Off center hole

[YoYo]

Hi folks,

As I'm a beginner of pen turning, I have already failed a few blanks. I cut them a little too short, turned too much and blanks cracked. Now, I don't know why the hole I drilled on my lathe is off center. First, I noticed that the tail head is wobbling, so I stopped and checked to make sure everything is tight. Before I started drilling, the drill bit pointed to the blank right at the center. When it's half way through, I started hearing the squeaky noise. So, after I done drilling, the hole on the other end is off center. I have a Rikon lathe by the way.
Can someone help me with this issue?
Thank you.

 

[KenB259]

Hi folks,

As I'm a beginner of pen turning, I have already failed a few blanks. I cut them a little too short, turned too much and blanks cracked. Now, I don't know why the hole I drilled on my lathe is off center. First, I noticed that the tail head is wobbling, so I stopped and checked to make sure everything is tight. Before I started drilling, the drill bit pointed to the blank right at the center. When it's half way through, I started hearing the squeaky noise. So, after I done drilling, the hole on the other end is off center. I have a Rikon lathe by the way.
Can someone help me with this issue?
Thank you.

Can you post a photo of your setup?

 

[Aurelius]

It sounds like your tailstock might not be aligned inline with the axis of your headstock. If that were the case, you would be drilling at a slight angle so, as you go further in, it would rub against the edges of the hole and create the squeaking you are hearing.
If you have an dial indicator, run it along the length of the drill and I bet you'd find it isn't straight.

 

[jttheclockman]

Many things can be the problem but start with the obvious. Lay the bit on a true flat surface and roll it. See if it has a hump. Next is your lathe level both langthwise and width wise? next is if you are using brad point bits they have a tendency to follow grain lines so if you are using a heavy grained wood that can be a problem. The thinner the bit the better chance of bending when drilling. Keep bit sharp and cool is a must.How are you holding the blank in the head stock? Is it spinning true. Lets start there.

 

[YoYo]

Hi Ken,

Please see attached pictures. My husband suggested me to use center ing bits. Don't know if they would help. As you can see the hole of the blank, it's off.

 

[jttheclockman]

Your problem is your blank is off center. If you are going to use that type chuck place corners that are opposite in each groove of that chuck it centers the blank. That is a long bit and easy to bend with grain of wood.

 

[wouldentu2?]

That drill bit works best if you use a 1\4" center bit first actually drilling into the blank until the flutes are covered. This ensures the bit starts straight. I've drilled 600+ blanks 4.25" long and 1\2" square and they are always drill straight.

 

[rherrell]

Use a shorter drill bit, long ones flex and tend to drift off center.

 

[Paul in OKC]

One other thing is how often are you backing the bit out? Also if there is much play in the tail stock itself, before locking down put a little pressure on the base so it is against one side of the lathe bed, then try pulling it against the other to see if that helps. Hope that makes sense.

 

[KenB259]

You have the same setup I use. As mentioned , get a set of short centering bits. If you're not doing segmenting, the off center hole you show doesn't even matter. When you square up the ends, you square to the brass tube. Also as mentioned those long bits like to flex.

 

[jeporter02]

It's not uncommon that my holes are slightly off center, but it has never made a difference in the finished pen. As Ken B mentioned above, once you square the blank to the tube and you turn it down, you won't be able to notice.

 

[egnald]

Greetings from Nebraska. I am in the camp with Rick Herrell, try a shorter drill bit. I have had that problem before when drilling a hole to be tapped. Just by adding the extra rigidity of a shorter screw-machine (stubby) drill bit was what fixed it for me. Even if you start with a stubby and then switch over to your chip-clearing bit, the starter hole should provide some bearing surface to help contain the longer bit. - Dave

 

[Mortalis]

Looking at the picture of the blank in the jaws being way out of center to the drill bit makes me wonder if your jaws are not in the scroll correctly. YOur blank is positioned correctly within the jaws
Also, I'm in the camp with jeporter02. I've drilled many a blank that way and the end result is fine.

 

[monophoto]

A number of good points here:

1. check that your tailstock is aligned with the headstock. Put a cone center in the tail stock and a spur drive in the headstock, move the tailstock to the left, and make sure that the tips of the centers meet. Its not unusual to see misalignment in the horizontal plane, and there should be some screws holding the headstock to the bedways that you can loosen to sift it to correct misalignmnent on that plane. If there is misalignment in the vertical plane, you need to contact the lathe manufacturer - something is wrong.
2. check that the jaws are installed on the proper sliders.
3. use a shorter drill bit - standard 'jobber length' bits tend to have less flex and are usually fine unless you are building a kit with an unusually long body turning.
4. use a starter bit to create a dimple, and then align the drill bit on that dimple. Standard twist drill bits will track better than spur bits.
5. drill from one end - make sure the entry hole is centered, but unless you are using a segmented blank, don't worry about whether the exit hole is centered. Off center is fine as long as you have a complete hole with at least 1/16" of material all around the exit hole.
6. stop drilling frequently, back out the bit, and clear the swarf.
7. with the tailstock lock loosened, try rotating it about an imaginary vertical axis. If there is any rotation (even a fraction of a degree), that could cause the hole to be misaligned. In that case, start the drilling process by using the tip of a skew chisel to identify the exact center of the rotating blank, and then align the tip of the drill bit to that dimple before locking down the tailstock.

