McNaaughton Coring System

[Jeff Walters]

Hi. All,
Just wondering if anyone is using a coring system with a Nova DVR XP lathe and what their experience is. My Nov is wired for 115 Volts so it is 1.5 HP. I’m thinking of getting one however I saw a video of someone using it on a Robust American Beauty which is 3 HP and he was bogging it down.
Would I be wasting my money on a coring system?
Jeff

[Dick Strauss]

You can core on almost any lathe. I once did a coring demo on a 12" 3/4-1 hp lathe using the Oneway coring system. With lower hp lathes you have to pulse the coring cutter into the wood instead of maintaining steady pressure. Yes it is slower, but it can be done.

I can stall a 3 hp lathe with bowl gouge if I take a heavy enough cut (it is especially easy as the diameter increase) or I can choose to take a lighter cut and not stall the lathe. We have the choice how we trea our tools. In the bowl gouge case we take a smaller cut and remove less wood per revolution. In the coring case we take less wood off per reveolution by pulsing since we can't take a smaller cut.

The McN is mid-priced but has a steeper learning curve, especially if the knives arrive improperly bent. I'm not a fan of the system or company because it suffers from quality control lapses from time to time and the owner of the company resorts to personal attacks rather than attempting to help address a customer issue. When a company owner shows that they aren't willing to help, I choose not to buy their products!

If you decide to buy a coring system from them, RoboHippy AKA Reed Gray is a good resource for how to bend the mishapen knives into the correct shapes! He posts here often and if you search for this entries here you can gain a wealth of knowledge about coring!

[Jeffrey J Smith]

I bought the macnaughton system back when I was using a 1.5 hp Jet 1642 and it works fine. Did I stall it occasionally? Yep, but, as mentioned above, you can stall almost every lathe made regardless of the horsepower. Lighter cuts, pulsing the blade work to eliminates stalls.
There’s been endless discussion of the learning curve for the macnaughton system; but it’s just a tool. Every tool has a learning curve and I’m not aware of one that makes it simple. You’ve got to play by the rules the tool dictates. From my experience, the macnaughton seems to be totally dependent on the entry angle of the blade. Once you discover how to find that angle and use the correct blade you’re home free (nearly). I’m not by any measure an expert - only attempted a nested set a couple of times, but I use it nearly every time I rough blanks to save the ‘guts’ from becoming shavings - mostly going for three roughouts from an average size blank.
Reed Gray, Dale Bonertz and Mike Mahoney all have excellent information on using the system. The AAW Journal also has an article by Dale that explains his system. Go through the information, make sure your blades are sharp and spend a day with a pile of blanks practicing. It’s largely muscle memory and consistency, not rocket science.

[Dale Bonertz]

Jeff said it very well. If you're going to just core smaller bowls the woodcut system will do you fine. Larger to medium bowls either the Oneway or MacNaughton. MacNaughton has more flexibility and is faster to set up and use once you become familiar with it. Oneway is a good system but more money and limited on shapes. Any and all should work on your DVR.

[Mike Goetzke]

I'm not a frequent turner but took good notes watching the experts videos (Reed, Mike, & Dale). Little scary at first but like Jeff said setup is the most important part. Lower HP lathe may actually be better.

I have a warning of an issue I had. I was coring with the smallest arm - it was brand new. Something happened and all of the sudden the cutter arm looked like a pretzel! Didn't feel like the tool was struggling at all. I looked to see what might have caused this and noticed the tool rest was all the way down. Thinking it over I probably never tightened it enough for the coring forces. So after that I always make sure the tool rest is nice and tight for all turnings. While I type I was thinking maybe I should use a post collar to help with this?

I did contact Reed after this because I remembered reading he had re-bent the arms before. He was kind enough to walk me through it and the arm looks good as new (almost).

Mike

[Reed Gray]

Perhaps it is time for me to do another coring video with the McNaughton... As I say, 'Every one who has ever tried to use it swears at it. Every one who knows how to use it swears by it.'

