I actually like the single flute countersinks but as it is one flute the cutting action is a bit unbalanced so maybe on a small mill this can cause a orbiting motion. I don't know the Sieg SX3 personally but it will have a dovetail adjustment to reduce any side to side slop in the head.

Tony

I’ve not had any problems countersinking on my mill. I don’t normally use single flute countersinks for metal though, only wood. All my metalwork countersinks are three flute apart from a couple of the snail type with a hole.

In my experience, single 'flute' countersinks (crossdrilled hole type?) perform best if they are allowed to 'float' and centre themselves, so are good if the machine is not rigid.

For countersunk recesses use a countersink ground to the just over screwhead diameter so there is a small parallel counterbore to hide the edge of the screwhead.

Ian P

Demurrers might be, but cutters are more 'snail' shape

As said a single flute will be slower cutting than say a 3 flute countersink but they tend to chatter less so you don't get a "corrugated" edge like you can with multi-flute CSK bits. I just run them slowly with steady pressure and a few drops of cutting fluid.

Also like Ian says if these holes are for M6 CSK screws then the 12.4mm size driven just below the surface gives a neater looking hole as the screws have a short cylindrical edge and not a sharp one.

This is on the similar sized X3 using quill feed and about 200rpm. with the two sizes of ARC bits, sorry about the measurement, not easy to do looking through the camera when zoomed in rather than at the callipers

I mostly use 3 flute countersinks. I would agree with using the quill and quite a high force is needed. The cutting edges are long and require a significant force to cut rather than rub. I run smaller countersinks at 5-600rpm as I'm too idle to change in to backgear on the mill. However, for this 1" countersink I dropped to 200rpm:

The 1" countersink was in a job lot of tooling I bought from a fellow member of the local gliding club but seemed to cut ok.

When countersinking for screws I don't faff about with a parallel section. For a start it's not a defined diameter. What is defined are a minimum head diameter and a theoretical sharp head diameter. For M6 the numbers are 11.73mm and 13.44mm respectively. I simply countersink to 13.5mm, but always with a sanity check using the screw, as the tolerance on head depth for M6 is 0.2mm.

Andrew

Just my own taste but I much prefer csk screws to finish looking like Jason shows on the second hole in his video, I think it looks a lot neater than having the band around the screw head. I have a set of 3 flute csk bits which work well enough but for M3 to M8 I mainly use a set of stub drills which I reground to 90 degree and are sized to the screw head diameter plus a tad. They work really well, always cut clean, no chatter and leave a good finish.