We have a new requirement that requires the insertion of two keyway holes in a 20 mm thick mild steel bar. Dimensions are:

keyway width = 4.673 mm
keyway depth = 2.2 mm
Keyhole diam = 28.575 mm

This is a simple keyhole. We are looking for the most economical way to cut this keyhole. We can easily drill the keyhole. The keyway is the issue. We have looked at buying a used keyseating machine, possibly a Mitts/Merrill No. 1, or a Morrison No. 1, but this seems like overkill for this simple job. We don't have access to a broach or a large press to do punching. Before we shell out several thousand dollars for a keyseater, and then have to go through the pain of learning how to use it, learning what additional accessories we will need, etc. etc. we would like to explore whether there might be a simpler solution using more conventional tooling or methods. We will need to make 5-10,000 keyholes a year on a pretty steady basis, will be doing it in Mexico, and must do this at absolutely minimum cost. The hole accomodates a keyed bolt.

We would appreciate getting some forum input and advice. Thank you all in advance for your assistance.

For this type of thing, a hole with a key slot the two conventional approaches are: Boring the the hole and then cutting the keyway using a keyway cutter. Boring the hole and then using a broach.

If this is just a bolt hole and does not need high precision you can maybe get away with just drilling the hole but cutting the keyway will need you to choose one of the two methods; keyway cutter or broach....these are the simple methods. Or possibly you could consider filing it to be simpler but I doubt it would be economic; not even in Mexico.

Thanks for the feedback. This brings up the next question I guess. This is pointed at someone who has some experience on the key cutting machines. Would the basic keyseater (or key cutter) such as the models that I mentioned above, do the job? Not having used one before, are they relatively easy for operators to learn? In looking for a used machine are there any pitfalls that we should try to avoid? If we buy a basic machine (there are several on e-Bay right now) what additional tooling would we need to make one of these useable?

Sorry for what probably seem like silly questions, but this is new territory for us. We previously had these holes punched at another offshore location that had a 500 T press and a custom die.

Thanks again for the assistance.

I cannot answer your specific questions about the keyseater; I was the guy that bored the holes which were then handed over to the guy who ran the keyseater. I am a Machinist (note the capital M) he was just a machine operator :); running a keyseater is pretty simple. What I can tell you is that broaching is much, much faster than keyseating and for your application I suspect that drilling followed by broaching is the best solution. Punching a hole with the keyseat using a custom punch and die might need 500 tons but broaching a drilled hole will need only a fraction of this. I suggest you look for a broach and press capable of pushing it; you should be down in the less than 100 ton region; in the long run it will probably be less cost and faster than keyseating.

dkeene, How large are the workpieces? If one person can readily handle them, a simple arbor press and Minuteman broach should be able to economicaly cut the keyway. 4.673 mm (.184") X 2.2 mm (.087") 20mm (.787") is pretty close to a 3/16" broach.

Thanks for the feedback. FYI, The workpieces are 445 mm in length and 90 mm wide and as I mentioned earlier, 20 mm thick. The keyholes go near the opposite ends of the bar.

We'll look at the broach idea more closely and see if that can be accomplished more easily than the keyseater. I am not familiar with the Minuteman Broach, but I'll do some research.

Thanks for the your assistance. This dialog is proving to be very helpful.