Coring

[Tom Bucanan]

If you could choose a system for coring, which one would it be and why?

[Jason Clark2]

I chose the McNaughton system when I was in the market about 18 months ago. It was about half the price of a comparable Oneway system and allows you to core non standard bowl shapes easier than the Oneway. It does have a fairly steep learning curve, which is the primary I highly recommend purchasing the Mike Mahoney video or spending some time with someone who owns and useds the system as the written instructions are nearly worthless.


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Jason

[Bill Blasic]

I'm down here at Turning 2007 and just purchased the McNaughton, pored over all pros and cons of all setups and I went with it for its perceived versatility.

[Skip Spaulding]

Tom, I bought the McNaughton system after reading all the input on this site. I have a Nova 1624 and the cutters work good if I don't force them. Probably larger motor (2-3hp) would be faster. I just turn for fun so there is no great rush. Like any tool there is a learning curve! A good video would sure help.

[Paul Andrews]

Tom, In my opinion the McNaughton system is the most versatile. Do not waste your money on the small blades. The regular and jumbo blades will get all the use. As stated, the video will help but it takes hands on experience to learn the proper feed rate.

[Tom Bucanan]

I agree that the McNaughton system is much more versitile, but is it more dangerous. How big of a bowl would you feel safe coring. It seems like there is alot of tool overhanging the "tool rest." Also, can you keep the tailstock engaged when coring?
Thanks for all your help

[Jim Becker]

I'll likely get the McNaughton at such point as I acquire a coring system for the reasons stated. Do note that you need at least 2hp to use them effectively...coring systems are not a good idea for lower powered lathes.

[Kevin McPeek]

I have the McNaughton also, for many of the reasons listed above. I use it on my DVR XP and it handles everything pretty well. I have only the medium knives and have cored as large as my lathe will swing.
IMO (In the beginning) you're as likely to rip the bowl out of the chuck as you are to stall the lathe, I've done both. Now that I've cored about a dozen sets I'd say I down the the occasional stall but usually because I am trying to go too long without clearing the chips or I'm just trying to go too fast.
I use the power grip jaws now and have rarely knocked a bowl off center.

[Paul Andrews]

I agree that the McNaughton system is much more versitile, but is it more dangerous. How big of a bowl would you feel safe coring. It seems like there is alot of tool overhanging the "tool rest." Also, can you keep the tailstock engaged when coring?
Thanks for all your help

Is it more dangerous? Possibly at first when you are still in the learning mode. The tool gate that the blade feeds through is well designed and will handle the blade overhang as long as it is set up properly (ie. everything tight). Also as indicated in the video you must hold up on the back of the tool handle. The largest bowl I have cored width wide is about 15"-16". You might be able to core wider bowls but you lose depth.

I have used the tail stock on rare occasions with the largest of the jumbo blades. My tail stock the wheel seems to get in the way of my normal feed angle. If you are coring a shallower bowl then it is possible depending on your tail stock design.

One trick to shorten the learning curve is to make the largest tenon your chuck will hold. Also make the tenon deeper than normal, you want the maximum bite possible. I use the stronghold chuck with the largest deepest jaws they sell. Where I encountered the most problems (blanks snapping the tenon and orbiting the shop) was on natural edge pieces. Until the blade is firmly embedded and cutting continuous wood you are likely to have problems. The blades want to pull themselves into the piece. I found the best way for me is to hold the blade with the thumb and first finger of the left hand just behind the gate and hold the blade back, only allowing the fingers to move the blade forward a fraction at a time until the blade is firmly into the wood.

[Martin Braun]

I have the McNaughton, and there certainly are a number of subtleties that can improve the experience if accounted for. I have found that the moisture content, internal stresses, and hardness of the wood can play a significant role. A moist, soft wood with lot's of internal stresses can make for a frustrating afternoon. The chips get hung up in the kerf. The wood may start to close up the kerf at 2 spots, 180' from each other. The cutter may have a tendendacy to dig/tear instead of cut. A harder, straight grained piece of wood, allowed to dry for a bit, can be cored with ease. That's been my experience. Whether a Oneway system would be more robust to the former, I can't say.

[Tom Bucanan]

I guess the McNaughton system must be a better system. Has anyone used the Oneway? Even better, has anyone used both?

