On larger machines i have worked on they have a taper dowel which is reamed when in vertical position to remove the dowel it has a thread which has a nut on which when tightened extracts the dowel. This stopps the head rotating and sets the head in vertical position.

David

On 12 November 2023 at 08:28 JasonB Said:

I believe it is actually lever 2 that locks the head, lever 3 rotates the collar on the threaded column to raise and lower the head, see video

…

Apologies … it was rather early when I posted

I was hoping that the collar acted as a big lock-nut.

Oops !

MichaelG.

Assuming you had a proper milling chuck and vice.

Did you lock all the moving surfaces not in use?

Did you use the apron wheel to drive the cut.

Don’t climb mill on that machine.

Doesn’t the Clarke have a backlash adjustment on the apron?

It’s when the mill seems to be self feeding and the cutter effectively tries to climb out of the cut as it pulls it’s self along. It can be a quite violent process if you are taking a relatively large cut that will find any slop in the setup or mill that’s a bit wobbly.

Climb milling is where the feed is in the same direction as cutter rotation. (i e. On a vertical mill, a cutter revolving clockwise, viewed from above, removing metal on one edge of the work, and the work being fed in the same direction.

This means that the cutter will tend to grip the work, rather like a pinion on a rack, and pull the work along.

With hobby, or any machine lacking backlash elimination, this is NOT good.

It might produce a better surface finish, but the cutter is likely to grab the work with disastrous consequences.

So, normally the work is fed against the cutter, so that the cutter tries to push the work away.

Hope that this makes it a little more plain.

Have heard that the CL500M is prone to movement. If the column cannot be locked firmly enough, maybe an additional clamp for the column could be added

Adding a clamp, with positive locking with a pin would restrict the versatility of the machine, because the column could only be moved up or down in fixed increments, of say 20 or 25mm. (for a 6 or 8mm diameter locking pin) because of the spacing of the holes made in the column.

You might be able to get away with a smaller diameter pin,.

What is the pitch of the thread?

You might be able to drill a small hole, for the pin, at the bottom of the thread, to reduce the increment to the pitch of the thread

Even a 3mm pin, allied to the existing locking arrangements may be sufficient to prevent the head from swinging.

Sounds like Catch 22 in that ideally, you need a mill to keep all the holes in line.

Possibly:

Hold the column between chuck and Tailstock; mount a “jig”. with a hole at centre height, in the toolpost, and having aligned on one thread, use the Leadscrew to increment the Saddle after each hole has bee drilled.

HTH

Howard