How to clean-up small tapped threads?

[martik777]

How can I machine these 10-32 threads to look cleaner at the entrance?

 

[benmychree]

Usually done with a countersink, which by the looks of it you might lose too many threads, I'd try a 3 cornered scraper.

 

[Illinoyance]

Ditto: countersink.

 

[pdentrem]

If not using a countersink etc, Spin a ball bearing on a stick of some sort with valve lapping compound. Using a drill and orbit while spinning.

 

[ChazzC]

Small ball-end carbide “Dremel” bit. I keep a couple of different diameter ones mounted in pin vises in a drawer with other deburring tools.

 

[OTmachine]

I like using a spherical, ball shaped mounted stone, 1/8” shank thru the hole mounted in a die grinder. https://www.amazon.com/GRINDING-STONE-SET-shank-mounted-MATERIAL-MAXIMUM/dp/B001F4PVS6

 

[Flyinfool]

Ideally you want to c'sink the holes before tapping. The c'sink should be just to the OD of the thread. In cases like this where there are not a lot of threads I use a 120° c'sink to match the angle of the tooth profile. Those first imperfect threads due to the Diameter of the part are not really holding much anyhow.
You can try a c'sink now but keeping it centered will require that the c'sinking be done on the mill or the cutter jump all over.

 

[mattthemuppet2]

The problem is that these holes are tapped radially and then a taper is cut on the OD. Even on a straight surface countersinking a hole will produce an oval countersink. Here countersinking before tapping won't work, as that countersink will disappear when the taper is cut, and countersinking afterwards would have to be perpendicular to the taper, not inline with the tapped hole.

I don't think there's really much else to do than touch them up with a burr or small stone. From a design perspective, if these are designed to hold something (presumably these are some kind of tapered threaded extension?) then it'll be tough finding set screws short enough to not protrude above the surface of the taper and still have some means of tightening them. If having the set screws protrude above the surface then it would make more sense to have a steeper taper after the last threaded hole.

 

[Eyerelief]

I concur with the idea of using as shallow a countersink as possible, but I see the conundrum. Since your outer surface is cylindrical and not flat, you will be in pretty deep before you get 360* countersunk. Not knowing the purpose this might seem silly, but I have been known to counter bore with an end mill until I have a flat area completely around the hole. Something like this:

 

[martik777]

I went over them lightly with a stone, looks a little better but still not perfect. Will order a carbide debur bit for the next job. These are used to secure a steel cable - don't need to look pretty.