[Scott Hubl]

I recently bought the McNaughton standard system at my local Woodcraft, I haven't used it yet.
I do have both of Bill Grumbines DVD's he touches on its use a little bit .
I did just order Mike Mahoney's DVD on the McNaughton Center Saver, so I'm looking forward to more detailed use of it when it arrives, before giving it a try.:D

[Reed Gray]

I have done a number of posts on this subject, but here goes some of it again. I have all three systems. I use the McNaughton for 95% of the cores I do. It is also the most versatile of the 3 systems out there. You can core regualr bowl shapes, you can core shallow platters, and you can core deeper bowls. The other systems are pretty limited here. With the McNaughton, I use the standard and mini sets of blades for almost all of the cores that I do. I do use the Oneway for coring bowls over 14 inch diameter. It is more stable when reaching out on larger bowls. You can easily core 14 inch bowls with the standard McNaughton. The McNaughton is much faster than the Oneway for me. The things I don't like about the Oneway are the price, sharpening the cutters (they have to be unscrewed from the blade, held up to the grinder and then screwed back onto the blade), and that you have to turn off the lathe to advance the support finger, which on a big bowl can be 3 to 5 times.

The hardest thing to learn about the McNaughton, is to counter its tendency to drift off track as you core. It wants to drift to the outside of the track. This leads to binding. You have to come back to the top of the cut and remove a bit on the inside of the cut, or some on the outside of the cut, or you can bump the tool rest in towards the center (which will tend to send the cut a bit deeper). Once you learn to correct for the drifting, then all you have to figure out is how to tell how deep or shallow you are cutting. The easiest way to do this is to get the laser pointer that McNaughton has. It really helps!!!! I developed the habit of aiming a bit shallow because I went through the bottom of too many bowls. Better safe than sorry. Well, with the pointer, I can aim for the perfect core every time, and if I am off course, I can see it before I bottom out, and correct my aim. Also if I am too shallow, I can see it, and aim deeper. I did modify it a bit, but it is a good addition to the tool. I suppose that you can build your own also.

Now, for mounting your blank, you have 2 choices, a recess or a tenon. I use the recess. I can core 18 inch bowls with a recess on my big Vicmark which has jaws 2 5/8 inch wide. A tenon works well also, but I don't do it that way. What you do need to do is use a tenon that is at least 1/3 the diameter of your bowl, and you want the fit of the jaws to be close to the diameter of your tenon. With a recess, pretty much the same thing, a foot that is 1/3 to 1/2 the diameter of your bowl, which is a standard design thing anyway, and a recess that is slightly bigger than your jaws. You need a certain amount of meat fot the jaws to expand into. If you have 2 inch wide jaws, and your foot is 2 1/2 inch wide, there will be little wood for the jaws to push into, and you may blow out the edge when tightening up, or a catch can blow it up also. The idea is that the more steel that is contacting the wood, the better your hold will be. If you have a 3 inch mortice, and 1 1/2 inch jaws, or a 5 inch tenon, and 3 inch jaws, you will be touching the wood in only a few places. So, 2 inch wide jaws, then 2 1/8 inch wide mortice, or less, and 3 inch wide jaws, then 3 1/4 inch wide tenon. Depth of the mortice or tenon for me is usually about 3/16 on bigger bowls, or up to 1/4 on 18 inch bowls. I never go less than 1/8 inch.

For horsepower needs, all 3 of the systems have cutters that are 3/8 inch wide, with the exception of the mini McNaughton, which is 1/4 inch wide. Because of the spear point design, they remove a shaving 1/2 inch wide, and 3/8 inch wide respectively. If you can remove a shaving that wide with a scraper (all coring systems cut as scrapers), then you can core. With a 1 hp lathe, you can core, but you may find that you need to turn the rpm up, and take lighter shavings. I have ground the points off my McNaughton blades so I now get shavings 3/8 inch wide, and 1/4 inch wide respectively. The point works best if you are trying to cut the blank out totally, rather than cutting down most of the way and then breaking/twisting it out. If you are coring croth or burl, this works better because the grain isn't running straight across the cutting line, and you can rip the bottom out of your bowl.

The Oneway and the Woodcut are good systems, and easy to use because they are on a pivot point, and not free handed like the McNaughton. Both can be moved towards or away from the center to get slightly flatter or deeper cuts. With the Oneway, if you go to the extremes, the support finger can bind up in the cut because it is set for a pretty specific radius cut. The Woodcut is nice, but the big blade is a 5 inch radius, and won't core much wider than that. It requires the tailstock to be engaged to use safely.

Check out my other posts, but this is most of what I have said before, but I always change how I say things, each time. Let me know if I can help.

