Drilling rusty metal

[maxpower_hd]

Hey guys, It has been a while.

I am installing a section of new flooring in a semi-trailer. I replaced the I-Beam floor supports in the rear section due to rot. I installed new oak flooring on top in the rear ten feet of the trailer. The issue I am having is where the old supports are. They have some rust on them and when I drill the holes for the flooring screws they are eating up the bit almost immediately. I am able to drill literally dozens of holes with one bit in the new steel supports but I cannot even drill one in the old steel with one bit. It is frustrating. These are good quality HSS and HSCO drills and go through the new steel like butter. I am using tapping oil.

Any ideas? One thought is to pre-drill with a smaller sized bit like a 1/8". Another thought is to drill through the wood only, use a center punch to mark the steel and then drill. The larger bit is a 7/32". My last thought is to grind the steel from underneath and drill up instead of down through the flooring. But since it is an I-Beam I would have to either cut small section out of the bottom flange or drill at an angle. Plus I would have to slide the wheels back which takes more time.

If I had known before I started how hard it was going to be to drill through I would have replaced one more support or at least took a grinder to the areas I had to drill. Too late for that now.

Thanks

 

[GirlnAgarage]

What kind of speed are you using?


Came back, was thinking about this..wondering if the bit is already hot from drilling through the oak by the time you get to the steel, if it's causing some of the issue. Maybe your idea to go from underneath to drill steel first. Plus you could take a wire wheel or grinder to the surface to knock the rust off, punch your hole, them get to drilling. You'd lose the ability to keep oil on there though if you're working upside down.

 

[fsae0607]

Can you take a wire wheel on an angle grinder to the metal first? Knock all the rust off then drill.

 

[lakelandcat]

Hey guys, It has been a while.

I am installing a section of new flooring in a semi-trailer. I replaced the I-Beam floor supports in the rear section due to rot. I installed new oak flooring on top in the rear ten feet of the trailer. The issue I am having is where the old supports are. They have some rust on them and when I drill the holes for the flooring screws they are eating up the bit almost immediately. I am able to drill literally dozens of holes with one bit in the new steel supports but I cannot even drill one in the old steel with one bit. It is frustrating. These are good quality HSS and HSCO drills and go through the new steel like butter. I am using tapping oil.

Any ideas? One thought is to pre-drill with a smaller sized bit like a 1/8". Another thought is to drill through the wood only, use a center punch to mark the steel and then drill. The larger bit is a 7/32". My last thought is to grind the steel from underneath and drill up instead of down through the flooring. But since it is an I-Beam I would have to either cut small section out of the bottom flange or drill at an angle. Plus I would have to slide the wheels back which takes more time.

If I had known before I started how hard it was going to be to drill through I would have replaced one more support or at least took a grinder to the areas I had to drill. Too late for that now.

Thanks

Don't get offended, are you sure you have the drill clockwise and not counterclockwise? I have done this more than once, and always kick myself for being a *****.

 

[PugetDude]

Try a cobalt pilot bit.

 

[larry_g]

You might have to move up to a carbide bit. Not real forgiving in a hand drill but the iron oxide will not be as likely to harm/dull it.

lg
no neat sig line

 

[raferguson]

Most likely, the old steel is very high carbon steel, probably comparable in hardness with the bits that you are using. You will have better luck with brand new high quality bits, which is what I use on stainless. The hardware store bits are not going to do it. I would probably use 1/8" bits as pilot bits. I buy 1/8 inch steel drill bits by the dozen. They last me quite a while, but I tend to use them in a drill press.

I would note that if they are very high carbon steel, you should not weld them.

I don't think that the rust has anything to do with it.

One more thought: Can you use the old holes? Drill up from the bottom? Don't drill new holes, use the existing holes.

 

[firebirdparts]

I agree. I suspect the difference is the material you are drilling, not the rust. You need a harder drill bit and you'l have to sharpen them as necessary. Oiling them might help too.

 

[rsanter]

There are a couple of contributing factors.
The rust is abrasive and has a negative effect on the edge, then you continue to drill.
The process of rusting/oxidation also has a hardening effect on the surface material.

Use a wire wheel.
When you start to drill, go slower and use oil at coolant.
Once you get that drill bit into the material you can speed up a bit

 

[catalytic]

I have drilled a lot of rusty metal. If it's really rusted, the top layer is way, way harder than the rest, as you've noticed. Wire wheeling takes off the surface rust but not this hard layer. Once you can get the drill to bite through, the rest feels easy.

