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Thread: Kobra users: how do you clean up the inside of hollow forms?

  1. #1
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    Kobra users: how do you clean up the inside of hollow forms?

    I had my first go with the Kobra last night, wondering how most of you deal with the ridges left by the small cutter? Even with the laser, I find it difficult to get a smooth surface in areas I can't see easily, beyond the first inch or so of the neck of the form. I know they make a scraper, but only for the largest boring bar, which it seems would necessitate a fairly large hole in a smaller form. I tried to use a Monster bar with scraper, but the flat spot for the set screws is in a different location so it won't work (set screws catch the corner of the flat)

    I suppose another question might be how smooth (even) does the inside of a form need to be? I would like to have it feel even at least as far as prying fingers might explore. Thanks.

    Dan
    Eternity is an awfully long time, especially toward the end.

    -Woody Allen-

    Critiques on works posted are always welcome

  2. #2
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    Make the hole small enough so you can't get a finger in.

  3. #3
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    Dan I'm not familiar with the Kobra, I clean up the inside of HF on my Monster with the swan neck bar and a round cutter installed. Maybe you could grind a flat spot for the set screws.
    Fred

  4. #4
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    On my monster I use the hunter style cutter on the swan neck to clean mine.
    Bernie

    Never put off until tomorrow what you can do the day after tomorrow.

    To succeed in life, you need three things: a wishbone, a backbone and a funnybone.



  5. #5
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    Just to clarify, the only shortcoming of the Kobra to me is that with the exception of the 1" boring bar which can take a 1" round cutter, it only uses 3/16" tool steel cutter. There are different heads for straight, 22 degree, and 45 degree angled cutters, but no scraper attachments for the smaller bars. I had hoped that I could use the Monster bars in the Kobra, but the way the two different brands are milled with flats for the setscrews to seat against make this impossible. I'm hoping to find a smaller bar that accepts scrapers and will fit in the Kobra.

    I talked to Al Crandall today, and he suggested grinding another cutter at a much wider radius, so I'll give that a try.

    Dan
    Eternity is an awfully long time, especially toward the end.

    -Woody Allen-

    Critiques on works posted are always welcome

  6. #6
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    Hi Dan,
    The adapter that Kobra has for a one inch disk type cutter is tapered at the end so that a one inch cutter does work in the one inch boring bar. This being said I made a couple of 3/4" swan neck tools that hold a one inch disk type cutter that I can put in a handle or the Kobra to clean up the inside. Since I did free hand hollowing for years i usually use these tools free hand since I'm only removing a very small amount of material.. Swan neck tools are only used under the lip and down the side until one reaches a point at which they can use a straight tool. Free handing to this distance is not a problem for me even on very large forms. It is when a go past 9" deep on the form that the advantage of the Kobra comes into play and when I'm hogging out the bulk of the material. I use my John Jordan 3/4" hollowing tools when I want to leave the opening less than 1 1/4" across. John uses just his tools with the 3/16" cutters to hollow out his wonderful forms. His feeling is the outside is what is important on Hollow Forms, but he does smooth the inside pretty dang well with just the little cutter. One other thing you will notice with the Kobra is that it becomes easier to use the more you use it. The bearing seem to losing up just enough to make them even smoother.
    Happy Tuning,
    Jack

  7. #7
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    Quote Originally Posted by Fred Belknap View Post
    .... I'm not familiar with the Kobra....
    Fred,
    Here are some cell phone pics to give you an idea of some of the differences between the Kobra and the Monster when discussions come up. kobra-monster 003 (Small).jpg In fairness to the Monster, the bar on my Kobra is a 1-1/4" x 24" special order. It comes with a 1" x 16" bar normally. kobra-monster 010 (Small).JPGkobra-monster 011 (Small).JPGI ordered an adapter that lets me use my Monster bars on the Kobra, so I can use the Hunter cutter on the Monster bar in the Kobra for most ridge clean up. kobra-monster 012 (Small).JPG Like Dan, I'm still looking for a way to use the Monster cutter heads in the Kobra bar, because the Monster comes with a much more versatile cutter selection. The Kobra also has it's own adjustable tool rest.kobra-monster 024 (Small).jpg

  8. #8
    Not to get too far off topic, but how do you guys like the Kobra laser? Ted, which laser do you like better? Is there enough stability to keep the beam from dancing around or moving too much?

