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Starrett Oops Arbor

Enlarging a hole can present a tricky problem, whether it’s an existing hole that needs enlarging, or somebody made an “oops” and used the wrong size hole saw. How do you center the hole saw at the same location and keep it from wandering? This question drove the engineers at Starrett to develop the Oops Arbor.

As long as the new hole is 3/16″ larger than the old hole, you can use the Oops Arbor to pilot the larger hole saw with a second hole saw the size of the original hole. The Oops Arbor’s 1/4″ shank replaces the normal pilot bit for most hole saw mandrels and accepts both 1/2″ and 5/8″ threaded cutters.

You can get the Oops Arbor for as little as $6.  What’s it worth to be the hero next time somebody makes an Oops?

Oops Arbor [Starret]
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Via Amazon [What’s This?]


16 Responses to Enlarge Holes With The Starrett Oops Arbor

  1. Fred says:

    This is nothing new from Starrett.
    We bought the ones we have in the late 1990’s for about $5 each.
    We now carry them with other arbors in our hole-saw boxes.

    Before that we would try one of 2 different approaches:
    1) If we had access to both sides of the hole we would clamp a scrap of wood to the back side and then retrive the cut plug – put it back in the hole as a centering guide and hold it in place either with glue or a few brads.
    2) cut the new hole in a piece of scrap and the center it over the old hole and either clamp or brad it in place as a drilling guide.

    Unfortunate for all of this – we like Milwaukee and Greenlee selfeed bits a lot better than hole saws for most wood boring (e.g. rough-in) work – leaving the hole saws for such tasks as metal cutting (e.g. steel doors). If you cut the wrong size with a selffeed – its back to sanwiching scraps onto both sides and fabricating a plug for the middle. We try to studiously avoid such mistakes.

    We also have put up some fiber-cement siding – but find that the bimetal holesaws don’t last in that application – and like holesaws with carbide teeth.

  2. Fred,

    I never said it was new, I only said “drove the engineers at Starrett to develop…” It was a guess that the engineers at Starret designed this, maybe they bought or poached the design from some-one else. That’s a bit of creative license that maybe I took to far. It’s tedious to write post after post with the sentence X makes Y for Z, and frankly it would probably bore our readers right off the blog.

    That said, I do want to be as accurate as possible, so thank you for your information and experiences. I do remember certain magazines that promoted this like it was a new tool a while ago, and it’s interesting to know that it’s been around for a while.

  3. PutnamEco says:

    Same idea, different take on solution. A hole saw alignment guide.


  4. Fred says:

    The tricitylock solution looks like an elegant tool albeit a bit pricey.

    My comment about the Starrett Oops being around for a while was not to deprecate it – but rather to point out that it has stood some test of time and finds a home in our toolboxes. Lots of tools seem to come onto the market and then disappear. Hopefully those that don’t make it are ones that do not fill any niche at all.
    I like this blog – because it helps showcase some of the new – allowing folks to comment and share experiences. It’s also good to showcase older products, that may be a bit off of the mainstream, to introduce or reinitroduce them – and let folks share.
    I’m always looking for ways to improve productivity, enhance safety etc – and I appreciate that this forum helps.

  5. Frank Townend says:

    I remember seeing a different product configuration to solve this problem and a quick search brought me to [ http://www.centurydrill.com/# ]. This company makes the CoPilot which “replaces” the pilot drill with an extended arbor that holds the smaller hole saw backwards. The Product page is here: [ http://www.centurydrill.com/1/pdf/Hole%20Saws/CoPilot.pdf ] The price may or may not be comparable with the Starrett.

  6. Chuck Cage posted the Tri-City Lock hole saw alignment guides a while ago on Toolmonger:

    Toolmonger » Blog Archive » Reader Find: Hole Saw Alignment Guides

    He came to the same conclusion that they were a little pricey

  7. Mr P says:

    Got one a year ago never used it yet. Most of the time i don’t want the larger hole on center to the old hole so i have to set up a jig anyway.

  8. some_other_dave says:

    If the hole is small enough, a Unibit should do the job quite well…

  9. Fred says:

    Unibits and their various cousins – work well for fairly thin materials where the thickness is consistent with the length of the shoulder of the drill step.
    They are great for enlarging holes on electrical boxes and that’s maybe why they are offered by Greenlee and Klein. Knockout punches are the step up for this application – when a large size hole is needed – the hydraulic ones being more costly – but beefier than the screw/ratchet type.

  10. james b says:

    I seem to recall welding a metal plug back in the wrong sized hole to use the same pilot hole twice.
    Now if they could just make one that would make a hole smaller after I drill it too big . . .

  11. Kurt Greiner says:

    A unibit would be a good choice if the target size of the finished hole is not larger than 1 3/8″ – I haven’t seen one bigger than this – the unibit design would make anything much larger expensive, heavy and unwieldy.

    For operations within their limits, I love unibits. I work with Plexiglas a lot, and they easily make a nice hole from 1/8 to about 1/2; you can go larger but you need to use more care and a lighter touch.

    I don’t use hole saws nearly as often, but if I did this arbor would seem like a good investment to save material and time on a job.

  12. Fred says:

    Re Kurt Greiner

    Some years ago, Lucite and Plexiglas and a few other plastic materials were all the rage in doctors office around here – and in local banks. We got a reputation for doing this work and had a lot of it. At that time we bought sets of specialized drill bits (Hansen brand) that had a sharper point, different flute geometry and seemed to scrape the hole sides as they cut. We went to these to avoid spidering and breakout as the drill exited the hole. I recall that they were a big improvement over using our regular twist drills.

    I’m guessing that someone still makes these.

  13. tooldork says:

    Bosch has one of these that works with their Quick Change system. It will also works with other company’s hole saws.

    Saw it in Remodeling Magazine:


  14. rodney says:

    Or if you are cheap like me, pound a tapered wooden plug into the hole and start over with a regular hole saw

  15. Floyd says:

    If you do not have an oops arbor,you need if you work with home repair. This works great and I love it.

  16. Bruce says:

    This is a fake picture. The tool works but it has a 1/2″-20 smaller diameter section and a 5/8″-18 threaded bottom section. The bottom section will take a 2-1/2 inch hole saw as shown in the picture but the inside hole saw can be no larger than 1-1/4 inch to thread onto the 1/2″-20 section of this tool. The inside hole saw would be half the diameter of the 2-1/2″ hole saw shown in the picture so it was obviously staged by the Starret product management people.

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