I recently finished a major rebuild of a Tom Senior E type milling machine.  This is the light round column mill with the S type vertical head.

The machine as purchased was in reasonable condition mechanically, but with rough paintwork. It had good slides and no major wear anywhere.  Nevertheless I rebuild the head very carefully with new oilite buses and taper roller bearings.  I also fitted a 3 phase motor and VFD.

The machine was set up very carefully. Accurately trammed and with gibs adjusted for no shake. It runs very sweetly, with no strange noises.

Now the problem:

If I take a cut in the y direction everything seems normal.  For the sake of argument, with a 150 thou height of cut on the side of a EN3 mild steel block, with a very shallow 30 thou deep cut, everything goes very smoothly and quietly. (new 3/8in 4 flute cutter running at 600 rpm and about 3in/min feed.  Cutter held in MT2 taper ER25 chuck).

However, when I switch to an x axis cut, without changing any settings, I get a painful high pitched squeal for the duration of the cut. It makes no difference whether I traverse left to right or right to left (conventional not climb milling)

I have tried changing the depth and height of the cut with little effect.  If I reduce the spindle speed to 400 rpm, the frequency and level of the noise drops, but it is still there.  Increasing the speed to 700 rpm increases the frequency of the noise, and it is still painfully loud. Doubling the feed rate reduces the noise but doesn’t stop it. Changing drive belt tension does nothing.  The quality of the cut is not noticeably different in the 2 directions.

I cannot for the life of me think of a reason why it should cut quietly the y direction, but emit this load squeal in x.

Any suggestions would be very welcome indeed.

Thanks

Mike