I believe that Steve Russel has some comments about the McNaughton on his web site also.

robo hippy

[steve johnson]

Reed, can you describe how you sharpen the Mcnaughtons? I have a 180 cbn wheel. What angle do you suggest? When you ground off the point, does it work better on say a Nova 1624?
thanks,
Steve

[Faust M. Ruggiero]

Tom,
I own the Oneway system. It is easy to set up, easy to use and comes with a fool proof jig to sharpen the cutting tips. Personally, my question is why do you want to core. Do you want to make nested sets, or is your interest more in saving chips and making a second bowl from a large blank. Let me give you my take. I only use my coring set up for the following: If I have a large blank, say 18" or larger and I feel I can make a core that is 14" (my most popular bowl size). The math works like this, I want to keep 1 3/4" thick rim if this is a rough out and the cutter will chew up 3/8". The first core will be 14" diameter and need to be left 1 3/8" rim width so the second core (third bowl) will be 11" rough diameter. Anything smaller than that I don't usually keep since it will be small and shallow. I give them to friends with smaller lathes. However, I don't often have 20" bowl blanks. These are all roughed out bowls left to dry and second turn.
I occasionally have a bowl blank so pretty I want to preserve all of it I can. I will core these rather than turn pretty wood into curls. Again, not that often.
Even more rarely, I have a decent size burl. These I might turn to finish thickness, 1/4" or so, and get as many as I can to make a set.
The down side to the Oneway system is the bowl shape. The profile of every bowl except the largest is determined to some extent by the shape and swing of the knife. You can always cut a bowl thick enough to reshape it somewhat.
Coring rigs are expensive. The McNaughton system considerably cheaper than the Oneway and a good reason to buy it. It is a lot harder to master. The Oneway will allow you to be successful the first time you use it. Choose what you want to do and what you want to spend and you can make a decision.
faust

[Reed Gray]

I don't know if any one else besides me uses the squared off point. I prefer it, mostly because it has less surface area than the spear point. I do tend to plunge straight in rather than the 'fish tail' method that Mike Mahoney uses or used. With the square tip, if I plunge straight in, there is a lot less surface area engaged than there is if I plunge straight in with the spear point. If I need to open up the kerf, I come back to the top and take 1/16 off one side or the other. For me it just cuts easier. I have found that the chips seem to eject easier as well.

For sharpening, most of the time a 220 grit diamond hone on the bevel is all you need. A couple of side swipes and you are done. The coarser the hone, the better as in a 600 grit one is not enough. If I grind it, I don't really know what the angle is, but is around 70 degrees. Mostly I hold the blade straight up and down (same orientation as when in the support fingers) hold the blade so the heel is on the grinding wheel, and lower it till the sparks are coming over the top. You do not EVER want to tough the top of the cutting blade with anything at all abrasive. A very thin veneer if a harder metal is bonded to the top of the blade, and a hone will cut through it.

Your Nova should be able to handle the McNaughton without too much problem. I believe is has 6 speed ranges and at least a 1 hp motor. Having a 2 hp motor and 220 volt current is better though. You will want it on the lower ranges for coring. If you are continually stalling your lathe, it could be a couple of things. Belt tension is one. You want enough so the lathe will cut without effort, but slack enough so if you do dig in, the belt will slip. I don't think it is possible for the belt not to slip with a catch, and I have stalled my Robust, in the middle speed range with mine a lot of times, and I do tighten it up. If you are not stalling when you start coring, but start to stall it when you are down inside, this comes, most of the time from shavings building up inside the cut, or your kerf is kind of wobbly. The wobble comes, most of the time from pulling the blade out to clear chips and then starting up the cut again. A lot of the time, it restarts off to one side or the other. If you do this a lot, it gets worse. You can eventually learn to feel these, and to also cut/trim the bumps off. The other reason for the binding, is the blade seems to always drift to the outside of the kerf as you cut. Not a real problem on small cores, but big problem on big cores. If you have ever pulled out the blade and see burn marks on it, or got your fingers burned from touching the blade after you pull it out, or seen burn marks on the core or the bowl you are coring, this is because the blade has drifted (blade is one slightly tighter curve/arc, and the kerf is a slightly flatter curve/arc). This is why you come back to the top and open up the kerf slightly wider.

