[Eldon_Joh]

As most of you probably know the dovetail clamp has its limitations.

I did not take definitive measurements prior to this modification, but it is now up to somewhere around 5-10 pounds per thousandth inch of deflection in the x axis, at the spindle. (this is the axis of direction that distorts the spindle the most)

As it is now I'm running into the limits of the 10-32 screws holding the dovetail plate to the Z axis slide.

The spindle is much stiffer in the Z and Y axis than the x axis, the Z axis is on the order of .003 inches of vertical deflection, if I lift the machine by the spindle, i think it weighs about 100 pounds. (neglecting backlash)

(edit: it is the x axis deflection that is the most problematic, as those forces twist the entire vertical tube structure of the machine, as well as wrench on the z axis slide (see the photo in my second post, the addition of a bolt to suck the side plates forward is a major improvement as well))

I would like to replace the dovetail plate with a steel dovetail, welded to a steel plate, as this would permit bolting the dovetail plate to the z axis slide with say, a 3 inch by 4 inch bolt pattern, rather than a 3 inch by 1 inch bolt pattern. but i haven't done that yet, don't think i need to.

anyhow, thought you guys might be made aware of this limitation and the 2$ solution. (i used a stainless steel bolt, bought at ace hardware for too much lol)

[Jeff-Birt]

How many times do you lift the machine by the spindle while you are machining? Under its own power the spindle will deflect perhaps 0.003" if you stall the stepper motor out. By that time your milling bit will be flexing like crazy so that 0.003" from the Z axis flexing does not amount to much. If you stall out an axia on any machine tool you will be able to measure the flex 'somewhere', that does not mean there is something wrong with the machine, it just means your doing something wrong to get to that point.

Don't get me wrong I like to see guys thinking bout how to make things better but you can run into the same issue you get into with a car. You put in a bigger motor and then the transmission goes out, so you fit a beefier transmission and the rear ends goes out, etc, etc. If you drive the car with the stock motor you could have gotten 250,000 miles out of the whole drive train (but then you would not have that big motor in there.)

[Eldon_Joh]

Attachment 183906
Um, I also built a cradle to hold it together.

I wouldn't normally complain about the stiffness, but i got tired of carbide bits bouncing off tool steel instead of cutting into it.
Who knows, i'll probably break the ball bearings in the spindle next.

The steppers are NEMA23 425oz/in 2.8A but i only run them at 2.2 amps. so i don't have enough torque to snap most 0.25 inch 4 flute end mills