What's new
What's new

Best magnetic drill for 7/16" holes in 3/4" steel plate ?

Milacron

Administrator
Staff member
Joined
Dec 15, 2000
Location
SC, USA
Can the "hollow end mill" type drill that small ? Might need to drill 150 holes.... do any of them have power feed ? Drill would be upright (i.e. not drilling horizontally or upside down) so weight not a major issue. Budget.. spending 500 bucks would be nice but willing to go to $1,500 if necessary.
 
Can the "hollow end mill" type drill that small ? Might need to drill 150 holes.... do any of them have power feed ? Drill would be upright (i.e. not drilling horizontally or upside down) so weight not a major issue. Budget.. spending 500 bucks would be nice but willing to go to $1,500 if necessary.

The tool you describe is an annular cutter. And yes they are commonly available in 7/16"D. And yes mag drills are available with power feed. In the future I would encourage you to take a few minutes and google simple questions before asking a community like this. You will have better luck saving the brain trust here for questions that aren't easy answered with a few words in a search engine....

https://www.homedepot.com/p/Drill-A...th-3-4-in-Weldon-Shank-DWC5-530-210/304852945

Hougen HMD927 Two Speed Power Feed Portable Magnetic Drill
 
Hougen mag drills rock. And, yes, the annular cutter and auto feed will do that job no issues. I used to do similar in 5/8 plate all the time.
 
Yeaaaaa, I noticed who I replied to after I submitted that reply. On the bright side, I was kinda polite, and slightly helpful. Now off to cry in my corner...
 
If you choose to buy one, I suggest going for bigger/better than entry level model. I’m NOT talking about off brand cheapies. I bought the entry level Slugger made by Fein, and I honestly wish I would have gotten the next size/model up. It can only fit the short annular cutters.

I bet DrHook’s model is much stronger/rigid/ & has a more powerful magnet than this one.
 
a hougen is the best of the best.
but for 7/16", id go standard spiral unless its a massive plate.
and yes, mag drills can get a regular jacobs chuck to use a regular drill but and not an expensive annular cutter for 7/16"

ive drilled 150 holes in stainless with a good drillco drill bit and some coolant to prevent the bit from getting too hot.
 
I have a Milwaukee 4204-1 and I love the versatility of it. It is reversible for tapping holes and has variable speed so you can slow it way down for big countersinks and such.
 
I was wondering about that... 7/16" seems pretty small for an annular cutter

Yeah, it's sort of right at the interface between annular and spiral. 9/16 is where I go annular. The depth of the drill would push me to spiral with extra horsepower and appropriate RPM.

With that many holes, I'd go with the Hougen HMD905...it's still easier to move around than the milwaukee's, but has the horsepower to push through. And for an extra couple hundred compared to the 904, you are getting dual speeds and a more versatile machine for future uses. (dual speed, for larger diameter annular cutters)
 
Yeaaaaa, I noticed who I replied to after I submitted that reply. On the bright side, I was kinda polite, and slightly helpful. Now off to cry in my corner...

Off with his ead !

Seriously, I don't see an apology to Milacron in your posting.....:skep:

This "new generation" with the "smart phones".....Ugh.
 
Last edited:
I like annular cutters, a lot. But....are they 'the' thing to use over a twist drill? For larger holes, and holes that need to be more precise...yes. But if you just need to drill some basic 7/16" holes for a bolt to pass through....is a twist drill faster and cheaper?
 
you really don't want to use an annular cutter if you are drilling hot rolled or rusty plate at 7/16. the annular cutter will dull really quickly on scale or rust, and resharpening one isn't nearly as easy as is a twist drill.

the big advantage of annular cutters is they remove less metal for a given size hole than a twist drill, and take proportionately less feed pressure. that advantage is basically lost under 1/2", and they cost a lot more too.

as a way of visualizing the work savings, the size of the slug is a good guide. I don't know what size the slug is on a 7/16 slugger, but it can't be much more than 1/4 or so, meaning you are saving the effort of drilling a 1/4" hole.

It would make sense is if you were set up drilling larger holes with a mag drill, and had a few 7/16 to do as well. it would save setup time to pop one in.

I don't have a specific brand/model recommendation but make sure it has the upward travel to fit the chuck and the 7/16 twist drill.

happy drilling!

P.S., do get a unit that takes annular cutters (3/4 weldon spindle), and a auxiliary Jacobs chuck, so that you can use the slugger bits in the future when drilling larger holes!
 
For 7/16" holes I don't see any advantage to using an annular cutter. I think a drill would be just as fast.
As the holes get larger then, yeah, an annular cutter becomes much more efficient.

How often are you going to do this job? Is this a one time job or something that will repeat many times?
How accurate do the holes have to be?

I ask simply because it it's a one shot deal you might be just as well off with a used machine. I recently
made myself a new welding table with a grid of drilled holes for anchor points. I picked up an old Black
& Decker mag drill for 180 bucks (CDN) and it did the job just fine. It's pretty big and a bit clunky but for
drilling holes in a table it was more than adequate. My table top was 3/4" thick and I used an ordinary
1/2" drill bit--worked a treat...
 
Yes, you can use an expensive mag drill with powerfeed and yes you can buy a 7/16" rotabroach which costs $40 to sharpen.

But there are alternatives. I own a cheap Polish mag drill which has a no. 2 Morse taper spindle. It comes with a 3/4" pot chuck for rotabroach tooling, but I use it more often with a regular drill chuck installed. Yes, I still have to pull the feed handle, but OTOH I can sharpen a 7/16" drill in less than a minute.

metalmagpie

drillingFireboxBackPlates.jpg
 
I think 150 7/16" holes through 3/4" is going to go quickly and not need power feed. In my time with mag drills, it usually takes longer and more effort to get the drill positioned than to drill the hole. And you get the primal feeling of POWER when you pull down hard on the handle and hear the motor slow down a little.

I have a Hougen HMD904 and it would be more than adequate for the job. You would need a drill chuck for it. They sell one. About $1k.

I also pleasantly surprised myself with China special core drill on Amazon a few years ago. The local rental place rents expensive high end Husquavas. Clutch didn't work on the brand new rental drill and it about broke my wrists / arms / collar bone. So soured on high end core drills, I bought a $300 core drill to drill a couple of 4" holes through 6" reinforced concrete. I've used it about 30 times and it works just fine and hasn't tried to kill me like the high end drill did. I suspect that China is making some mag drills that are similar. Cheap and functional enough.
 
I was wondering about that... 7/16" seems pretty small for an annular cutter

yep, they are most available 1/2" and over, that is where the drill bits start to require large hp to drive it. plus you are saving much more drilling 1" with a 1/8 thick annular cutter then the 7/16" where the slug is the same as the center starting guide bit essentially.
I always use about 1/8' bit for a starter hole then just drill with a 7/16" as the first bit allows it to not have to push the center chisel tip through the material.
 








 
Back
Top