A Cheap Way to Drill Cotter-Pin Holes in Bolts (for newbies like me)

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Model T Ford Forum: Forum 2012: A Cheap Way to Drill Cotter-Pin Holes in Bolts (for newbies like me)
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Coiro on Friday, October 26, 2012 - 02:00 am:


This is a really neat jig for drilling cotter-pin holes in bolts, but the darned thing costs about fifty bucks, assuming you can find one somewhere. There's a much cheaper albeit less elegant way to put a cotter-pin hole through a bolt that works pretty well—and the most pricey thing you'll have to buy is a really good cobalt drill-bit. Good tools are supposed to be expensive, but this cobalt bit only costs about four bucks—same as a gallon of gas.



The bolt you'll start out with should be about a 5-hardness. That's strong enough without being too hard to drill (We're not working on spacecraft or nuclear subs, here). Of course, buy the correct size castle-nut, but you'll also need two regular hex-nuts.

Stick one of the hex nuts in your vice and use a punch to dent the center of one of the flats.



Then, with a regular hand-held drill and that cobalt bit, put a hole though one side of the nut.



If your hole isn't centered perfectly, you have five remaining opportunities on that nut to get it right. You only need one acceptably centered hole.

Measure the spot on the bolt where you want to put the cotter-pin hole and put a dot there with a magic marker.



Spin the un-drilled hex-nut all the way down the shank of the bolt and then screw on the drilled nut. While looking through the hole in the side of the nut, find the magic marker dot. Now, take out a wrench and use the un-drilled nut as a jam-nut to lock everything in place. Try to get the flats on both hex-nuts to line up.



Clamp the stuck-together bolt & nuts unit into your vice, poke your drill-bit through the hole in the side of the nut and drill a little more than halfway through the bolt.



Unscrew the holed hex-nut, line up the flats on the bolt-head with the flats on the remaining hex nut and clamp the unit in the vice. Poke your drill-bit into the hole in the bolt and drill the rest of the way through.



Don't remove the hex-nut just yet. Clean the threads up with a wire brush and then spin the hex-nut up and down the bolt to chase the threads. Take the hex-nut off and finish cleaning up the threads with the wire brush.



And there you have it: Easy to do, without incurring the cost of a fancy drilling jig.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner, Vancouver, WA on Friday, October 26, 2012 - 02:07 am:

So simple, awesome work Bob. I have wanted one of those jigs for years but never felt rich enough. Your way works and I love a good shop fix.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Dufault on Friday, October 26, 2012 - 07:09 am:

Another elegant, simple answer to :"How do I do this?" question.
Thanks Bob.

Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Wolf on Friday, October 26, 2012 - 07:17 am:

Bob;
I have one of those drilling jigs. Bought it at a swap meet, many yrs. ago. The only way to go.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Cassara Long Island, NY on Friday, October 26, 2012 - 08:01 am:

Drill press with a v-block and a table vise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Friday, October 26, 2012 - 08:53 am:

Texas Ts this one for $31.95

Holder


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Friday, October 26, 2012 - 09:01 am:

Great minds think alike, or two heads with a single thought. This one adds the other end of the bolt.

http://www.mtfca.com/discus/messages/257047/291846.html?1338043969


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Wolf on Friday, October 26, 2012 - 09:07 am:

James;
Don't remember paying that much. Maybe $15.00 or $20.00.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Milton,WA on Friday, October 26, 2012 - 09:57 am:

What is your time worth ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith on Friday, October 26, 2012 - 11:04 am:

I've used mine a half dozen times, and it's worn out! It should be heat treated, so it can be used more than a few times. It's a great item other than that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Zahorik on Friday, October 26, 2012 - 11:14 am:

There is always the satisfaction of doing it yourself. Nice job.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Coiro on Friday, October 26, 2012 - 12:07 pm:

It took between ten and fifteen minutes to drill that bolt (including taking the pictures), so even though it's not as lightning fast as using a jig or drill-press, it's still fairly quick—twice as quick if you've already done it once before, because the reusable hex-nut will have already been drilled from the first time. So, what, maybe seven or eight minutes?

Like I said, this technique is not the most elegant way of going about it, but for the cost of a $4 drill bit (assuming you don't already have one), it's the cheapest way to get the same job done.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Friday, October 26, 2012 - 12:07 pm:

I was thinking about doing it only a little different then Bob's way. I was going to mark the spot where I wanted the hole then using a castle nut to line up the mark put the bolt in the vice so the head and nut are clamped in place. That would mean that I would be a little off the mark when the head of the bolt and nut were lined up. Then using the recess in the castle nut drill the hole.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Friday, October 26, 2012 - 03:19 pm:

About fifty years ago, I was taught to use a small round file between two threads where you want the hole in the bolt. File it just enough to make a nearly flat spot between those two threads. A drill press helps, but I have used electric hand drills. "Usually", the drill bit will start easily in the nearly flat spot. Sometimes you have to rotate the bolt a little to get it drilled straight through the bolt. A small drill press vise helps, but I usually just hold the bolt in my fingers even though the vise (I have two) is sitting right there.
Afterwards, use the small round file on the other end of the hole, file a similar nearly flat spot across the hole. That usually cleans up the threads nicely.
It takes me about two minutes from start to finish.
I do like the drilled nut idea! It should help others. Thank you for sharing it!
Drive carefully, and enjoy, W2


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