Drill bit for stainless steel

[montidale]

I have a broken off bolt in a frame. I want to drill it out and re-tap it. It is a half inch bolt. It appears that the bolt is stainless steel. I’ve tried various drill bits and it doesn’t even touch it. Can anybody recommend the proper drill bit for removing this bolt? There were four bolt broken off. I was able to get three of them, but one of them will not drill out. I can’t use heat because the frame is recently painted. Any suggestions?

 

[thelonepatriot]

I use left handed drill bits when removing broken bolts. I start with a small bit to drill a pilot hole. Then I switch to a larger bit and often it will snag the bolt when I start drilling and unscrew it. I don't know what kind of bit will drill through stainless steel. Maybe a cobalt bit would do it.

 

[Jim.ME]

A good cobalt bit should work. Use a cutting fluid for stainless.

Do you know why it broke? Stainless likes to gall if not properly lubricated. Plain stainless is not great for stressed applications in my opinion, and having stainless in a frame application makes me wonder what the frame is.

 

[DoubleO7]

Yea SS really likes to gall (weld) itself to what it is threaded into.
If it is broken off below the surface, use a transfer center bunch to get the exact center.
As you will likely have to drill it out to the tap drill size.
You won't be able to pick the remaining thread out.

 

[Mule Meat]

I like Tungsten Carbide bits for stainless.

I do not know the exact terminology. It happens when you press to hard or the bit is spinning to fast. The metal being drilled gets hot and becomes harder than the drill bit. Similar to friction welding. I know when it happens it is a pain to find a drill bit that cut through it.

 

[Janicholson]

Once SS has been stressed and mushed around from drilling or sawing witha dull bit, or one that gets dull, the surface material where the disturbed metal is located becomes super hard and nearly impossible to drill even with a new bit. I would use a Dremel tool with a diamond bit to grind out the surface where the failed effort made it hard. Only a few thousandths of an inch is needed to get to softer metal. Do use a lube like Tap Magic and moderate continuous force. Jim

 

[urbancase]

Try a masonry bit , if you can get close to the size you want. I went that route a few times.

 

[drsportster]

Drill smoothly as possible to avoid stopping and work hardening

 

[Watthour]

Whatever you attempt, I would suggest beginning with a much smaller pilot hole to the depth you desire, then have your way with your weapon of choice. If the pilot goes badly, you can step up a size or two to clear out the problem area.

Among the multitude of problems with many stainless alloys as a material is the tendency to be soft compared to carbon steels. Some of my worst days have been rooted in 17-4 PH, 316L, and 2203/2205 (lean-duplex) stainless being materially weak, thereby grabbing whatever tooling applied to it almost as badly as copper or raw tin billets. Losing a $900 spade in a $1400 billet of 17-4 is not a good morning. Once the hard spots start forming, it's time to go bigger and modify the feed/speed to take out a bigger chip. Most twist drills are not optimized for chip flow in softer materials like that.

400-series SS doesn't normally cause those headaches since it includes a lot more iron in the mix.

 

[Watthour]

Drill smoothly as possible to avoid stopping and work hardening

Better advice has not been given!

 

[Lumbersawyer]

Drill slow with even cutting feed pressure. Too much speed and light feed will work harden SS. A carbide burr will work too, if a cobalt drill doesn't work.

 

[Watthour]

Drill slow with even cutting feed pressure. Too much speed and light feed will work harden SS. A carbide burr will work too, if a cobalt drill doesn't work.

Thank you for clarifying that. I worked with someone who thought that "high-speed steel" cutting tools bore some relationship to the operation speed instead of feed rate for chip flow. I never did get him broken of that habit, despite having to undo the damage created multiple times.

I've been successful with HSS twist drills using Anchorlube, lard oil, and other coolants. Even mineral oil is better than nothing. A carbide center drill is a marvelous way to deep-pilot a hole in many cases, and lessens the risk of flex breakage compared to smaller diameter twist drills. A guy has to make things as easy as possible whenever the opportunity arises.

 

[montidale]

Thanks, everyone for the advice .The frame is only about a 1/2 inch to 3/4 of an inch thick At the most. My son thinks he can get a good drillbit at his work. I’m thinking it’s a carbide drill. I did have a grinding bit on my dremel. I didn’t have much luck with that. I haven’t worked at it too hard yet because the paint is still a little green. Hopefully I can give it another try next week once the paint sets up a little better. I wanted to drill it out before I painted. But I only had a small window to get the painting done.

 

[Snattlerake]

I use left handed drill bits when removing broken bolts. I start with a small bit to drill a pilot hole. Then I switch to a larger bit and often it will snag the bolt when I start drilling and unscrew it. I don't know what kind of bit will drill through stainless steel. Maybe a cobalt bit would do it.

Left handed COBALT drills.

https://www.amazon.com/High-Speed-Titanium-Nitride-Hardened-Stainless/dp/B0DCBDQ2WN/ref=asc_df_B0DCBDQ2WN?

 

[showcrop]

To summarize: left handed; cobalt; lots of pressure; slow speed.

 

[4wdtom]

As others have said stainless will work harden when it is cut or worked. You must have the next cutting edge that comes along under the work hardened surface. This means a lot of cutting feed pressure to get the cutting edge taking a good chip. Slow speed, and always a sharp cutting edge. If dull sharpen it and finish with a fine hand stone. If it isn't cutting it is dulling and work hardening the surface. And if possible a good cutting oil.

 

[RJKeith]

What ever you find to drill it, make sure you get the absolute center of the bolt as you will likely have to re-tap the hole. If it is stainless and anti seize was not used, it is likely the threads have chemically welded themselves together.

 

[Hobo,NC]

I have a broken off bolt in a frame. I want to drill it out and re-tap it. It is a half inch bolt. It appears that the bolt is stainless steel. I’ve tried various drill bits and it doesn’t even touch it. Can anybody recommend the proper drill bit for removing this bolt? There were four bolt broken off. I was able to get three of them, but one of them will not drill out. I can’t use heat because the frame is recently painted. Any suggestions?

The lack of bits and the ability to sharpen a bit gives grave results. I buy bits in packs of 10 and bill them to the job. Work the drill in spurts on-off on-off when you see its not cutting put a new bit in it. You may only get a few spurts of cutting action when they are all not cutting go sharpen them. Its a high expense but the results pay off in productivity. You can ruin an expensive bit just as fast as you do a HSS and a left handed bit that does not cut is preforming useless work.

How you start this job = real good are real fudgen bad.

 

[Ray,IN]

Thanks, everyone for the advice .The frame is only about a 1/2 inch to 3/4 of an inch thick At the most. My son thinks he can get a good drillbit at his work. I’m thinking it’s a carbide drill. I did have a grinding bit on my dremel. I didn’t have much luck with that. I haven’t worked at it too hard yet because the paint is still a little green. Hopefully I can give it another try next week once the paint sets up a little better. I wanted to drill it out before I painted. But I only had a small window to get the painting done.

As recommend previously, center-punch the broken bolt first, everything following will be much easier.

 

[Mule Meat]

"The frame is only about a 1/2 inch to 3/4 of an inch thick..."

Just noticed that the frame is only 1/2 to 3/4" thick.
Is there any way to drill it from the back side?
If so a drill bit turning clockwise on the back side will have the front side turning in a counter clockwise direction. That will have the bolt turning in the direction it needs to be removed.