Good or Bad Idea to Drill Out a Ring Terminal Hole to Fit a Larger Threaded Post

lesabret

New member
I recently ordered and received a batch of custom cables in #2 awg for a power supply layout.
The cables look great and very well made, but I messed up in communicating what I wanted and two
of the cables have a 5/16 ring terminal where I need a 3/8 ring terminal.

I can re-order the two cables and get them correctly made, but I was wondering the risk
from an electrical standpoint if I just open the holes in the two terminals.

The inside surface of the terminal will no longer be tinned, but will be exposed copper after running a drill through the hole.
The terminal flat which actually contacts the surface of the mating components will remain tinned.
I want to know how concerned I should be about the inside exposed section (the thickness of the terminal) relative
to corrosion or other unintended consequences I may not even be aware of.

If it's not a big deal, I'd prefer to save the time and the money it takes to re-order the two pieces.
If it's a bad idea to drill out the terminals, then I'll want to do the right thing and re-order the cable with the correct terminals.

Thanks
 

dwh

Tail-End Charlie
From 4.5 sixteenths to 6 sixteenths. If the surrounding meat of the terminal is still fairly thick I wouldn't worry about it. Also you can tin them yourself.
 

Haf-E

Expedition Leader
No big deal to drill them out - but it can be tricky as the drill bit will grab the terminal and can twist it up into a pretzel quickly. Best to hold it in a vise or with something strong like vice grips while drilling. I've used a step type drill bit with good success too. You might even consider filing them instead with a round file.

The tin plating is not critical - it helps around batteries and in marine environments where corrosion is a bigger issue. If you put an anti-corrosion coating on them its really not an issue.
 

pugslyyy

Expedition Vehicle Engineer Guy
No big deal to drill them out - but it can be tricky as the drill bit will grab the terminal and can twist it up into a pretzel quickly. Best to hold it in a vise or with something strong like vice grips while drilling. I've used a step type drill bit with good success too. You might even consider filing them instead with a round file.

The tin plating is not critical - it helps around batteries and in marine environments where corrosion is a bigger issue. If you put an anti-corrosion coating on them its really not an issue.

Yep. Not that I've ever done that before or anything. :oops:

If you can avoid the operator-induced defect it will be fine.
 

mtnbike28

Expedition Leader
I have used the wire cutters and snipped the top of the "O" and spread it enough to go over the post.
 

rayra

Expedition Leader
Inconsequential. Just take care enlarging the hole. Don't try and do it all in one bite. step up in drill sizes for a cleaner hole. put the cable connector in a vise if you can.
 

Herbie

Rendezvous Conspirator
As someone who has also buggered up more than a few ring terminals trying to enlarge the hole, take it from an expert: Tapered Reamer

220px-Taper_reamer_K-442.jpg
 

AndrewP

Explorer
I just had to enlarge a bunch for my new dual battery lay out. I had Piles of 1 ga 5/16 ring terminals and no 3/8 which I needed in 2 spots. The trick is to install on the cable first, crimp and heat shrink, the the cable gives you some meat to hang on to. Drilled out in seconds with a step bit in my drill press. Worked so well and so easily, the I see no reason to stock 3/8 terminals.
 

Tennmogger

Explorer
Copper is easy to form so just use a tapered punch and a loose vise to enlarge the hole. No metal is removed so current capacity does not drop. Don't clamp the vise on anything, just use it as a backup for supporting the terminal. The hole gets bigger as you drive the punch down through the hole slowly. Then flatten the connector because it will cup out a little. Repeat the enlarge-flatten cycle until the bolt fits.

Bob
 

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