Drilling accurate depth holes

[Bob SillitoeParticipant @bobsillitoe83708]

Hi,

I need to drill a 3mm dia hole on my lathe but to a fairly accurate depth. The graduations on my tailstock barrel are 1/16″ but I need more accuracy than that. Just wondering if anyone has any suggestions about how I can measure how deep I am drilling?

Thanks

Bob

[Peter Cook 6Participant @petercook6]

What type of lathe?

Two quick options I can think of. One is to position a dial gauge so that it measures the travel of the tailstock. Touch the drill off on the face of the work and zero the dial gauge, then it will measure the hole depth.

A second is to make/buy a small stop collar that fastens round the drill (grub screw?). Set the collar so that the required depth of the hole is the distance from the tip to the collar. Then you will stop drilling when the collar touches the face of the work.

[JasonBModerator @jasonb]

Touch drill bit against the end of the workpiece.

Put a bit of square bar or back end of a tool bit in the toolpost and bring it upto the front of the chuck, zero handwheel dial.

Now move the bar towards the work by the depth of your hole using hopefully more accurately marked graduations.

Drill hole until the bar stops the chuck going any further,

[DalboyParticipant @dalboy]

If possible make a gauge up like this. Always handy for future projects I got the gauge from Machine DRO and some small pieces of Ali plate from my stockpile.

[BazyleParticipant @bazyle]

Bit of masking tape round the drill at the designated distance. If that isn’t accurate enough you need to decide if it is the tip of the drill or the edge that is your required distance then clean up the hole with a D-bit.

[Bo’sunParticipant @bosun58570]

[Clive FosterParticipant @clivefoster55965]

Sometimes a semi-sacrificial tool is the way to go. Drill a through hole is a suitable bit of material to make a sleeve and fit a setscrew to clamp it to the drill. Adjust so the drill projects the same as the depth needed and make the hole.

Once done put it the possibly useful bits box for next time. Which will either never happen or, if it does, the tool will have migrated to that dimension that stores stuff until the week after you need it!

Generally best to go touch undersize when drilling so the sleeve has t be worked onto the drill. I’d do the setscrew hole before drilling.

Good way to get some use out of the short ends that aren’t long enough to hold in the chuck.

Clive

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