Centering a hole saw in a preexisting hole (and 5 trips to Home Depot)

gjmontll

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Again the "water filtration faucet" mounted on our kitchen sink was dripping and lacks any way to overhaul it. Although the nearby (3 blocks from here) Home Depot had the exact replacement, I opted for an improved one. That was Trip #1 to HD.
Yesterday I started on the replacement, and realized I should also change the under sink filter. Back to HD for the filter, Trip #2, but despite what the inventory said, they had none on the shelf. So Trip #3 to our city's other HD (3 miles away.) They had it, but I was unsure because it looks different that the older ones. It did fit.
HD Trip 4 was to get some new plumbing fittings for the filter, and I redid my tee-connection that splits the filter output to both the faucet and the refrigerator.
Making progress, but then late yesterday afternoon, in the midst of doing the replacement, I realized the new unit required a larger mounting hole (1 1/4") through the stainless steel sink.
Back to HD, Trip #4. They have a few different brands for hole saws, but for each, they were out of the 1.25" models. So I took a chance with a 1 3/8" Milwaukee hole saw and had to get the right arbor for it.
But how can I center the hole saw properly in the old hole? Good thing that I'm a hobby-machinist...
I hacksawed off a few inches of 1" aluminum rod to make a jig. Note: Three months ago I had shoulder surgery and am just finishing a month of physical therapy, this would be a good test of my recovery status. I passed the test. (I'm glad that it was my non-dominant arm and that it was not an inch of steel).
On my Logan 820 lathe, I reduced the stock's diameter to match the sink's existing hole (0.750"), but left a full diameter flange at the outer end. Then drilled out the bore to mate with the arbor's 1/4" drill and parted it off.
Ready to cut? Nope. My portable drill's chuck wouldn't take the 7/16" hex head of the arbor. I really didn't want to make yet another HD run for a bigger drill. Instead I put a 7/16" socket on the arbor and used a 1/4" to 3//8" socket adapter to my drill. Not the most robust connection, but it would have to suffice.
And it all worked as planned. Inserted the jig into the old hole, used some cutting oil and that Hole Dozer did the job.
If I'd had planned all this out, I might have taken more pictures, but I didn't plan to write this posting until after everything was done, and getting the kitchen back to it's working order was our priority. This morning, getting all the lines hooked back up and not leaking(!) was trial and error and one final HD trip #5 for a few more compression fittings.

Greg
 

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A job well done.

Now, just for fun, try to thick how an NON hobby machinist would have done it.......
 
Worse, you could pay a plumber and we aren't cheap. Your lost weekend ain't cheap either.
 
Glad you got it done.

I would have taken a 3/4" hole saw removed the bit, then slide it on the drill bit backwards of other hole saw and tighten the it to that bit. I'm not as talented as you.
 
Guess how a "real" plumber would have done it? I shudder to think- nibbling tool? Hole looking like a bomb crater? Why not- nobody's gonna see it
 
I would think that a pro would have something like a Greenlee punch and do it fast, accurate, no mess, and right.

Heck, I am a hobbyist and I have a Greenlee punche for making accurate holes in sheet metal.
 
Nice trick! I'll have to remember it if I ever need a bigger hole in my stone countertop.
 
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