Segmenting Have you ever made a blank you’re scared to turn?

[KenB259]

I guess I'm a little ahead of myself here. Assuming you've created a blank where, as you say, the center of the design is the center of the blank, what methodology do you use to then ensure the center of the hole you drill stays at the center of the design? I ask because I know I'm not drilling "straight down the middle" right now with the pen jaws on my chuck, jacobs chuck, and square-ish blanks. As I mentioned, it's not a big concern when dealing with most single-material blanks.


What's the setup here? The bit in the collet chuck in the headstock, the live center in the tailstock, and hold the blank stationary with your hand?

Well I use Nova pen chucks in a Nova G3 chuck. I start the drilling with a stubby center finding bit. That stubby bit is a game changer and wish I had started out with them. Using pen chucks the blanks can't be "squarish ", they need to be square and mine are within a couple thou, on segmented ones. I've read some here bashing pen chucks but my experience is they work great and they are precise. If everything starts out square, it's pretty hard to not drill in the center.

 

[jrista]

Drill holes using a collet chuck and a pointed live center to line things up.

John, any chance you could show this somehow? I'm not entirely sure I understand how this is done...

 

[jttheclockman]

I guess I'm a little ahead of myself here. Assuming you've created a blank where, as you say, the center of the design is the center of the blank, what methodology do you use to then ensure the center of the hole you drill stays at the center of the design? I ask because I know I'm not drilling "straight down the middle" right now with the pen jaws on my chuck, jacobs chuck, and square-ish blanks. As I mentioned, it's not a big concern when dealing with most single-material blanks.


What's the setup here? The bit in the collet chuck in the headstock, the live center in the tailstock, and hold the blank stationary with your hand?

I am guessing that both Vince and Jon are asking about my turning a blank round. First as I said in my post there are different methods I use for different scenarios of blanks. I think the one in question is the round ones. I never trust a round blank to be true round and when I want to make a square blank round I use same method. I first find centers on both ends (will talk square for now) Just take a straight edge and mark a line from one corner to opposite corner and then do the other twos corners and now you have an X and the center is then accented by use of an awl to create a divot. I take that blank and put between a dead center in headstock and a pointed live center in the tailstock Degree of point is no necessary to be known but I always use 60 degrees. I line the points with the divots. Tighten down and now round the blank down just enough to get rid of the square sides and it is totally round. I make sure it is the same diameter all the way through the blank. Much easier to work with. If you turn this should be an easy task. Use whatever tool you prefer. I always finish with a skew. Now my blank is perfectly round. I then take one end and stick it in a collet chuck of the right size. Now just because you use a collet chuck does not mean the blank is true. To do that I use the pointed live center in tailstock to line up the divot in the blank from previous operation. When you do that and lock it down everything is now centered. You lock the collet chuck and it will hold it in place. You can test this by starting the lathe and the blank should run true with no wobble. Turn off lathe and change out the live center in the tailstock and replace with a drill chuck of your choice. I always start any tube hole with a starter bit so that is what I put in drill chuck. Then I switch this out to the proper size the tube calls for.

Now I am writing a bunch of this stuff because I am not sure what kit you are using and if you are using the same blank for top and bottom on a 2 piece kit. If so then drill the smaller tube hole first and measure how deep you need to drill for tube. Mark drill bit with a piece of tape and drill. Now you can part that section off with a parting tool or skew or take blank off and cut on a saw. But what you have to drill the top part is to once again line the blank up as mentioned in above instructions. You now have a starting hole on the one end or you can flip it over and use the divot and again use the pointed live center. Your choice. Then make the switch again and drill with larger bit.

I hope this answers the questions and if not just ask away and I will try again. I use this same method when setting up a blank on lathe to use my router to make slots in a blank. I Always work with a round blank when doing that. Here is an example and also one where I am building the blank on the tube after I cut all pieces and drilled them.