A case of the shakes

[Art Moore]

I have a cheap HF 10X18 lathe that I use for turning pens and small spindles. It has developed a shake when drilling pen blanks - but only wooden ones. With acrylic it's solid as a rock. I've cleaned the belt and pulleys, have retightened all the bolts, and have tried making a starter dimple with a center drill. So far, no luck in getting rid of the shake. I've taken all the side to side slop out of the quill, but it still has a very small amount of upward deflection - so small that trying to use a single piece of masking tape as a shim is too much to allow the quill to retract into the tail stock (which is tight when locked down).

Does anyone have a suggestion on where to go next? I've got to be missing something!!

[Clint Bach]

Use sharper/ better drill bits? New drill bits?

c

[Don Jarvie]

If I am understanding correctly the drill bit is wobbling or the blank is wobbling so you are getting off center holes after drilling, correct?

If the blank is wobbling make sure its square and seated in the chuck correctly. I've had this issue and now I make a dimple in the blank and set it loosely in the chuck and pull the tailstock with the drill in it up to the blank and set it in the dimple then tighten the chuck. This will make sure the blank will be set right and eliminate the wobble.

If the drill bit is wobbling then I just go very slow and keep backing the bit out frequently.

If you still have an issue then consider drilling the holes on a drill press and use a barrel trimmer to square the ends of the blank to the hole. This way if the holes are off center the trimmer will square the ends and account for this so when the blank is turned it will come out even.

I hope this helps.

[John K Jordan]

I'm assuming you are drilling on the lathe like most, with the wood held in a chuck and the drill bit in a jacobs chuck in the tailstock on a morse taper mandrel.

Is the vibration from the hole deflecting off center, following the fibers in the wood? If so, you should be able to see the bit deflect while drilling.
I always start holes with a center drill. I usually use the largest one in the set.

center drills.jpg

Could the bit or bits be getting dull? If so, perhaps try a new bit. Some like the standard grind, some like brad point.

It's important that the drill bit be perfectly aligned with the lathe axis, otherwise the bit can enter in the center then try to drill off at an angle, or enter off-axis, either can make the hole too big or cause the kind of vibration you mention. If the bit has some upward slant as you mentioned I think that would the first thing I'd try to solve. Might first check the morse taper socket in the tailstock to see if there is any dust or buildup that needed to be cleaned or a burr that is causing the jacobs chuck to not sit parallel to the bed. If you have a dial indicator and can mount a piece of perfectly straight drill rod in the chuck you could move and lock the tailstock down and see if the rod is parallel to the bed. (The lathe bed must also be perfectly straight.)

I use a taper cleaner occasionally. If there is a scratch or burr inside it may need to be carefully filed or sanded away with a piece of sandpaper on a dowel rod. And of course check the drill chuck MT for burrs. I've had to remove burrs on tapers more than once. (If the taper ever spins in the headstock or quill either or both surfaces can be galled.) Shimming may be the only fix in some cases.

Is the lathe aligned? One quick check is to put point centers in the headstock and tailstock and slide the tailstock up till they are almost touching. The points should line up exactly, assuming no problems with the morse tapers as mentioned above. If the points are off left or right, the bed may be twisted and can usually be untwisted by adjusting the height of one leg. If off vertically, shimming may be in order. I've shimmed a problem case with shim stock used by machinists and mechanics. The leaves in a feeler gauge can make good shims. Before shimming anything, check the mating surface on the bottom of the tailstock for nicks or dents.

Is the jacobs chuck in good condition? When I can, I use a taper shank bit instead of mounting a bit in a drill chuck. These fit right in the tailstock quill and eliminate distance and some possible sources of deflection. Unfortunately I don't have them in every size. The same diameter bit in a jacobs chuck:

taper_2_IMG_20160919_094945.jpg taper_1_IMG_20160919_094408.jpg

Does your quill have an adjustment to take up play? Mine has a set screw on the far side. Is the lathe old, maybe parts worn? (Hey, Christmas is coming, a new lathe would look great under the tree! )

Do you know another turner with a similar lathe you can try using with your chuck and drill bit and everything? If it shows the same problem, substituting things one at a time might narrow down the problem. If they have the same lathe, you might even try your tailstock on their lathe to make sure that's not the problem.

