problem with davys D bits

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problem with davys D bits

Post by ttoberer » Fri Jun 05, 2009 10:02 am

Davy if you are out there, I have had trouble with your style of D bit. The hole drilled in the center keeps the drill going straight, but it will only drill about a half an inch before the little node created by the hole which centers the drill also prevents it from continuing. to solve this I had to run a twist bit to drill out the node before each progression. traditional D bits dont have this problem. Did I do somthing wrong? Tim

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Re: problem with davys D bits

Post by snoogie » Fri Jun 05, 2009 5:45 pm

I've had this same issue with Davy's style of D bits. Two things which seem to help...

one is to have the hole you drill in the center, shallower than the area you remove to make the D. I know that doesn't sound too clear, so the objective is to have a flat space at the place where the D becomes an O for the little node of wood to go so it'll break off. If you drill the hole deeper than that, then the node will become a spindle for the D bit to turn on, and then the cutting edge won't be able to make further progress.

The second option if the first one doesn't work, use a smaller D bit than the one you're currently cutting with to reach inside and break off the little node of wood.

Hope that helps.

Davy, please let us know if there's a better trick. I love the D, easy to make and last a long time between sharpenings.

There is no try, only do or not do - Yoda

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David Stephenson
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Re: problem with davys D bits

Post by David Stephenson » Mon Jun 22, 2009 3:03 pm


This does happen from time to time, timber to timber, if it does simply insert a plain flat ended blade to break off the guide pip in the middle so the drill can pick up and drill again.

I sometimes use an extended normal drill bit that is soldered to the end of a slightly thinner rod, if you are making this kind of drill you can need a metal lathe to cut a small male spigot onto the back end of the drill bit, which is normally made softer than the rest of the bit to prevent shattering, if its too hard heat her up to soften it and let it cool down naturally.

Then drill the end of you silver steel rod to accomodate the spigot on the end of the drill, file a small flat area into the male drill spigot so that the silver solder can flow to the bottom of the hole, otherwise you won't have a good solder joint and the drill could come adrift inside the pilot hole ruining the job once its stuck in there.

I have started to use Bhills step boring technique on some of my chanters to prevent ovalling at the bell end and use a steady bearing on the outside end of the chanter blank, and sometimes without, depends upon the timber being used.

A word of advice on the D drills, try not to make the cutting step no bigger that 9/16" as they tend to wander on the narrower gauges, and try to make the tip slightly higher than the back of the cut away so there is a slight ramp along the cutting platform, (higher at the cutting tip) so it holds the waste in place as your withdrawing the drilling rod.
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