drilling on the lathe

[fafow]

I am not sure what I'm doing wrong, but I am having problems drilling my blanks on the lathe. I have a jacobs chuck in the tail stock and have a Nova G3 chuck holding the blank in the headstock. My lathe is a Jet 1236. If I don't get the blank centered perfectly in the chuck, then the hole that is drilled is larger than it would be if I drilled it on my drill press. If I cut my own blanks, I rarely get them perfectly square, so I will have even more of a problem with this. I was thinking the best thing would be to have the drill in the headstock and have something in the tailstock holding the wood, but I have no idea what I could put in the tailstock to hole the wood in place. Any ideas what I am doing wrong?

 

[jkeithrussell]

It sounds to me like you might have some wobble. Are you drilling the hole in the entire blank, or just one barrel at a time?

 

[TellicoTurning]

Craig,
Without actually seeing your step by step procedure, I'm not sure I have a good answer, but here's what I do..
I use a CMG3 chuck from PSI.. it came with 4 bar like jaws that I attach.. they are tapered where they meet the wood, so the amount of metal on the wood is limited and appears to more or less center the blank if it is relatively square. An unsquare blank (is there such a word as unsquare?) will be held by the two sides on the longest dimension of the retangular blank. I also do a cross mark from corner to corner to more or less find center on the end that will address the drill bit. When I'm setting the blank into the chuck, I will place the point of my drill bit at the center of the blank, then tighten the chuck. This more or less centers the blank between the chuck and the drill bit. Then you can drill as usual and should get a relatively clean hole.

If you have a set of pin jaws for your chuck they should work as well using the same technique.

 

[wdcav1952]

Craig,

Not to sound like I'm taking a shot at you, but you mentioned two important issues in your post.

1. Cut your blanks square.

2. Center your blank exactly in the chuck.

Anything else is asking for inaccurate drilling. You might also consider turning your blanks round before you drill them. A round blank might be more easily centered in your chuck.

 

[Chasper]

Put the Jacobs and bit in the headstock. Use and awl to mark the blank for the desired entry and exit points for the bit. Hold the blank with a pliers, align the live center point on the tailstock into one awl mark, start the bit into the other awl mark, hang on to the pliers and use the handle on the tailstock to crank the blank into the bit. Stop before you get all the way through or you will drill into you live center.

It won't matter how out of square the blank is, just make sure you have the entry and exit points where you want them.

 

[altaciii]

I drill a 1/4" hole in cut blanks and turn them round. Then I put them in the lathe and step drill to the proper size for a larger pen or for the Euro just drill from there.

 

[thewishman]

Blanks don't need to be square to drill on the lathe. I use a Nova Midi chuck and make sure that the corners of the blank are in (or near) the center of the jaws. Don't try to put the corners in the spaces between the jaws - that makes it harder to center them correctly.

 

[fafow]

Thanks for the input, everyone. I have some more ideas to try. Turning the blank round first seems to be the surest way to get it centered on the chuck before drilling, but I will also take the advice of others here and see what works best for me with the least amount of additional effort (not that I'm lazy or anything)


PS. Cav, I didn't think you were taking a shot at me at all. thanks for the input.

Craig

 

[jhs494]

I always take the time to use a center drill first then drill them undersize, then drill my finish hole size. I always use the lathe with the drill bit in a jacobs chuck in the tailstock. I really don't worry much about how square the blank is as long as it's close.
I add those extra steps of center drill and undersize drill but I feel it helps to relieve some of the work on my finish bit. The hole stays closer to size this way for me.
Please keep in mind I make pens for a hobby and the extra step doesn't bother me.
Just my two cents!

 

[VisExp]

I also don't want to take a shot at you, but how are you advancing the tailstock? Are you just pushing it along the lathe bed or are you locking it in place and turning the handle?

I round my blanks to 3/4" round. I use a 3/4" wrench as a gauge to do this. Then I hold the blank in a PSI collet chuck at the headstock, and drill with a jacobs chuck in the tailstock. I always drill first with a center bit. I don't use an undersize bit.