There are 2 issues I have with the tool. One is that the blades do not have a perfect arc of a circle bend in them, the last about 1 1/2 inches of the blade go more straight rather than following the curve of the rest of the blade. Two is the aiming of the blade is not simple and takes a while to figure out.

So, the blades: I am guessing that they are bent to form in one of the bending lever/roller type things. This does work, but it is impossible to get enough leverage on the very tip to get it to bend perfectly. In manufacturing, if they want a perfect arc, they bend a couple of inches longer than they need, and then cut off the end. Since the tip goes more straight, the blades always follow that straight top, which is why this system always drifts to the outside of the cut. On small cores, this isn't much of a problem. On big cores, it is a major problem, with the trajectory being off 1/2 of more of an inch. This is why you see just about every one who uses this tool open up the kerf at the top of the cut so the blade can go more towards the center, which is the intended path. I think the easiest way to fix this would be to heat the tip with a torch, and then hammer it on a form, probably 2 forms, one for the inside and one for the outside of the blade. No clue as to what this would do to the metal that is laminated onto the tip for cutting. I have put a couple of my blades in a vice, well, just the tip, and applied a hammer. This helps some, and I even have one blade that tracks to the inside. If you try to take the cut in one pass on a bigger bowl, some times you can do it as long as there is enough torque on your lathe. You can and will see smoke coming out of the cut, you can hear the noise of the blade as it binds in the cut, and when you pull the blade out, if you touch it, some times it is hot enough to raise blisters. You will also see burn marks in/on the wood. You can learn to work around this.

The aiming part takes some practice. Simple version is that if the blade you are using matches the curve on the outside of the bowl, if you try to keep an even wall thickness as you go down with the core, you will go through the bottom of the bowl and put notches in your chuck jaws. You need to aim more towards the center of the bowl. Both Dale and I hold the blades up over the top of the bowl to help with the aim. This is a link that I recently found which takes that process one step farther, and first time I saw it, I was 'well, why didn't I think of that?' A good idea:

https://www.youtube.com/watch?v=NOAfJZEKCFc

There is one other problem with the McNaughton that seems to evade a lot of users. This coring system, and the others, both the Oneway and Woodcut are scrapers. We all know, or should know that with scrapers, on the inside of a bowl, you need to be at or slightly above the center of the bowl line because if you get a catch, the tool drops out of the cut, where if you are below center and get a catch, it digs in deeper. So, to set the height of your tool rest for coring, I think they say to use the long blade, lift up on the handle, and center the cutting tip on the center of the bowl or a spur drive point. Well, not bad, but not accurate. I do have a stop collar that goes around the post of my coring tool rest. I had several instances of the tool rest vibrating loose and falling down before I figured this one out. For setting the height, I don't do it by the book. A point that has been missed is that lifting the handle does not equal the pressure on the cutting tip as you near the center of the bowl. If you add the long lever and the flex in the system, with a long blade, this can put you as much as 1/2 inch below the center of the bowl line, and the inevitable catches will dig in deeper. If you have ever tried to take out the nub left when the core is free, you can see what I mean. I start 1/4 inch above center, (I added a 1/4 inch piece of plywood to the top of the collar), at least, on bigger bowls. When I get near the end of the cut, I can now 'feel' if the cutter is below center of the bowl. I then can raise the tool rest slightly higher. This does, almost, eliminate most of the problems. You still need to practice. I think being below center creates most of the vibration and catching issues there are with this tool. It doesn't correct the drift.

robo hippy

[Mike Nathal]

I start 1/4 inch above center, .............
robo hippy

Curious, at about the 6 minute mark he states he cuts below center. I have only cored once, I was not getting a smooth cut until I raised my tool height. But his cutting is exceptionally smooth (vibration -free). .

