2mm Drill Bit Broke in 20dia SS Rod

If you use too slow of a feed rate, the SS can work harden and become very difficult to drill/mill/cut. I have had best success with fairly high drill pressure and feed rate, with kerosene as a coolant/lubricant. If the curl or chips are binding, back the drill out a few times to get another fresh cut.

I am using plain oil & cutting oil. 1st time when i use High feed rate centre drill broke when it touched object.

Slow feed rate & oil worked but for this time thing went wrong.

Bye

Hello when the drill bit disintegrates when it touched the object then I would suspect that the drill bit did not ht the center of the rotating object or the drill was asymetrical sharpened. With small drill bits this is fatal.

So when I was tought the trade we always had at first use a short & stuby machinists drill to really establish the center of rotation. under these circumstances smaller drill bits start better. I also was tought that the correct rpms for the drill size can be obtained from a list in any machinists handbook. Getting the piece out is hell - I think the best is redo the job.

Dont think so i will get EDM.

Thanks

A crazy idea but that I have used with some success.

Line the inside of the hole with insulation. Then lower the weld wire from a mig torch to just touch. Switch on in bursts . You may burn the bit of drill out. also if it heats the bit to red heat, another HSS drill will cut it, but carefully.

As Truman indicated, a plunge EDM can do it rather easily, although not very rapidly. Including setup, it would take me most of an hour to do it, depending on how long the broken piece is. I have removed several broken taps and small drills that way.

When looking for someone to do it, make sure you specify plunge EDM. In my limited experience, wire EDMs are more common, but they won't do this job.

You don't say where you are located, but I suspect it is not in the USA...

You can think of leaving it in an acid bath that have very low reactivity with SS 304 but can etch HSS (DRILL) quickly.

You might want to try heating the rod- but that depends on what the rod is going to be used for- getting it hot enough to turn loose of the drill bit will likely change the crystal structure.

Can you drill from the other end?

Try A real quick fix, use a strong Magnet and hold under the hole and bump the rod on a solid surface.

This is a two-step process.

First, build a simple electromagnet using a large washer- maybe 6-8 mm larger than the rod's diameter and wrap it with a single loop of AWG 12 insulated wire. Set up a switch connected to a 12 VDC battery and each end of the wire coil.

Place the rod inside that magnet assembly with the drill hole on the bottom and the magnet about 15 mm above the likely location of the drill end.

Connect the leads of a welding unit to each end of the rod and hold the rod with a vise grip using about 2 mm of fiberglass insulation between the jaws of the vise grip and the rod- clamp tight but not enough to damage the rods finish.

Power up the welder slowly to begin heating the rod due to resistance. When the rod is too hot to touch, stop increasing the power of the welder but keep it running.

Energize the electromagnet and slowly (1 mm per second) begin to lift the rod through the magnet ring.

When the the welding lead at the lower end of the rod gets within 10 mm of the magnet, turn off the welder and disconnect the lower lead connection. Continue to extract the rod through the magnet.

When it passes through the magnet, the dirll bit should be extracted and caught by the magnet. Turn off the magnet and the drill will fall to the floor.

Then- use adequate lube oil to continue drilling the COOLED rod.

By the way- IF the drill is not extracted the first time, REPEAT the process but heat the rod another few amps hotter the second time.

You usually weld using the same metal, so if a slightly smaller HSS drill was wrapped in insulating/Teflon tape (to stop it contacting the sides of the hole), connected to a switched on stick welder, then pushed down the hole till it contacts the broken bit, maybe it would weld itself to the other part......at least it stands a chance!

Once connected/welded, turn the new HSS drill a little anticlockwise first as the original drill bit end is probably slightly "buried" on a cut in the SS rod (nobody else mentioned that!), which is probably why it won't drop out!

By the way, I have never done this myself, but I had an acquaintance that according to him did it fairly regularly on expensive castings, but don't ask me what metal!, with good results - he said!

It stands a chance I feel......

Best of luck.

if all else fails.. throw it away and start again.. this time.. take your time and lubricate correctly and drill at a suitable speed.. but i think you know the last part already!!

Put it in a vise and get a small sharp cold chisel and give it a wack. Need a point or small chiesel, If you grind one down to a small size do not heat it up. Sharpen it manual on a sharpening stone or keep it cool best you can. I am not sure how far down in the hole your piece of bit is. Hopefully you can get a chiesel point down in there and find an edge to bang (pry force) A small screw driver may work for you but use caution bang little easy.You have a two hard brittle materials striking each other-easy to crack one. After one wack manally pry at it. Do not bang so hard you bend up your rod. Perhaps you can grab at it with a diagonal cutter (wire cutter plyers). Some of them are tiny and perhaps can get a bite on your piece of bit.

If your bit was starting to break through the other side when itr broke, bank on that side with a Tiny punch (round flat end, no point). Keep at it you can get it out. Just do not use so much force that you wreak your piece. That piece of drill bit is jambed in but it is a tapper so once it is jared it can come loose.

I would think something like H2SO4 would get rid of a lot of the drill before it ate much 304. Would pay to check with a chemist. If not that, there will be something else to do it. Rex Devantier.

Please do hammring at opposite side of drill hole to remove breaked drill bit 2nd part.