Cutting cirlces with rotozip?

Discussion in 'Archived Threads 2001-2004' started by Adam O, Apr 24, 2002.

  1. Adam O

    Adam O Stunt Coordinator

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    Im starting my diy sub and have picked up all of the supplies i'll need. I dont have a plunge router but do have a rotozip. The only circle jigs for this go up to a ridiculous 6" in radius. Obviously I need something bigger, my circles need to be around 24.5", do u have any suggestions? A home made jig? An extension onto the small 6" radius jig? Will free-handing the cut be precise enough?

    Thanks Alot.

    Adam
     
  2. ThomasW

    ThomasW Cinematographer

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    RotoZip tools are good when used for their intended purpose. One of those isn't cutting thick MDF. You'll burn up the tool trying to cutout parts if you're making a tube sub. They simply lack adequate power for this type of operation

    You'd be better of hand cutting with a saber saw than trying to hand cut with a RotoZip
     
  3. Adam O

    Adam O Stunt Coordinator

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    Thanks Thomas.
     
  4. Patrick Sun

    Patrick Sun Studio Mogul

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    If you're on a budget, a cheap plunge router costs around $60-$70, and the carbide tipped spiral upcut 1/4" bit costs around $15-$20. A router/jig from Sears costs me around $20. I've gotten plenty of use from this small investment (just be sure to wear earplugs, mask, and eyes protection).
     
  5. Chris_Kelly

    Chris_Kelly Auditioning

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    LOL!! I've cut a number of holes in 3/4" MDF with my little dremmel...poor thing! It hasn't burned up yet but I've prolly cut a few years off its life.

    I can't do it all in one cut tho. I have to make a cut about 1/8" deep at a time...then lower the bit and cut again...repeat until all the way thru.

    It works but it's very time consuming. The RotoZip has quite a bit more power than my regular version Dremmel so it should actually be able to do a little better/faster.

    BUT....if you're going to spend the money for a RotoZip, you may as well go ahead and buy the router and tools....those RotoZips aren't exactly cheap!
     
  6. ThomasW

    ThomasW Cinematographer

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  7. Chris_Kelly

    Chris_Kelly Auditioning

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    So it'd take me 4 hrs instead of 2 to cut a 12" diam. hole [​IMG]
    Naw....I've GOT to invest in a plunge router myself.
     
  8. Greg_R

    Greg_R Screenwriter

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    You should take multiple passes with a router as well. If you don't want to invest in a circle jig, a piece of hardboard (masonite) works well. Cut a long rectangle & nail one end to the exact center of your intended circle. Mount the router on the other end so the distance from the outside of the bit is equal to the hole size you want. Mounting the router involves removing the plastic baseplate and using those screws to attach the hardboard. To change the diameter of the hole, move the nail toward or away from the router...
     
  9. Jon Torres

    Jon Torres Second Unit

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    I've got a craftsman cutting tool (similar to rotozip) and have cut through 3/4" MDF for DVC 12 with one pass. I also use it for the terminal cups. The 1/8" rotozip bits break easy though.

    If you're on a tight budget like me, you'll work with what you have. Next sub I'll use a jigsaw and cutting tool for the driver cutout. Eventually, I'll pick up a router.
     
  10. Adam O

    Adam O Stunt Coordinator

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    Well actually I already have a rotozip. If I had the money I wouldn't be questioning buying a router.

    On another note Im half done my homemade circle jigs for the roto. They are not unlike most of the ones seen here. I also tried free handing the top/bottom plugs, this resulted in a less than circular outcome, however I dont believe the slight elipticalness will effect the building as my tube is 44" in length.

    EDIT: I used the circle jig and it worked quite well I also used it to cut the port hole. The problem is the sides are not perfectly circular all the way around and they are not square to the surface of the MDF for some reason.

    Thanks for all the info,

    Adam
     
  11. jack x

    jack x Stunt Coordinator

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    I also have a craftsman cutting tool (similar to rotozip) and have cut through 3/4" MDF with one pass. And I have not had any bits break yet. I think mine has a 4 amp motor - so not the most powerful.

    I also have a router, but it is only 3/4 horse and I prefer the rotary tool for cutting thru mdf.

    best of luck!
     
  12. Chris_Kelly

    Chris_Kelly Auditioning

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    Jack,

    By my own 30 second calculation, the 4 Amp rotozip equates to roughly 3/4HP as well.

    The RotoZip has always had one thing I REALLY wished the Dremmel had......the circular jig tool thingy for cutting these blasted circles!!!

    If you're cutting holes in 3/4" MDF in one pass with a RotoZip, I may just have to go out and buy one these things...along with that nifty circular hole cutting tool.
     
  13. JonWB

    JonWB Agent

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    I'm sure Rotozip has a Web site somewhere, I don't know the URL off the top of my head. I just wanted to point out that there are two different circle cutting "jigs" for the standard Rotozip tools. The smaller one (that I have) only goes up to a 12" or 15" circle (I can't remember which) the other one one is much nicer and will cut up to a 22" circle (I believe). Again you'd want to check out what the exact numbers are for each one, I just wanted people to be aware that there are two types/sizes...
     
  14. Greg_R

    Greg_R Screenwriter

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    Once you see (hear) a bit snap off at 20k RPM and ricochet around the room before embedding itself into a wall you'll want use 1/2 shank bits and take multiple passes...
     
  15. Alexis

    Alexis Stunt Coordinator

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    I tried to use a dewalt rotary tool to try to cut a 1 inch thick piece of regular particle board, and the bit started to heat up and melt the particle board after about 3 inches. This was with the default bit that came with it and I was making a straight cut. I promptly switched to a handdaw and finished the job faster and more smoothly. I was not very impressed with the rotary tool, based on this experience.

    I did use a dremel with cutting attachment to go through some hardboard, and that went well.
     
  16. ChristopherJ

    ChristopherJ Extra

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    I did all of my cuts in 3/4" MDF with my Rotozip. Really no problem with heat, etc.

    I made a really rough and ugly circle jig with some plexy glass. I used the rotozip to do all the cutting in the plexyglass. It is hard to explain and I don't have a digital camera to speak of. Basically I cut a long slot in the plexy glass for a crew with a nut and two washers to hold it in place in the slot. The rotozip was attached using all but the metal piece from the circle jig. Worked great, just took my time. Unless you want the excuse to buy a router, it would probably be easier by the accounts I have read, I would recommend that you make do with what you have. The sanding/grinding attachment works great on MDF too!
     

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