How to transfer a 1 1/16" hole?

[bad_idea]

With a transfer punch of course. Unfortunately I don't have one that large. I found one on Amazon for $25 shipped. I don't want to spend that much on a punch that I will rarely have a use for, if ever again.

I don't have access to a lathe to turn a bushing to use with a 1/2" transfer punch.

I need to transfer (4) 1 1/16" holes from a pump and motor foundation that is approx 4'x5' that weighs 1200 lbs or so. The foundation will be bolted down w/ 1" bolts. The base of the foundation is made of 4x4x1/2 square tube with a steel pipe through the corners for the bolt holes.

I'm thinking use a 1 1/16" drill bit in a hand drill to mark the center of the hole. It doesn't have to be precision, I just have to be able to get (4) 1" bolts in. The steel pipe in the foundation corners should guide the drill bit nicely to keep it centered. Once I have a mark in the center of each hole, then rig the foundation off of the base and use a mag based drill to drill the holes.

Any better ideas? BTW... this is on a ship for a pump feeding a reverse osmosis unit.

 

[Strouty]

I would use a 1 1/16" hole saw, then you can get a nice center mark.

 

[Steevo]

I would use a 1 1/16" hole saw, then you can get a nice center mark.

That was my first thought as well.

 

[R.Anderson]

A socket works well for a bushing, just find a transfer punch that fits the square hole snug.

 

[lilscorpion]

I would use a 1 1/16" hole saw, then you can get a nice center mark.

Socket or hole saw works well, have done both in the past. if you don't have the size you need, you can use a compass do figure the center by following these steps: Use a pencil. Trace the circle (in your case, each of the bolt holes of the flange). Put a dot at two points 90 degrees apart on the circumference of the traced circle(s). Guess at 90, doesn't really matter. Measure the width (diameter) of the circle. Get a compass and set it to the measure of 1/2 the width of the circle (the radius). Swing the compass from each dot and the intersection of your two arcs is the center point. In the pic below, if the red circles are the same diameter as the black one, the intersection of the red circles will be the center of the black one. To check your work, swing an arc from the newly found center point and the compass should trace the original circle perfectly. These steps work for any diameter circle, just gotta get the right sized compass. I keep one in my box that's adjustable to maybe a 8" radius.

Using a compass

They're cheap, you can find them in school supplies at just about any store including most grocery stores for a couple bucks.
http://www.amazon.com/dp/B00290LPDU/?tag=atomicindus08-20

 

[bad_idea]

Socket or a hole saw as a bushing for a transfer punch? I love it. Just the type of solution I was looking for, cheap and easy. GJ came through again. Thanks guys.

 

[Sureshot]

I have also used tape to get a better fit with what is on hand.

 

[rlitman]

I would use a 1 1/16" hole saw, then you can get a nice center mark.

Close, but holesaws have a drill bit in the center. For one thing, that bit can wobble a bit, and for another, a drill bit isn't the best for marking.

I would use a forschner bit. That is made from a solid piece, it has straight sides that will index better in a hole (unlike the blade kerf in a hole saw that will leave some play), and the center is an actual point that can be used for marking. Heck, you won't even damage it if you give a few light taps on the shaft, and the shaft is one with the center point (also unlike a hole saw).

 

[Strouty]

Close, but holesaws have a drill bit in the center. For one thing, that bit can wobble a bit, and for another, a drill bit isn't the best for marking.

I would use a forschner bit. That is made from a solid piece, it has straight sides that will index better in a hole (unlike the blade kerf in a hole saw that will leave some play), and the center is an actual point that can be used for marking. Heck, you won't even damage it if you give a few light taps on the shaft, and the shaft is one with the center point (also unlike a hole saw).

I would be afraid it would damage the forstner bit, they are for wood. As for the hole saw, the bit in the center should not wobble unless it is loose or you have a damaged one. The original hole would keep it so close to centered you should have a mark for the center and outside diameter too.

 

[rlitman]

A forschner bit is for wood, but in using it this way, the cutting edges wouldn't touch anything. In the very center of the two chisels is a pyramid shaped point that does nothing but locate the center and stick out just a tiny bit. You won't hurt it by tapping on it enough to make a mark.

The pilot is always tight in the arbor, but the saw cup is the part that can move. It is designed to have a little "float" in it. Perhaps not enough to make a difference though.

If you use a hole saw by actually spinning it, the blade kerf will scratch up the inside of the hole you are transferring from. Is this a problem? That depends.

I don't like the idea of just tapping the hole saw to make a mark with the pilot bit. A drill bit makes for an awful center punch, and the back of the pilot bit is not exposed where you could tap on it.

 

[sberry]

I might torch some holes in it and use some big flat washers, if I didn't have a torch handy would use a tape measure to get it close and use 1 1/8 hole saw, you can put some nuts on bolts to straighten with sledge in most cases to fit any error. 99% of this type of thing is not precision, in general construction a lot of bolt hole sizes within 20% could be acceptable. Air comp has 4 feet with 1/2 holes in it but a couple 3/8 Hilti style bolts hold it down steady forever other than direct hit with a forklift. Building columns on pre engineered, holes 1/4 inch over and some big washers.

I see a workbench the other day in residential garage, every connection in 4 inch channel frame drilled and reamed, 4 bolts per joint and had purpose bought grade 8 bolts.

 

[sberry]

I read this a little wrong but simple like the holesaw or socket is a great idea and depending if I had mag drill handy and the specifics can drill a hole with the saw in a 1/2 plate in a couple minutes if I need to be in a hurry with a holesaw and a battery drill.

 

[rsanter]

Use a half in transfer punch
Use 3-5 'k' drill bits around it as centering spacers

Bob

 

[racingtadpole]

Seeing as accuracy isnt super critical, take a punch push it against the edge of the hole and make four marks spaced at roughly 90 degrees round the hole. Join the dots. Where the two lines meet is your centre.

 

[joe49]

How about lay it out with a tape. Or if you can set it just scribe the inside of the holes from there you can either just eye ball it or find center of the scribe circles.