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  1. #1
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    Default The use and economics of spiral heads

    Just wondering if there's been any sort of cost analysis of maintaining spiral cutter heads versus the usual straight knives.

    At $6-$8 a pop for each individual 4 sided cutter it would cost $450 - $600 to replace all 75 on a 15" thickie. Carbatec's spiel is that they'll last 12-20 times longer than a normal HSS knife set. How well does that spiral cutter cost match their life compared to the replacement cost, resharpening cost and life of common knives?

    If a section of the spiral cutters get completely wrecked (hit a nail or something) and you replace just the damaged ones, do the new cutters leave a slightly different (presumably deeper) cut than the older ones? Could the same thing happen just from uneven wear across the full width of the spiral?

    Given their supposedly superior performance, is it anticipated that spirals will eventually replace knives on all levels of machinery or will knives hang around for ever as a truly budget option?

    A penny for your thoughts
    Every time you make a typo, the errorists win.

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  3. #2
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    Default

    Quote Originally Posted by RedShirtGuy View Post
    Given their supposedly superior performance, is it anticipated that spirals will eventually replace knives on all levels of machinery or will knives hang around for ever as a truly budget option?
    Given that you can buy a complete cheap thicknesser for less than what the spiral head sells for, I don't see them replacing knives on all levels unless the price comes down considerably.

  4. #3
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    Default

    I agree with you redshirt guy,I was talked out of fitting a spiral cutting head based on my use of my thicky and the cost of replacing individual parts. As you said $5-6 each against $60 odd for a spare set of blades and a cost of $22 to sharpen a set that can be done many times.
    After being talked out of this I did spend $60 odd for a good jig for setting the blades,this I felt was a good investment as the first time set up of this jig(and only set up) means that change over of blades is very quick and accurate.

  5. #4
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    FenceFurniture is offline The prize lies beneath - hidden in full view
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    Default

    Not to forget the other benefits of a Spiral head
    • Quieter
    • Better finish, particularly with difficult or cranky timbers (and we do seem to have planty of those here)
    • Much smaller chips for dust collection, which quite probably means you may be able to use a lower powered extractor and smaller ducting (say 4" instead of 5 or 6")


    That last point is of interest (to me anyway) because smaller chips needs smaller pipes to keep the airspeed up to keep the smaller chips in suspension (think of a large leaf or plastic bag that can be carried along by a smallish breeze, but the smaller leaves and dust need a stronger (faster) wind to pick them up).

    I suspect that within 5 years Spiral heads will become the norm, and conventional blades may even cease to be on option on new machines. No vested interest or anything, just a personal forecast. As demand increases surely the price will come down (some, anyway). Early adopters always pay more, in just about any technology.

    I wouldn't think that a new individual spiral cutter would have any appreciable increased cutting depth over a used one - I think that they would be blunt before they reduced in height profile.

    Good thinking though, to query these things.
    Regards, FenceFurniture

    COLT DRILLS GROUP BUY
    Jan-Feb 2019 Click to send me an email

  6. #5
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    Default The Cutter.

    Hi All,
    Although, not being a Woodworker as such, I have seen these Cutters in action.
    One of the best bits is, they are only Approx. 85 Decibels.
    Those small Thicknessers are so loud, they drive you out of the shed.
    So, they are expensive, & so are you Deaf yet. Even a good set of Earmuffs have trouble keeping the noise contained.
    I'm trying to convince Our Mens Shed that this is the way to go, but, so far to no avail, as it is the Expense.
    Regards,
    issatree.
    Have Lathe, Wood Travel.

  7. #6
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    Default

    Quote Originally Posted by RedShirtGuy View Post
    Just wondering if there's been any sort of cost analysis of maintaining spiral cutter heads versus the usual straight knives.

    At $6-$8 a pop for each individual 4 sided cutter it would cost $450 - $600 to replace all 75 on a 15" thickie. Carbatec's spiel is that they'll last 12-20 times longer than a normal HSS knife set. How well does that spiral cutter cost match their life compared to the replacement cost, resharpening cost and life of common knives?

