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



## gjmontll (Apr 30, 2022)

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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## Flyinfool (Apr 30, 2022)

A job well done.

Now, just for fun, try to thick how an NON hobby machinist would have done it.......


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## silence dogood (Apr 30, 2022)

Five trips? Not unusual for a plumbing problem. Has anyone gone to the hardware store just one trip to get the part and able to fix it the first time?


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## benmychree (Apr 30, 2022)

Everyone knows that a plumbing project takes at least 3 trips to the hardware store, perhaps we should up the ante?


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## Dhal22 (Apr 30, 2022)

Worse,  you could pay a plumber and we aren't cheap.   Your lost weekend ain't cheap either.


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## Gnpenning (Apr 30, 2022)

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.


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## markba633csi (May 1, 2022)

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


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## Flyinfool (May 1, 2022)

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.


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## ttabbal (May 1, 2022)

Nice trick! I'll have to remember it if I ever need a bigger hole in my stone countertop.


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## Just for fun (May 1, 2022)

Good jobs!  Thanks for sharing your repair journey.


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## gjmontll (May 1, 2022)

Flyinfool said:


> A job well done.
> 
> Now, just for fun, try to thick how an NON hobby machinist would have done it.......


That's an interesting wrinkle! 
 My first thought was "chain drilling," then getting out to the proper O.D. with a Dremel and grinder wheel. That's a bunch of work in an awkward stance.
Or maybe temporarily gluing a block of wood from underneath, plotting the center point on it, then drilling it for a hole saw's center drill. Then use the hole saw and knocking off the wood block. 
Similar to the approach I used would have been to get a 2" of 3/4" dowel, drill a longitudinal hole slightly undersized of the 1/4" guide drill, and press fitting it onto the drill bit to guide the hole saw. But freehand drilling would be problematic, I'd want my mill/drill, or at least a drill press.

Thanks for the question.


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## gjmontll (May 1, 2022)

Flyinfool said:


> 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.


You are right, but I don't have a set of punches (and see that just the Greenlee 1.25" alone costs $75). 
I never even thought of punches, haven't ever used them at home.
   Greg


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## gjmontll (May 1, 2022)

Gnpenning said:


> 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.


That might have worked, or not. While at HD, I saw that Milwaukee's arbor for 1.25" and larger hole saws was different that the one for smaller holes. It is basically the same approach as the alternative I mentioned a few minutes ago, drilling out a piece of 3/4" dowel and using it as a guide.
   Thanks, 
     Greg


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## Millalot (May 2, 2022)

gjmontll said:


> 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.
> ...


You should purchase some cone drills, cheap as chips on internet.


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## brino (May 2, 2022)

Good job; you got it done!

Another solution to centring a second hole saw in the cut out is this from Lee Valley tools:
https://www.leevalley.com/en-ca/sho...es/hole-cutters/52518-oops-arbor?item=30N0390

They call it the "Oops Arbor". It can mount two holes saws. The smaller one that cut the original hole is used as the "pilot" for the new larger one.
Of course the two hole saws need to fit the two threaded sections of the tool.

I have thought about making one, but it's way down the list.......

Brian


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## mmcmdl (May 2, 2022)

silence dogood said:


> Five trips? Not unusual for a plumbing problem. Has anyone gone to the hardware store just one trip to get the part and able to fix it the first time?





benmychree said:


> Everyone knows that a plumbing project takes at least 3 trips to the hardware store, perhaps we should up the ante?


I have an Ace Hardware store across the street from me and I feel as though I live there . I know this game well !


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## brino (May 2, 2022)

mmcmdl said:


> I have an Ace Hardware store across the street from me and I feel as though I live there . I know this game well !


Dave,
You should reciprocate!
That is, let the hardware store send customers your way when they don't have the wanted item.
Let them root thru your collection of goodies to find what they need; hammers, hardware, sanding belts, machinery, etc.
Your space problems will be eliminated! 
Brian


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## gjmontll (May 2, 2022)

Millalot said:


> You should purchase some cone drills, cheap as chips on internet.


Doh! Good idea! In fact, I just realized that I had bought one at HF a year or more ago. I just went to find it - it's still unopened! Says it's HSS so it could have done the job on the stainless steel.


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## Uncle_Rich (May 4, 2022)

silence dogood said:


> Five trips? Not unusual for a plumbing problem. Has anyone gone to the hardware store just one trip to get the part and able to fix it the first time?


Happened to me once, but only because of the 6 trips I took to buy things I thought I needed but didn't for the last project I undertook.


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## Uncle_Rich (May 4, 2022)

Flyinfool said:


> A job well done.
> 
> Now, just for fun, try to thick how an NON hobby machinist would have done it.......


Pretty sure I am one of the least "Machinists" on the site. My hole-saw allows for a center drill bit to be installed, combine that with an appropriate sized socket to fit the existing hole and correct sized drill bit to fit snugly into the drive socket, bingo bango centered enough for the water I drink! Or for the really non-machinist. Hire plumber to replace the entire sink, midway through, wife decides to remodel the kitchen. Hire contractor, spend 25k. Cheers !


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## FE427TP (Jul 4, 2022)

I made this recently for the same thing. Make sure to use a heavy washer to make it easier to unscrew, but you thread the big hole saw on first stack a couple washers to make sure the smaller on has some backing and won’t bottom out on the thread then thread the existing hole size of hole saw onto the front of the arbor and use the existing size hole as your arbor. I’ll try to see if I can figure out how to resize the image.


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