On 2008-10-15, Kelly Jones wrote:
Got a problem with my 9 x 42 horizontal - vertical mill (Grizzly).

Actually, probably more a problem with me.

Twice now the end mill has walked out of the collet and made unpleasant
looking marks on the table. Both times when making the cut the whole
machine has vibrated (not badly, but noticably). I have examined the
assembly for looseness, ensured the bolt is tight, and free of burrs and
chips, reduced the feed rate to a crawl, changed the speeds, and made sure I
had a sharp end mill. I really need some new ideas.

This is why endmill holders are made in sizes which fit collet
spindles. You want that -- either one with setscrews to grip by the
Weldon flats for US mills, or a special Clarkson collet chuck if you are
in the UK where you can get the threaded shank Clarkson type endmills.

Both of those resist the walking of the endmill out of the
collet on heavy cuts. (And I suspect that you were making fairly heavy
cuts -- or had a cheap or worn collet, but *never* trust a collet for
heavy cuts on larger endmills.

Oh yes -- also put sacrificial spacers between the workpiece and
the table to prevent those divots. :-)

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---