I used to have an oops arbor for my hole saws that let me put two hole saws on the same arbor. One the size of the hole that was too small, and one the size you wanted to drill it out to. The small hole saw acted as the pilot for the larger one, and kept the hole centered where it was.
Any one know of a current source?
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Hadn't ever seen one of those but that was a good idear someone had.
And now he could feel it- that inevitable craving for cookies! It happened every time he left his firewall down. -Heck '02
Starrethttp://www.mcfeelys.com/product/HS-0019/Starrett-quotOOPSquot-Arbor.
William the Geezer, the sequel to Billy the Kid - Shoe
When that happens, wedge the plug back in the hole with slivers and use the 1/4" drill bit center to center the larger hole saw. There's no friction on the center hole, so the plug stays put until you have the new hole started.
Most of the time I'm there years after the original hole was drilled.
Drill a hole in a scrap of 2x for a template, clamp the 2x to whatever you're working on, in the location you need, and drill away.
Once the holesaw has started cutting into your material, its pretty much self-guiding. The only problem is splitting out the back side of what you're drilling, but that can be taken care of simply by clamping a scrap of something to the back.
http://www.leevalley.com/wood/page.aspx?c=2&p=52518&cat=1,180,42316
I have one I bought from HD
I really needed one several times, but since I bought one I haven't needed it at all. Go figger...
I've never owned one but the threads on my normal arbor are long enough that I have used that technique, two hole saws on one arbor to guide the larger hole saw by the smaller hole saw riding in the too-small hole. Does that make sense? I've only had to do it a few times but have never had an issue getting the saws stuck on the arbor or locked together.
Ditto on just using the regular hole saw arbor. I used that trick once or twice many years before I ever heard of an "oops" arbor, and still don't understand the need. How often do you really need to make a larger hole... probably 4 times in my whole career so far.
blue mole has a mandrel that the threads are long enough. I think a few of the others do too.. I have soo many hole saws mandrals i can't remembr which is which. they are all interchangable