I have used Rotary tools for more years than I care to admit, mostly for Tile work ( re-grouting etc ). It is a fabulous tool but hard to achieve precision. I have found that the corded versions are not as susceptible to speed variations due to there amp power. Another factor is the diameter of the bit as well as its balance. If it vibrates you will achieve poor results . Another tool that works well if you need to keep the part flat or in plane is the oscillating tool made by Fein and a host of others. There are many attachments being made for this versatile tool. just my two cents.

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