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Drilling true using tailstock and jacobs chuck

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I feel kind of silly asking this but, I decided to make my first sphere and first needed to make a cup chuck for the headstock and a drilled and tapped cup to thread onto my oneway live center. MT2 cup chuck, no problem. Tailstock cup bumper, not so much. I'm having a hell of a time getting a true centered hole. I'll explain my process and hopefully someone can educate me on what I'm doing wrong or what's wrong with my lathe.

* put tenons on each end of a short chunk of wood and true it up.
* jacobs chuck in tailstock and drill hole and cut threads to match live center.
*reverse wood (drilled hole is now at my chuck) and shape the threaded cup chuck
*thread onto tailstock

The problem is, it's never true. there is always some offset between the threaded hole and the cup and it doesn't run true.

I've checked tail/headstock alignment by touching points and locking everything down. It's very very close but not exact. If it's not locked down my tailstock arm wiggles a bit. More than I would assume it should. So, when I drill, my bit always ends up off of center as I'm turning the tailstock wheel to advance the bit. It becomes more obvious the deeper I drill. If I lock it all down it can't be advanced.

Am I missing something completely obvious or is my lathe borked? My bits aren't bent and are sharp. Honestly I've experienced centering problems often but chalked it up to ignorance and newness to the hobby. Everytime I reverse a piece it needs to be re-trued which i understand is somewhat normal (especially with green wood).

I have no idea why making a sphere is so completely consuming to me currently, but, it is...

Thanks in advance
 
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I did a club demo a few weeks ago that shows a simplified method for turning a sphere. I make one cup (on the fly on the headstock) and use a rubber chair leg tip on the live center. Here's a link to the recording ... part you are asking about starts at about 18:10 into the video:
View: https://youtu.be/RcwPWVWWYYo
 

Tom Gall

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I feel kind of silly asking this but, I decided to make my first sphere and first needed to make a cup chuck for the headstock and a drilled and tapped cup to thread onto my oneway live center. MT2 cup chuck, no problem. Tailstock cup bumper, not so much. I'm having a hell of a time getting a true centered hole. I'll explain my process and hopefully someone can educate me on what I'm doing wrong or what's wrong with my lathe.

* put tenons on each end of a short chunk of wood and true it up.
* jacobs chuck in tailstock and drill hole and cut threads to match live center.
*reverse wood (drilled hole is now at my chuck) and shape the threaded cup chuck
*thread onto tailstock

The problem is, it's never true. there is always some offset between the threaded hole and the cup and it doesn't run true.

I've checked tail/headstock alignment by touching points and locking everything down. It's very very close but not exact. If it's not locked down my tailstock arm wiggles a bit. More than I would assume it should. So, when I drill, my bit always ends up off of center as I'm turning the tailstock wheel to advance the bit. It becomes more obvious the deeper I drill. If I lock it all down it can't be advanced.

Am I missing something completely obvious or is my lathe borked? My bits aren't bent and are sharp. Honestly I've experienced centering problems often but chalked it up to ignorance and newness to the hobby. Everytime I reverse a piece it needs to be re-trued which i understand is somewhat normal (especially with green wood).

I have no idea why making a sphere is so completely consuming to me currently, but, it is...

Thanks in advance
I'm not really sure if I understand your problem....but try this.

1). Drill and tap your threads as you have done - (or buy a 3/4x10 nut and epoxy in a hole)
2). Mount rough block onto threads of your Oneway live center.
3). Put live center into MT on your headstock. Drop a short nail (IIRC a short roofing nail works well) through the locking holes of the live center and tape over so the nail won't fall out.
4). Bring up the tailstock (with another cone center - live or dead) to hold the MT into the spindle. Turn to shape as needed. Remove TS to finish up. It should now run true with your live center.

If your headstock and tailstock centers don't line up that's another problem.
 
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sorry for the mushmouth. I'm having a hard time describing it.

both good ideas. Tom Gall, what is acceptable tolerance for the 2 centers to be off? I may be out 1/64 or 1/128? All I know is that when I try to drill anything it never ends up centered and the deeper the hole is the more noticeable it gets. Is there a way to check it without buying an expensive gauge? I noticed that whenever I touch a bit to the wood, as soon as it makes contact, it will shrug off to one side ever so slightly. Then, once I'm in a couple inches, it is very noticable. You can hear the bit only hitting in part of the hold (like I'm cutting air).

I've tried putting a concave divot with a skew, i've tried predrilling with a smaller diameter bit.

