Est. 1998 — 27 years of woodworking knowledge
coring big bowls
jorge
a question to the collective knowledge:
Is there a a tool or system to core bowls bigger than 20"?
Got a commission for a 22" bowl, it took a couple months to locate the wood, I'll be getting it this sunday and plan to turn it asap. My Powermatic 35-20b can hollow it, but not core it, but that would be such a waste...
Re: coring big bowls
JohnV
I use a MacNaughton coring system with this lathe. Power not a problem. If you haven't used one before, find someone to help or borrow one to practice before starting your commissioned piece.
Re: coring big bowls
Barry Irby
I have a McNaughton system. They make several sets of knives. Don't know if even the largest set will do a 20" bowl, but you could use any set and take the largest core you could and at least you will save that much.
A 22" bowl is huge. Be prepared to spend more time than you might think. Spin it fairly slowly to keep the rim speed down. Lots of surface area to deal with.
PS...
Barry Irby
There is a fairly steep learning curve with the McNaughton system. Probably not the best thing to start on your huge somewhat difficult to acquire blank. Perhaps a fellow turner with experience would come over and demonstrate or you could take the blank to them and let them core it for you.
Re: coring big bowls
john lucas
Let me go and measure my big coring knife for the McNaughton. I'm not sure it's the largest they offer. I bought this system about 8 years ago and my memory isn't that long. I'll get back with you in an hour or so.
OK it didn't take an hour
john lucas
If I waited an hour I would have forgotten. almost forgot 5 minutes after I went to the shop. My largest cutter is 12" so that should get to the middle of a 20" blank. I have a homemade cutter that is longer.
Re: coring big bowls
Philip Duffy
When using McN. system I have found it useful to ease up on the tension of the drive belt on my PM3520 so when the cutter binds - -and it will-- - the CB does not pop and the system allow you to recover quickly. But of course this binding never happens to me - - only to all you other guys and gals! P.
Re: coring big bowls
Reed Gray
I cored a piece of Madrone that was 22 inch in diameter once... Madrone cuts like butter. It did leave a thick outside bowl, maybe 1 inch plus rim. If you are going that deep, you want to make the kerf at least twice the width of the blade. The MacNaughton always drifts to the outside as you go in. Not a big problem with smaller bowls, but it gets way off on big ones. Also, when you are reaching that far off the tool rest, there is a lot of flex in the blade, so as you go in, you want to raise the tool rest, as much as half an inch on a piece that size. I have mine set, with a stop collar, at about 1/4 inch high any way. Cherry or most wet maple, no problem as they cut easily. Oak or locust, probably not. You can, if you are good with one, take a chainsaw and do plunge cuts, but that is master class only...
robo hippy
one method
John K Jordan
When the late Lissi Oland lived in Brasstown NC, she told me how she cored LARGE blanks.
Start at about 4:40 for the coring.
https://www.youtube.com/watch?v=1PMEJ7rirso
I have a complete set of the Oland tools still in the box that need to find a home.
I decided I'd rather turn smaller things.
JKJ
Re: PS...
jorge
Thanks Barry
I have the Mc Noughton system with 2 sets of blades plus one blade of the largest, that one can make a core close to18", but as 22" does not fit above the ways, there is no tailstock to keep that chunk on place. If I have to stop the lathe I must stop the gyrations of that big chunk with my hands, not a problem once it is smooth, but a risky proposition when it is all bumps and lumps, why stopping it with the hands? because of inertia, you stop the spindle and the 200# chunk keeps rotating and can unscrew from the spindle and fall. I think I will have to forget coring it
Re: coring big bowls
jorge
Hi Reed,
I wish I had madrone, it will be ash, with a wide band of sapwood and a dark hearth wood, stringy. I am thinking of removing as much as I can with the chainsaw, on the ground before mounting it
"The MacNaughton always drifts to the outside as you go in. Not a big problem with smaller bowls, but it gets way off on big ones" That is the reason I did stop using the Mac Naughton on the big bowls I did ruin a couple.
The wide kerf and raisin it are good advice, Thank you
Re: one method
jorge
Thanks John!
That lady is something else! and a big shop. I am thinking not to core it in the lathe, I can do plunge cuts on the ground before mounting it.
"I decided I'd rather turn smaller things" I am getting there, 20" tops, I did turn 3 of them this year and it is as much weight as I can lift these days.
