Mike & Gerhard,
That is a standard method for cutting slots such as that.
To eliminate the bouncing effect, you could try going down each side seperately with a smaller cutter to eliminate the climb milling while cleaning up the rough edges to almost full slot width, then go down with the full width cutter to clean things up.
Did you lock up the axis you weren't using? If not, the table will tend to rock side to side, so giving you problems. A lot of people blame lack of rigidity of the column for it, when it could just be incorrectly set gibs, or not having gibs locked when machining in the opposite axis.
But I can understand your concern about these smaller machines, the columns do have a tendency to rock 'n roll a bit.
Another thing to remember that I should have mentioned, and this concerns almost all sizes of machines and cutters that we tend to use. If you use the correct size cutter for a slot from the start, you will invariably get a very slightly oversized slot. I always go down with a one sized under cutter first, then finish off with the correct size.
Like all things in this game, everything plays it's role in getting what you want, as you are finding out. Machine rigidity, cutter type and quality, lubrication and swarf clearance, material, speeds and feeds plus anything else that the world wants to throw at you to stop you making what you want as accurately as you want it. As you get used to your machinery, and listen to what it is telling you, you will eventually be able get around most of these problems thru a bit of a tweak here or something else there, that is what is called machining experience. You are not alone when it comes to getting machining problems. When I get in my shop, I can guarantee that something will crop up, and I think all the experienced people on here will say the same, no matter how long you have been at it, something new always comes along to throw a spanner in the works.
Bogs
