Guys, can anyone explain why it gets harder to punch through metal when you are just about to finish the hole?
I’ve been drilling holes through my long spring traps and adding the lil booster spring in there and riveting them together. Also central swiveling all my 11 and 2 longs.
You start drilling and just about when you get to the end it gets harder..
I’ve often wondered why.

Are you using any lubricant??? Heat tends to do this. Also the end finish metal wall is weaker so you are getting a concave effect. So the whole drilling point isn’t being used.

Some materials tend to work harden from the heat build up during cutting. When you are about to break thru, the heat is concentrated in a smaller area. And if your drill is the least bit dull, it take more pressure and creates even more heat. A good cutting oil (not lubricating oil) or cutting fluid helps keep the drill cutting and not just rubbing which creates more heat.

Having the part clamped in a vise on a drill press, you have more control of down pressure to keep it cutting rather than rubbing and creating more heat. Also, the quality of the drill bit itself has a lot to do with how it cuts. There is lots of chineseium bits on the market that are junk for metal working.

When you drill any material, the effect you are feeling is actually as the tip is just starting to protrude out the other side. The "edge" of the hole you are creating is now grabbing the drill bit itself, causing a little binding on the side of the bit. The tip is no longer boring. With certain bit designs, you may actually have the bit jamb, and stop entirely if the drill isn't fixed, such as a drill press, and have the drill itself continue turning. Have smashed my knuckles a time or two drilling in tight places.

As you are breaking through the hole your heat is concentrated in the thinning metal. Use a lubricant and slow down your rpm. If your chips are blue your rpms are too fast. I have drilled holes for a living for 35 plus years.

Use some tap oil.

Thanks guys,,, now I know

Or just start out with a smaller hole and then drill the size hole you need.

Work harden. If yku are drilling multiple holes in a piece your next hole might be even harder to get started.

I second the rapid tap we switched from tap magic only thing I don’t like is the smell

We use it at work. You could probably use a drop of motor oil or any lubricant that absorbs some heat I imagine.