They sell! And the happy customer all smiles carrying her or his bowl is rewarding
Re: OK it didn't take an hour
jorge
Thank you John,
I do have one, yes it is 12" long but in my experience I can only go in 9 inches, so the core is around 18" tops.
Re: coring big bowls
Bill Boehme
The largest bowl can be as large as your lathe will handle, but the second bowl will max out at about 18 to 20 inches depending on how good you are. BTW, I would NOT recommend using the largest knives on the McNaughton until you have a lot of experience using the standard set of knives. The McNasty will make you humble in a hurry. I don't know the largest core that the Oneway can do, but it is far easier. The disadvantages of the Oneway are price and very tedious set up time.
Re: coring big bowls
Bill Boehme
John, It depends on how you set it up. If you want a shallow bowl then the largest kerf will be in the neighbor hood of 19 inches and a deep bowl will be less. Of course, it also depends on how large a center you can break off. You might be up a creek if you bottom out the coring knife and the center is too large to break the first core loose.
I did two 22" ash bowls last year - using McNaught
Joe Fleming
I cored two 22" bowls last year out of ash. I used the largest McNaughton blade. The bowls were about 10" deep. The cores were not the full amount of the possible take, but they were 18-19" in diameter and about 6-7 deep. Joe
Re: coring big bowls
Mike Brazeau
Where did you get the idea that the setup of the Oneway is tedious? I lost track of the number of posts here warning against using the McNaughton. If you only have one shot the only way to go is the Oneway. I have the Nos. 1,2 & 3 knives but did not purchase No. 4 as it is rare to make a bowl that size. It is speced at 16 1/2" but could probably do a bit bigger, but you have to break the bowl out so you cannot go too big. About 13 years ago, the first time I used mine I got three bowls, no problem.
Re: coring big bowls
jorge
Mike,
I have the OneWay as well, and have th e#4 knife, but the bowl will be 22" and my lathe, the Powermatic 3520b cannot fit it, so must slide the head all the way to the right and put the banjo in the extension table positioned 9 inch es lower, so the OneWay cannot be used
Re: coring big bowls
Mike Brazeau
Sorry Jorge, missed that aspect. Got any friends with a 2436? I did core a maximum sized cherry bowl once on my 2436 and the blank turned out to have a rotted limb section in it. Was such a disappointment. Still have the rough-out which I think is about 22". Monster sized bowl!
Re: coring big bowls
Walter Ahlgrim
Today my clubs demo was the blind turner Michael Blankenship cored 18 inch bowl on the club’s 35-20. He made the Oneway jig look like a great deal.
You may want to think very carefully about what you are doing, the bigger the bowl the more I want a tail stock. If you do not have the outboard bed you may want to get one.
Walta
Re: coring big bowls
jorge
Walter,
I core 20" bowls quite often and yes, I use the tailmstock always and yes I have the extension table, but this one will be 22" that means outrigged, so cannot core it in the 3520.
Sold 4 this year so far!
Re: coring big bowls
Peter Hyde
Powermatic sells a riser for their banjo so when the extension is installed in the low position the tool rest/ coring tool is at the right height. So I don't see what the problem is. If you have the biggest knives for the McMaughton or Oneway you should be able to core a bowl that size outboard. Tailstock support not absolutely essential. Use big chuck with dovetail jaws and correctly sized tenon or a faceplate and waste block.
Been there, done that.
Re: coring big bowls
jorge
Peter,
as far as I know, the raiser is for the biggest Powermatic maybe 3524? not for the 3520...
Re: PS... *LINK*
Karl_TN
Jorge, If you're concerned about a heavy blank spinning off when lathe is stopped then consider adding some set screws to your chuck/face plate. Also, don't forget to add an additional set screw to any chuck spindle adapters if used.
For what it's worth, Vicmarc sells a 'safety collar' for keeping chucks from backing off their lathe spindles. Can't say for sure if other manufactures have this option or not.
Re: coring big bowls
Peter Hyde
No When I bought the bed extension it came with the riser as a kit. It's a solid steel rod that is milled to fit in the 1" tool post hole on the banjo and the other end has a 1" hole and clamp to take the tool rest post. I have a 3520 and I wouldn't post info about something I haven't done or don't have
Here's pic.
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24" bowl