Also, if I extend my tailstock arm 3 inches and put pressure on it, it will not be solid unless it's locked on both the bed ways and the arm (which I believe is normal). It doesn't move much but you can hear it inside ever so slightly which leads me to believe that is possibly where the misalignment begins when advancing the tailstock arm while drilling. I could lock the arm and physically push the tailstock into the wood but I know that's not proper.

I suppose my morse taper on the jacobs chuck could be wonky as well...
 

hockenbery

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feel kind of silly asking this but, I decided to make my first sphere and first needed to make a cup chuck for the headstock and a drilled and tapped cup to thread onto my oneway live center. MT2 cup chuck, no problem. Tailstock cup bumper, not so much. I'm having a hell of a time getting a true centered hole. I'll explain my process and hopefully someone can educate me on what I'm doing wrong or what's wrong with my lathe.

( I plan to look at @GRJensen video). In the meantime.
I use a flat wooden pin cover on the live center and a cup on the drive side. This is something I learned from Christian Burchard around 1998. It always grips a slightly out of round ball much better than two cups.

i just drill a hole that fits closely over the Rotating part of the live center. 1.5” fits the mini lathe centers. I think it is 5/8 for the ONEWAY center. Oneway center needs a couple wraps of masking tape for a tight fit.
To make it I press the cover agains some Scrap wood In a chuck and turn it to about 1/2” diameter point and part in at a slight angle to make it the tiniest bit concave. May need to use a knife or chisel to clean off the face. Then glue a piece of leather on. The cup I use either a small cup held in a chuck or one on a wooden Morse taper. Best size for the cup is about 1/3 diameter of the sphere - a compromise between holding am allowing working room.

photos from the video
3EB53BD9-F4CD-46E9-B923-C50A90131203.png 81EBE9CD-07D4-48D0-86A3-52BB64B865B9.png

This video shows the use of the pin
B&B Demo 2010 AAW symposium -
View: https://www.youtube.com/watch?v=fmCvOP2Mpmw
 
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I make my live center attachments like Tom, except I use a draw bar. (see below)
Spinning the Jacobs chuck/drill bit in the headstock might show some wobble which could help eliminate a bad chuck or bent bit.

Another thing I've done is to tap the oneway live center to accept a draw bar. A 3/8 x 16 tap works without having to re-drill, at least in my live center...
View attachment 27578
 

Tom Gall

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Tom, ... "I may be out 1/64 or 1/128?" I'm sure mine is off more than that but never caused any real problems. Keep in mind that when you check the points they are as close to each other as they can be. When you pull the tailstock away that could change and be difficult to tell. Your bed may not be leveled in all directions (especially fore & aft) which would cause it rack slightly and be OC even more as you move away from the headstock - but still not a big problem IMO. Try this....advance your tailstock to start drilling (most times it will center itself in your divot) - THEN lock it down to advance the quill.

Your drill bits could be off and/or your Jacobs chuck. Do they run true in a drill press? BTW - you could just drill your block on the drill press and then tap it. :)
 
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I noticed that whenever I touch a bit to the wood, as soon as it makes contact, it will shrug off to one side ever so slightly. Then, once I'm in a couple inches, it is very noticable. You can hear the bit only hitting in part of the hold (like I'm cutting air).

I've tried putting a concave divot with a skew, i've tried predrilling with a smaller diameter bit.

Also, if I extend my tailstock arm 3 inches and put pressure on it, it will not be solid unless it's locked on both the bed ways and the arm (which I believe is normal). It doesn't move much but you can hear it inside ever so slightly which leads me to believe that is possibly where the misalignment begins when advancing the tailstock arm while drilling. I could lock the arm and physically push the tailstock into the wood but I know that's not proper.

I suppose my morse taper on the jacobs chuck could be wonky as well...

First go to Harbor Freight and buy a set of "center drill" bits. Probably 3 or 4 in a set. They are really short and are only for starting a hole.

Follow that up with a sharp drill bit. I find brad point bits usually drill straighter than standard twist drills.

On the tail stock tighten the locking lever down a little on the quill to take out some of the slop. It may or may not help.
 
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Jacobs chucks are not as precise as other mounting/holding contraptions we use.

One other thought--does it really need to be threaded? If it was a snug slide on fixture, with a square base to mate up with the 'shoulder' of the live center, wouldn't that work, without adding potential error from tapping?
 
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yes dean, that would work as well as a threaded connection. still leaves me with the problem though of the cup not being on center or the issue of a crooked drill hole unless i'm missing something obvious which is quite possible.

I remember having a jacobs chuck with no taper on it so i checked my amazon history and found the $9 mt2 i bought to put in the used chuck head. i ordered a new one of higher quality to test.

Thank you larry, i've seen the center drill bits at harbor freight for a couple bucks. I'll pick up a set to test.
 

