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 Post subject: Help
PostPosted: Thu Aug 20, 2015 11:16 am 
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Location: Hamilton, MS
I want to build a lamp from a 30 inch log. I will turn it to shape on the lathe. I need to drill a 3/8 inch hole straight thru the middle for the metal rod holds the top fixture and for the wire to run thru. Last time I tried this my bit with an extension welded to it didn't work. I could not hold the bit straight as I drilled and the hole wasn't even close to the center.
Any ideas or your experience with this would be great.

Thanks, George


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 Post subject: Re: Help
PostPosted: Thu Aug 20, 2015 12:12 pm 
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George,
The only way I know how to do it is to drill from both ends and meet in the middle. Even then you will have a hard time drilling straight.

I do this all the time but 30" is a lot. If you could just get it so you can see light through the hole, you can butcher out the middle because the bit will find the other hole and try to follow it.
let us know what you do.
Zulu

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 Post subject: Re: Help
PostPosted: Thu Aug 20, 2015 12:52 pm 
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One way is to rip the log and route out the passageway, then glue it back together. If you're careful the glue line won't show, or if it does, hide it with some molding after you turn it on the lathe. I don't know what diameter you're talking about, but you'll need to have something temporarily attached to the log when you rip it to prevent it from rolling. A couple pieces of squared up ply screwed to each end would probably do on the table saw if they're taller than the diameter of the log so the blade doesn't cut them in half. You might have to attach a long board to the fence also to guide the thing. If you have to bandsaw it you'll need a sled.

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 Post subject: Re: Help
PostPosted: Thu Aug 20, 2015 4:45 pm 
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 Post subject: Re: Help
PostPosted: Thu Aug 20, 2015 5:12 pm 
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Hey George,

I recommend a combination of Gene's and Zulu's ideas. Zulu's correct that a twist drill bit will follow a pilot hole. Gene's idea of routing (or ripping) a grove from one half will work well too. My only suggestion is that instead of ripping the log in half, you might want to consider riving (splitting) it. Use a froe, and a wooden maul. Wooden wedges will also help keep the split open as you move the froe down the log. Be careful with the froe, so as not to damage the sides of the split if possible.

Riving will part the log without a kerf loss. That way, when you join the pieces back together, there should be no visible line.

As suggested above, us a sled when ripping the groove on an uneven piece, for safety's sake.

Good luck,
Tom

ps. A log will check as it dries. The axial (annular) shrinkage being greater than the radial shrinkage makes that inevitable. Choose one of the checks to start your riving, and you will have less chance of a noticeable line, it being buried in the check.

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 Post subject: Re: Help
PostPosted: Thu Aug 20, 2015 10:28 pm 
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If you really don't like any of the ideas that involve cutting/splitting the log, here's my best shot:
Get a longish bit (12" or so), and drill as far as this will go with a drill press with the log carefully aligned to the quill of the drill press. Then finish the hole with whatever you can find that's long enough. The initial 12" hole should be pretty straight (assuming a decent bit), and will guide the longer bit. Do this BEFORE turning the log on the lathe. Use the two ends of the hole as the center to mount the log on the lathe. This will guarantee the hole will indeed be at the center of the turning.

As TMS mentioned, your log is going to check and/or split. Not sure what to say about that.


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 Post subject: Re: Help
PostPosted: Fri Aug 21, 2015 1:57 am 
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A rather talented machinist explained to me how gun barrels are drilled so accurately down the bore of a rifle.

The principle involves both the workpiece (gun barrel/lamp post) and the drill bit both turn which all but guarantees the drill bores true down the center. So ... if your tailstock is hollow, run the lamp auger through it while devising some way to turn the auger at the same time the workpiece is turning in the lathe.. Perhaps a vicegrip clamped onto the end of the auger bit or ...

The point is, you turn and drive the drill bit/auger in while the work is also turning on the lathe.

Full disclosure ..

I've not verified this since 1) I don't own a lamp auger and 2) I don't have any lamp projects on the horizon.

But I'm in anticipation of your results in the event you decide to put it to the test.

And, as suggested, use the holes at each end as centers.

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 Post subject: Re: Help
PostPosted: Fri Aug 21, 2015 5:49 am 
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A ship auger would be all I can come up with. Boring endgrain is not what it's for, but it will clear mush better than the narrow screw on the standard bits. As long as you use 3/8 setup at the top, makes no difference what the interior is. Give yourself some room to clear.


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 Post subject: Re: Help
PostPosted: Fri Aug 21, 2015 9:54 am 
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The longest drill bit that I own is a 5/6" x 12" and I've used it several times for different things. However when I bought it (at Lowe's) I noticed they have 18" long bits in various smaller diameters.
Maybe. with a bit of luck, you could drill a 3/8" hole using an 18" long bit from each end of the log and "more or less" have them meet. If you can get the two holes close to lining up (not exact) you can wiggle and turn the log and "wallow" the hole to a larger diameter in the middle of the log to allow your lamp pipe to go through.
Here is hoping for the best of luck to you!

Rog

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 Post subject: Re: Help
PostPosted: Sat Aug 22, 2015 7:02 pm 
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Location: Hamilton, MS
Thanks for all the advise. I had already drilled from both ends using a chuck in the tail stock of my router, and each hole was over half way thru the log. But they didn't meet. Tried a larger bit and still couldn't tell where my problem was. I gave up that idea and attached a board to the log to help keep it true and I split it on the table saw. One of my holes was perfect, straight down the middle. The other was so far off I would never get it right. How I messed up that bad I have no idea. Maybe a good steady rest for the piece would have helped me keep it straight. That is on my list of things to buy. I fixed the hole on the router table and glued it back together. Will try again tomorrow and post the finished lamp if I ever get it done.
Thanks again for your ideas.

George


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