macd
Well-Known Member
Obviously much depends where it is on the mast, but it's really not so large. Our Selden/Kemp mast has access covers several times larger than that: 40 x 100mm, at least.
Drilling holes
- Thread starter zoidberg
- Start date
Obviously much depends where it is on the mast, but it's really not so large. Our Selden/Kemp mast has access covers several times larger than that: 40 x 100mm, at least.
Laysula
Well-Known Member
Shorten the pilot drill in the arbour as much as you safely can to keep it away from halyards and wiring.
macd
Well-Known Member
...or take it out completely once you've made a good start on the 30mm hole. With care, the groove will keep it in place. (Tip: not a technique to be used whilst hanging on with one hand halfway up a mast.)
moomba
N/A
+1 for the Arbour found it to be the most effective tool
thinwater
Well-Known Member
+5 drilling most places.
I have a 1/4" stub that I sometimes replace the pilot drill with. Just an old drill that I cut the end off.
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Poignard
Well-Known Member
Or replace the pilot drill with a bit of steel or brass rod once it has penetrated the mast. If that touches halyards or wiring it won't do the any harm.
Baddox
Well-Known Member
Or prussic a line around the mast and tie it off to his harness. I’m sure he could manage that as a back-up.
Heckler
Well-Known Member
Use a hole saw, use some grease, it will collect the swarf, we used to do this when fitting helicoils in spark plug holes to avoid removing the head, wd40 evaporates by the way, that is why it isnt any good as lobg term lube. In the olden days I was taught that water is a good lubricant as long as there is enough of it! Thats why cutlass bearings last a long time!
zoidberg
Well-Known Member
I'm fitting a couple of these Selden T-backing wallplates, which match those already fitted higher up. The diameter of the 'raised ring' which should just fit into the 'ole is 30mm.
I'm grateful for the range of good advice. Thanks to all. A hole saw it is, and I may already have a suitable one. If not, I'll get a good new one from the excellent Avery Knight and Bowlers in boo'ful downtown Bath..... or Screwfix.
The mast is down and horizontal - having been painted a pristine white - so I'm not going to be dangling and wafting about in the breeze. I should be able to run a grp drain-rod or fish-tool up inside - with a greased U-section attached to catch swarf, as well as providing some determined suction.
I'll certainly drill a pilot, then use a 'modified' drill bit or rod to keep the holesaw centred, as recommended.
*** What I'm now puzzling over is what to use to hold the T-plates securely in place while fitting then pulling-up suitable rivets. They're 6.4mm, from a good rigger' store, and I'll drill 6.5mm pilots with a new drillbit. I'm aware of aviation sheet pins, which are neither easy to get around here nor cheap, and wonder if the resourceful congregation here has any good ideas to offer? ***
Lon nan Gruagach
Well-Known Member
As you can get a drain rod to the hole then you can fish a line to it.
Use 6mm x 40mm eye bolts with the eye inside the mast. Use 3 nuts per bolt, 1 to fix the plate, the others to lock nut the tip of the bolt to tighten against.
When you have finished with a bolt extract it with the line tied to the eye.
Might be tricky to bolt the 2 holes furthest from the 30mm one, but the nearest 2 ought to be ok.
john_morris_uk
Well-Known Member
I'm fitting a couple of these Selden T-backing wallplates, which match those already fitted higher up. The diameter of the 'raised ring' which should just fit into the 'ole is 30mm.
I'm grateful for the range of good advice. Thanks to all. A hole saw it is, and I may already have a suitable one. If not, I'll get a good new one from the excellent Avery Knight and Bowlers in boo'ful downtown Bath..... or Screwfix.
The mast is down and horizontal - having been painted a pristine white - so I'm not going to be dangling and wafting about in the breeze. I should be able to run a grp drain-rod or fish-tool up inside - with a greased U-section attached to catch swarf, as well as providing some determined suction.
I'll certainly drill a pilot, then use a 'modified' drill bit or rod to keep the holesaw centred, as recommended.
*** What I'm now puzzling over is what to use to hold the T-plates securely in place while fitting then pulling-up suitable rivets. They're 6.4mm, from a good rigger' store, and I'll drill 6.5mm pilots with a new drillbit. I'm aware of aviation sheet pins, which are neither easy to get around here nor cheap, and wonder if the resourceful congregation here has any good ideas to offer? ***
When I fitted one I seem to recall putting a ‘T’ shaped bit of scrap into the plate (the plate threads through the hole as you probably know) and pulling it up against the inside of the mast by hand. The rivets pulled the plate hard into place as they were drawn up and popped. An old rigging swaged fitting would be ideal. The scrap bin at a riggers is your friend.
