Another Trailer question

Iplayfarmer · Jul 18, 2005

Here's some more real world experience. I should have asked about this in the forum before I went shopping.

I'm using 3/8" carriage bolts through the wood deck of the trailer to secure the deck to the frame, and I don't have a good 3/8" drill bit. I decided to splurge and get a good bit since I knew I'd need to drill a bunch of holes. I asked the guy at the hardware store where I bought the bolts what would be the best bit for drilling through the steel frame of the trailer.

I got suckered into buying a cobalt drill bit for $17.00. I drilled three holes in the frame with it and then it stopped cutting. I took it back to the store and there was a different guy there. I told him what happened and asked again if this really was the best bit for what I was doing. He confirmed that the cobalt would do the trick. he let me exchange the bad bit for another new one and then told me not to push so hard on the drill.

The second bit was twice as good. It drilled about six holes and then stopped cutting. I didn't want to keep driving back and forth to the store all day (7 miles one way) so I sharpened the bit on my grinder and drilled another few holes. After three hours I had drilled 12 holes. (15 minutes per hole.)

I'll need about 80 holes before I'm done. I realize that at this rate I would be done with the trailer deck about Thanksgiving. I gave up and took the trailer to a friend who has a machine shop. He estimated about 30 minutes to get the whole thing done.

I told him my story about the drill bit and he confirmed two things...

1) Cobalt bits are no good for this application
2) I'm a sucker.

He pays about $5.00 per bit for his bits that drill through the frame in 11 seconds.

Bird · Jul 18, 2005

( weighs 5800 lbs empty and with a 6200 lb GVWR I only have 400 lbs of cargo. )

I'll take your word for it, but something's sure peculiar there. I never heard of a "half-ton" pickup that wouldn't handle over 1,000 pounds of cargo; usually rated for more like 1,500 pounds. I recently found that 600 pounds of ice in the back of my little Ford Ranger was hardly enough to tell I have anything in the bed, but I could definitely tell that I was overloaded when I hauled 1,368 pounds of concrete stepping stones plus the pallet they were on.

Highbeam · Jul 18, 2005

Well my 5800 lb pickup has the following non-GM options:

Sprayed in bedliner, frame mount step bars, leer fiberglass low canopy.

GM options are 4x4, 350, auto, 26 gallon fuel tank, extended cab, AC, tow package.

The truck is a very comfortable driver. The weight includes full fuel, my wife, and my weight. I've weighed several different times at different scales and they are all about the same. I pull an RV so I wanted to know real weights.

I really did look for lead bars in the frame since I've seen it done on pickups for more rear end weight. Nothing abnormal, just light duty half ton running gear.

The term "half ton" has no meaning like it did in previous decades. You now have half ton HD pickups with ratings more along the lines of the old 3/4 ton models. All it means is that the half ton is the lightest duty full size truck in that lineup.

RedRocker · Jul 18, 2005

How fast are you turning that bit? Sounds like your burning it up with too many RPM's.

Iplayfarmer · Jul 18, 2005

Sounds like your burning it up with too many RPM's. 

I thought about that after I burned up the first bit. I took it easy on the second bit, but it didn't really seem to help. The drill I was using is just a Harbor Freight tools cheapy. It's only a 2 amp drill. It's my "outside" drill.

What's the right RPM for this type of application anyway?

Also, what kind of bits really are the best for drilling through a steel trailer frame?

AlanB · Jul 18, 2005

Slow is the right RPM, the slower the better, there is no way you should have those problems out of a cobalt bit.

I do not want to come across wrong, but are you drilling in clockwise or standard drive? Any way your drill got reversed and you did not catch it?

Iplayfarmer · Jul 18, 2005

are you drilling in clockwise or standard drive? 

Good Question...I asked myself the same question many times throughout the process. It just didn't seem like I should be having that much trouble with a new bit. I was turning the bit the right direction the whole time...Clockwise when looking down at the hole from the top. (Counter clockwise if I'm looking down the bit from the tip.)

I fully believe that the problem was a result of something I was doing wrong. I'm just not sure what.

How much difference would the drill have made? Maybe I need to invest in a better "outside" drill. I've got a fairly good hobby wood shop and I try to keep my better tools in there.

keeney · Jul 18, 2005

Like most mechanical problems, these two suggestions should help:

1. more force

2. more lubrication.

1/2 joke, 1/2 true.

You need to be pushing hard enough on the bit for it to grab and cut, not just skid and spin on the metal. Also, some cutting oil will help keep it cool and help the chips clear out.

Another trick is to drill a small pilot hole first. Say 3/16ths. Do this with a higher RPM. Then re-drill the holes with the 3/8ths. The problem with any large drill bit is that the part in the middle doesn;t spin fast enough to cut while the outside edge goes too fast and just heats up. Putting a pilot hole in first will help you have enough force on the outer edges to cut well.

What I did on my trailer was to use some self-drilling, self-tapping screws through the wood decking. A couple of advantages: You don't have to line up holes in the wood and the frame - just go right through the wood from above, and you get a new "drill bit" on every hole.

boomer4snow · Jul 19, 2005

I dont think cobalt is even recommended to use in hand drills, Every one I have seen says to be used in stationary only setups (drillpress, mill etc) it is very strong and allows fater speeds while staying sharp, but it is really quite brittle and will snap quick with a side load. Good quality AMERICAN made high speed steel is your best bet. Hansons are pretty nice, Norseman, Champion etc...all much better than anything imported.

MadReferee · Jul 19, 2005

( Good quality AMERICAN made high speed steel is your best bet. )

Not always, and just because it is American doesn't always make it better. More expensive, probably, but better, not always. We make crap here too.

I have several Silver & Deming bits in the 1/2" to 1.5" range that are made in Poland. These are extremely high quality bits and still work fine to this day after being abused over and over again.

When looking for good drill bits one has to know what to look for and where to buy. Ask any machinist where he gets bits and what he uses. Then go buy some for yourself.