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How to bore/drill a 350mm long / 27 diamm hole

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emabear

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Advice, please. I am trying to find the best way of boring a 27mm dia hole though a 350 on a piece of hardwood. I have tried various methods on both the lathe and drill press but I suffer from burn out and trying to find long enough drills / forstner bits. Grateful for any help.

Mark
 

MikeG.

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I presume it's too late to split the piece in half and run a groove through each half before gluing back together?
 

billw

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Well I suppose the obvious answer is that it's two 175mm holes joined together, is there any reason why you can't drill in from either end? I assume it does run the full length since you say "through" rather than "into".

Or this......

 

emabear

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I presume it's too late to split the piece in half and run a groove through each half before gluing back together?
Yes, I had thought of that and it is an option however I ideally want to keep the cylinder intact both for stability and look
 

emabear

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Well I suppose the obvious answer is that it's two 175mm holes joined together, is there any reason why you can't drill in from either end? I assume it does run the full length since you say "through" rather than "into".

Or this......

Yes, tried that as ell but I want to turn the finished cylinder after boring and trying to get the two holes accurate is a nightmare. Interesting augers though and will look at these but they do tend to stray whilst drilling due to heat I think
 

toolsntat

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Looks like you could benefit from this method.

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.

Cheers Andy
 

Sheffield Tony

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Is this into end grain ? That's always hard work with an auger, but a Gedge pattern is the one of choice. If I want a hole through the middle of something I'm turning on a pole lathe where it isn't possible to bore it on the lathe, I will bore a hole first, turn a couple of plugs for the ends of hole, then put it on the lathe and turn the outside to be concentric with the pre-existing hole. This may of course not help power lathe turners at all. But trying to enlarge an existing hole is IME a lot harder then boring it the right size to start with. Auger lead screws won't feed, so you end up having to apply quite a lot of pressure, especially into end grain. Whilst trying somehow to grip a finished round object !
 

Sean Hellman

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WoodOwl do fantastic auger bits that long, as used by timber framers. I have a couple at around £80+ each. These really are the best I have ever used and comer very highly rated.
 

MusicMan

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A shell auger was traditional, and good for end grain, but requires a huge force for that size. Best to start it in the right direction with a conventional auger or Forstner bit. I have no comparison with WoodOwl's augers, which I suspect may be the best affordable modern tool for this job.

To enlarge an existing hole, a reamer is best. Home made D bits work very well, but require plenty of heft (and lubricate with beeswax). For a hole that size I would expect to need a 3 HP lathe.

These are not modern tools. One bass clarinet that I know from 1830 has two parallel holes about 24 mm diameter, 600 mm long in one hefty piece of boxwood. Bass Curtals exist with 2m bored holes. And remember that boring holes was common technology in the 17th - 19th C. Logs were end-drilled for water pipes and gun boring was big business.

Gun drills are still the most efficient way, but expensive and difficult to manage in that size (and need an air supply).
 

lexi

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This was a crude tool I made to bore through an Oak knee for a boat prop shaft. In from both ends and I met in middle after drilling pilot holes. It was made from a hole saw. Mandrel is in the centre of it for a guide in the pilot holes. It worked in that application. Sore on a drill machine with heat and smoke. That is Sessile Oak......hard!
 

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Jonzjob

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It may help to know just what you are making with the wood Mark? I have made a couple of standard type lamps and used the cut down the middle, route the 2 halves and glue back together. After the turning/sanding is done it is both stable and I have trouble finding the split.

The up-stand had to be done in 2 parts so that had to line up perfectly. The top arm had to have the hole finishing and exiting about an inch or so from the ends because of the knuckle and because of that the join is on show in the bottom photo, if you can find it?

No problems with the integrity as long as you use a good glue. I used Titebond 2 on this and another I made.
IMG_1029.JPG

IMG_1023.JPG
 

emabear

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Looks like you could benefit from this method.

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.

Cheers Andy
Thats a great idea - I will experiment and report back Thanks
 

MusicMan

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It helps to have the chuck end firmly anchored and a fixed steady, keeping the far end free to get any size auger in.
 

Rob_Mc

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You didn't mention what you were drilling but did mention a lathe. Can you not drill from either end with a saw tooth forstner bit as you would for a pepper mill, using a forstner bit extension if required to get you to the depth you need?



Example forstner bit extension;

 
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