As with any scraper, you need to be cutting at center height as determined by taking your longest blade, extending it all the way out, and pulling up on the handle. There is flex designed into the system. I use a spacer block around the tool rest post to keep this height. I also add some height, about 1/4 inch. Lifting the handle gives you one center height, but this does not compensate for the down ward pressure on the blade tip as you cut. If you have ever tried to remove the nub left when the core breaks out, you have seen this in action. You never want a scraper below center on the inside of a bowl because catches will tend to dig in deeper, especially when inside a kerf. If you get it too high, the vertical blade will have trouble fitting into the curved kerf. Being a tiny bit below center isn't a huge deal until you need to cut a core totally off, like with burl, crotch wood, or end grain. You need to raise the tool rest for that last little bit.

robo hippy

[Jeffrey J Smith]

I'll certainly defer to Reed for the details of using any of the systems, my experience is strictly with the MacNaughton. I learned to use it on a 1-1/2HP Jet 1642. While that's probably the least amount of horsepower that most people would recommend, it does work just fine. You learn at a slow, methodical pace that carries over well to a larger lathe. You also get used to hearing the scream of your belt as the thing stalls out periodically, further enhancing the development of a slow, methodical pace.
The learning curve may be steeper than the other fixed pivot systems out there, but there's no shortage of information available from helpful people like Reed and Mike Mahoney. I can heartily recommend both of their DVD's on the system. There's also an excellent YouTube video that Dale Bonertz (sp?) has out that explains another method of 'steering' the blade, or at least getting closer to predicting where your bottom will actually be.
I found early on that the path is pretty much set by the angle of entry you select when starting out - you can only compensate with steering up to a point. Dale's system of determining the entry angle is excellent.
By the way - since going to a 3 HP lathe, I still core at the leasurely pace I learned from trying to core on the Jet. No matter how much horsepower you bring to the party, it is still possible to stall it out when coring. And the noise a 3HP Robust AB makes when it stalls is remarkably similar to the noise generated by the 1-1/2HP Jet. I'm just not in that big a hurry.

Jeff

[steve johnson]

Thanks y'all, I am getting better with each try. Do you know how to buy Reed's DVD
?

[Reed Gray]

To core, or not to core, that is the question. My take on this is that if you are a bowl turner, and especially if you sell, you have to have a coring system. The McNaughton is the fastest one out there, once you learn to use it. I have found the Oneway to be a lot slower. With 6 inch deep blanks, I always used to take 4 cores (I turn to final thickness, let them dry and warp, then sand and finish). Now, I only word for 3 total bowls. Main reason is that I ended up with a lot of tea cup saucer sized bowls/plates that were almost more work than they were worth to finish and sell. For my business, I would sell as much $ wise in personal sized bowls as I would with family sized bowls. Some of the small ones would go as well, but not a lot. It is faster to core out the center than it is to turn it out, and I can turn pretty fast. A 4 bowl set from a 14 by 6 inch blank, turned to finish was about 45 to 50 minutes. almost half of that time was on the first bowl. I take the big core first, then each smaller bowl after that. The core already has the outside shaped, and most of the time, one or two passes down the outside, and it was done.

Rumors of reduced shaving piles are greatly exaggerated. Seems like I was turning out more bowls than before coring, and no real reduction in shavings, but more bowl production.

robo hippy

[Ralph Lindberg]

Just an addition, since I routinely core with a DVR-XP. Care with your feed rate is a requirement. If wired to 110V the DVR-XP produces about 1.5 HP, if wired to 220V the DVR-XP produces about 1-7/8 HP (this increase is due to the unique nature of the DVR motor, standard 110/220 motors do not produce this result)
I use the spear-point and also hone, i hone before every cut.
I actually have gotten to the point, since I have the gate setup with stop-collars for fast setup, where I core even when I don't "need" to as I can core faster then I can reduce the inside to chips. This gives me a core to toss in the fireplace.
Actually I also sometimes use the coring tools to cut down the height of bowl blanks, tossing this in the bucket for more firewood.

I really recommend the article in the current AAW journal, and urge everyone to download the PDF chart. This gives the radius and tool length of every cutter.

[Jim Burr]

One way on my 1642 because a One way is usable and the learning curve doesn't cost several hundred $$

[Peter Blair]

I really hate to 'toss my hat in the ring" but what the heck.
I have the Oneway and because it is sooo easy to set up I wouldn't trade it for anything else.
Yes, it isn't as flexible as I sometimes would like but from the first day I set it up it has performed flawlessly.
This probably shouldn't be taken into account but I use the base with the shorter post as an adjustable base for my router work.
Examples of this can be seen on my WordPress site, if you care.
http://woodbowlsandthings.wordpress.com