    I have both the 3/4" Jordan and Pencil Scorpion hollowing bars. I can't imagine that with the correct adapter with a grub screw system, that almost any bar can be secured to give flexibility in choosing cutters, including the larger teardrop type scrapers. Like what has been suggested, grind a flat for the grub screw, or even drill and tap a new hole for a different grub screw location.

    Good luck, Dan, and keep us posted how you make out, 'cause it will help us all out. I already am on the waiting list for the Kobra, but still want some feedback. Thanks............Mark

  9. #9
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    Ted looks like comparing apples to oranges.
    Fred

  10. #10
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    Quote Originally Posted by Mark Levitski View Post
    ...Ted, which laser do you like better? Is there enough stability to keep the beam from dancing around or moving too much?
    Mark,
    So far, the Kobra laser has been the more stable of the two. The upright holding bar is more substantial and the horizontal beam holding the laser is more substantial--it has to be, since it extends farther. Neither of the two systems bounce around a whole lot and the dots are nice and bright and steady. I've been having trouble with the monster laser case and if you look closely you can see it has a rubber band wrapped around it to keep the case top on securely. Adjustments are relatively easy with both systems, but if someone clever invents a small rack and pinion micro-adjustment device for these lasers I'll be all over it.
    Quote Originally Posted by Fred Belknap View Post
    Ted looks like comparing apples to oranges.
    Fred, It's really not a fair comparison. There's a big difference in price and they both do what they were designed to do. The extra money gets you more mass, bigger bearings, thicker metal etc. At one time in my youth I owned both a Porsche 928S and a Fiat 500. They both got you there, but the journey was a heck of a lot different.
    Last edited by Ted Calver; 02-08-2013 at 6:35 PM.

  11. #11
    Dan, the more I used the Kobra the better I got at a smooth finish. Gotta admit though that mine is back with Al. For some strange reason I couldn't keep it set right. Al of course is currently going through a big loss and I would imagine it will take some time for him to get back to doing his thing. As far as the Kobra goes, yes it does cost more but if you can spring for the extra you will sure be satisfied with the tool.
    Pete


    * It's better to be a lion for a day than a sheep for life - Sister Elizabeth Kenny *
    I think this equates nicely to wood turning as well . . . . .

  12. #12
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    Thanks to all who replied! I'll keep you updated with whatever I find or figure out.

    Mark --- I find the Kobra laser to be much easier to adjust than that of the Monster. First of all, it's all done with one clamping screw rather than two for Monster. The clamps on the Monster I find hard to get tight, and doing so often throws off the adjustment. Once set, they both work well, but the Kobra is a lot easer to set.

    Dan
    Eternity is an awfully long time, especially toward the end.

    -Woody Allen-

    Critiques on works posted are always welcome

  13. #13
    Dan, I might suggest that since your shop is pretty "full" you might store the Monster in my shop.

  14. #14
    I agree with Mark. The Kobra laser is a treat to set up and use especially since I made and us a "C" type steady.
    Pete


    * It's better to be a lion for a day than a sheep for life - Sister Elizabeth Kenny *
    I think this equates nicely to wood turning as well . . . . .

  15. #15
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    Quote Originally Posted by Hayes Rutherford View Post
    Dan, I might suggest that since your shop is pretty "full" you might store the Monster in my shop.
    Hayes, as far as I know, at this point you don't have a shop....yet. how is it coming?

    Dan
    Eternity is an awfully long time, especially toward the end.

    -Woody Allen-

    Critiques on works posted are always welcome

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