Mcnaughton Center saver users

Discussion in 'Woodturning Discussion Forum' started by chrisdaniels, May 2, 2016.

  1. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Here is what I found with my HF digital caliper. Measuring at several locations on each of my four blades, the thickness for my large and standard blades were very close to 5.8 millimeters or a bit less than 0.23 inch.
     
  2. john lucas

    john lucas

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    Ideally the steel needs to be tempered to a spring steel tempering. not just the edge but the whole thing. At least that's what I think. I didn't do that on mine because at the time I didn't have a forge or any way to heat treat a whole piece of steel that size. If it's a big spring it won't break if bent and will tend to return to it's normal shape. A properly made knife should be treated to the point you can bend it and it won't break. Of course it should be hard enough to hold a good edge but a really hard edge will be too brittle. We need a different tempering for a tool that is basically the shaft of the cutting edge. It needs to be stiff but have enough spring to not break. I've been doing some research but right now I'm still a good ways from having my forge set up. I also purchased a steel bender at a yard sale just recently that should help me bend the arc better. I have a very limited set of tools for my McNaughton because I rarely have rare wood that's worth saving by coring. I bought the set because a lady left me a really sweet box elder log and wanted 3 big bowls for her sons. If I turned them there wouldn't be anything left of the log so I bought the coring system and made some really nice bowls for me as well. I did the first set really well and was proud of myself for watching Mike Mahoney and few other core. Then I tried some Walnut bowls and fought it like crazy and broke one of the cutters. That's what got me into making my own. I'll try to measure the steel in a few minutes when I get out to the shop. It is thicker than 1/4" If I remember correctly but not as thick as 5/16. I'll let you know in about an hour.
    I had Mike Hunter retip one of my tools and I like it a lot better.
     
  3. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Maybe your system is the original design. The blades on the new M8 are slightly less than 1/4" thick for both large and standard sizes. I like it he idea of using replaceable carbide tips.
     
  4. john lucas

    john lucas

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    I just measured all my blades. The bigger ones were about .275. The middle size was .250 and the smaller ones were around .235. Actually the .250 is the one I made now that I think of it.
     
  5. Paul Gilbert

    Paul Gilbert

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    I just measured my new, still in the box, standard set and got 0.228 on all three blades. The curves measure 9.5, 5, <4.5 on Bill's pdf checker.
     
    Last edited: Oct 10, 2016
  6. Bill Boehme

    Bill Boehme Administrator Staff Member

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    In post #37 I have a second chart that covers the smaller range. On my small standard blade the radius is 3.5".
     
  7. robo hippy

    robo hippy

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    I don't think I mentioned this here before, but the old blades were cast stainless steel. I had some carbide tips put on some old blades, and they were just totally wrong. I took them off by twisting in a vice, which took off some of the metal. It had that powdered look to it, and not the shiny finish of the blade. Not totally sure, but they do cast stainless...

    robo hippy
     
  8. Fred Belknap

    Fred Belknap

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    I just finished coring a maple burl using the middle size regular blade. It was easy to set the center about 5/8" above center, I have a spacer on the toolrest to get the center, and after stalling the lathe umteen times it stopped cutting. I had to drop the center back to center to finish the cut. It was a smallish burl so two pieces is all I could get. Lathe on low belt set around 600 rpm, stalls and squealing belts is the name of the day.
     
  9. Emiliano Achaval

    Emiliano Achaval

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    I think you guys are worrying to much about things that are not important. You have to practice with the McNaughton to get better... The learning curve is steep, it helps if you take a lesson from someone like Mike Mahoney or Andi Cole. I'm lucky Andi is a 30 minute flight away... I got one out today, Its not pretty, but, its a $175 bowl and not shavings on the floor...
     

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  10. JeffSmith

    JeffSmith

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    I've been using the bowl saver for a few years now. I found the simplist way to find the entry angle, for me, is to set the tool on top of the mounted blank,, as Al describes, with the tip where I want it to end up. The shank of he blade is at the forward edge, the same distance from the outside of the blank as the turret. Pinch the blade between two fingers (like the turret posts) and slowly withdraw the blade until the tip is between your fingertips (it's the reverse path you want the tool to make through the blank). As you withdraw the blade, the handle end will pivot around. When the tip is between your fingers, the handle will be at the correct angle of entry for the cut to proceed on the same path.
    Takes way longer to describe than it does to do, but it works quite well for me.
     
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  11. Emiliano Achaval

    Emiliano Achaval

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    I will have to try your tip...
     
