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Thread: Jointer cutter RPM and power??

  1. #1
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    Jointer cutter RPM and power??

    Re-furbishing/updating my old Craftsman 4-1/8" jointer (all cast iron). The old motor is showing signs of wear (shaft play). I have a Craftsman 1-hp. motor in good shape that I can use in place of the old one. Here's the rub:

    The jointer originally came with a 1/3hp 1750 RPM motor. The V-belt pulley system was set up to run the cutters at 4500 RPM. My new motor runs at 3450 RPM. Using a 4" drive pulley and a 2-1/2" driven pulley, the cutter is spinning at a cool 5520 RPM. Is this too fast? Is it in any way "dangerous" to life and limb? I always heard that the more cuts per second results in a smoother finish cut. Does this apply, or is that just for routers?
    Thanks, Butch.

  2. #2
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    Personally, I would change it out to a 3 or 3.25" pulley. A 3" driven pulley will get you 4600 rpm.

    Regards,

    Ron

  3. #3
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    I would agree with Ron. There must be a reason jointers don't run faster than they do.

    John

  4. #4
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    Quote Originally Posted by Butch Butler View Post
    Re-furbishing/updating my old Craftsman 4-1/8" jointer (all cast iron). The old motor is showing signs of wear (shaft play). I have a Craftsman 1-hp. motor in good shape that I can use in place of the old one. Here's the rub:

    The jointer originally came with a 1/3hp 1750 RPM motor. The V-belt pulley system was set up to run the cutters at 4500 RPM. My new motor runs at 3450 RPM. Using a 4" drive pulley and a 2-1/2" driven pulley, the cutter is spinning at a cool 5520 RPM. Is this too fast? Is it in any way "dangerous" to life and limb? I always heard that the more cuts per second results in a smoother finish cut. Does this apply, or is that just for routers?
    Thanks, Butch.
    Perhaps I misunderstand. Same pulleys used for both motors? My calculations come up with 2760 rpm using a 4" motor pulley and 2.5" cutter pulley.

    4"/2.5"=1.6 x 1725rpm = 2760 rpm

    Running the same pulleys with a 3450 rpm motor does give 5520 rpm. Not too much for a small jointer IMO. (except it might finish up an old set of bearings) To err on the safe side, you can reduce the motor pulley to 3" and run the jointer at 4140 rpm.
    Necessisity is the Mother of Invention, But If it Ain't Broke don't Fix It !!

  5. #5
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    Chip, you missed the point about the motor RPM changing to 3,450 RPM, which does give 5,520 RPM at the cutter head with the chosen pulleys.

    I would reduce the cutter head speed to near original by selecting different pulleys.

    Yes, cutter head speed affects finish quality, however so does feed rate.

    On a jointer you feed yourself, you can push the stock at a slower rate, increasing the finish quality.........Regards, Rod.

  6. #6
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    Can you swap the motor and cutterhead pulleys? Then you'd have a speed that is a little slower like 2150 rpms. You'd need to feed a little slower but the cutterhead bearings should last longer.

  7. #7
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    I still have an old 6" Craftsman Jointer, (model 103.20620) that I bought new for my dad, but I'm out of town for a while and can't look at the manual. Those jointers were sold WITHOUT a motor included, so the manual stated a 4500 RPM cutterhead speed when installing a motor IIRC, but I do not remember if that was stated as MAX Rpm or recommended Rpm.
    "Some Mistakes provide Too many Learning Opportunities to Make only Once".

  8. #8
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    I'm not saying it is safe to run yours this fast but check some specks many jointers run 5000 rpm or a bit more

    Phil

  9. #9
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    No Rod, I didn't miss anything. My calculations do in fact arrive at the same 5520 rpm with a 3450 rpm motor. I was a bit incredulous that the jointer originally ran at only 2720 rpm. That is pretty slow--even for babbitt bearings. But with only a 1/3 hp, 1750 rpm motor, a larger motor pulley would reduce cutterhead torque as rpm's increase. So, maybe 2720 rpm was the factory's optimum spec.

