Two Questions

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Stuart

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Jun 2, 2004
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My first question regard drilling blanks. I don't always seem to get them exactly straight but since I'm using scraps this hasn't caused a problem. What is happening though is the holes are too tight for the tubes at least fifty percent of the time. I will need to go back and run the bit through a second time. I've tried changing the drill speed but it doesn't seem to make any difference. What steps should I take to correct this?

The second question regards the pens. They apper to be very slightly oval from time to time. They might be fine when put together but when twisted they will be a very slight off center. Once again, what steps should I take to correct this?
 
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Daniel

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For question one, I would say the blank is getting to hot when drilling. pull the bit out more often to let the chips clear and possibly increase drill speed. what you are looking for is a drill speed and feed rate that causes the chips to fountain out of the top of the blank. this will happen in any blank for only so long when they stop shooting out they are building up around the drill bit and causing friction.

the second question, for one reson or another the mandrel is getting flexed when turning the oval pens. this could be due to using to much force to cut if your tools are not sharp or you are cutting hard material. or you may have tightened the nut to tight and this can cause the mandrel to flex. the other problem would be your tail stock is not lined up straight. my tail stock rides on a pipe and I have to be careful about getting it lined up each time.
those are my first guesses. of course now set back and wait for the barrage of other possibilities [:)]
 

timdaleiden

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Originally posted by Stuart
<br /> What is happening though is the holes are too tight for the tubes at least fifty percent of the time.

The second question regards the pens. They apper to be very slightly oval from time to time. They might be fine when put together but when twisted they will be a very slight off center. Once again, what steps should I take to correct this?

I have never had problem number one, but Daniel may have the answer. Just clear the flutes of the drill bit frequently so you avoid overheating. I imagine you may be getting a buildup of dust and oils.

Problem number two is common and is easily fixed. Most common cause is (as Daniel said) a flexed mandrel. Knurled nut too tight, offset tailstock, junk embedded in morse taper hole, tailstock too tight (or loose), something is not lined up true. Test it with blanks loaded as usual, and use a pencil rested on tool rest. Allow it to touch the bushings, and see if it is marked on one side only.

One other thing is relying too heavily sandpaper for final demension. A sharp tool, on a trued mandrel, will take off an even layer, Sand paper may not.
 

ilikewood

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Don't forget that one of the most common "oval" problems are when the blanks are not squared to the tube. If they are not square, when you tighten the mandrel nut, the off-square blanks will cause the shaft to flex.

As far as the drilled hole being too tight, the others have stated the case well. The only additional point might be if the blanks are not completely dry when you drill. The heat build-up will actually steam the wood causing it to swell.
 

YoYoSpin

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I've run into this tight brass tube problem before, when drilling soft woods like Buckeye Burl...when drilling these soft woods, there is often some tear-out that causes the tube to bind against the wood fibers inside the hole. If this is the problem, the only solution I know of is to re-drill the hole, and clear out the fibers.
 

daledut

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Swanton, Ohio, USA.
Let me add one more on the drilling. Use a slightly larger bit like a "J" instead of a 7mm. The glue the tubes with Poly U glue. This gives enough room to avoid all of the tight hole issues and the PU glue to fill in the slight gap.
 
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