Turning speed w/130mm chuck

[Hilel Salomon]

I've been having fun/frustration with my McNaughton coring tools and after some unhappy instances realized that part of the problem was when I made the tenon too small or too long. I've used the Oneway #4 jaws and thought I might also use the Supernova 130mm jaws as well. When I looked at the manual though, it said that the 130mm jaws should never be used at more than 400 rpm. That seems awfully slow. Have any of you experienced problems at higher speeds? I have much better luck coring at about 700 rpm.
All advice is welcome-- including criticism.
Thanks, Hilel

[Gordon Seto]

The manual was written by the company's liability attorneys.

[Kevin McPeek]

I have cored using the stadard Nova Jaws and the PowerGrip Jaws on a SN2 chuck. I have never lost a tenon with the PowerGrips but have lost a few with the standard jaws. Tenons don't have to be huge as long as they are cut properly. I rarely use one more that 1/4" tall, maybe 3/8" on a coring bowl. The best grip with the jaws are where it has the most contact, ie when the jaws are perfectly round. That is the size I shoot for, may just a little larger. Maybe someone else can talk better about Oneway jaws, I haven't ever used them.

I don't think I would use the 130mm Nova jaws for coring, they are primarily intended to grip in expansion, IIRC they are not even dovetailed on the inside. I have used them with about a 1/8" recess to turn a 17+" platter but not sure I would use them coring.

I tend to core a little slower that you, I'd say about 550-650 depending on the bowl. I'm not saying thats right, that's just what works for me.

[Bernie Weishapl]

Use the power grip jaws Hilel. They will hold better than the 130 mm jaws.

[Reed Gray]

I consider 400 to be slow for coring, although when I first started coring, that seemed high. For mounting your bowl, you want the tenon to be about 1/3 minimum the diameter of your bowl, so a 12 inch bowl should have about a 4 inch tenon. It is a leverage thing. Too small, and the torque forces can break a tenon, even if you don't have a catch. For me, I use a recess and expand into it. With my big Vicmarc, the jaws are 2 5/8 inches wide. With a 3/16 inch deep recess, I can core up to about 18 inches with no problems. It has taked several years to learn, through trial and error, how much speed to use safely, how much cutting pressure to use, and the appropriate dimentions of the recess that are needed. The closer the fit of the recess or the tenon is to the jaws, the better your grip is. So, if you are using a tenon, and your jaws close down to 3 inches wide, then you want a 3 1/4 inch diameter tenon. If your tenon is 5 inches wide, then you won't get nearly as much steel on the wood with a smaller tenon. Also, when clamping onto a tenon, if your jaws clamp onto the tenon with 2 jaws on the end grain, and 2 on the side grain, the wood fibers will compress differently (less compression on the end grain, and more on the side grain). Rotate about 45 degrees so that you clamp on a bias to the grain. Learning to core with the McNaughton is frustrating, but it is the best coring tool out there.
robo hippy

[Hilel Salomon]

Thanks to all of you. I'll try the powerjaws too. My second pair of #4's from Oneway are smooth and dovetailed, so I'm not too sure of them. Lee Valley has sold almost all of their sn2's, and I think that I got the last jaw only one. Incidentally, I ordered the apprentice inserts for them and they work fine. If I decide to reverse spin them, I'll tap a hole for a grub screw.I may break down and post some pics, but the fact is that my stuff pales by comparison to the bowls you guys make.Neer the less, I really learn from both your postings and your finished stuff.
Hilel
PS, the Charlotte Woodworking show in March will have CS as one of the vendors.
Hilel.

[Chris Barnett]

Just checked my set, and the jaws do have really large internal dovetails. This jaw set was recommended by an instructor for large work, so I do not understand the reluctance to use :confused:. The low speed was perhaps related to higher mass associated with these large jaws. The 130mm jaw set is the only set specified for the 6 inch faceplate-ring by Nova. I wonder now if the 130mm is really the appropriate jawset for larger work since several comments here do not recommend it for coring :confused:. Being new to turning, I rely on posts like these to spend my bucks. Please excuse if I comment out of place.
Regarding the powergrips you recommend, are you speaking of the Titan powergrips or the standard powergrips. If I too need to change, I want to know what to change to this time. Thanks and do not mean to hijack.

[Hilel Salomon]

Chris,

Not only didn't you "hijack" the post, but you asked questions the answers to which I also would like to see. I started to look into the powergrip jaws as well and saw those for Titans and for the regular novas. so....?
Hilel

[Kevin McPeek]

As mentioned above, I use the Power Grips for the SN2 (regular Nova). If you have a Titan chuck then get the PowerGrip jaws for that. Either set-up will work fine.

Chris, the reason why you see the 130mm jaws listed for the 6" faceplate ring is because they are the only jaws that expand that far. You are correct in saying they are intended for large work, but really how often do you need a 5" tennon? I like them for plate and platters because it's easy to hide the recess since you can make it so shallow.

Another reason I like the Powergrip jaws is that they are a little taller and give you more room to work close to the foot