    As I suggested previously, a 3" pulley on the new 3450 rpm motor would give a very decent 4140 rpm cutter speed.
    Last edited by Chip Lindley; 02-22-2011 at 7:01 PM.
    Necessisity is the Mother of Invention, But If it Ain't Broke don't Fix It !!

  10. #10
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    Quote Originally Posted by Norman Hitt View Post
    I still have an old 6" Craftsman Jointer, (model 103.20620) that I bought new for my dad, but I'm out of town for a while and can't look at the manual. Those jointers were sold WITHOUT a motor included, so the manual stated a 4500 RPM cutterhead speed when installing a motor IIRC, but I do not remember if that was stated as MAX Rpm or recommended Rpm.
    Norm, you are correct.....the jointer DID originally come without a motor - only the driven pulley was installed, which was a 2" pulley. The manual simply states that a 1750rpm motor equipped with a 5" pulley will result in the recommended 4500rpm operating speed.
    What I have ended up doing is using the 3450rpm 1hp motor with a 4" pulley and changed the driven pulley to a 3", which gives me 4600rpm...close enough!....Thanks to all!........Butch

    **Actually, my math doesn't jive with the manual......I end up with 4375 rpm using their specs, but its a moot point now....also the extra 1/2hp I now have may come in handy someday............bb
    Last edited by Butch Butler; 02-22-2011 at 9:33 PM. Reason: forgot sumptin......

  11. #11
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    Leaving aside the cutterhead speed, a horse is a lot of power for a 4" jointer. My Craftsman does just fine on half a horse. Of course, if it's what you have laying around...

    Kirk

  12. #12
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    Quote Originally Posted by Butch Butler View Post
    Norm, you are correct.....the jointer DID originally come without a motor - only the driven pulley was installed, which was a 2" pulley. The manual simply states that a 1750rpm motor equipped with a 5" pulley will result in the recommended 4500rpm operating speed.
    What I have ended up doing is using the 3450rpm 1hp motor with a 4" pulley and changed the driven pulley to a 3", which gives me 4600rpm...close enough!....Thanks to all!........Butch

    **Actually, my math doesn't jive with the manual......I end up with 4375 rpm using their specs, but its a moot point now....also the extra 1/2hp I now have may come in handy someday............bb
    What a coincidence, a few years back the 3/4 HP motor on the Craftsman Contr saw I had given my Dad gave up and I found a place to get a pretty good price on a 1 Hp TEFC Baldor but it seemed so heavy I just had the 3/4 Hp rebuilt, soooo... I decided I would put it on the Jointer instead, but I haven't got a pulley for it yet, but it should really pep that little jointer up. Haven't really needed it since there are two more jointers in the shop but it will be handy for quick and small things that I do now on my buddy's 6" Rigid that he has stored in my shop, (along with a few other tools).
    "Some Mistakes provide Too many Learning Opportunities to Make only Once".

  13. #13
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    If that is one of the old Parks built jointers, I had one of those I used on jobsites. Very nice little jointer.

    One word of caution. If the guard is missing that covers the cutter when the fence is shifted in toward the operator, make a new one. My brother was cleaning it up and took mine off and didn't put it back on. I used to hook a finger over the fence when running small stock to hold it tight. I didn't realize that he had removed the guard, ran my finger into the cutter. It was not pleasant.

  14. #14
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    Quote Originally Posted by Chip Lindley View Post
    No Rod, I didn't miss anything. My calculations do in fact arrive at the same 5520 rpm with a 3450 rpm motor. I was a bit incredulous that the jointer originally ran at only 2720 rpm. That is pretty slow--even for babbitt bearings. But with only a 1/3 hp, 1750 rpm motor, a larger motor pulley would reduce cutterhead torque as rpm's increase. So, maybe 2720 rpm was the factory's optimum spec.

    As I suggested previously, a 3" pulley on the new 3450 rpm motor would give a very decent 4140 rpm cutter speed.

    Sorry Chip, I mis-understood your post, however the OP did indicate that originally the cutter ran at 4,500 RPM, he didn't state what size pulleys were originally used.

    Regards, Rod.

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