Use a laser!
More seriously the first thing I thought of when reading your first post was use a gun drill. I can't think of anything better.
09-09-2011 #33projectile vomit
id use my ovation as a chopping board but id build a teleporter and beam the stuff in there before i touched the paint job on my jackson.
if you ever get around to drilling though you have got to video that!
it may seem mean but if you are going to projectile vomit all over that very posh peice of wood i have just got to see it :rofl:
Me again, had the chance to mull this a little.
Here's the immediate problem - just about every implementation of gun drilling has the drill static & the workpiece turing - that's fine when your workpiece is circular (gun barrel, kids musical recorder etc)...just lob the workpiece in a collet - it's perfect centred...job done.
But if the workpiece is a guitar neck (ie odd shaped!), then that's not gonna work very well (to much potential for it to be misaligned ...especially at the far end)
Therefore I reckon I need to have the gun drill bit turning & mount the guitar neck on a static table/bed - the problem here is, gun drills always have compressed air squirted down their centre (to expel the chips from the cutting end) ....so how do you supply/maintain compressed air down the centre of a drill bit that is turning? (ie what's the name of the part that allows a static pneumatic hose to connect to something that is spinning)
Last edited by HankMcSpank; 13-09-2011 at 10:11 AM.
A rotary union or swivel joint.
There a couple cross-sectional views on this page - http://www.filtonltd.co.uk/products_swivel.php
Basic ones only use two o-rings with glide rings, while more complex/higher duty ones will use ball bearings with lip seals. It all depends on speed/pressure/type of fluid.
im assuming you will be reaching through the spindle bore to get at the opening in the end of the tool ??? might be worth knocking something up for the time being, brass tube with a lose (ish) fit inside the tool coolant bore
if you have a pretty decent compresser it'll keep up with a leaky joint at least till you have proven the concept and start an all out production
Not sure that works. You'd think all rotations were relative, but are they? :naughty:
If you spin the workpiece you define a line through it, the axis of rotation.
If you spin the drill you define squat.
If a turning drill goes off line, it's centre is still the slowest moving part of the cut.
If a stationary drill goes off line, it isn't.
Question is, is that how a long gun drill bit keeps itself on target?
They cut and burnish.
Robin has it bang on (saved me a lot of typing :)) gun drills only work because the job is spinning.
That said: I think, with the right technique, you could drill 500mm into a soft-ish material without too much drift.
First, grab yourself some wood of the same type as the neck to practice on.
Use a sequence of drills each a 1/2 mm or so smaller than the last. (you might be able to do it with one drill, but that doesn't give you the option of 'correcting' the path slightly)
Fix (braze or silver solder) the smaller drills into the end of steel rods the diameter of the previous drill. (concentricity is obviously important, as is a correctly sharpened drill).
I've drilled an 8" deep blind hole in steel using this technique with a 4mm jobber bit that was just a press-fit into the end of a silver steel rod ( I pinned it to the rod to stop the drill turning)
The first drill hole is the most important. Make a sequence of sleeves to align the rod in the first hole, so the drill is guided for its whole length.
Drill using lots of pecking (3-6mm in, then pull out and clear the chips) .
If you don't have a long bed lathe handy, then some kind of long sliding rig is essential.
It's a difficult, not an impossible job.
Last edited by BillTodd; 13-09-2011 at 07:01 PM. Reason: adding picture
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