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Amulet
Well-Known Member
I predict it will end in tears... The pilot drill will wander before the holesaw has bitten in properly. I like the idea of a router with the correct bit and jig, but it it asking a bit too much engineering.
I'd put my money on the step drill among the options listed. I've had success using it with similar tasks. I don't know how much wibble room you have on exactly where the hole ends up, but I think a step drill will be pretty good at staying on target.
I'd put my money on the step drill among the options listed. I've had success using it with similar tasks. I don't know how much wibble room you have on exactly where the hole ends up, but I think a step drill will be pretty good at staying on target.
zoidberg
Well-Known Member
That is, of course, my concern.
However, I do have a section of broken mast of nearly-similar diameter.... so I can try out the various options. I might even try one of the spare Forstners I inherited.
sarabande
Well-Known Member
I suspect that as Forstner bits are for creating blind holes in wood, you may be disappointed, unless you modify the tip geometry. Perhaps a spiral fluted reamer after a pilot hole ? A left handed one would be better.
john_morris_uk
Well-Known Member
Not sure why you’ve suddenly injected such pessimism.
I predict that if he centre pops the position and gets a small sharp cobalt drill and drills a pilot hole first. Then drills a hole the size of the hole saw centre drill bit and then uses a proper hole saw, he will end up with a perfect 30mm hole.
This all assumes he’s got a modicum of skill in holding a drill steady,,, but if he followed the steps above the skill levels are about as low as you can get short of manipulating the mast into a bench press drill!
savageseadog
Well-Known Member
I agree. An accurately marked and centre punched hole and a hole saw will do the job perfectly. You'd have to be a really dud operator to wander offline. I suggested routing the hole earlier, it will give a cleaner cut but the swarf will fly everywhere.
rogerthebodger
Well-Known Member
If the OP is concerned about the hole ending up oversize just drill it smaller say 28mm then file it out with a half round file.
zoidberg
Well-Known Member
Right, forget the Forstner thingy..... not least 'cos I forget where I've put them. And even if I were able to take the mast to the bench press drill(s) - or vice versa - there's not enough 'throat' to accommodate the workpiece and the drill-bit. So....
Now if the test-piece on the broken mast section ( I have several to play with ) doesn't go well, I'll try a smaller/28mm hole saw and some 'enginuity' in the shape of a half-round file..... or maybe a cone cutter. When the time comes, I'll post a pic or two on here, just for larfs, showing the finished article and how I intend to use it/them.
As for 'holding a drill steady' I recently had to use a 165mm diamond core drill with a B-I-G SDS machine, handheld and overhead, to get through 4 - yes, 4 - layers of founds. ( the local branch of Lloyds! ) The first 'ole was neat, round and accurate. The second was a bit less so. And the third.... The fourth was a beech, ending up oval and about 270 x 420mm - but I had to use the hammer/chisel action on that, for the jamming-torque was huge, threatening to break a wrist or two. I'm pleased to report that the required 110mm OSMA drainpipe fitted through, without much coercion...... and with only a limited need for cosmetic mortar!
Now if the test-piece on the broken mast section ( I have several to play with ) doesn't go well, I'll try a smaller/28mm hole saw and some 'enginuity' in the shape of a half-round file..... or maybe a cone cutter. When the time comes, I'll post a pic or two on here, just for larfs, showing the finished article and how I intend to use it/them.
As for 'holding a drill steady' I recently had to use a 165mm diamond core drill with a B-I-G SDS machine, handheld and overhead, to get through 4 - yes, 4 - layers of founds. ( the local branch of Lloyds! ) The first 'ole was neat, round and accurate. The second was a bit less so. And the third.... The fourth was a beech, ending up oval and about 270 x 420mm - but I had to use the hammer/chisel action on that, for the jamming-torque was huge, threatening to break a wrist or two. I'm pleased to report that the required 110mm OSMA drainpipe fitted through, without much coercion...... and with only a limited need for cosmetic mortar!
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Amulet
Well-Known Member
Extensive first-hand cock-up experience.
An insight (maybe) : if you could replace the pilot drill with a simple non-cutting rod, I can imagine drilling the pilot hole first and then using the hole saw with this blank arbor. But if this was a good idea surely someone would have already thought of it.
If others have done this as described successfully themselves then I bow to their superior knowledge (and skill). I have tried and failed.
