Enlarging a hole in a bulkhead.
- Thread starter Ross
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I usually
Ross, Option #1- If the hole is round I affix a piece of wood larger than the new hole to be drilled to back side of the bulkhead. I then screw a centered piece of wood to it's face thus bringing it flush with the face of the bulkhead. By doing this I now have a piece of wood, as you would drilling a virgin hole, to drill into with the pilot bit and keep it centered so the hole saw does not wander. Option #2- I drill the proper size hole, with my hole saw, in a piece of plywood that is larger than the hole then affix this to the back side of the bulkhead. I Then use my laminate trimmer or router with a bearing guided flush cut bit to trace the hole from the patterned board residing behind the bulkhead... P.S. If you use a hole saw to drill through gelcoat ALWAYS cut through the gelcoat layer with the drill spinning the hole saw in reverse! This eliminates chipping the gelcoat and leaves a perfectly clean hole. Once through the gelcoat simply flip your drill back to forward. I learned this trick a long time ago for drilling through laquer painted finishes & upholstery in antique autos..
Ross, Option #1- If the hole is round I affix a piece of wood larger than the new hole to be drilled to back side of the bulkhead. I then screw a centered piece of wood to it's face thus bringing it flush with the face of the bulkhead. By doing this I now have a piece of wood, as you would drilling a virgin hole, to drill into with the pilot bit and keep it centered so the hole saw does not wander. Option #2- I drill the proper size hole, with my hole saw, in a piece of plywood that is larger than the hole then affix this to the back side of the bulkhead. I Then use my laminate trimmer or router with a bearing guided flush cut bit to trace the hole from the patterned board residing behind the bulkhead... P.S. If you use a hole saw to drill through gelcoat ALWAYS cut through the gelcoat layer with the drill spinning the hole saw in reverse! This eliminates chipping the gelcoat and leaves a perfectly clean hole. Once through the gelcoat simply flip your drill back to forward. I learned this trick a long time ago for drilling through laquer painted finishes & upholstery in antique autos..
Maine Sail, That's great. Hadn't thought to use a router
and since most of my work has been in wood running the saw backwards in plastic never occured to me. I often am faced with enlarging a hole and just saw the new size in some scrap and affix this over the existing hole and use that as the guide for sawing the new hole.
and since most of my work has been in wood running the saw backwards in plastic never occured to me. I often am faced with enlarging a hole and just saw the new size in some scrap and affix this over the existing hole and use that as the guide for sawing the new hole.
Ross,
I've been using a Greenlee quick change hole saw kit for a few years now and one feature is the hole saw is screwed to the arbor so I found a couple of longer screws and threw them into the kit so there handy when I need them but before having that kit I kind of remember puting two hole saws on my standard arbors,maybe I had longer threads and pins on them like the one Tim had a link to.
I've been using a Greenlee quick change hole saw kit for a few years now and one feature is the hole saw is screwed to the arbor so I found a couple of longer screws and threw them into the kit so there handy when I need them but before having that kit I kind of remember puting two hole saws on my standard arbors,maybe I had longer threads and pins on them like the one Tim had a link to.
I wish I had one of the special
holesaw arbors mentioned by Timo42 as that seems to be the perfect tool. The last time I had to enlarge an instrument hole was on my old C&C some 15 years ago and didn't know of such a special tool. Since the new instrument I was installing (depth sounder) had a about a 3/8" bezel, the neatness of the old hole didn't matter much as it was going to be covered up. I cut a cardboard circle the size of the new and larger hole and taped it over the old hole from the inside. Marked the outline of it with a pencil and then cut it larger with a Dremel tool with a cutting disk. I smoothed out the edges afterward with a sanding burr, gooped up the hole with caulk and installed the new sounder. This worked well enough, but my guess is that the special holesaw arbor would have done it better.
holesaw arbors mentioned by Timo42 as that seems to be the perfect tool. The last time I had to enlarge an instrument hole was on my old C&C some 15 years ago and didn't know of such a special tool. Since the new instrument I was installing (depth sounder) had a about a 3/8" bezel, the neatness of the old hole didn't matter much as it was going to be covered up. I cut a cardboard circle the size of the new and larger hole and taped it over the old hole from the inside. Marked the outline of it with a pencil and then cut it larger with a Dremel tool with a cutting disk. I smoothed out the edges afterward with a sanding burr, gooped up the hole with caulk and installed the new sounder. This worked well enough, but my guess is that the special holesaw arbor would have done it better.
I had hopes for this thread but this is gold!!!!
Thanks Rad and Tim. ;D edit to add: I just checked the catalog and it appears that the Rockler arbor replaces the pilot drill. That way the saw serves as the pilot for the existing hole. Very fine thinking.
Thanks Rad and Tim. ;D edit to add: I just checked the catalog and it appears that the Rockler arbor replaces the pilot drill. That way the saw serves as the pilot for the existing hole. Very fine thinking.
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