Balancing tool holder

[adamchapman]

Hi,

I bought a Craftsman Quickrout kit recently for my 1/4 inch router.
YouTube- Craftsman QuickRout ATC Tool Release Tests YouTube- Craftsman QuickRout Review for Possible ATC
When I turn the router on, I get a good deal of vibration from it and it makes a deep pitched humming sound.

I assume it's unbalanced, but don't know how to balance it!

I really appreciate any advice.

[vger]

Adam,

I see nobody replied back on how to balance the Quickrout adapter. It might be a bit of a chalange for something that size.

First you will need something that can measure the vibration with repeatability. A vibration pickup (asselerometer) can be bought for $$$ or, you can make one. A very small speaker, from headphones perhaps, will work. You may want to attach a small amount of wieght to the center of the speaker, a small flat washer with hot glue should work. You may want to put the speaker in a housing of some sort with a means of attaching it near the bearing of the router or whatever is turning the part to be balanced. Then you will need someting to measure the output of the pickup. There are some programs that run an FFT from your sound card that will work... here is just one of them
Free Download Spectrum Ananlyzer pro lab 4.3 - State-of-The-Art spectrum analyzer
Connect your vibration pickup to the line input of your sound card and with the pickup mounted to the router, run it at a repeatable speed. If it's a variable speed router, set the speed and leave it there, don't adjust during the process.

On the FFT display, one peak will show up that is related to the rotation speed of the router. Record that measurement as "Initial" You may need to convert the indicated measurement so that an increase in level is an increasing number. If the scale on the FFT is in -db, you can just use a ruler to measure the hight of the peak.

On a piece of paper, use a compas to draw a circle with a radius equal to the "Initial" reading. Use a protractor to put marks at 0 deg, 120 deg, and 240 deg on that circle.

Now take a piece of material, drill rod, or round stock, the diameter of the shank in the holder and mill or grind a a step on one end to make a small unbalance in the stock. Chuck that piece in the adapter with the heavy side in line with a known (marked) spot on the adapter. You will need to mark the adapter at 0 deg, 120 deg, and 240 deg. If it has a hex nut on it that makes it pretty easy. Run the router again and record the measurement. It should be a little different, either more or less, it doesn't matter which, than the intitial. If it is not at least about 20% different, then a larger unbalance on the stock piece may be needed. Set your compass to the radius of that reading and draw a circle with the center at the 0 deg mark on the Initial circle.

Rotate the stock piece so the heavy side is alligned with the 120 deg point on the adapter and repeat the measurement process and draw a circle with the center on the 120 deg point on the initial circle. The 0 deg circle and the 120 deg circle, should overlap. If not, you need a greater unbalance on your stock piece and start over.

Do the same thing with the weight and circle center at the 240 deg locations. You should see that the three "trial" circles cross over one another, or come very close at one point.

A line drawn from the center of the "initial" circle through the cross point of the other three will be at the angle that weight needs to be added to the adapter to balance it. Or... you can remove weight at the point 180 deg away from that angle.

If you choose to remove wieght, just file or grind a very small amount off, and remeasure the vibration. If the vibration decreases, take a tiny bit more off. Repeat untill you are happy with the vibration.

There are ways of calculating exactly how much to remove, or add, based on the radial unbalance the trial wieght provides, and the ratio of the cross point to the intitial, but it's pretty complex.

Happy balancing
Steve

[ger21]

It also might be an issue of runout causing the unbalanced condition.

[ImanCarrot]

Once you get it balanced as good as you can, try different speeds, sometimes you can hit a harmonic on the RPM which will cause vibrations.