How to fix poorly drilled holes

[Bill C]

Hi all,
I am fixing up a trailer that I picked up from my neighbor for free. There are some holes (approx 1/2” diameter) drilled in the frame for routing the wiring but it looks like they were cut with a torch. They are very out-of-round and jagged. I’d like to clean them up and make the holes round so they don’t chafe the wiring harness. The frame is 1/4” thick steel angle and C-channel.
What is the best method to clean these up? Do I just chuck up my step drill bit and hope for the best? Seems like that would wreck the bit due to possible chatter from trying to steady the hand-held drill. Would I have better luck using a bridge/car reamer? Or would they chatter like crazy too due to the out-of roundness/jagged condition of the existing holes. I don’t own one and they can be spendy, but it could be nice to have one in the tool box.

How would you guys clean up these holes. See attached pics.

 

[Gummi Bear]

They are blown in with a torch

Cobalt drill bit is how I’ve cleaned them up before.

I stick a grommet in there before pulling new wire.


Either that, or I run conduit under the trailer, and abandon those holes






I went to the woods because I wished to live deliberately...

Henry David Thoreau

 

[metaleltr]

I would try a step drill if available. Bridge reamer would work but I doubt you are looking to buy a special tool for the one job.

 

[LXCam]

I’d use a large step bit but suggest backing up the hole with a piece of 2x. Reason is step bits cut like **** into wood and it will help control your feed and most importantly keep the bit centered on the cut and mitigate catching an edge.

 

[Bill C]

Yea I figured they were made with a torch. There is conduit on the A-frame tongue for the wiring, But once it gets under the decking, the conduit stops. I plan to use grommets in the holes but would like get em more uniform first. Also not sure I’ve seen a rubber grommet for such thick (1/4”) steel. Most seem to be for 1/8” or thinner.

 

[Bill C]

I’d use a large step bit but suggest backing up the hole with a piece of 2x. Reason is step bits cut like **** into wood and it will help control your feed and most importantly keep the bit centered on the cut and mitigate catching an edge.

I like the idea of using a back-up piece of lumber. I believe that would really help with the chatter I am concerned about. Probably would give it a go with one my cheap HF step drills as opposed to my nicer ones.

I would try a step drill if available. Bridge reamer would work but I doubt you are looking to buy a special tool for the one job.

I’ve had situations in the past with misaligned holes where a bridge reamer could have been nice to have. But still a chunk of $$$. If it make nice and quick work of this particular task, I’d spend the money. Hell the trailer was free.

 

[PugetDude]

1/4" shank conical mounted grinding stone in a die grinder or high speed drill will round them up so you don't ruin your step drill.

 

[Farrier]

Put a grommet in it

 

[ClappedOutBport]

Trying to drill those is going to hurt your wrist, your bits, and your pride. Grommet them and move on with your life.

 

[sberry]

They will clean with a step bit but ideally grind any slag off first. Shove plastic pipe thru.

 

[nh_yota]

Don't make it complicated - grommets will conform to oddly shaped holes so they don't need to be perfectly round.

Knock the sharp bits off with a round file or a die grinder and stick a properly-sized grommet in the hole to protect the wires.

 

[matt_i]

If you have the small diameter sanding drums for the dremel it will clean it up nicely.

Secondary would be a rat tail file, faster but more exercise too

 

[jimkinney]

Burr bit in a die grinder, or a round file to take off the high points before you try drilling, to save you wrists and bits.

 

[duc916]

Look for grommets at McMaster Carr website, they will have the size and thickness needed.

 

[larry_g]

I'm amazed that most everyone has to recommend a power tool. Me I just grab a hand file and with a few strokes have a hole good enough to use grommet in and move along. If I needing a good round hole then file it near round and finish with a step drill.

lg
no neat sig line

 

[rlitman]

I'm amazed that most everyone has to recommend a power tool. Me I just grab a hand file and with a few strokes have a hole good enough to use grommet in and move along. If I needing a good round hole then file it near round and finish with a step drill.

lg
no neat sig line

I'm all about hand tools, but my files (except a few cheap ones I keep around) don't touch rusty metal. That just dulls them down.

A regular twist drill bit is not made to enlarge holes. That's a great way to turn a nice cobalt bit into trash.

Step drills enlarge holes nicely (plus leave you a much rounder hole in sheet than most opther options), and the cheap ones from HF are reasonably disposable. That's what I'd use.

A die grinder with a stone (I hate stones) or carbide burr is an option, but enlarging a hole with a die grinder is a tricky and dangerous operation. I might try this, but I probably wouldn't, since choosing the right burr and tightening it in a collet takes more time than chucking a step bit in the closest drill at hand.

