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Keeping the head from turning on a cheap mill

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CrazyModder:
Hello,

I'm using a cheap mill (known as "HBM 16" over here in Europe). It mostly does OK for me, but if I'm milling very heavily then the column may start to swivel slightly. This can lead to rather drastic results, the least of which being a bad mis-cut, and any X/Y numbers being invalidated.

I've attached an image of the machine. The culprit is the clamping mechanism at the base - no matter how tight, it still allows the column to turn if the force is too large. The column is very smooth, after all.

I'm thinking about boring some holes into the column in a straight line (maybe 1" apart), and one hole into the base. Then I could insert a tight-fitting pin to keep it from turning. But I'm not sure if the column might warp a little bit from all the holes, or if the forces may rip the base apart (probably not, but who knows).

The column is 70mm (~ 2.8") in diameter and solid.

Thanks for any comments! Did anyone here solve this problem on a similar machine?

BillTodd:
You're asking abit too much of that mill  IMHO.  Check your feeds and speeds.

Most of the fixes (including my wishbone stabiliser)are to keep the head alignment while lifting or lowering the head.

Drilling and pinning will only show up the lack of rigidity of the design i'm afraid :(

Bill

Swarfing:
A question? is the rack fixed on the column or does it float like a pillar drill? I have an Arboga where the rack is fixed and there is a jib to the side of it to take up the slack. If it is a floater then you could look at fixing the rack to the column and fit a jib strip. This is just a suggestion only?

CrazyModder:
@Bill, I'm aware of the limitations of the machine, and am taking a pretty long time with most cuts. But it does work well for me most times (roughing end mills make mild steel seem to be pretty soft...). I did replace the hollow column with a massive one, and that helped tremendously.

The problem occurs when I am just at the border of (in)sanity (with regards to depth of cut ;) ), and the swiveling creeps in slowly without me noticing; most times the workpiece is ruined then (especially when using flood cooling so I don't see much). I've not done the pinning because it seems pretty unsatisfactory to me - for once it will only allow "stepped" heights of the head. And I'm really not comfortable drilling holes into the base itself. Hence, looking for more ideas. What do you mean by "show up the lack of rigidity"?

@Swarfing, the column is losely coupled with the base and with the head. The base is slotted and must be clamped with the small(ish) screw that sticks out to the left, thus grabbing the column. The head is clamped to the column with some other mechanism that seems to hold pretty tight. The base clamp is opened to move the column+head up or down; the head clamp needs only to be opened to rotate the head. The head does not move up/down on the column.

The problem occurs in the base clamp, not in the head clamp.

BillTodd:
+The problem occurs in the base clamp, not in the head clamp.

Ah! In that case pinning would be a fix:)

Bill

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