Tapping in thick steel

I am making light pole bases with a572 grade 50 steel 1.5” thick. I cut the plates, basically a 14” square with a 4” hole in the center, on my cnc oxy fuel table. I then need to drill and tap 4 through holes in the corners. I forget the exact size, but it’s either 7/8 or 1” corse thread. Also drill and tap one small blind hole, about 1/4”diameter. So far all I’ve done is drill the holes with a Milwaukee mag drill, using a template for hole layout, then hand tap the holes. I have an order coming up for 27 of these plates, with a possible 38 more to follow. There must be a better, faster way to do this. Methods I have considered: powered tapping arm, tapping head for the mag drill, tapping with impact wrench.

Ideally I would be able to retrofit a drill head on my cnc table (it’s a 5x10’ with water table made by shopsabre) to drill the holes automatically. The company that made the table can do it however I would have to bring the table to them. Problem is they are in Minnesota and I am in Alaska.

Any suggestions?

a nice big radial arm drill will do it

Larry Dickman said:

a nice big radial arm drill will do it

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The OP mentioned using an "Impact wrench" to tap said holes....

Get one of these up there - like on a BARGE.

BIG Radial Arm Drill Press 5’x 15” - tools - by owner - sale

You'll then have a machine actually intended for such work

Who needs a "tapping head" ?

And one for 1"-8 is spendy.

Why just reveal what else you have in your shop ?

I'm sure we could help, but like many initial postings,
this is like pulling teeth.

The OP is sorry for mentioning using an “Impact wrench”

Ok digger doug I will enlighten you as to what I have in my shop. I have a cnc oxy fuel table and a mag drill. And an assortment of standard hand tools. And a car and a mini van because my shop is my garage. That’s it. Are you always this friendly and welcoming?

SuperUPer said:

. Are you always this friendly and welcoming?

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Ignore it, ……...FWIW you caught him on a good day.

SuperUPer said:

Ok digger doug I will enlighten you as to what I have in my shop. I have a cnc oxy fuel table and a mag drill. And an assortment of standard hand tools. And a car and a mini van because my shop is my garage. That’s it. Are you always this friendly and welcoming?

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Im sure he does not mean it, i certainly don't want to piss off someone that can load a 1 1/2" steel plate on a oxy fuel table with your list of equipment. Really kinda curious how you transport it on the top of a mini van too . No disrespect here, but that jobs really pushing it with your setup by the sound of things. As to the oxy fuel table drilling, maybe but im real dubious the structure would take the kinda torque to tap those holes. Must be a very serious gantry!

You can get some pretty big air tappers, really not sure if a mag drill would hold hard enough to get that kinda tourque to tap 1" coarse threads, thats IMHO asking a lot. but im kinda with the others, a radial arm drill is the non cnc industry approach to this kinda part and has been for over a century . A radial drill even a small one will wind that tap in there like its going through butter!

Your mag base drill should drive a 1"x 8 tap...........assuming its not a rotobroach type machine..........if it will drive a 1 " drill bit ,then it will certainly drive a 1"tap.............you can likely also crib a bit on the thread depth,who is gonna strip a 1" thread..............Ive done thousands of light pole bases ,every one was a single cut path ,including the bolt holes.........I ve never heard of threading the base.....does the base need to be galvanized....the threads will need recutting.

SuperUPer said:

Ok digger doug I will enlighten you as to what I have in my shop. I have a cnc oxy fuel table and a mag drill. And an assortment of standard hand tools. And a car and a mini van because my shop is my garage. That’s it. Are you always this friendly and welcoming?

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You want my help or not asshat ?

john.k said:

Your mag base drill should drive a 1"x 8 tap...........assuming its not a rotobroach type machine..........if it will drive a 1 " drill bit ,then it will certainly drive a 1"tap.............you can likely also crib a bit on the thread depth,who is gonna strip a 1" thread..............Ive done thousands of light pole bases ,every one was a single cut path ,including the bolt holes.........I ve never heard of threading the base.....does the base need to be galvanized....the threads will need recutting.

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He has a minivan....that is all.

adama said:

Im sure he does not mean it, i certainly don't want to piss off someone that can load a 1 1/2" steel plate on a oxy fuel table with your list of equipment. Really kinda curious how you transport it on the top of a mini van too . No disrespect here, but that jobs really pushing it with your setup by the sound of things. As to the oxy fuel table drilling, maybe but im real dubious the structure would take the kinda torque to tap those holes. Must be a very serious gantry!

