Tailstock rigidness

Just a comment on the 8L and using the tailstock.

Due to the placement of the tool post the tail stock must be extended fully with a long center in order to turn using a center.

I was turning HRS (mild), 3/4 inch diameter down to .625. The work was held in the 3-jaw and supported with a center. The work between the chuck and center was about 4 inches.

.020 depth, .008 feed, small rad 35 degree carbide. (Center high as it should be) Tons of chatter. Reducing feed to .005 helped. Had to use a lot of pressure on both the tailstock spindle clamp and the tailstock clamp which reduced the chatter some more but not all. I also saw a lot of tailstock spindle deflection. New carbide so not the tool.

Looking at the setup the tailstock spindle is so far out the clamp is right at the back end so the reality is that the clamp is on the end of the spindle which means that it is actually not properly clamping. (pressure is on the end inside so the spindle can actually float inside the tailstock the amount of clearance.

The fix is a longer tailstock spindle which Tormach should be including. This way the clamp would work correctly, when locked the would be sufficient spindle on both sides of the clamp to securely hold it against the bore of the tailstock. To see this visually think pressure lines from the clamp through the spindle to the bore - the pressure lines should be a triangle similar to a roof truss pushing out 30 to 60 degrees from the clamp - as the spindle is right at the end there is only a pin point of pressure. Not good.

I am going to make one 2 inches longer. I need to order an M10-1.25 LH tap 1st. Simple project. I have an MT2 reamer, but I am going to to the taper in the 8L for fun.

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