I am replacing raw water intake thru-hull and ball valve properly. PO had a simple Marelon ball valve screwed onto bronze thru-hull using non-epoxied plywood as a backing plate. I have a new thru-hull (Conbraco bronze...old one was too corroded to locking nut and had to be cut off) with a Conbraco full flow flange valve http://www.conbraco.com/products/marine/techtemplate1.asp?section=A&category=285&pid=78-100-01. For a backing plate, I have 1/2" thick FRP (Fiberglass Reinforced Plastic from McMaster-Carr (www.mcmastercarr.com and search for part number 8537K26)) which I will sand to fit contour of hull and bond into place. Question is this: What kind of bit/hole saw do I need to 1. cut hole in FRP? 2. drill holes through hull to bolt flange of valve? I would like to assume carbide will do the job, but I want to be sure. Also, slow speed or fast speed? Thanks.
Cutting hole in hull ... what bit?
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Lenox Hole Saw bits
I've had good luck cutting holes with Lenox Hole Saw bits that come in a variety ofsizes. You also need an arbor to fit the hole saw. These types of hole saws are readily available at a number of place. See link below or buy them at Sears, for example. The arbor has a drill bit which sort of cuts a pilot hole and then the how saw digs in. I've found that putting masking tape over the area to be cut, and cutting slowly with a regular power drill, does a nice job.
I've had good luck cutting holes with Lenox Hole Saw bits that come in a variety ofsizes. You also need an arbor to fit the hole saw. These types of hole saws are readily available at a number of place. See link below or buy them at Sears, for example. The arbor has a drill bit which sort of cuts a pilot hole and then the how saw digs in. I've found that putting masking tape over the area to be cut, and cutting slowly with a regular power drill, does a nice job.
cutting the hole
When you drill the hole, if is practical, drill from both sides with the hole saw. If you do that, you will minimize the splintering and jagged edge of the opposite side you are drilling. Also, you may be better off using marine plywood for the backing plate rather than the reinforced fiberglass. The reason being that the plywood will flex a little and be less prone to a leak because the plastic was not an exact fit.
When you drill the hole, if is practical, drill from both sides with the hole saw. If you do that, you will minimize the splintering and jagged edge of the opposite side you are drilling. Also, you may be better off using marine plywood for the backing plate rather than the reinforced fiberglass. The reason being that the plywood will flex a little and be less prone to a leak because the plastic was not an exact fit.
Whole in hull
Hi Lenox works great, take it nice and easy with a gentle pressure, like the other reader stated cut from one side for 1/4 to 1/2 inch before your pilot hole gets a little rounded out, the kerf will prevent splintering then go in from the other side while bearing in mind your angles of cut, Hope this helps, if you want to find an old piece of scrap and practice and give yourself a little confidence sometimes we can be our own worst enemy Ron
Hi Lenox works great, take it nice and easy with a gentle pressure, like the other reader stated cut from one side for 1/4 to 1/2 inch before your pilot hole gets a little rounded out, the kerf will prevent splintering then go in from the other side while bearing in mind your angles of cut, Hope this helps, if you want to find an old piece of scrap and practice and give yourself a little confidence sometimes we can be our own worst enemy Ron
Hole Saw
I agree with using a hole saw rather than a regular spiral or spade bit to drill the hole. A spiral bit that size will be pretty expensive if you can even find one. Spade bits make nasty ugly holes with lots of jagged edges in fiberglass. Could also take a big chip out of the gelcoat when it breaks through. As to speed, keep the drill speed pretty slow to avoid overheating the teeth on the saw. If you overheat them, they'll get dull pretty quickly and ruin your nice hole saw. It'll also cut better if you regularly remove the bit from the hole and blow out the dust and debris. Debris will also clog up the teeth and make them overheat.
I agree with using a hole saw rather than a regular spiral or spade bit to drill the hole. A spiral bit that size will be pretty expensive if you can even find one. Spade bits make nasty ugly holes with lots of jagged edges in fiberglass. Could also take a big chip out of the gelcoat when it breaks through. As to speed, keep the drill speed pretty slow to avoid overheating the teeth on the saw. If you overheat them, they'll get dull pretty quickly and ruin your nice hole saw. It'll also cut better if you regularly remove the bit from the hole and blow out the dust and debris. Debris will also clog up the teeth and make them overheat.
your frp should cut using wood cutting tools
i would close the existing hole and mount the fitting to one side or the other to eliminate leakage from deteriorated fiber glass
i would close the existing hole and mount the fitting to one side or the other to eliminate leakage from deteriorated fiber glass
Deteriorating fiberglass...none seen
No indication of deterioration. Just dry-rotted backing plate and corroded thru-hull. No signs of leakage. Betting that dry-rotting comes from 20+ years of condensation rather than a leak.
No indication of deterioration. Just dry-rotted backing plate and corroded thru-hull. No signs of leakage. Betting that dry-rotting comes from 20+ years of condensation rather than a leak.
If you are trying to enlarge an existing hole
you can cut the new size hole in some scrap. Fasten the piece with the new hole over the existing hole with hot melt glue and use the hole as a pilot for the new size hole in the hull. Lenox, Milwaukee, and Hilti make the best hole saws. Be sure that the mandril you purchase will fit you drill chuck. They can be had in 3/8 inch and 7/16 inch both will fit the saws but may be too large for you drill chuck.
you can cut the new size hole in some scrap. Fasten the piece with the new hole over the existing hole with hot melt glue and use the hole as a pilot for the new size hole in the hull. Lenox, Milwaukee, and Hilti make the best hole saws. Be sure that the mandril you purchase will fit you drill chuck. They can be had in 3/8 inch and 7/16 inch both will fit the saws but may be too large for you drill chuck.
forstner bits
If you have Forstner bits in your tool collection, they make nice smooth holes in fg. Go slow, and if they heat up, stop and let them cool, otherwise the fg will stick to the bit.
If you have Forstner bits in your tool collection, they make nice smooth holes in fg. Go slow, and if they heat up, stop and let them cool, otherwise the fg will stick to the bit.
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