Drilling Hardened Steel

[cdhknives]

I have this knife blade almost complete and one pin hole is out of place. I would like to move it over about 1/4", to the red dot in the picture. Since handle scales will cover, the extra holes are of no consequence, but for symmetry's sake I want this one hole centered in the rectangle of the 4 smaller holes.

Steel is a knife blade tang, ATS-34 at about RC60, about 5/16" thick, with cryo treatment. The hole is just over 1/4" (F drill, before hardening). I can live with a clean 1/4" hole. A larger hole is better. THe pin through will be a 1/4" Moasic tube, so a little slop is good and it'll be tight when epoxied in place.

I have (4 and 2 flute) new SGS TiN coated carbide endmills in 1/8", 1/4", 3/16", and 3/8", a lathe with collets, and a milling attachment, no mill. No carbide drills. I don't expect my drill press is rigid enough to drill this. I don't know if the milling attachment is rigid enough for this. It is the Atlas standard unit in like new condition.

I have MT2 backing plates for my tailstock for drilling but they require hand holding the blade. Not my first choice.

My first thought is to clamp it in the milling attachment and bore straight through with the 3/8" endmill. I could also use the 1/4" mill and try and walk it over. I could plunge the 3/8" mill through the side of the existing hole and walk it over. I could plunge it 2-3 times to take 1/4 moon slices to enlarge the hole in the direction I want. I really don't know the best way to approach this cut.

Is this a case where lube on carbide tooling might be a good idea?

 

[markknx]

Not sure I am understanding your issue right. are you wanting to move the bigger hole to center on the red dot? if so just center the end mill where you want it and plunge in nice and easy. Keep your rpms on the low side, at least till you see how it cuts. You could anneal the blade to make it easier to drill.

Of course you know the standard price for advice here is Pics. when complete
Mark

 

[T Bredehoft]

Just how hard is it? RC 40? you might make it with a new sharp drill, but try a center drill first.

 

[Cobra]

I had good luck using Bosch spade carbide drills from Home Depot for drilling the hardened body of a sine vise for hold downs.
Run the drill as fast as your mill or drill press will go and use compressed air to keep chips clear and provide cooling. if the chips are not kept clear, they will jam with the blade of the drill and shatter it.
Should not be a problem.

 

[Billh50]

On steel that is RC60 I would use a carbide drill before I would even think of using an end mill. If the end mill is not center cutting it will want to chatter and break before you get through.

 

[janvanruth]

masonry drill

 

[RJSakowski]

If you are sliding a hole over slightly, a diamond burr in a Dremel might be the ticket. If a new hole, a carbide drill would work, A carbide end mill could move a hole if you take your time and don't push the process. Big box DIY stores and HF have diamond burr sets at very reasonable prices.

 

[cdhknives]

My endmills are center cutting.

I can plunge through the existing 1/4" hole and walk the hole over another 1/4" or so..IF this lathe mill attachment is rigid enough...???

 

[cdhknives]

Annealing ATS-34 is a 1500F+ and 30 minute+ process and would ruin the heat treatment too far away from the hole. Warping is also a possibility.

 

[T Bredehoft]

Should your milling attachment be solidly mounted without vibration, yes you can walk a mill sideways, also, you might put a little pressure on it sideways, and move the carriage in and out a bit, to encourage cutting. If you encounter chatter, try something else, Chatter will break a carbide mill in an instant.