Enlarging a 7/8" hole to 1"?

[Wade Lippman]

I bought a used fiberglass sailboat. It has a 7/8" drain plug that is missing the stopper. I can't find any 7/8" plugs, so I am going to replace it with a 1" plug. That obviously requires me to enlarge the existing hole. On a drill press that would be easy, but getting the sailboat on my drill press would be tough.

I have two ideas...
1) Draw a 1" circle over the existing hole and enlarge it with a multitool. My experience is that multitools are not particularly precise, so I m reluctant to do this.
2) I have a cove router bit that has a full diameter of 1". Put in a drill, it should self center in the 7/8" hole and then enlarge it to 1". Or maybe not.

Comments or other ideas would be appreciated.

Or, I could fiberglass over the existing hole and put a new one elsewhere. I have a brad point carbide 1" drill.

[Lee Schierer]

Make a 7/8 dowel and drill a 1/4" hole on center inton one end. Place the dowel in the existing hole. Then enlarge the hole wit a 1" hole saw using the 1/4" hole as a guide to enlarge the existing hole.

Or just buy this 7/8" plug: https://www.amazon.com/Attwood-Brass-Handle-T-Handle-Drain/dp/B0000AZAOW/ref=sr_1_5?ie=UTF8&qid=1546451969&sr=8-5&keywords=boat+drain+plug

[Dan Friedrichs]

Step drill bit: https://www.amazon.com/HUELE-Titaniu...df_B06Y25PFMZ/

[Mike Hollingsworth]

Cut a 1" hole in a board with the brad point bit. Put it over the hole and use it as a guide.

[daryl moses]

Turn down the 1" plug to 7/8".

[Bruce Page]

Look again for drain plugs. I saw lots of options when I googled 7/8" drain plug.

[Wade Lippman]

Look again for drain plugs. I saw lots of options when I googled 7/8" drain plug.

Yes, lots come up when you google 7/8" drain plug; sadly nothing that comes up actually is.
This is what I ordered. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

A lot of interesting suggestions to enlarge the hole; maybe the step drill is best, though the template is cheaper.

[Tom M King]

How thick is it where the hole needs to go? What type of plug-screw in, t-handle screw type, or lever handle. What type of boat? No sleeve for the plug? I might have one.

[Wade Lippman]

How thick is it where the hole needs to go? What type of plug-screw in, t-handle screw type, or lever handle. What type of boat? No sleeve for the plug? I might have one.

Very thin; certainly no more than 1/16". The old one is similar to the link I posted.

[Mike Cutler]

Wade

Defender Marine is only 3 miles from where I work. They're one of the largest Marine supply companies in the US and world. If you give me a picture of the plug area, the hull name type, along with the dimension, I'll stop by Defender Marine for you.
I'd hate to see you drill a hole in a boat hull you don't need to.

[Tom M King]

So the female threaded part is still there, and you just need a replacement plug? What type of boat is it? I used to have a small sailboat business, and have a lot of leftover parts.

[Wade Lippman]

two.jpgone.jpg

The above are the front and back of the drain from the Precision 15K. It was missing the plug when I got it, but I presume it is a tube with two nubs on the end for engaging the drain.
It is not in good condition, so I would prefer to replace it rather than just get a plug for it, but a 7/8" would be great, rather than drilling for a 1".

Humorously....
As I typed this, it occurred to me that I should check Precision's website to see if they sell parts. They say they sell the drain for $7 plus shipping. I will call them tomorrow and see if it is 7/8". Maybe.
It is my fourth sailboat, but the first from a company that was still in business; so it took me a while to think of this.

[Prashun Patel]

Drill a 7/8” plug with a hole saw and then switch to a 1” hole saw. Thread the 7/8” plug onto the pilot bit and wrap with a couple layers of blue tape to make up most of the kerf.


I have done this and it makes a passable hole.

[Tom M King]

Glad you found a source. I don't know who makes Precision's hardware. There aren't but so many manufacturers. Simplest to get one from them. I know I don't have any of them.

such as Ronstan: https://www.ronstan.com/marine/range.asp?RnID=125 edited to correct wrong link

[Perry Hilbert Jr]

I had a bad experience with electricity as a kid and avoid working on anything electrical as much as possible. BUT, I would rather try to connect 440 volts to something than ruin a boat. I would find a way to make a plug rather than drill a hole.