That's waht I said ....a few months ago?
Post no. 30:
Mystery solved! My cheap bosch jigsaw with a bosch 9" blade cut right through a scrap of rough-cut 4x6 timber. It didn't drift more than 1/16th top to bottom. Ordered a roundnose bit from Home Depot, will update with photos of the process as soon as I have a chance to buy a real 6x6.
Nobody goes actually back and reads these replies.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)