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What tool for making precise cuts in metal trailer?

TJP

Hi folks'

I need to make some cuts into my trailer for the new lights to fit. I was wondering what I would be best using to make the cuts?

As you can see in images I would need to cut a circle for the plug and to lengthen the pre existing horizontal circle.

Cheers.

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EricL

Hello @TJP

Thank you for sharing your question in regard to what tool to use to drill precise cuts. I propose looking at using https://www.bunnings.com.au/full-boar-m2-step-drills-3-pack_p0327744 or similar. My best advice is to use https://www.bunnings.com.au/sutton-tools-250ml-cutting-fluid_p6320395 to reduce cutting friction on the steel. Please remember to wear personal protection such as gloves, goggles and a mask.

Let me call on our experienced members @Dave-1, @Nailbag, @TedBear, @JoeAzza and @DIY4Knuckleheds for their recommendations.

If you need further assistance, please let us know.

Eric

Dave-1

Good Evening @TJP

I would mark out the distance between the two bolts (looks like 60-70mm apart) The center hole looks like maybe a 30mm hole saw will do the job. (Just guessing atm) I would mark a new vertical line say 10mm off the edge of the straight vertical slot you have. That way no need to try and drill a hole in the slot and you have a straight surface to work with. The hole saw will cut through the edge of the slot but that wont matter. (If the bolts are 6mm I would drill 8mm holes to make it easier to fit and adjust.

A 10mm drill bit held in your gloves and twisted on the 6mm holes will chamfer any burs, and a round file will help with burs for the larger hole saw sized hole.

Dave

Nailbag

Hi @TJP I would use the step bits to round out the slot to accommodate the plug. Ideally with a drill that’s fitted with a side handle as there is a good chance the bit will bite hard until the opening starts to round out. Then a normal HSS bit for the two bolt holes.

Nailbag

Noyade

Wow! What an ignorant old man I am! I thought LED light fittings for trailers would be flush with the metal needing small holes for the wiring and anchor points?

So they all require a hole somewhere around 30-32mm to fit the coaxial?

I did consider LED indicators recently but I think now me and Thomas Edison will stick with what I presently have.

TJP

Thank you very much everyone for your valuable advice.

I will keep you posted on my progress and any hurdles to come.

Regards,

MikeTNZ

Hi @TJP,

Not sure if this advice is helpful at all, but looking at this, if you have a MIG welder, you could mark the centre of where you need to drill your hole with a holesaw (I personally wouldn't use a step drill, because it will go all over the place as you start) and weld a washer to centre the holesaw arbor, this will make cutting the hole a lot easier and safer, just make sure to use plenty of cutting fluid on the holesaw.

One other thing, when you go to fit the lights, use neutral cure silicone sealant around the edges of the fittings and around where the cables enter from the rear, water ingress can cause all sorts of issues, corrosion being the worst of them, I never trust the rubber seals that come with trailer lights, I've replaced 100's of them on our work trailers.

Cheers,

Mike T.

TJP

Hi @MikeTNZ

Unfortunately no, I don't have a MIG welder, but thankyou for the advice and especially for the silicone suggestion.

TJP

Going to tackle this job this week.

With the step drills they would go on a corded hammer drill yes?

Regards,

Dave-1

Good Afternoon @TJP

Nooooo to the corded hammer drill. I would be using a torqued drill or just a normal drill, corded or battery. As you are going through steel I would prefer a corded drill.

Dave

JacobZ

Hi @TJP,

If you mean a hammer drill like this https://www.bunnings.com.au/ryobi-18v-one-hammer-drill-all-rounder-kit-r18pd24_p0539759 , then yes you can use it, just make sure it isn't set on the hammer function.

If you mean a rotary hammer drill, such as this https://www.bunnings.com.au/ozito-1500w-5j-rotary-hammer-drill-kit-rhd-1550_p0382377 , then no, this would not be advisable. The impacting motion will cause the drill bit to bounce, which can snap the drill bit. Definitely not advisable.

Let me know if you have any further questions.

Jacob

TJP

@Dave-1

Thanks Dave, I only have a normal battery drill on hand, so I spose it will have to do.

👍

Dave-1

Afternoon @TJP

:) A normal battery drill should be fine, just take it easy and let the drill do the work, dont put effort into the push.

Dave

TJP

Thanks @Dave-1 @JacobZ

Yes the all rounder is the exact one I have.

