaw Sizes...
Reply #1 - Jun 18th, 2017 at 11:11am
 
Mine are almost always pragmatic so I stay with about 1/3 base to bowl diameter.  So for a 12" a 4" base or for 15" a 5" base.
My preference is a recess but I do use tenons also.  Sometimes I use both, roughing with a 100mm recess then final turning with my 70mm using a tenon.  Or roughing with the 70mm in recess then a 50mm tenon if the item is smaller.
That probably wasn't much help but it has not been a problem removing excess during the final turning.  I try to use the largest possible especially when green.  For example using the 50mm jaws there is 3X the amount of wood to break away in a recess as there is in a tenon.
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Glenn Jacobs
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Re: Preferred Jaw Sizes...
Reply #2 - Jun 20th, 2017 at 3:44pm
 
All depends on what jaws you have. I use my 50mm for anything that fits my 16 inch lathe. The more round and balanced the blank the better.

Glenn J.
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robo_hippy
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Re: Preferred Jaw Sizes...
Reply #3 - Jun 27th, 2017 at 9:58am
 
Most of the time I use my big Vicmark chuck. Jaws on it are about 2 5/8 diameter for the recess. Going over about 15 inches is a bit of a chore with some vibration issues, but it holds fine. Going bigger won't hurt at all. A recess is my finished bottom.

robo hippy
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Ed Weber
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Re: Preferred Jaw Sizes...
Reply #4 - Jun 28th, 2017 at 10:39am
 
A few extra things to consider that the others brought up.
Are you going to use the tenon or recess (jaw size) as you finished base size?
How aggressively do you remove wood?
Using jaws with a larger capacity than necessary can help with vibration as well as leave enough extra material to refine the base after it is removed from the chuck. (reverse mounted and finalized)
IMO, For the size you mentioned I would use the 100mm jaws. A 70mm jaw would have enough holding power for that size but possibly be too small for the foot. A 50mm jaw  would only be recommended in recess mode, there is not enough wood in a tenon for the diameter you mentioned.
A 100mm jaw requires approximately a 3 1/2" tenon or 4" recess, this is more than enough holding power for those size blanks, even for coring them out.
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« Last Edit: Jun 28th, 2017 at 10:40am by Ed Weber »  
 
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Steve Nicholson
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Re: Preferred Jaw Sizes...
Reply #5 - Jul 3rd, 2017 at 4:00pm
 
I use Super Nova chucks with a 100mm jaw with a dovetail recess and support with the tailstock.
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John Grace
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Re: Preferred Jaw Sizes...
Reply #6 - Jul 4th, 2017 at 3:55pm
 
Update...

I finished rough turning four of the six oak blanks this weekend and used my SN2 70mm jaws as that was the largest I have.  Supported with the tailstock, I didn't have any issues aside from a lot of staining that took some work to clean off.  I must say, it sure is different turning a 16" diameter blank that weighs at or about 30 pounds when I started off...like a gigantic fly-wheel.

That said...I did find a new Rustoleum rust remover product.  Smelled the same as other products I've used but this version comes in a gel and 'clings' better to the iron surface to be cleaned better.
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Don Stephan
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Re: Preferred Jaw Sizes...
Reply #7 - Jul 4th, 2017 at 6:49pm
 
When the banjo or tailstock drags on the lathe ways, I spray some WD-40 on the ways and move the banjo and tailstock back and forth.
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Arlin Eastman
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Re: Preferred Jaw Sizes...
Reply #8 - Jul 8th, 2017 at 1:13pm
 
The AAW and others say to make a tennon 40% of the bowl   Also some people say a tennon or inside dovetail and I have used both. 

Good luck on the turning and am envious about all the spalted maple.  Thumbs Up
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