Ream 1" hole In Steel Plate

[CCI]

It's a stretch, but given the range of experience here maybe somebody knows.
I got some parts fabricated in 1/4" mild steel plate, and the shop burned the holes not accurately. They need to be 1" diameter, round, and all in the same relative location so the pins line up. As it is now, the holes are not round and only a little less than one inch. I would have been better off if they didn't put any holes in at all.
My experience with drill bits is if I try to run a 1" bit through these holes all I will do is shatter the outer cutting edges of the bit.
Thinking about a bridge plate reamer but wondering if anyone here has a better idea.

 

[c502cid]

I'd run a step drill bit.

 

[wrcsixeight]

If the holes are not centered..where desired...and too small then i would be thinking carbide rotary burr on dremel to bring hole towards desired center. Then Step drill bit if perfectly round is required.

Will.still likely have to step drill bigger than 1" though , unless you are a human cnc machine.

 

[Ihatetochangeoil]

It's a stretch, but given the range of experience here maybe somebody knows.
I got some parts fabricated in 1/4" mild steel plate, and the shop burned the holes not accurately. They need to be 1" diameter, round, and all in the same relative location so the pins line up. As it is now, the holes are not round and only a little less than one inch. I would have been better off if they didn't put any holes in at all.
My experience with drill bits is if I try to run a 1" bit through these holes all I will do is shatter the outer cutting edges of the bit.
Thinking about a bridge plate reamer but wondering if anyone here has a better idea.

You don't say how many holes, how far off they are, what your end goal is or post any pictures????

If you've got the torque to turn a 1" reamer, you've got power but not necessarily accuracy. The reamer, like electricity, will take the path of least resistance; if the holes are already off centered, the reamer will only expand your problems. I like the guy who suggested a carbide burr on a dremel tool....but a dremel tool on 1/4" steel is like painting a barn with a toothbrush. I'd want an air powered tool that will put out some decent torque, unless you have a lot of time to spend. And carbide burr tools ain't cheap.

More years of fabrication shop experience than I want to admit. PM me anything you want about details.

 

[tom slick]

Bridge reamer is the correct tool

 

[Dave9]

Carbide tipped hole saw, preferably in a drill press. You put a plate under the work with a hole where you want dead center to be for the pilot drill bit, to hold the hole saw accurate as it remakes the hole. Both plates must be securely clamped down, of course. Once you have the first plate done, if it can be flat-clamped to the 2nd plate that needs to match, you can use it as an additional guide.

 

[bullwinkle]

I've done it with marking the hole, using a center punch to mark small drilling spots all around the outside (back from the line 1/2 the distance of the smaller drill bit I'm using), drill holes all around the outside, connect the dots with a stone on a die grinder, or even a torch with a steady hand. Use a die grinder to smooth out the rough spots. Doable, not too easy. The holes will stop you from making the hole too big with a torch if you direct the heat towards the inside of the hole.

 

[Kestas]

Are you expecting to do this by hand? This would be difficult. It would be best done with a milling machine or drill press.

 

[CCI]

Are you expecting to do this by hand? This would be difficult. It would be best done with a milling machine or drill press.

It's a couple dozen holes, I've got a small drill press with MT2 taper and a 3-jaw chuck, I can get it turning plenty slow.

 

[CCI]

Bridge reamer is the correct tool

Thinking seriously about buying one but I might try the hole saw trick first.

 

[CCI]

Carbide tipped hole saw, preferably in a drill press. You put a plate under the work with a hole where you want dead center to be for the pilot drill bit, to hold the hole saw accurate as it remakes the hole. Both plates must be securely clamped down, of course. Once you have the first plate done, if it can be flat-clamped to the 2nd plate that needs to match, you can use it as an additional guide.

Never even crossed my mind, not a bad idea at all. I could even tack weld the plates together and use a fence to index them.