 

[Bretny]

Just dont run the wires through them. There not actually holding the wire anyway there just suspended from the holes. If you have to use the holes put a piece of plastic or rubber tube through the holes that's about 2in long and zip tie the tube on the wire.

 

[Kevin54]

If the holes were blowed in with a torch, most likely you are going to have hardened edges. And going at it with a drill bit will grab. The easiest way, if you don't have a Dremel is to go to TSC or someplace like that and pick up a rotary burr or two and chuck them in your drill to round out the holes. Make sure you use a grommet in the holes before running the wires through.

 

[joe49]

I have bridge reamers and step drills and would not ruin them on that. Grind the slag off, then die grinder or a twist drill will work better if you make a centering hole in another thicker piece of plate to clamp on as a guide. Though I would do the grinding the slag, then heat the hole area to cherry, and drive a bull pin into it twice, once from each side.

 

[JPinSTL]

Or ignore those jagged existing holes. Drill some new round "clean" holes for your grommets. The trailer builders are in a hurry so they blow the hole with a torch. They don't care about the wiring job either. Just as long as the lights work on your 1st drive home.

 

[larry_g]

Or ignore those jagged existing holes. Drill some new round "clean" holes for your grommets. The trailer builders are in a hurry so they blow the hole with a torch. They don't care about the wiring job either. Just as long as the lights work on your 1st drive home.

Ya know, this is probably the best solution yet...

lg
no neat sig line

 

[jeepinerdeep]

I’d use a large step bit but suggest backing up the hole with a piece of 2x. Reason is step bits cut like **** into wood and it will help control your feed and most importantly keep the bit centered on the cut and mitigate catching an edge.

This. It'll work.

A reamer wants a mostly round hole to start in, you'll drive yourself nuts.

 

[Muckin_Slusher]

Weld them closed.

 

[2oolhound]

Weld them closed.

My thoughts too. Or I'd hit it with a die grinder and carbide burr. They seem like big holes for trailer wiring.

There are grommets for 1/4". Most "Kits" usually have a couple.

 

[Bill C]

Wow guys, thanks for all the advice. There is certainly more than one way to skin a cat.
I think I’ll get some grommets from McMaster and do my best with either the Ol’ rat tail file (gotta see how hard that torch made the steel) or die grinder to knock down the biggest chunks of slag. Then I’ll let the grommet form nicely to the general out-of-roundness. That should be good enough for a simple “Free” utility trailer

 

[ZRX61]

I'd put a piece of copper behind the holes, fill them with weld, then flap wheel them flush.

 

[kazlx]

File it or hit it with a dremel with whatever works to smooth it out and throw a grommet in it and be done. Or like mentioned, run the wires another way and leave it. I don't think that trailer is losing a beauty pageant from a few torched out holes.

 

[The Cobbler]

where are the holes , can you put side lights or reflectors over them to hide them?

 

[DieselNut88]

You can use conduit chase ******* in the holes after you clean them up.

 

[tarbellb]

Step drill bit, cheapies from HF, get a 2 packs.

Grommet after.

Or, plug weld with copper plate like suggested and grind flush.

Leave the Dremel for you model car hobby.

 

[Farrier]

Nobody said it yet

 

[Monza Harry]

I'll suggest using a couple of the suggestions together. Plug weld those holes shut as suggested by a few above, and pretty up as desired. Then drill new holes 9/16" or 37/64" dia. [away from the weld] and tap for 3/8 NPT , this will allow the use of a "strain relief" the ones with the rubber compression grommet, this will anchor the wiring and in tubing applications will keep the inside of the tubing dry.
https://www.grainger.ca/en/product/...9673!!!g!573582201044!&cm_mmc=PPC:+Google+PPC this link is for reference only, I have seen these in 3/8" @ the home Depot, searching may be required, you can try asking for help, but I end up helping about three customers with each visit and the staff does one. Harry

 

[PugetDude]

Nobody said it yet

It’s a trailer, not a screen door.

 

[LXCam]

It’s a trailer, not a screen door.

But a case of it could make it a boat.

 

[kerrynzl]

Wires never go through the hole perpendicular. So use a die grinder to grind diagonally. eg: inside back and outside front [or vice versa]

Now you cant buy a diagonal grommet so............

Hot glue is your friend ! Centralize the wire and hot glue around it.
When it cools glue the other side.

I've done this for years and never had a wire chafe.

 

[JamesW]

I'd hit it with a grinder to smooth and then fill it with a nut/bolt/washer that is used to hold an adel to route the wire someplace else.