As I look at the pictures, it seems to me that that something is off by a considerable amount. The drill bit should be centering on the hole, but the picture seems to show it centering to the left edge of the hole. That looks to me like horizontal plane misalignment - that is, a combination of points (1) and (7).

 

[jttheclockman]

The blank is not sitting in the chuck properly. Take a close look at it. Maybe they just set this up to take a photo to show the operation as Ken asked but One corner is correct in the groove of the chuck and the top is sitting on the flat of the blank and not the corner in the groove of the chuck Plain to see if this is how he is drilling it is wrong and needs to be corrected and probably hole center gets better.

 

[YoYo]

I checked everything but everything seemed fine. I tried the center bit and it seemed like it solved the issue so far. Thanks for the comments.

 

[YoYo]

Many things can be the problem but start with the obvious. Lay the bit on a true flat surface and roll it. See if it has a hump. Next is your lathe level both langthwise and width wise? next is if you are using brad point bits they have a tendency to follow grain lines so if you are using a heavy grained wood that can be a problem. The thinner the bit the better chance of bending when drilling. Keep bit sharp and cool is a must.How are you holding the blank in the head stock? Is it spinning true. Lets start there.

I did roll the bit on a flat surface and there is no hump. What isbrad point bits? Can we sharpen bits?

 

[monophoto]

What isbrad point bits? Can we sharpen bits?

A standard twist drill bit has two cutting edges at the tip that come to a point - 118 degree included angle for general purpose and wood bits, or 135 degree included angle for bits intended for steel. When used in wood, a standard twist drill bit centers itself in its own hole and remains centered in that hole. It works best when there is a starter hole drilled by either a starter bit or a smaller drill bit. Cutting a dimple with the tip of a skew also works well.

The shaft of a brad point bit is similar to the shaft of a standard twist drill bit, but the end is different - there are two cutting edges that are essentially straight (not angled), but there is also a sharp spur where those edges meet at the center of the bit, and there are two sharp wings at the outer periphery of the cutting edges. Brad point bits are specialty bits intended for use mainly in face grain timber where the centered spur can be used to start the hole - it isn't necessary to have a pilot hole. The sharp wings at the edge of the bit cut the face grain fibers to produce a clean entry and exit for the hole. However, brad point bits don't work as well in end grain because the bit can drift off axis, following the grain of the wood. If the bit deviates from the initial axis, those wings create a new hole that the bit tries to center in - and that process can repeat itself allowing the bit to follow the boundary between the hard and soft growth rings in the wood.

Can you sharpen bits - yes, perhaps. With practice, you can sharpen larger standard twist drill bits with a diamond paddle or even a bench grinder although a bit sharpener makes the job easier. Brad point bits require special tooling to sharpen - some drill bit sharpeners such as the Drill Doctor claim to be able to sharpen brad point bits. Smaller bits are difficult to sharpen because they are so small, so it probably makes sense to just replace them when they get dull. Larger bits are expensive to replace, so it makes sense to learn to sharpen them.

I try to avoid sharpening drill bits by having one set of bits that I use exclusively in wood, and another set that I reserve for metal. The bits used in wood don't get dull as fast as bits used in metal, and therefore don't need sharpening as often..

 

[YoYo]

A standard twist drill bit has two cutting edges at the tip that come to a point - 118 degree included angle for general purpose and wood bits, or 135 degree included angle for bits intended for steel. When used in wood, a standard twist drill bit centers itself in its own hole and remains centered in that hole. It works best when there is a starter hole drilled by either a starter bit or a smaller drill bit. Cutting a dimple with the tip of a skew also works well.

View attachment 351940

The shaft of a brad point bit is similar to the shaft of a standard twist drill bit, but the end is different - there are two cutting edges that are essentially straight (not angled), but there is also a sharp spur where those edges meet at the center of the bit, and there are two sharp wings at the outer periphery of the cutting edges. Brad point bits are specialty bits intended for use mainly in face grain timber where the centered spur can be used to start the hole - it isn't necessary to have a pilot hole. The sharp wings at the edge of the bit cut the face grain fibers to produce a clean entry and exit for the hole. However, brad point bits don't work as well in end grain because the bit can drift off axis, following the grain of the wood. If the bit deviates from the initial axis, those wings create a new hole that the bit tries to center in - and that process can repeat itself allowing the bit to follow the boundary between the hard and soft growth rings in the wood.
View attachment 351939

Can you sharpen bits - yes, perhaps. With practice, you can sharpen larger standard twist drill bits with a diamond paddle or even a bench grinder although a bit sharpener makes the job easier. Brad point bits require special tooling to sharpen - some drill bit sharpeners such as the Drill Doctor claim to be able to sharpen brad point bits. Smaller bits are difficult to sharpen because they are so small, so it probably makes sense to just replace them when they get dull. Larger bits are expensive to replace, so it makes sense to learn to sharpen them.

I try to avoid sharpening drill bits by having one set of bits that I use exclusively in wood, and another set that I reserve for metal. The bits used in wood don't get dull as fast as bits used in metal, and therefore don't need sharpening as often..

I bought a better one from home depot. But, I need to sharpen my barrel trimmer. Thank you all the information, very helpful.