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Tim C

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I need to bore out 400-500mm x 10-20mm holes in one of my projects. My current augur bits aren't long enough and don't remain centred once you start drilling deep. Any suggestions either for long eg Forstner bits (can't find online so far) or for an extension bar that I could lock a drill into?
 

toolsntat

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Doing the hole first can be a good idea to achieve this.


Cheers Andy
 

toolsntat

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I'm confused, Andy! Tim
Sorry Tim, hadn't realised the explanation of how I did it is missing.
It was a rough turn to achieve a cylinder and then used a lamp cable auger through the hollow tailstock.
This gave me the centres for turning the finished roller followed by manually boring from both ends with another auger the right size.
To guide that auger I placed a wallplug over the thread and allowed it to follow the lamp cable hole.
EDIT, just realised you may not be working on a lathe....
Cheers Andy
 

u38cg

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This is how we bore long holes on woodwinds - normally much narrower but bigger sizes should only make it straighter. You need a bit of silver steel and then grind a flat on the end, about 3-4 times the diameter, and then grind an oblique cutting face. I would also relieve most of the shaft, just leaving enough to guide a straight hole. You drill by "pecking", go in about the length of the flat then withdraw to dump the plug of shavings. I use beeswax to lubricate. Drill a pilot hole first, just deep enough to get it straight.

Obviously this will generate large forces but then if you're drilling holes that size this probably isn't new information, but do be careful - maybe make smaller ones first and build up. I put handles on mine, easier than holding in the tailstock, but it has to be a handle that will be safe if the tool starts spinning - a T-handle at this size will take your wrist with it.



IMG_20200922_150941647.jpg
 

Tim C

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Sorry Tim, hadn't realised the explanation of how I did it is missing.
It was a rough turn to achieve a cylinder and then used a lamp cable auger through the hollow tailstock.
This gave me the centres for turning the finished roller followed by manually boring from both ends with another auger the right size.
To guide that auger I placed a wallplug over the thread and allowed it to follow the lamp cable hole.
EDIT, just realised you may not be working on a lathe....
Cheers Andy
Andy, thanks for the extra explanation! This is similar to what I've been doing with an augur fixed into a drill extension, but it wanders a lot on the way through and leaves a lot of eccentric mess which is difficult to clean up. I think I shall try the other suggestion of grinding a cutting edge on some thick bar. Thanks anyway, Tim
 

Tim C

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This is how we bore long holes on woodwinds - normally much narrower but bigger sizes should only make it straighter. You need a bit of silver steel and then grind a flat on the end, about 3-4 times the diameter, and then grind an oblique cutting face. I would also relieve most of the shaft, just leaving enough to guide a straight hole. You drill by "pecking", go in about the length of the flat then withdraw to dump the plug of shavings. I use beeswax to lubricate. Drill a pilot hole first, just deep enough to get it straight.

Obviously this will generate large forces but then if you're drilling holes that size this probably isn't new information, but do be careful - maybe make smaller ones first and build up. I put handles on mine, easier than holding in the tailstock, but it has to be a handle that will be safe if the tool starts spinning - a T-handle at this size will take your wrist with it.



View attachment 92793
Thanks, that's a great idea as it allows me to use a heavy bar that hopefully won't wobble too much over distance. I appreciate the point about torsion. Will need to remain patient! By 'relieve' I guess you mean reduce the diameter a bit on the following sections of the bar, with the grinder, in absence of a metal lathe?
 

u38cg

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Yes, sorry, reduce the diameter just enough to stop it rubbing. Oh and again, maybe an obvious point, but this thing will not follow a smaller hole, it's a one-pass cut. You also see these kinds of drill made with a rounded nose, which is why they're usually called D-bit drills/reamers.
 

marcros

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Yes, sorry, reduce the diameter just enough to stop it rubbing. Oh and again, maybe an obvious point, but this thing will not follow a smaller hole, it's a one-pass cut. You also see these kinds of drill made with a rounded nose, which is why they're usually called D-bit drills/reamers.
I have a hole to make which needs to be fairly accurate, but is only about 50mm long. I was planning to drill out just undersized and then make a d reamer to make it to exact size. Are you saying that I should allow the d bit to do more cutting than the 1/2mm or so that I was planning?

(it is boxwood if that makes a difference)
 

Cooper

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This is how we bore long holes on woodwinds - normally much narrower but bigger sizes should only make it straighter. You need a bit of silver steel and then grind a flat on the end, about 3-4 times the diameter, and then grind an oblique cutting face. I would also relieve most of the shaft, just leaving enough to guide a straight hole. You drill by "pecking", go in about the length of the flat then withdraw to dump the plug of shavings. I use beeswax to lubricate. Drill a pilot hole first, just deep enough to get it straight.
I'm trying to make what I call a swany whistle, though it may be called a slide whistle. I've just got from Amazon a set of 300mm bits. I also go a 12mm centre drill. I held my Oak piece in the chuck and made a centre hole, then bored an 8mm hole all the way through a little bit at a time and then 12mm for 180mm When I took it out of the lathe the holes were curved!! I thought the bits might follow the centre but they just drifted off. The work piece stayed straight in the chuck.
The first whistle I made I got as far as I could with a 12mm twist bit and then used a stiff masonry bit (The only long bit I had) for the rest of the way, a very rough hole but at least it was straight. I hoped the new bits would be an improvement. Any advice please? I was wondering if I could grind the tip of the masonry bit? Is it safe to grind tipped drills?
Thanks
Martin
 

dizjasta

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You could try using a cove cutter to route a semicircular shape in two timber pieces and glue them together to produce an internal circular profile. The exterior could then be shaped for the dimension required. It may be possible to produce a length of timber for several whistles at one attempt.
 

u38cg

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> Are you saying that I should allow the d bit to do more cutting than the 1/2mm or so that I was planning?

