Precision Oversizing: Making a hole in the frame go from 1.250in to 1.875in

[Deaf Bob]

That's the trouble with you Bob. Every time I go to start a fight with you, I just give the f' up because you already agree with me...

Geniuses think alike?
Or we do things simular... The right way?
Pick away cuz someday we may disagree..

[yellomalibu]

Interesting ideas. Putting two hole saws on one shank wouldn't have occurred to me (using the smaller saw as the pilot/ centering device), and it may work if the shank has enough thread to hold two saws.

Also filling the hole and using a correct sized hole saw is high on the list of ways. Since I don't weld, I would jam a piece of wood in the hole, mark center, predrill with a small, sharp bit to prevent the hole saw from "walking", then use the correct size hole saw to drill the new diameter.

[anotheridiot]

I have been asking about redrilling the axles from an 8". Well, when I put the chevy rim on the axle, there was far too much gap between the hub and the center of the rim to even be able to consider it to be in the middle. So I bought some 5/8 bar, used a 2.875 hole saw to cut a blank, then used the smaller hole saw thru the same pilot hole to drillout the center and end up with a spacer. I welded to the center hub of the axle to help keep the center of the rim in place while I used a .625 drill to go thru the rim and mark the center where I tapped the 1/2-20 where each stud will go.

So I guess in an ass backwards way, the idea was in my head. The hex shanks on the hole saws are just a little over an inch long, so it just made sense to me to use one as a pilot and should cost somewhere around 20.00 for both saws I am sure they could be centered and welded together too, but really would just need a 1/4 inch bolt and you can just bolt them together since you dont need the pilot anyway.

[CTX-SLPR]

Here's mine

I do like the idea of using a second hole saw as a pilot and instead of a normal mandrel using a bolt with the head cut off and a backer nut and washer. However I am concerned about the "oversize" that a hole saw seems to always give when I use one. For example the 4in hole saw I just used gives 4.025in holes.

I think I'm probably going to buy a 1.250in hole saw but mainly use it to center the pilot hole in the opening before snugging the bolts down on the backer/pilot plate.

[CTX-SLPR]

So I was at the local welding shop today getting some more gas for my welder and spotted these guys: http://championcuttingtool.com/champ...tters-ct7.html
According to the catalog they have a 1-7/8in cutter. Think this would be a cleaner cutting option with less of the "oversized" I mentioned earlier?

[anotheridiot]

I dont think you are looking at having to be that precise for this application. Thats a tool you would invest in if you were punching knockouts in switchgear on a daily basis. For 2 holes I would spend the 10.00 and consider it disposable.But honestly, I dont think you would ruin a bi metal if you drilled 2 holes in .500 steel.

[Huskinhano]

Greenlee punches (I've got a box of 'em) are made for thin material, not frame stuff. The hole-saw scheme is what I'd do, but you'll never get the hole stepped up a size with a drum sander unless you've got all day. Or one of these:

[ATTACH]n1114868[/ATTACH]

and one of these:

[ATTACH]n1114869[/ATTACH]

...and you can cut serious metal, quickly. Just have a scribe line to cut to, and a steady hand (!), the carbide burr is the thing 'cause they cut steel like nothing else, the best $20 you'll ever spend. You might even choose to forgo the hole-saw step. They also throw some nasty-ass chips that will stick into your skin like tiny slivers so have a magnifying glass and tweezers handy, and sweep or vacuum up after yourself. With this in your toolbox you'll never have a reason to shy away from a little metal removal. Works on aluminum also, with cutting wax (must-have for alum.). Don't get the cutter too hot in either case, have some-type coolant around for it, and it's carbide so don't let it bang on stuff, the shock will chip the teeth off.

Also works well (even better in certain cases) with the angle-version of the above grinder. Just takes some muscle and your arms torquing on it from the right angle so it doesn't chatter.

This is exactly what I was going to say about the punches, they're made for sheetmetal. And at the diameter you're talking about, you'd want a hydraulic punch. I was also going to say exactly the same with the die grinder. It's not too hard to get the shape you want. I personally like the the 90* version, I find at least for me it's easier to control. The key when using the die grinder is slow and steady is the quickest way. Use some of the blue lay out die that machinist use, scribe the circle and cut.

USE A FACE SHIELD! The tailings from the bit are little razor blades and they will find their way into your eyes without a shield. Don't make too much out of being with in .001".

This is what I have used on my car.