    If a section of the spiral cutters get completely wrecked (hit a nail or something) and you replace just the damaged ones, do the new cutters leave a slightly different (presumably deeper) cut than the older ones? Could the same thing happen just from uneven wear across the full width of the spiral?

    Given their supposedly superior performance, is it anticipated that spirals will eventually replace knives on all levels of machinery or will knives hang around for ever as a truly budget option?

    A penny for your thoughts
    Got a Shelix head in the buzzer (16") and thicknesser (24") at work and I'll try to answer your questions in order (I'll focus on the thicknesser as that's the more common upgrade).

    Price:

    The Byrd carbide inserts are about $35 for a box of 10 if you buy direct from the US (cheaper in lots of 100s or 1000s). They are not quite square, but have a 4" radius on the cutting edges so the corner points don't actually touch the timber - no points means no lines.

    Life/wear:
    To get the most out of the cutters, we only rotate every second row; effectively allowing 7 "sharpens" plus the original setup from the factory per set. We've had the head for 18 months and we're halfway through the cycle.

    The head has 10 rows of 25 tips so: 25*$35 = $875 every 3 years in an industrial environment machining anything from pine to recycled blackbutt - I would imagine much longer life (maybe double or more depending on timber) with just weekend-warrior use.

    Furthermore, while carbide doesn't hold a 'scary-sharp' edge as well as HSS, it holds a working edge for much longer; which leads to my next point.

    With use, HSS knives will develop a bow toward the centre due to uneven wear and no matter how hard you try to spread work across the width of the machine the centre always seems to cop the most; so not only do you end up with a poor finish from blunt knives, it's not truly flat either. Because carbide is so much more wear resistant, this just doesn't happen. Even if you have to rotate a few chipped tips there's no noticeable change in surface quality because the dimensional difference between used and fresh edges is almost zero.

    Sharpening Time:
    Aside from not having to do it as often, there's no need to worry about jigs and knife protrusion when rotating the inserts - they're self-aligning and are spot on first time, every time. There's also the advantage of not having to send out a set of knives each time you get a chip. I haven't timed it, but rotating 125 tips takes me around 30-40 mins; replacing a full set will obviously take much longer.

    Noise:
    I measured the noise levels before and after the swap.
    Straight knives no load: 90dB(A), 5mm cut in 150x50 vic ash @ 12m/min: 102dB(A)
    Shelix head no load: 87dB(A), 5mm cut in 150x50 vic ash @ 12m/min: 93dB(A)

    Every 3dB is double the sound level so I'll just leave those numbers to speak for themselves.

    Conclusion:
    Better finish, less noise, longer life and more convenient. Do you need it? Maybe. Is it worth it? Definitely.

    Phew, that's a lot of words for this time of night. Happy to answer any other questions that people have.

    Usual disclaimer: I'm not involved with, or have a financial interest in any company involved in the production or sale of the stuff above, etc.

  8. #7
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    Default

    Great stuff elan (and all). Thanks

    I've got no doubt that they're the way to go. I've had to resort to a thickness sander at TAFE or a saw at home to "plane" a lot of the timber I've cut myself because the crazy grain just explodes under straight knives. That's the biggest factor for me wanting a spiral head - even a dodgy non-helical Carbatec one. It's just so hard to pull together for the big spend as a constantly broke backyard hack (without at least a dedicated long term budget and saving plan for replacement cutters).

    In a business environment I imagine the cost pays for itself in less time and wages spent preparing stock, maintenance, and less wear on machines. At home it sounds like something you'd almost forget about (kind of like my car rego and insurance )

    It seems everything about them besides the initial cost are huge pluses. That "cost over time" thing is sometimes hard to recognise and a big single spend on new cutters can be difficult at the time unless you remember the YEARS between having to do it rather than regularly handing over smaller amounts in the same time which could possibly equate to the same total amount anyway. In a way, straight knives are the rental and spirals are the outright purchase.

    Still, you get what you pay for and these heads really sound like they're worth every red cent (or is that 'silver 5 cents' these days?)
    Every time you make a typo, the errorists win.

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