You can get some pretty big air tappers, really not sure if a mag drill would hold hard enough to get that kinda tourque to tap 1" coarse threads, thats IMHO asking a lot. but im kinda with the others, a radial arm drill is the non cnc industry approach to this kinda part and has been for over a century . A radial drill even a small one will wind that tap in there like its going through butter!

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It’s mostly technique: use a lot of lower back with a twisting jerking motion. Also it’s 1.5 metric inches, really not as heavy as it sounds.

But for real I use a 3 ton engine hoist, drill and tap a hole in the center of the plate and thread in an eye bolt. It’s not easy but it works for now. I have a couple lifting magnets on order and I’m working my way towards some kind of gantry hoist. And the truck and trailer are outside. Nobody asked what’s outside the shop??

SuperUPer,

Just tell Douggy that your minivan has a "Trump 2020" bumper sticker on it, and he'll be less hostile.

john.k said:

Your mag base drill should drive a 1"x 8 tap...........assuming its not a rotobroach type machine..........if it will drive a 1 " drill bit ,then it will certainly drive a 1"tap.............you can likely also crib a bit on the thread depth,who is gonna strip a 1" thread..............Ive done thousands of light pole bases ,every one was a single cut path ,including the bolt holes.........I ve never heard of threading the base.....does the base need to be galvanized....the threads will need recutting.

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It sounds like a little back story may be useful here. Get your pliers ready, double D, I’m about to unwillingly surrender some more information. I worked for a pile driver for about 6 years so I’m pretty familiar with light pole bases and their installation. This particular style is the only one I’ve seen that has threaded holes. Most of them, like you say are one or two cut paths with the bolt holes being slotted in. It must be a unique Alaska DOT spec for this base because I’ve only done it on state jobs. No galvanizing necessary.

I started my business almost a year ago as a part time gig. I have a full time government job (welding, fabrication, and a little machining which I am pretty new to) that I don’t plan on quitting till I get full retirement. I only have one customer, the pile driver that I worked for. I pretty much exclusively cut pile caps out of 3/4” to 2” steel. With my current methods I have cut approximately 10 sheets of steel 4’x8’ or larger. It works ok but will be improved with easier loading and unloading. I have only done 2 of the DOT caps to date, but as I said, I have a larger order coming up. Sounds like a radial arm press is the ticket but not sure it’s feasible quite yet with my limited floor space. As for the cnc table mounted drill, I really don’t know if it could handle this heavy duty steel. It is a stout gantry (2 4x4 steel square tubes one on top the other) but the company mainly does routers not really thick steel. It might only be good for drilling and not tapping. My mag drill is huge, drills 1” holes no problem. But it has a standard keyed chuck that to me seems like it would slip trying to hold a bigger tap.

digger doug said:

You want my help or not asshat ?

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Doesn’t seem like you have any to offer. If you do it’s like pulling teeth to get it. We should be friends

digger doug said:

He has a minivan....that is all.

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Yep and I’m comfortable enough with my masculinity to drive it. Unlike those internet tough guys...

SuperUPer said:

My mag drill is huge, drills 1” holes no problem. But it has a standard keyed chuck that to me seems like it would slip trying to hold a bigger tap.

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Yeah I agree with you it probably would slip. Could you possibly grind 3 flats on the shank of the tap?

Brent

I would first check the spec for thread depth........if there isnt one ,you could probably get away with 30% engagement,even 50% would lower cutting force by a large margin.........a common way to make taps drive in a chuck is to put a couple of spots of mig .....I think you might be better making a drive adaptor to fit the square on the tap and the drill..............the main problem with taps is the shank is so hard,the chuck cant grip ,this is the same problem had with carbide drills,where diamond coated chucks are needed to grip.

No way a Mag Drill that handles a 1” drill will turn a 1” Tap. You can look up the torque requirements easily, it isn’t going to happen. You are a welder, make a tapping arm like a pantograph cutting torch and mount a suitable gear motor with the torque needed on it. A hollow shaft style worm gear reducer would make it easy to make a tap driver. PM me if you’d like help selecting parts.