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Old 08-19-2019, 11:20 AM
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Default In situ drilling

Is there an easy way to rig up to drill 14 - 3/4" holes through 3/8 mild steel on something too awkward to get in my drillpress or mill drill?


I do not own a mag drill. I do have a couple of 1/2" drills and a lathe. Some kind of jig I could build?
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Old 08-19-2019, 12:10 PM
BukitCase BukitCase is offline
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I have one of these
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Just a tad cheaper than a mag drill, works in handheld ones, center punch where you want the hole and its pilot keeps it there.

Probably only about TEN TIMES EASIER THAN A TWIST DRILL, but maybe I'm just gettin' (GOT) old ... Steve

PS - they're meant for sheet metal, but any size larger than the mandrel will cut 1/2" deep.
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Old 08-19-2019, 12:40 PM
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If you've got a big enough drill motor--you'll need something with at least 1/2" capacity so you can use Prentiss drills. Bigger is better because it generally means that you'll have something that will turn at a slower RPM.

Personally for that small number of holes I'd just step drill them--start out at 1/4", move to 1/2", maybe on to 5/8" and then final drill at 3/4". I wouldn't bother with any kind of a jig or fixture unless the holes need to be really accurate and really square to the plate. One thing I would make is a longer reaction arm to replace the small handle on the side of the drill. Make it 3 or 4 ft. long and have a helper hold it when you're working so the drill doesn't try to twist out of your hands.

I've got a big ol' Black and Decker drill--probably dates back to the sixties--that has a 3/4" chuck on it. It's probably good for 1-1/2 HP or so and turns about 300 RPM under load. It uses 3/4" pipe for the reaction handle. I have free-drilled 1-1/2" holes with it using a helper with a 5 ft. length of pipe. As long as you can control the reaction torque it drills like crazy. You definitely need the long handle though; if you don't use on it'll take you for a nice ride.

If we could figure out how to get the beast to you I'd be happy to lend it to you. How soon do you have to drill the holes?

The drill in the picture isn't ours but it's very similar...
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Old 08-19-2019, 01:09 PM
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Quote:
Originally Posted by LKeithR View Post
If you've got a big enough drill motor--you'll need something with at least 1/2" capacity so you can use Prentiss drills. Bigger is better because it generally means that you'll have something that will turn at a slower RPM.

Personally for that small number of holes I'd just step drill them--start out at 1/4", move to 1/2", maybe on to 5/8" and then final drill at 3/4". I wouldn't bother with any kind of a jig or fixture unless the holes need to be really accurate and really square to the plate. One thing I would make is a longer reaction arm to replace the small handle on the side of the drill. Make it 3 or 4 ft. long and have a helper hold it when you're working so the drill doesn't try to twist out of your hands.

I've got a big ol' Black and Decker drill--probably dates back to the sixties--that has a 3/4" chuck on it. It's probably good for 1-1/2 HP or so and turns about 300 RPM under load. It uses 3/4" pipe for the reaction handle. I have free-drilled 1-1/2" holes with it using a helper with a 5 ft. length of pipe. As long as you can control the reaction torque it drills like crazy. You definitely need the long handle though; if you don't use on it'll take you for a nice ride.

If we could figure out how to get the beast to you I'd be happy to lend it to you. How soon do you have to drill the holes?

The drill in the picture isn't ours but it's very similar...
Yours is Black and Decker, mine is a Skil. Same kind of drill motor. I have a couple sets of Chicom 1/2" shank " blacksmith" or smith and prestiss drill bits too. I was looking for a way to get a bit better control. I am looking to match drill a set of bolt on cutting edges, so step drilling mean spotting with a full size drill switching to pilot drill and maybe two steps between.

I won't have the cutting edges till Friday, so have some time to figure something out..... I may end up just doing it with the drill motor alone, but I would like to come up with something just a hair more elegant.
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Old 08-19-2019, 01:50 PM
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So you have a big plow or something to drill the holes in to install a replaceable cutting edge?

Those big drills are a beast and will beat you if left on their own. Kieth has put it well with the long handle. to control reactive torque.

Can you clamp a bar on one end of the victim to get started?

If so, clamp a pipe or flatbar on the end of the bucket so the long pipe from the drill can rest against it. Set you drill in position and then have another piece of pipe to go back to the upright and hinge on the upright, you may be able to use a flat bar with a hole in it so it will catch on the upright to get the leverage pipe in place, set that piece of pipe on top or through the D handle and use it for leverage to press down on the drill like a drill press. Get one hole drilled and then use the new hole to attach everything to, rinse and repeat till you are finished.

Like a t post puller type setup.

Scott
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Old 08-19-2019, 02:04 PM
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Quote:
Originally Posted by camdigger View Post
...so step drilling mean spotting with a full size drill switching to pilot drill and maybe two steps between...
You could make up a simple transfer punch to locate the holes--I've done that before when I didn't have the right size.

Quote:
...but I would like to come up with something just a hair more elegant...
You mean you want something a bit more sophisticated than an "Alberta Solution"...
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Old 08-19-2019, 02:06 PM
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Can’t recall if Gerry has a mag drill or not. I have a so-so one here at the house though.

I also have one of the old school, high torque portable drills. I also have the ‘stand’ they clamped into to use them as a sort of drill press. Before I got the mag drill, I would use that as a sort of portable radial drill. Offset the drill so it isn’t over the base, and then clamp the base down to the surface.


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Old 08-19-2019, 02:19 PM
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Quote:
Originally Posted by greywynd View Post
Can’t recall if Gerry has a mag drill or not. I have a so-so one here at the house though.

I also have one of the old school, high torque portable drills. I also have the ‘stand’ they clamped into to use them as a sort of drill press. Before I got the mag drill, I would use that as a sort of portable radial drill. Offset the drill so it isn’t over the base, and then clamp the base down to the surface.


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The drill motor carrier is closer to what I am thinking of.The other thing I thought of is a feed mechanism I saw on a hot tapping machine.....hmmm.

My plan is to clamp the cutting edge in place. Locate the holes by using a transfer punch or spotting with the full size drill. Step drill starting with a split point drill roughly 1/4" diameter, then 1/2", then full 3/4". I know what an arm breaker the big Skil drill motor can be, so was looking for accuracy and safety.
Sometimes, the best way is to knuckle down and just do it....
Not exactly sure how yet, but I'll get the holes drilled after I get the cutting edges here. In the meantime, I need to figure out why my plasma machine is giving a line voltage error at lunchtime. The vagaries of a rural service, maybe?
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Old 08-19-2019, 04:00 PM
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I also have one of those spiteful old drills Don't use it much but it spends all it's time planning to hurt me.
long reaction bar and a variac are my tricks to control it.
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Old 08-19-2019, 04:11 PM
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Just do it with the mill drill You could make a stand and clamp it so it doesn't get away
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