Breaking centre drills

[HopperParticipant @hopper]

Assuming that the lathe is the Portass PD5 you mentioned in another thread, when you tighten the tailstock clamping handle, it should pull the tailstock up against the angled dovetail side of the flat bed ways, so it will always clamp in the same position, so no need to worry about that.

But there is adjustment side to side to align the body of the tailstock with the headstock spindle if the centre drill is not drilling right on centre. The body of the tailstock and the base are two separate pieces, with an adjusting dovetail or step slide running sideways for this purpose.

Other than that, use the largest centre drill you can, at the highest RPM you can.

Use a good quality name brand centre drill. Not cheap no-name junk.

Use a pecking motion to keep clearing the chips and to keep the tip cool.

Flood it with whatever oil you have in the nearest oil can, to keep the tip cool and lubricated.

Don't try to drill the chamfered part of the hole to full depth on the centre drill. Only a third to halfway is needed to make enough of an angled face for the tailstock centre to engage with in use.

And as said already, forget centre drills for starting drilled holes. Use a spotting drill instead. Or a very large centre drill and just use the very point to put a small divot in the job to start your first drill proper. Reserve centre drills for when you actually need to use a tailstock centre in the hole afterwards.

Edited By Hopper on 09/09/2022 11:07:07

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 09/09/2022 10:53:34:

Assuming that the lathe is the Portass PD5 you mentioned in another thread …

.

Strangely … When I looked back at previous threads, there was a photo : but I cannot find an Album

If it’s the Portass lathe, the underlying problem could be headstock alignment

… I would check that before exploring other avenues.

MichaelG.

.

 

.

In case it’s not obvious:

Quote from lathes.co.uk

”Offered in two forms, one as the simplest kind cast as one piece, the other with a separate bas that allowed it to be set-over for the turning of slight tapers.”

Edited By Michael Gilligan on 09/09/2022 12:52:28

[VicParticipant @vic]

I rarely use centre drills these days, unless it’s actually for use with a centre. I locate holes with a spotting drill and not broken one yet!

[old martParticipant @oldmart]

Because of the small diameter of the nose of centre drills, the maximum speed available should be used, together with lubrication. The extended nose is there for a purpose, to make sure the flanks of a centre are making contact without the point touching. For drilling, a spot drill would be preferred, or I use a "centre" drill with a 90 degree flank rather then the 60 degree intended for using with a centre.

[Author]

Posts