Bill Boehme

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I feel kind of silly asking this but, I decided to make my first sphere and first needed to make a cup chuck for the headstock and a drilled and tapped cup to thread onto my oneway live center. MT2 cup chuck, no problem. Tailstock cup bumper, not so much. I'm having a hell of a time getting a true centered hole. I'll explain my process and hopefully someone can educate me on what I'm doing wrong or what's wrong with my lathe.

* put tenons on each end of a short chunk of wood and true it up.
* jacobs chuck in tailstock and drill hole and cut threads to match live center.
*reverse wood (drilled hole is now at my chuck) and shape the threaded cup chuck
*thread onto tailstock

The problem is, it's never true. there is always some offset between the threaded hole and the cup and it doesn't run true.

I've checked tail/headstock alignment by touching points and locking everything down. It's very very close but not exact. If it's not locked down my tailstock arm wiggles a bit. More than I would assume it should. So, when I drill, my bit always ends up off of center as I'm turning the tailstock wheel to advance the bit. It becomes more obvious the deeper I drill. If I lock it all down it can't be advanced.

Am I missing something completely obvious or is my lathe borked? My bits aren't bent and are sharp. Honestly I've experienced centering problems often but chalked it up to ignorance and newness to the hobby. Everytime I reverse a piece it needs to be re-trued which i understand is somewhat normal (especially with green wood).

I have no idea why making a sphere is so completely consuming to me currently, but, it is...

Thanks in advance

Something to memorize: Threads are for fastening and not for alignment ... not for metal and especially not for a non-homogeneous compressible hygroscopic material like wood. You could make a wood cup chuck that can be threaded onto a live center and then true it up by putting it on a Robust Cup Center to get it trued up and that should work well enough.on either the Robust or Oneway live center. Alignment doesn't have to be perfect. In fact, no lathe is perfect especially woodturning lathes.

I like Al's solution. It is simple and easy.

Drilling holes in wood without the drill "walking" can sometimes be a challenge especially if the wood growth rings have soft earlywood and hard latewood. The solution could be either to use a larger diameter drill or if you need a small pilot hole then use a spotting drill (you could also use a center drill). When you switch to a regular twist drill after drilling a pilot hole, use light pressure and back the drill out frequently to clear the flutes of swarf. It's hard (more like impossible) to drill a straight hole very deep in wood with a small diameter twist drill.

Most woodturning lathes have a bit of looseness in the tailstock quill which will have a big impact on the hole drifting off center. Hopefully, your lathe has setscrews to allow you to tune out the free play. I did some fine tuning to the tailstock quill on my lathe by using a diamond card to slightly chamfer the sharp edges of the keyway. I also chamfered the edges of the keystock. Finally, I lubricated all the sliding parts with CRC Heavy Duty Silicone. Don't get any lubricant in the Morse taper socket of the quill.

Since we're not building parts for the International Space Station we don't need to get overly concerned about precision for most woodturning activities. Turning spheres are an interesting challenge and is great for testing your turning skill.
 
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First go to Harbor Freight and buy a set of "center drill" bits. Probably 3 or 4 in a set. They are really short and are only for starting a hole.

Follow that up with a sharp drill bit. I find brad point bits usually drill straighter than standard twist drills.

On the tail stock tighten the locking lever down a little on the quill to take out some of the slop. It may or may not help.

Center drills are sore point for me, let me correct part of this quote which is a common misconception. Center drills are not intended for "starting a hole". A center drill's only intended purpose is to establish a seat for a lathe center, usually 60 degrees. Now, in the case of wood a center drill can be used to spot holes, it isn't a good habit to get into though. Especially a bad habit if it's also used to spot holes in metal (how many woodturners haven't also drilled metal?).

The reason it's not a recommended spotting tool is it's fragile small diameter tip. Those tips break off easily, and that broken tip is embedded in your workpiece, not easily removed. Take a look at most any collection of machinist's hints and you'll likely find several difficult methods of removing tips of center drills. The miss use of center drills is so common that my local CC machining program still teaches the incorrect usage.

A spotting drill is the correct tool to to use in spotting holes. A spotting drill is usually a short stiff drill that starts easily without a tendency to "walk" off center.

As to drilling deep, on center holes in wood, the best I've seen is a special tool called a gun drill. Gun drills are readily available on eBay. I helped a flute maker build a gun drill setup on his lathe to accurately drill a wood flute body full depth from one end using compressed air to clear chips.
 

hockenbery

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feel kind of silly asking this but, I decided to make my first sphere and first needed to make a cup chuck for the headstock and a drilled and tapped cup to thread onto my oneway live center. MT2 cup chuck, no problem. Tailstock cup bumper, not so much.

is your goal turning balls or getting a true running tail center cup? They are not the same.
if the goal is turning balls try making a pin tailstock cover or use a rubber foot.
This is IMHO a much better solution than 2 cups. More positive hold, more working room, better grip on out of round balls.