  12. john lucas

    john lucas

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    Here is a photo of my bending jig I build to make the McNaughton cutters. This was homemade. The different holes are to set the rear pin a different distance from the big pin. I now have one of the Harbour Freight metal benders which should do a better job if I build some larger circular bending adaptors.
     

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  13. robo hippy

    robo hippy

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    Your bending jig is close to what you need. Have you ever seen a rebar bender? You have one smaller pin, like the one in your picture, and a rotating wheel or larger pin, again like the one in the picture, then you also have a handle with a pin in it for leverage close to the pivot point. Bending the very tip requires a lot of leverage, more than you can apply with just your hands. I would also suggest that you cut the profile on the nose before you bend it. It does need to be tapered so it will fit down inside the small radius at the center of the bowl. If it is full height, it won't go down all the way.

    robo hippy
     
  14. Bill Boehme

    Bill Boehme Administrator Staff Member

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    When you bend the bar it would probably be easier to cut off the straight section near the tip rather than trying to curve it all the way to the end.

    John, do you anneal the bar before bending?
     
  15. john lucas

    john lucas

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    Bill the steel I used was tool steel and came annealed. I don't necessarily recommend tool steel unless you intend to temper it to spring hardness. Then it's important to know what kind of steel it is so you can know how to harden and anneal. It's just what I had handy in that size. I usually have 3 foot lengths so it was easy to put some gloves on and just bend it and cut it to length when I was done. I have also put a piece of pipe over the metal to bend but be careful. It takes a fair amount of force to bend this metal and if the pipe comes off you get to run across the room trying to catch your balance and of course crash into things while doing that. Not that I know you understand I'm just guessing. :)
     
  16. Bill Weaver

    Bill Weaver

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    All I got to say is mine is on the shelf drawing dust. Never could master it and probably never will.
     
  17. Chuck Lobaito

    Chuck Lobaito

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    Practice, practice, practice. I practiced with a cottonwood from a tree from our house and another from our neighbors. Made about a 100 cores in 2 weeks. You really have to watch multiple videos to get the hang of it. Mahoney's video is great overall learning aid, Robohippy's gives a different perspective, and Boener's video gives you the math and measurements. Also, I learned to use a shorter handle for better control. A long handle does not actually help if you are doing it right.

    If I have not cored in a while, then I watch them again and again.

    BTW the cottonwood cores became milk painted utilitarian bowls.
     
  18. Zach LaPerriere

    Zach LaPerriere

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    Coring Spalted and Softer Woods

    Thank you, everyone. I've found this thread very useful. I'm hoping to resurrect the thread and hear what others do for spalted and softer woods.

    I'm coring spalted red alder, which is both soft and spalted. Tear out is aweful, which makes the going painfully and the chips love to plug. Here's what helps:
    1. cutting a wider groove at the rim
    2. spray water—too a certain extent
    3. constant blowing 100 psi with the air chuck to clear chips

    I don't have that much experience with the McNaughton, but I can make a decent core in a harder wood in a quarter of the time, maybe less.

    Part of me wonders if I purchased the wrong coring system for these softer woods. I was drawn to greater versatility of the McNaughton, but I wonder if cutters like the Oneway would cut better in softer woods. I own Hannes Michaelsen's Magnus Tool and the acute angled carbide cutter slices through these softer woods like butter. I can make a 16" platter in 20-30 seconds. Of course the Magnus Tool is only for cutting straight cores, and the cutter on the Magnus probably wouldn't work with a curved coring knife, but I suspect a different style of cutter might work better than the McNaughton scraping cutter.

    As always, thanks for any thoughts or ideas.
     
  19. hockenbery

    hockenbery AAW Advisor Staff Member

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    I don't core at all anymore and never cored soft woods. They don't like to scrape and sometimes the torn fibers want to bind in a narrow curf - making a relief cut eliminates the binding.

    A friend who was one of the best people I know at using the McNaughton switched to the ONEWAY.
    When I asked her why? She said, " it is so much easier to use. It only does hemisphere shaped bowls but that is mostly what I turn and I still have the McNaughton if there is something I can't core with the ONEWAY."
     
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  20. Zach LaPerriere

    Zach LaPerriere

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    Thank you, Al. I may have to try the Oneway. At least it's cheaper than the McNaughton! :D

    I've tried some mighty thick relief cuts, and though it helps, it doesn't eliminate the troubles once the knife is in several inches. And the speed at which it cuts compounded by the relief cut...it makes patience I virtue in short supply! Then there's the 3/8" or so of torn out grain that needs removing from both the bowl and the core. Painful.

    Here's why I persisted in coring...a beautiful sunburst spalting pattern. When these are finished it's just over the top.
    starburst.1.jpg
     

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