 

[fafow]

Keith, I was thinking about this yesterday. the majority of the time I was pushing the tailstock and that could very well be the problem. I think there were a few times where I locked it in place and cranked the handle, then unlocked and advanced the tailstock, locked again and cranked the handle, etc. My memory being hazy at best (and I don't even use CA for a finish so I can't use the fumes as an excuse), I don't recall if there was a difference in the size of the hole drilled, but next time i will be sure to lock the tailstock and use that method before getting more drastic. but, rounding the wood is a good idea as well because it has to be rounded anyway, so why not do that before drilling.

Still don't know why people are worried about offending me with their comments. If I'm not getting true holes drilled, then I must be doing something wrong. I'll take all the ideas that are offered. One or more have to help.

 

[Chasper]

You didn't mention what you were drilling, probably wood since you mentioned the problem of not being perfectly square.

There are some resins that if you drill too fast will get hot and the shavings will melt into a knarly snake shape which can get between the bit and the sides of the hole, causing a wobble and hole that is wallowed out bigger than it should be. With wood it is usually that the blank is not mounted square in the chuck or the lathe is out of alignment. If you lathe were that far out of alignment you would be having major troubles in turning.

 

[Dan_F]

What I do:

I start by marking the center of the blank on either end, usually by drawing lines from opposite corners. Then, using a #4 center drill (with built in 60 degree countersink), I drill a shallow hole in each end, that leaves a little bit of the hole countersunk. This will allow the dead center to create enough friction to turn the blank, and the live center in the tailstock to effectively center the blank. The countersunk hole is most important on the drive end.

Then I turn the blank round between centers, with a 60 degree dead center in the drive position, and a 60 degree live center in the tail stock. I shoot for about a 3/4" diameter, as consistent across the blank as possible. The degree to which it is consistent in diameter is directly related to how well it will center when re-chucked the next time.

Once the blank is round, I go to my collet chuck, but the same could be done with a 4 jaw chuck. None of these chucks will always align the blank true, so the key is to use your live center to center the blank in the chuck.

Place the hole in the tail end of the blank in the live center, then position the tail stock so that the drive end of the blank is in the jaws of the chuck. I don't force the end of the blank against the back of the chuck, as that could alter the alignment, so leave just enough space to prevent that.

Now for tightening the chuck, it can be difficult to hold the blank against the live center while tightening the chuck without introducing side pressure, which might throw off the alignment, especially after the blank is cut in half for drilling, so I use a dowel placed through the headstock, to push the blank against the live center while the jaws are being tightened.

Using this procedure, it's possible to align the blank true in the chuck, and, more importantly, to re-align in the same orientation if need be. Use of a collet chuck greatly increases repeat-ability.

Dan

 

[Rangertrek]

Lathe drilling

I use the same setup as Ozmandus. It has worked for me since I converted to this method. Even if the blank is not square, I can line it up in the chuck and bring up the point of the bit for centering.

One extra step I take is to draw a line down the center of one side of the blank. I use this line to roughly line up the blank wiht the teeth on the chuch. This helps start the blank in a horizontal position and then I adjust as needed after the bit is brought up to the wood.

I have had much better outcomes with this than on my sloppy drill press.
Good luck.

 

[Morris129]

This is he way all experts say to do. Insert the blank start the lathe and bring up your bit to the spinning blank and let the bit find the center before you lock down the tailstock. I have done this for years and nevert had a off center or oversize hole. If you still have a problem you have a aligniment problem.

 

[NewLondon88]

I never under-drilled (except on metal) until recently when I did it by accident.
Drilling too small goes very quickly, and then drilling a larger hole where there is
already a smaller hole goes much faster and doesn't heat up as much.

I think it is faster to drill twice than to drill once with the larger bit. Of course,
this isn't helping the original poster..

 

[Blind_Squirrel]

Make sure your drill bits are sharp. A dull bit can lead to large, oor holes.

 

[nwcatman]

do what CHASPER said. saves a ton of time and works everytime because ur headstock and tailstock are in line w/each other. theres a demo on youtube on this. everytime you do it you'll think "why didn't i think of this". works great for antler.