@GRJensen has shown a method he developed - using a rubber cover on the tail center. It is nearly identical to the method Christian Burchard taught me in the 90’s. I showed the small wooden cover I make. It provides more working room than the rubber foot and perhaps a less sponges hold.
I have been teaching this method for over 20 years and 100% of my students have been able to make a ball.

For anyone wanting to turn balls I suggest you give the wooden pin a try.
 
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john lucas

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I cut threads in the wood. Screw it on my live center. Then I put a cotter pin through the live center locking hole (this is on a Oneway or Powermatic live center). Then I put this in the headstock and turn the cup for my spheres or for that matter any other odd live center wooden adaptor. That way it is perfectly aligned. As far as drilling a perfect hole I use the toe of my skew to make a depression dead center. Then start my drill in that hole. The drill still may wander dues to different hardnesses of wood but this method has worked as well or better than the centering drills.
 
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I did a club demo a few weeks ago that shows a simplified method for turning a sphere. I make one cup (on the fly on the headstock) and use a rubber chair leg tip on the live center. Here's a link to the recording ... part you are asking about starts at about 18:10 into the video:
View: https://youtu.be/RcwPWVWWYYo
That is one pretty lathe and accessories Gerald!! So if you clean things after using........oh well, haha!! Nice demo as well Brother!!
 
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That is one pretty lathe and accessories Gerald!! So if you clean things after using........oh well, haha!! Nice demo as well Brother!!
Thanks! A wise man once told me "A clean shop is a safe shop"
 
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Gun drill ehh. Funny enough a flute and pipe stem for a native style pipe is on the short list of projects.

The final goal is a sphere. I'm about 2 steps into this process and expecting at least half a dozen more bumps along the road if it's based on past projects. Ton of excellent info and input here for me. Appreciate all of it. All my projects begin with an idea. I do a bit of research then make an attempt or 2. Usually something doesn't work so I have to adjust. Then something else, then something else, rinse repeat until i've completed the goal. Usually these things that go wrong are all unforeseen problems. It's frustrating or exciting depending on the day. Turning is simple right? spin wood, make something round. I love turning because I could do this for the next 30 years and still learn something every day going forward starting year 31.
 

Tom Gall

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yeah my drill press is garbage. I'm going to swap out the jacobs chuck and see how that does.
Another test I forgot to mention was to put your Jacobs chuck with drill bit in the headstock - turn on the lathe at slow speed - if either is not true you will see the tip of the bit rotate around in a circle. But, as others have said there are work-arounds and should not affect your final goal of turning a sphere.
 
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Oooo, good call. I've had issues from day one but most of them have turned out to be user error. If my lathe is needing repair though, that is the most important thing in my opinion. Having put the various parts in various ends of the lathe, this is what it looks like. The tailstock absolutely needs adjusting. How terrible it is, I'm not sure. Maybe someone can chime in?center 1.jpg center 2.jpg
 

john lucas

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Just because the points line up doesnt mean it will.drill a true hole. The tailstock or headstock can be twisted or canted. Take your infmdex.fingers and touch them together. Now keeping the together move your wrists up or down or sideways and you will see what I mean. Doesnt have to be off more than a few thousands. Add the extension of a drill chuck and 4" drill bit and it can now be off 20 30 or 40 thousands very easily. These are not metal lathes and lack the precision for that kind of accuracy. To find out if my Powermatic was accurate I jury rigged a laser rifle.scope alignment tool to the tailstock. Slid it out to the end of bed. When rotated it scribed about a 1/4" circle around a drive center in the headstock. I think that's not bad for 34" of extension. I tried the same thing in the headstock and got maybe 1/8" circle. Now some of that could have been the Morse taper collet I used to hold the laser.but i pulled.it out and re inserted it numerous times.and got very close.to identical.readings.
 
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One other thing to keep in mind is the tolerance between the bed ways and the tailstock. Some manufacturers leave a larger gap to facilitate easy movement when the tailstock isn't locked down, and they all wear with use. The tailstock on the Jet 1640 I turned on for many years had about 3/16" side to side movement when unlocked. I got used to giving it a push to the right before locking every time I needed it to register to the same spot. Getting a new lathe solved the problem, but may have been the more expensive option. You can shim with brass stock if it's way off...
 
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