[Reed Gray]

I remember making a comment to him about that, but don't think I got a response. How much chatter you get depends a lot on the wood. Cherry or Madrone, won't chatter as much as black locust. If you are having to force the tool at all, your blade is most likely bound up in the kerf, or you need to clear the chips. Learning to go light handed with this tool is the same as learning to 'float' the bevel on your gouges. I think it is easier with gouges...

robo hippy

[Maria Alvarado]

The experts have already chimed in, I will only add that I have the Nova 1624, which is the belt driven version of yours and using the 'pulsing' method I have had few issues coring cherry or maple. It is a real learning curve! You will want to pay attention to blade size. With a 16" swing you probably can get away with the Standard set and/or smaller to give you up to 14" cores. I also find the tailstock gets in the way if you are trying to support your work on smaller and certain shapes of cores. Reed has lots of good advice That said, it's great getting more bowls from a blank. Have fun!

[Jeff Walters]

Thank you to everyone who responded to my message. It has been really helpful. As soon as I get the money saved up I believe I’ll be getting a McNaughton queen system. And if I have problems I’ll be back online here. 😁

[Mike Hunter]

To chew up HP it is the combination of SFPM, feed rate, and depth of cut. SFPM or RPM chews up the HP, so it is best to run the lathe at the lower RPM. Next is feed rate, so it is best to keep the feed rate low to minimize the HP requirements. The cutter does not know if it is taking 1/8" DOC or 1/32" DOC, so it is minimal on the HP consumed, but you may overcome the strength of the blade and make a pretzel.

[Dale Bonertz]

As Reed mentioned you want to be above center when you line up the tip, about 1/4". This is for two reasons, 1st as you extend the blade through the turret in its full extension you will notice that it runs down hill a little. You can test this by just extending the tip through the turret and measure it to the bed of the lathe then extend it all the way through the turret and measure again and you will see that it is a bit lower (make sure you hold handle up tight so the blade is against the t-arm. The second reason is force, as you core and the more you extend the blade from the turret there is more force pushing it down. When you set the height of the blade make sure it is fully extended from the turret when you set it 1/4" above center. When you do that and then the force on the blade when coring and being pushed down you will be cutting at center when you reach the bottom.

Reed also mentioned that the blade may get very hot. You can spray WD 40 in the kerf at about the 1:00 to 3:00 position while coring (mostly when using the larger blades is this neccesary). It will slick the walls so shavings eject easier and cool the blade thus shrinking the swelled blade from heat to glide in the kerf much smoother. No the WD40 will not stain the wood, at least I have never noticed staining, and if it did it would be on the surface only which would get turned away anyway. I do need to mention I do this while the bowl is turning and the tool is in the kerf but not cutting. Once done spraying I re-engage the tool cutting edge. Watch the chips come flying out and the tool glides well again. I hope that makes sense for you all.

[George Heatherly]

I have a DVR and a McNaughton. Just as others have said, it is certainly possible to use the combination. My personal experience is that if I stall the lathe, it is not a gentle process. I find it very jarring! I would almost be afraid to use it with a really powerful lathe for fear that it might take the tool away from me.

I do like the system. It just seems much nicer to get 3 bowls from a large blank instead of only one bowl and a huge pile of shavings.

[David Bolson]

Hi. All,
Just wondering if anyone is using a coring system with a Nova DVR XP lathe and what their experience is.
Jeff

I have a Nova 2024 (same electronics/motor as DVR XP) and I use the Oneway coring system. Never came close to stalling. I don't think you're supposed to push so hard with a coring system that it even could stall. Good luck!

[Reed Gray]

Dale, as near as I can tell, the heat on the blade comes from it rubbing on the wood, not from the cutting. The rubbing is because the blade does not track true, and as you go deeper and the blade drifts to the outside of the bowl, the inside/core is rubbing on the inside of the blade. I have tried WD 40 and Pam, which is canola oil, and just don't use them any more. A slightly higher rpm and a single kerf, rather than a more open kerf help the chips come flying out. Before I ground my points down square, I had more problems with clogging. I did retip a few blades with tantung, and kept them square as well.

robo hippy