[Brad @ SCJB]

I need to enlarge a gauge hole to a 3-3/8"....there is already a 2-1/16" hole there

i have some ideas, but wanted to see if anyone had anything different in mind or match up what i did.

I went to home depot and couldn't find a 3-3/8 hole saw...they were only 3...3.25...3.5...etc so i was thinking i could cut it to 3 and use a drill saw to enlarge it. using a hole saw would be tricky since there is no center point reference....maybe camp a piece of plywood on the back of the dash?

or maybe use a compass to mark the hole and cut it close with a jig saw and use the drill saw to fine cut it to the line drawn by the compass.

theres not much room for error...so im trying to think it through thoroughly before i do it.

[2savage4you]

Wild shot but check Ebay for the right 3 3/8 hole saw before you hack it up


2sav

[76 Bonneville]

 I would go with the wood clamped to the back side and a 2" plug screwed (off center) to it. Then you can run the 3 1/4" hole saw and just clran it up w/ a drum sander in the drill. If youre going to use a jig saw they make a reverse blade that cuts on the downstroke, make sure you have enough pressure on it so that it dosnt start jumping on you. We use them to do cut outs in laminate tops- bocsh 101br is the blade we use.

[2savage4you]

quick check on Ebay and they have the 3 3/8 hole saw but it was for cutting granite.  But they must make a 3 3/8 for wood?


2sav

[Brad @ SCJB]

yeah, ive done numerous searches on ebay ....and im pretty search savvy.

[Josh@JBP]

Last time i did it I got real ballsy(stupid) and did it free hand hole saw no pilot, cocked it at the slightest of angle to get started and then layed it down, came out perfect but I reallized afterward how dumb it was.

But I would typically do what 76 Bonneville said and clamp a chunk of wood in behind the old gauge hole, but I would use an extra long pilot insted to get my center.  U might actually be avble to get away with 3.25 hole saw, alot of tacks/speedos are a little loose in a 3.375 hole.

[76 Bonneville]

Standard pilot, just add a 2" diameter plug in to the existing hole, fastened to the backer board. After starting the pilot hole, reverse the drill to score through the gel to keep it from chipping. Then go for it.

[UNDONE]

Like Josh said, use the 3 1/4". That's what my Livorsi 3 3/8" fit into perfect. I ran into the same dilemma and was figuring I'd just use the 3 1/4" then custom dremel it to fit. Well the gauge dropped right into the 3 1/4" hole without any modification...

[Brad @ SCJB]

i will put a caliper on the gauge tonight to see what its true diameter is...even if its really 3.325"...3.25" will be close enough then i can use a drum sander or something similar to open it up further.

[82daytona]

you can get any hole saw size you need pretty much try toolcrib.com or you could use a rotozip

[Ralph Brunt]

hole saw = chipped glass and off center hole, what i do is get a barrell sander and follow a template that i have transfered to the area

[82daytona]

use blue tape and shouldnt chip or if you get a granite hole saw with tape it wont chip for sure

[CHROMEY]

it all depends on how you handle your tool  keep a good grip on it, omar will show you how...

[old rigger]

You take a 2 1/8 hole saw and cut a chunk of 3/4 inch plywood with it. Take the plug out of the hole saw which will be 2 1/16, the size of your hole in the dash and tap the plug in place in the offending dash hole. With any luck it will be a tight fit, if not wrap it a few time with tape and drive it in. then you can cut the new hole in the dash with no worries.

You can swing by my house this Sunday after the LB swap, I'm about a mile from the place, and I can load you up with all the hole saws you need, even one of my old school 1/2 drive Millwakee drills...if you promise to return them. I've not got a few tools back from a few guys over on hot boat over the past couple of years so I don't offer them out as much.

Or you can drag the boat over here and we can do it at my place. 

[old rigger]

One thing to remember, besides never using the wrong saw for the job, is that you're going to change the spacing between the other gauges, depending where the new larger gauge is going. All the gauges are, or should be, spaced equally amongst themselves, giving a pleasing, soothing  effect to the eye. Switching to a larger gauge can make the open space between the gauges smaller, un-even, mis-matched,  creating havoc in your brain each time you glance at the dash and see the nice flow has been replaced by kaos.

Just plan carefullly. 

[Brad @ SCJB]

Thanks oldrigger....i really appreciate the offer.

i did it last night successfully.....I used a 3.25 whole saw and just used the back piece of wood. i re-rigged the mandrel so that the piolet drill stuck out further to reach the backside piece of wood.....then eyeballed the center point marking and measured it a few times from every angel...then drilled....came out perfect. The guage ended up being 3.3"...the whole i was drilling was 3.0".....so after the 3.25" cut, i used a barrel sander to open up the hole until the gauge would only fit if i forced it.....then i hand sanded the hole until it smoothly glided in.

yes, the dash looks like chaos now as you mentioned, but this will only be my 'race' setup. the tach and wheel will be swapped depending on the application (full interior lake boat or  single seater race boat)....here is some pictures....

[attachimg=1]

[attachimg=2]

[attachimg=3]

The whole where the tach sits now will also use a angel bezel to turn it in the direction of the driver. I am aware i will have to cut out more to get the bezel to fit...including the wood that will be displaced by the angel.

[old rigger]

Cool. But you said you were enlarging a 2 1/16 gauge hole, not a steering hole?

Didn't know you were building an old race boat. I like the dual foot throttles, never seen that kind of set up before.

[Brad @ SCJB]

Cool.

Didn't know you were building an old race boat. I like the dual foot throttles, never seen that kind of set up before.

the one on the left is the pump for the keg tap 

nah, they arent even mounted in there yet...i was just mockin some stuff up.

[old rigger]

nah, they arent even mounted in there yet...i was just mockin some stuff up.

duh

[76 Bonneville]

 I,ve knew  that Brad is a little different, but never noticed his 2 right right feet.