Drilling Chrome shaft
I would like to drill .500 inch holes in 2.25 diameter Chrome induction hardened 1050 shaft material.What is the best tooling to start and drill the holes accurately.
Any advise will be appreciated.
We usually heated the spot where the hole was going in and out to anneal the surface of the shaft. Then HSS will usually drill it ok.
If you want to leave it hard as is, you'll need carbide drills.
Drill on center from the end or crosswise? If the hardening left the bar with a soft core, it makes a big difference where you want to drill.
I made a part from Thomson 60 Case shaft once. It had a soft core, so it was easy to drill and bore a hole down the center from one end. Then I used an oxy-acetylene torch to draw the temper (not really annealing) from a spot on the side of the shaft so I could drill and tap for a set screw.
The holes I want to drill are through the diameter of the chrome shaft
Originally Posted by L Vanice
Thomson 60 Case is case-hardened. That's where the name comes from.
The hardened layer is thicker than most such products, but once you breach it, the core is easily drilled.
I use carbide
I regularly drill grease channels in induction hardened pins. The material grade is CK45, which I believe is equivalent to EN8, or SAE 1043. The channels are halfway through the diameter (cross hole) into a hole drilled in the bore. The hardened layer is usually 4-5mm thick. HSS wont scratch it but a carbide drill whistles through. These holes are only up to 1/4" diameter so the carbide drill is not THAT expensive. I imagine a 1/2" would be costly but the small ones I have used (1 of each size) haven't yet had to be sharpened so they seem to last.
Forgot to mention; the suppliers claim 58-60 Rc for the ind hard layer
Last edited by BACH; 06-02-2008 at 01:03 AM.
Use a carbide die drill. They arnt to terribly expensive.
I have hand sharpened carbide masonry drills with a diamond wheel so that they drill hardened steel very well. Masonry drills are very cheap, especially at pawn shops and flea markets. Die drills are OK, but I have only found a few at the cheap places and have never bought a new one at retail.
I also use masonry bits to drill even in HSS. You can grind a little negative rake on the cutting edge to help. The big concern is to not let the drill get too hot,or the brazed bit will melt in the seam. I generally run the bits pretty fast,but haven't had to drill a 1/2" hole that way. Usually 1/4" or smaller. You need to buy a few extra bits and experiment with speed. Also,resharpen the bit for every few holes if you have a diamond grinder. I was drilling solid HSS old power hacksaw blades to make knives from,and found that I needed to keep the bits sharp,or they would burst the blade in half. These were solid HSS all the way across,not just welded on HSS teeth.
Thanks fellows for the drill information.
As you know I am weak on this issue of drilling harder steels.
What do you recommend I use to start the hole in the chrome shaft.Would I want a carbide center drill or a carbide spotting drill.Is it wise to grind a flat spot to start the drill.To maintain accuracy is it standard procedure to run the 1/2 drill bit through or drill a pilot hole first.