No, reaming is fine - have to admit I'm not sure where the line is drawn between reaming and following a pilot hole (with an actual D bit, that is, not the straight cutting edges in my original pic), but reaming is a common use for D bits.

> When I took it out of the lathe the holes were curved!!

Twist drills wander off centre by their nature and there's nothing you can do to make them go straight other than drill a straight pilot hole for them to follow. The choice of oak is probably not helping but you'll do better with D bits or (if you fancy investing in it) gun drills. There is a group on Facebook for whistle and flute makers who probably know much more about drilling large straight holes than I do (I stick to narrow straight holes...)
 

Adam Pinson

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This is how we bore long holes on woodwinds - normally much narrower but bigger sizes should only make it straighter. You need a bit of silver steel and then grind a flat on the end, about 3-4 times the diameter, and then grind an oblique cutting face. I would also relieve most of the shaft, just leaving enough to guide a straight hole. You drill by "pecking", go in about the length of the flat then withdraw to dump the plug of shavings. I use beeswax to lubricate. Drill a pilot hole first, just deep enough to get it straight.

Obviously this will generate large forces but then if you're drilling holes that size this probably isn't new information, but do be careful - maybe make smaller ones first and build up. I put handles on mine, easier than holding in the tailstock, but it has to be a handle that will be safe if the tool starts spinning - a T-handle at this size will take your wrist with it.



View attachment 92793
Nice, i like to make custom tools.
 

Inspector

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I was wondering if I could grind the tip of the masonry bit? Is it safe to grind tipped drills?
Thanks
Martin
Carbide can be ground but not with a bench grinder and regular wheels. You need special wheels made for grinding carbide, don't quote me but I believe they are green, or you have to use diamond wheels and they need coolant. Carbide will eat regular wheels for brekky and still not get a good edge on them.

Pete
 

Cooper

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Carbide can be ground but not with a bench grinder and regular wheels. You need special wheels made for grinding carbide, don't quote me but I believe they are green, or you have to use diamond wheels and they need coolant. Carbide will eat regular wheels for brekky and still not get a good edge on them.

Pete
Thanks Pete, you've saved me from possibly making a big mistake.
Martin
 

J-G

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...You need special wheels made for grinding carbide, don't quote me but I believe they are green, or you have to use diamond wheels and they need coolant. Carbide will eat regular wheels for brekky and still not get a good edge on them.

Pete
Green it is Pete - the counter-intuitive issue is that they are SOFTER than regular 'Grey' wheels - so do wear out quicker and need dressing more often.

I also use Diamond wheels and never use coolant.
 

Inspector

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The plant I worked in had a CNC grinder and all the carbide cutters were ground wet with diamond wheels. They didn't use the green wheels for anything. Aluminum oxide for all the HSS cutters.

Pete
 

J-G

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The plant I worked in had a CNC grinder and all the carbide cutters were ground wet with diamond wheels. They didn't use the green wheels for anything. Aluminum oxide for all the HSS cutters.

Pete
I've remembered that as an apprentice (1956-62), my stint in the tool stores entailed sharpening Brazed tip precision turning tools and they WERE done on a cutter/grinder that was flooded with coolant.

Today I'm only dealing with solid carbide drills - or 'Masonry' drills - so not quite the same. It often surprises friends when I tell them I re-grind 0.8mm Ø drills by hand :) though I do go up to about 6mm as well for solid Carbide and around 14mm for 'Masonry', only resorting to the Cutter/Grinder where I want accurate (say) 90° countersink/chamfer cutters.

HSS Lathe tools are re-shaped on AlumOxide but finished on Diamond.
 

Jackbequick

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On a combination circular saw, planer, spindle borer the last is commonly used for dowling. The borer is checked to the planer drum.

There is an adjustable supporting plate below the borer and one can slide the timber to be drilled firmly onto the (horizontal) drill. Setting aside the making of a straight wind instrument in several sections rather than turning in a lathe I'd be looking to make a secure bed and jig for the drilling and drill into firmly secured square section then later turning the wind instrument 'round'. I'd go that way rather than trying to drill into round stock.

A speed-bore bit ...more accurate than the tool illustrated can give a clean hole however will wobble over any distance....say more than 20 cms unless the extension bar is same diameter as the speed bore blade. As well, you normally cannot do two sizings of a hole with a speed-bore (it is possible but I won't go into it here)

Whilst not a fan of using HSS metal stock drilling drills in timber they give an advantage of ready availability and 'micro-sizes', There's a lot of size difference in drilling "10mm" rather than "20mm".

My offering is that you find access to a (probably older) combination saw...they usually had wooden trays on rollers to feed the timber into the circular saw...and devise a firmly locating jig to use the horizontal doweling tool and table. You may need a step-down drill (bit) to drill at 20mm.

I imagine the bore, for a woodwind, then needs careful polishing with a rotating sandpaper attachment..after the style of a brake cylinder polishing device. The timber you use should be straight drained and flawless to avoid the drill 'biting' or jarring or chattering. The bore size will have to be practically or mathematically gauged for harmonics.
 

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