Hole in granite countertop for kitchen faucet slightly small

Get a 1-3/8" diamond hole saw.

Create your 1-3/8" template secure it to the counter (make sure it won't move). I'd use something at least 1.5" thick so that the hole saw stays plumb. The template will serve in place of a pilot bit.

The Rigid 1-3/8" diamond hole saw from Home Depot is $28.

Buy a concrete paver while you are at it so you can get a little practice before you go all in on your countertop.

Overall, the answer suggesting you get a professional to do it is the route to go. Make it someone else's problem and make sure to hold them accountable if they damage the counter.

Realistically though, if you get someone to show up at your home and pay them $30-75 like https://diy.stackexchange.com/a/211482/42053 suggests then accountability will be non-existent. At $30-75 you're just asking them to roll the dice because you don't have the equipment to do so. If this is a screwup then get the manufacturer to fix it because I sure as sin know that I wouldn't risk being held responsible for a couple grand countertop for $30-75 bucks. If they screw up then they'll just suggest a vanity cap and call it a day.

---

However, this forum post shares precisely your problem: https://www.ridgidforum.com/forum/mechanical-trades/professional-plumbing-discussion/42023-need-to-enlarge-a-granite-top-hole

Option 1:

Home depot now sells bits by ridgid that are an inexpensive diamond grit core bit.

The other way is to get a 1/8'' - 1/4'' carbide burr in a high speed dremel/ die grinder and route it out slowly.

I always use water/ wet sponge to keep the dust down and keep things cool.

Option 2:

I have the rotozip Floor Tile Bit XB-FTC1 1/4" diamond surfaced bit that I use in my rotozip for things like this and for some tile cutting and shaping. works awesome and is quite easy to control and handle.

Option 3:

I've never done this in granite so I can't tell you if it will work. It can be done in Corian.

Make a template in the diameter you want the hole to be in a piece of plywood. Make it big enough to provide a flat surface for your router to ride on. Clamp or otherwise secure the template where you want the hole to be located, maybe some double stick tape will work.

Use your router and a carbide pattern bit to enlarge the hole following the pattern with the router and bit.

If you go with the RIDGID diamond bit in your drill, you can still use the template secured to the countertop with double stick tape. Make the hole in the template the same size as the OD of the bit. Secure the template at the new hole location.

Now you can use the drill with less worry about the bit wandering.

Option 4:

I pick up the phone and call the nearest Granite fab shop. I don't do granite and I'm dang sure not paying to replace that high dollar slab when I mess it up.

You might able to use 2 hole saw bits. One that fit snugly inside the existing hole and a larger one for the hole size you need. Nest the smaller one inside the larger one on one mandrel. The smaller one will keep you centered and the larger one will drill its size.

I saw a technique for enlarging holes in wood that might translate.

The trick was to nest two hole saws on the same arbor. The inner (smaller) saw acts as a guide to keep the larger (outer) saw centered. Alternatively, a suitably sized plug of polyurethane or similar, on the arbor could have the same effect- keeping the surrounding saw centered in the existing hole.

This may not be feasible with diamond grit hole saws, but I thought it was clever and might be worth considering.

Good luck!

This one's $500, but it's how it's done. I don't remember mine being so expensive; shop around. On the far left is the core bit you don't need. Second and third are the core polishers that you do: "Dia-Plus Resin Drum Wheel: Wet" except both of those in that kit are 2 inch.

You'll (really) want a badass grinder like that (variable speed and has a 12 AMP motor), and a drum wheel that will fit in your hole. My kit came with smaller drums; everything you'd need (not pictured; might be from Bosh, IDK...).

Sink Cutting and Polishing Package

diamondtoolstore.com

If its new , i would consider sending it back.However if you want to proceed there are some options you need to consider.

I want you understand since the hole has been drilled already it complicates things alot, a hole saw needs a material to grab on (pilot bit), in order to prevent it from skidding around in a manner akin to writing with your non dominant hand.

Your Options:

1. Send it off to be cut with a water jet(best option).
2. use a router with a diamond bit and try to eyeball it going by hand (draw circumference on existing hole).
3. use a step drill bit with lots of water(sacrificial).Surface thickness must not exceed distance between step or must not have a final size greater than 1 1/4" (last size of step in bit).
4. Use a nested holesaw (TCT bit) , some holesaws allow you to put in two holesaws on a single arbor, a smaller and bigger bit , so you use the smaller holesaw as a guide for the bigger one.You need to drill from top and bottom surface about like 10% or your going chip the surface when the bit breaks through the surface!.
5. turn a wood block of 1 1/4" on a lathe and plug the hole and use a diamond core bit with a drill , same thing about drilling both sides applies with lube mentioned in option 4.

Note: with all methods you need to apply lubricant/water when cutting to keep the dust down and/or wear a p2/n95 mask(full/half respirator). Silicosis is no joke , you don't want to be out of breath due to lung problems later in life...trust me it's bad.