correct drill bit for drilling rv frame?

[mslim]

I had to remount the mud flaps on my 35' fifth wheeler today because they were scraping on the body skirt. It seemed a simple job once I got the wheel off to peer into the wheel well. The left side went well. All I had to do was pull the mud flap off and drill a couple of holes through the plastic offset about 1/4" from the original holes. I did the same thing on the right side except one of the two holes was drilled to close to the edge of the mud flap and the offset hole wouldn't have worked. I mounted the flap on one sheet metal screw and proceeded to drill a new hole in the mudflap and the RV frame outrigger. I started drilling with my new Viking HSS bit at a slow speed with a little PB Blaster (that's all I had with me) for lube. I did manage to literally make a dent in the frame with that bit, but I knew I had the wrong tool for the job.

What's the correct bit for this kind of hard steel? Is it Cobalt or something better? I know I can get Milwaukee or Dewalt cobalt bits at the big box stores but would I be better off going to Grainger or Fastenal for an industrial grade bit?

Puzzled

Slim

 

[Neggy]

cobalt or titanium

 

[Wrench97]

All I've ever used on truck frames is high speed steel mechanics bits start small and work your way up to the size you need. Not all HSS bits are created equal.

 

[isb cornbinder]

I always use a high quality HSS bit and drill to one size under, then ream to fit. Two flute bits tend to make an three oval hole.
Never have the threads of the fastener in the drilled hole. FASTENAL have a good selection and something for your situation.

 

[mike93lx]

The frame isn't hardened steel. Any sharp bit, running properly should do it. What diameter hole were you going for? Maybe a pilot and then to size would help

 

[timgunn1962]

Are you using a handheld drill?

Any fairly decent HSS bit "should" do the job. If you have spun the drill without cutting, you'll have work-hardened the surface and made life difficult for yourself. You will need to use a fresh (new or correctly-sharpened) drill bit and try again. Turn it slow and feed it hard. You will only really get one chance to get through the hardened surface, so make it count.

As the drill cuts, it will work-harden the material adjacent to the cut. The idea is that the drill feeds enough that it is cutting just below the hard skin left by the last pass of the cutting edge. If you let up at all on the feed, so the drill stops cutting, it will skate on the surface and cause further work-hardening.

A machinist would possibly use Cobalt HSS or Carbide for materials prone to work-hardening, but these harder materials are brittle: the drillbits are great in a rigid setup, but not for use in a handheld drill.

The real trick is not lousing things up in the first place, but it's not always possible and I usually carry a few TCT drills with me for sitework. The Carbide tip on a steel shank gives a tough assembly with a hard cutting edge and this doesn't tend to break when used in a handheld drill.

I have bought them as "TCT hard plate drills" from locksmiths when in a bind, but they really know how to charge and I now carry my own.

 

[mslim]

Yeah handheld Makita LXT drill w/ a 5/32" bit. Tight space in there. It's just under the floorpan. The factory used self drilling sheetmetal screws to attach the flaps but I can't see anyway a screw could have cut through this steel on its on.

 

[seber]

Frame members cannot be hardened. HSS should be more than adequate. Are your bits sharp?

 

[Showkey]

Google has 1000’s of hits on the frame drill. Some frame members are harder and tougher than others.

Drilling holes into frame?

www.plowsite.com

 

[mslim]

Frame members cannot be hardened. HSS should be more than adequate. Are your bits sharp?

Yes brand new Viking. If I've drilled anything with it, it was only aluminum. No problem with previous use of bits from this set but I seldom have to drill steel.

 

[gungatim]

LGR

 

[mslim]

Arctic Fox makes their own frames. Most RV manufacturers use a Lippert frame. Perhaps the steel spec is different?

 

[DeeKay]

I'd stick to HSS, I buy TiN coated jobbers usually and they work for just about everything that's not an "exotic" metal.
Personally I think Cobalt bits are a waste of money for hand drilling; they are too brittle and break too easily if it grabs.

You said you've used that bit to drill aluminum before, any chance the tip is clogged with a chunk?

 

[mike93lx]

Arctic Fox makes their own frames. Most RV manufacturers use a Lippert frame. Perhaps the steel spec is different?

The steel may be harder, but it is not hardened

 

[mslim]

I'd stick to HSS, I buy TiN coated jobbers usually and they work for just about everything that's not an "exotic" metal.
Personally I think Cobalt bits are a waste of money for hand drilling; they are too brittle and break too easily if it grabs.

You said you've used that bit to drill aluminum before, any chance the tip is clogged with a chunk?

Not that particular size bit. Not clogged w/ aluminum chunk.

 

[metlmunchr]

Likely running the drill too slow. A standard HSS drill will drill any common steel at a surface speed of 80 to 100 ft/minute. For a 5/32 drill, that's about 2000 to 2500 rpms. If you don't have anything but PB Blaster, you're better off to drill dry.

FWIW, most people tend to run small drills way too slow and large drills way too fast. Same applies to all sorts of rotating tools, and applies often to pros as well as diy guys. I've seen people in machine shops run 4" face mills carrying $80 worth of carbide inserts at 1600 ft/minute in steel and curse the inserts for not being worth a damn because they burn up in 5 minutes when the insert package is laying within sight and clearly states a max speed of 600 ft/min right on the box.

 

[dr_clyde]

Likely running the drill too slow. A standard HSS drill will drill any common steel at a surface speed of 80 to 100 ft/minute. For a 5/32 drill, that's about 2000 to 2500 rpms. If you don't have anything but PB Blaster, you're better off to drill dry.

FWIW, most people tend to run small drills way too slow and large drills way too fast. Same applies to all sorts of rotating tools, and applies often to pros as well as diy guys. I've seen people in machine shops run 4" face mills carrying $80 worth of carbide inserts at 1600 ft/minute in steel and curse the inserts for not being worth a damn because they burn up in 5 minutes when the insert package is laying within sight and clearly states a max speed of 600 ft/min right on the box.

Agree 100%. Speeds and feeds are more important than any “miracle bit”.

Pretty much any common HSS twist drill should drill that frame. Spin it to the correct rpm, use sufficient feed pressure. It does need to be sharp.

 

[FMB4]

Irwin colbalt drills are my go-to bits for harder steels. Haven't had one fail on me yet (But I'm still trying).

 

[mrjaw14]

I was wondering what a good set of cobalt bits was