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After countless hours of delays waiting on my air compressor to catch up from using my die grinder I got fed up and went in search of a better way.

I found a Roto Zip at Lowes. I took the depth adjustable base off because it was in the way and not needed. It has 3 different size collets and one is perfect for carbide bits which I am using a lot. It also works with the mandrel for sand paper rolls. It does not have one small enough for Dremel so you still need your Dremel. If you haven't looked at these the electric motor has plenty of torque and they spin at 30,000 rpms. At that speed you have to be careful how much you take off and especially if you are working on aluminum heads. I'm having to be careful with cast iron. I if had one of these when I started on my heads I would have been done weeks ago.

 

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Used for hanging Sheetrock, to cut out for plugs light fixtures light switches etc... Never thought about using one that way but they def spin fast enough (actually probably to fast but usable as you said) and have plenty of torque. I still have mine from my construction days but its a DeWalt brand...
 

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Not for sure what my DeWalt turns rpm wise, if i think about it I'll pick it up next time I walk by it and check it...
 

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I just bought an electric high RPM grinder like a Dremal that is a Craftsman. Its got variable speed (5,000 - 32,000 RPM), uses Dremal or Craftsman bits and felt smaller and lighter in my hand than the Dremal brand.

I also have a tool similar to the one shown but it's angled at 90 degrees at the head and is intended for stuff like drywall, wood, plastic, etc. but the bits aren't interchangable between the two tools.

John
 

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The RotoZip is certainly capable in RPMs, but I would suggest you experiment to see if you can hold it in a braced position. I use various grinders, but for most of the heavy work, I use an electric die grinder that is about 14" long. This is important to bracing it to both reduce fatigue, but also have much better control of the cutting. The technique I was taught is to fix the head at the correct height and angle to allow bracing of the grinder with two hands firmly against the hip. The position is much like you would hold a heavy machine gun for hip-shooting.

To grind accurately and smoothly, the hands do not move the grinder - your body does, swiveling at the hips like a turret. You can take amazing amounts of metal out in one pass so accurately, that in just a few passes (while changing the head fixture angle), a finishing roll is all you need to blend the flat cuts into the final form. In-fact, you have to be careful to avoid cutting too much on any one pass, as it's easy to take 1/8 to 3/16" in a single pass, which may be too much when cutting successive angles on a radius. Remember, you don't use a carbide cutter to 'work' the metal like a sanding drum - you cut with it.

Experiment making braced cuts all over a junk head. It doesn't take long to find the 'feel' moving against the cut like scooping ice cream. HTH

David
 

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Discussion Starter #7
I have made good progress with the roto zipper. It is fairly easy to brace when I need to bear down but I spend more time with it just gliding over the surfaces fairly lightly. At those rpms and with decent carbide bits which I have it really can remove some material. Bits of cast iron dust fly everywhere. It won't do the Eastwood sandpaper rolls. Yes I did actually try one. It slings those apart in like 3 seconds.

I am asking myself at this point,,, WILL THIS EVER END???? At some point I am going to have to simply declare good enough and go take the things to the machine shop. I just hope that I didn't go too thin anywhere. I studied cut aways of these heads for some time so I think I should be ok.

This roto zip is the closest thing I could find to an electric die grinder. I didn't know anybody made such a thing.
 

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I am asking myself at this point,,, WILL THIS EVER END???? At some point I am going to have to simply declare good enough and go take the things to the machine shop.
You're done when you either

  • make them as even as you can by eye and feel and you're tired of it, or
  • until your manometer says they have as close to average flow as possible down each port, your string shows there is no flow separation, and the different ports are flowing as even as as possible, or
  • until your flow meter says you've met your target and they're all even.
Every head porter has their own tricks, and one rule of mine is to do a little on one port, and then match the rest of them to that. Check for flow and separation. Then go back and do a little more and match them, etc. This way you can stop at any point that you've matched them and they will at least flow evenly.

David
 

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Discussion Starter #9
I don't have a manometer or flow bench. I will just cc them. I am almost done. A little more polishing tomorrow and I think I can haul them over to the machine shop.
 

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Then you're on the first option. When you feel good that they are as even as possible, throw 'em at the machinist, bolt 'em on the engine, tune them in and see what you get.
:tup:
David
 
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