Even on a big drill press or mill, you ave to pull pretty hard on the quill to get through that top layer. Can you quickly hit the spots where you're drilling with an angle grinder/grinding wheel/flap sander/dremel with a carbide burr / dremel with a grinding stone? Just something to get through the top crust?

 

[Jazz1]

That’s hard steel in those ribs. You’ll need quality bits. Self tapping hardened screws to install boards

 

[MJD1]

Needle scaler or chipping hammer to knock the scale off. Grind to shiny metal and drill.

 

[maxpower_hd]

Sorry for the slow replies guys. Thanks for all the advice. I tried virtually ALL of these things before I even posted. This job is now complete BTW.

I am using high quality industrial bits both HSS and HSCO. The only bit I haven't tried is carbide.

I was using copious amounts of cutting fluid with no help. I was drilling through the wood, stopping and squirting oil in the hole then drilling the steel.

The steel is not high carbon steel. It is the same steel as the new supports, just rusty and even scaling in some spots but the line must be drawn someplace before replacing the entire 48 feet of floor. LOL

I could have grinded the rust off first but I had already laid all the flooring in and was fastening it as I went from Read to front. This was at the front portion of the new flooring so it was already too late to do this.

I tried different speeds from slow to fast. Fast no good, slow no good. Medium was best.

What I ended up doing was using two drills. One to pre-drill the wood and then set aside. Then I used a punch to center punch the steel. Then I used a 1/8 pilot drill. Then back to the 7/32 which is what I started with in the wood. That worked but was a PITA.

I have since however ground the rust off in other repairs and that does the trick. So as long as I can remember to do that before I install any wood I should be OK.

Thanks again guys.

 

[d.mcfarland]

There are a couple of contributing factors.
The rust is abrasive and has a negative effect on the edge, then you continue to drill.
The process of rusting/oxidation also has a hardening effect on the surface material.

Use a wire wheel.
When you start to drill, go slower and use oil at coolant.
Once you get that drill bit into the material you can speed up a bit

Sounds like you were right.

 

[Augus7us]

Sounds like you were right.

Maybe. I can say for sure we have no way of knowing whether the old steel was high carbon or not. Well unless you sent a sample to a lab with a mass spectrometer. But I would agree that its not, my understanding is they don't generally use high carbon for stuff like that. Maybe 1045 or something similar but while its hardenable to a degree, its not what I consider high carbon.

In the future carbide is what you want. It is not forgiving in that you can break them easily but I heat treat a lot of steel and on occassion I have to drill through it. I've heard all kinds of methods but the only one that works every time is a carbide bit. Fair amount of pressure and going real slow will let you cut many holes with one carbide bit.

Given what did work for you, I would have to say you were over heating your drills, or that plus the rust acting like an abrasive did them in.

-Clint

 

[Charlie51]

Have you ever tried to drill a hole in an old bedframe? I think slag in the old wrought-iron frames is what makes drilling so difficult.

 

[jubilee]

When we used to refloor oilfield semi flatbeds we’d snap a chalk line on wood at edge of stringer. Drill pilot holes in wood on chalk line. Drive spikes thru wood. Tack weld spike to stringer. To remove just grind off tack weld.

 

[rayra]

If the OP thinks rust makes a difference, he's probably also misusing the drill and overheating the bits and ruining their cutting ability.

Drill the wood only, use a centering punch, drill a pilot hole with a new sharp cool bit and don't bear down hard on the drill. And use an appropriate drill speed.


eta adn if you drill up from below you'll have a hard tim egettign your holes visually aligned on the top / visible surface and you will also be very likely to splinter the oak all to hell.

 

[545_days]

When we used to refloor oilfield semi flatbeds we’d snap a chalk line on wood at edge of stringer. Drill pilot holes in wood on chalk line. Drive spikes thru wood. Tack weld spike to stringer. To remove just grind off tack weld.

I don't have any trailers to refloor, but that idea is genius, and I am filing it away in my brain. Someday it will come in useful. Thank you.

 

[laser3kw]

The way the OP finished is about the only way to go. The oak flooring is brutal on drill bits. Another option is concrete drill bits slightly undersized of the deck screw.

 

[Sureshot]

I don't have any trailers to refloor, but that idea is genius, and I am filing it away in my brain. Someday it will come in useful. Thank you.

I'm having trouble following this. Can you elaborate?
The stringer is the crossmember?

 

[benjamintmiller]

I'm having trouble following this. Can you elaborate?
The stringer is the crossmember?

Yeah, he's saying to drive the nails next to the cross member instead of drilling through it, then weld the nails to the cross member. I wish I'd heard this before I drilled 156 holes in the cross members of my trailer...