Cheers lads,

Noyade

As the sun goes down I thought I'd try this myself. My steel is 3mm and I started by making a bottom hole with the step-drill - no issues making a 10mm hole.

Cut out the slot and make a 'mark to start'…

(I personally wouldn't use a step drill, because it will go all over the place as you start) - @MikeTNZ

Mike - I am in agreement with you sir. It really has a mind of its own at the start but even as you progress it doesn't like that gap cause as the cutter advances and rotates it tends to wanna bite and 'lock' - if that makes sense.

Even with 1050 watts and variable speed I stopped at the 20mm diameter. Just doesn't feel safe. I would certainly be going with Mike's welded washer technique and with a hole saw. Just an amateur's opinion.

Dave-1

Evening @Noyade

:) Love that you tested it out!

Thanks for the information :)

Dave

EricL

Hello @Noyade

Once again, thank you for the fantastic demonstration.

Eric

TJP

@Noyade thank you for this!

This is invaluable.

Noyade

"This is invaluable."

Actually I don't think it is @TJP. Probably a case of a dull man living a dull life with dull tools. This morning I tried a welded nut on a new slot. With hindsight a piece of metal pop-riveted to the fame possibly would be better. But the nut is exactly 6mm internal diameter - perfect for the hole-saw pilot - and I was hoping the small diameter meant at the end the hole-saw removes most of the slag damage to the paintwork (it did).

Today - a 800 watt 550 rpm DeWalt spade drill.

Do you know the metal thickness of the trailer at the area you're drilling? What is that slot width? (I've been working on 10mm).

But I gotta say, I felt much better and safer with this method than yesterday. I'd be looking at a hole saw. But whatever you do this weekend - keep us posted.

Cheers!

TJP

Hi @Noyade

Th trailer thickness appears to be 1mm and the slot is 4mm wide.

Thank you for all the effort you're putting in.

Noyade

"thickness appears to be 1mm and the slot is 4mm wide."

My apologies then @TJP - I suspect I have oversized the experiment - and you won't have any trouble step-drilling with those dimensions. I should have asked you earlier. Sorry.

I did look around the suburb this afternoon (taking my wife to her GP) and I saw quite a few trailers on the kerb and front yards. All had LED lighting - but all had small cable holes at the back - none were 32mm with locking pins. Are your lights illustrated above the only alternative for your trailer?

Cheers and good luck

Dave-1

hahahahahah @Noyade

:) I have done the same when figuring out retaining walls/steps/balconys :) We must look suss as walking around looking at stuff especially when we have a tape measure :D

Dave

TJP

Hi @Noyade ,

No- The lights I went with weren't the only option. I went with them as they were a plug'n'play setup.

Of course, not taking into account, the alteration I would need to make to the trailer.

DOH!,

TJP

Hi lads'

Attempted the light install today and all was going well until I went to attach the wiring to the led. As you can see in the picture, I can't lock the cable to the light to make a solid seal as there seems to be to much of a gap between the led and plug, even though the light sits flush with the steel.

Would I be best discarding the lock mechanism and perhaps using another form of sealant?

Cheers,

JacobZ

Hi @TJP,

Given there is a round rebate around the plug attachment point -

I get the impression that the answer is to make that central hole bigger to accommodate the plug. As long as the threaded studs stay in the same place, which they will, it shouldn't move, so I don't see any reason making that central hole larger would cause any issues.

What was the outer diameter of that rebate? Will the step drill bit work?

Jacob

TJP

Hi @JacobZ

The diameter is 35mm step drill goes up to 32mm. Bugger..

JacobZ

Hi @TJP,

Is the diameter across the top of the plug of the plug also 35mm?

If it were smaller, which would make sense to me, you may get away with the 32mm.

Otherwise, we may need to look at an alternative solution such as attaching a piece of sacrificial timber over the hole using the bolts, then using a https://www.bunnings.com.au/sutton-tools-35mm-viper-cobalt-bi-metal-holesaw_p0588909 to enlarge the hole.

Let me know what you think.

Jacob

TJP

Hi @JacobZ

Only checked the lamp side. I will confirm the plug diameter once home.

TJP

Good news, plug is 26mm in diameter and so is the current hole size. Will increase to 28mm.

JacobZ

Phew @TJP.

Glad to hear it.

Good luck!

Jacob

TJP

Fits well with a little bit of wiggle room. Just need to get rid of the burs now annnnnd replace the washers that were lost to the unknown. 😁

Cheers,