That's all I can think of at the moment.

JKJ

I have a cheap HF 10X18 lathe that I use for turning pens and small spindles. It has developed a shake when drilling pen blanks - but only wooden ones. With acrylic it's solid as a rock. I've cleaned the belt and pulleys, have retightened all the bolts, and have tried making a starter dimple with a center drill. So far, no luck in getting rid of the shake. I've taken all the side to side slop out of the quill, but it still has a very small amount of upward deflection - so small that trying to use a single piece of masking tape as a shim is too much to allow the quill to retract into the tail stock (which is tight when locked down).

Does anyone have a suggestion on where to go next? I've got to be missing something!!

[Art Moore]

I'm assuming you are drilling on the lathelike most, with the wood held in a chuck and the drill bit in a jacobs chuck inthe tailstock on a morse taper mandrel.

Is the vibration from the hole deflecting off center, following the fibers inthe wood? If so, you should be able to see the bit deflect while drilling.
I always start holes with a center drill. I usually use the largest one in theset. JKJ

It appears to be. As soon as the bit touches the blank,it deflects; looks like it moves slightly upwards and towards the right, even afterusing a center drill to dimple the blank first. But – Acrylics drill straightand true. That leads me to think you’re right on point – it’s got to begrabbing the grain.

Could thebit or bits be getting dull? If so, perhaps try a new bit. Some like thestandard grind, some like brad point.

It's important that the drill bit be perfectly aligned with the lathe axis,otherwise the bit can enter in the center then try to drill off at an angle, orenter off-axis, either can make the hole too big or cause the kind of vibrationyou mention. If the bit has some upward slant as you mentioned I think thatwould the first thing I'd try to solve. Might first check the morse tapersocket in the tailstock to see if there is any dust or buildup that needed tobe cleaned or a burr that is causing the jacobs chuck to not sit parallel tothe bed. If you have a dial indicator and can mount a piece of perfectlystraight drill rod in the chuck you could move and lock the tailstock down andsee if the rod is parallel to the bed. (The lathe bed must also be perfectlystraight.) JKJ

It doesn’t matter if it’s an old bit or a brand new bit,the problem is the same. I’ve removed the quill from the tailstock, cleaned itwith acetone, and carefully inspected it for burrs and I can see none. I boughta new jacobs chuck as well – no change.The HF lathe has so much play in it that I haveto carefully align it when I set the bit up next to the blank (which is mountedin one of PSI’s dedicated Pen Drilling Chucks.The entry holes in the blanks areoversized due to the shake, but the exit holes are the correct size. I cancompensate by cutting the blanks about 3/8 to ½ inch oversized, but that’s justa crutch to use until I can get this figured out.

I use ataper cleaner occasionally. If there is a scratch or burr inside it may need tobe carefully filed or sanded away with a piece of sandpaper on a dowel rod. Andof course check the drill chuck MT for burrs. I've had to remove burrs ontapers more than once. (If the taper ever spins in the headstock or quilleither or both surfaces can be galled.) Shimming may be the only fix in somecases. JKJ

I can’t see a burr anywhere inside the quill, and thejacobs chucks are smooth and clean.

Is thelathe aligned? One quick check is to put point centers in the headstock andtailstock and slide the tailstock up till they are almost touching. The pointsshould line up exactly, assuming no problems with the morse tapers as mentionedabove. If the points are off left or right, the bed may be twisted and canusually be untwisted by adjusting the height of one leg. If off vertically,shimming may be in order. I've shimmed a problem case with shim stock used bymachinists and mechanics. The leaves in a feeler gauge can make good shims.Before shimming anything, check the mating surface on the bottom of thetailstock for nicks or dents. JKJ

With so much slop in this lathe tailstock, I have tomanually slide the thing back and forth to get a good alignment, but thevertical alignment is spot on. I’ve made a jig that I can drop in behind thetailstock that will help align it when I move the tailstock along the bed.

Is thejacobs chuck in good condition? When I can, I use a taper shank bit instead ofmounting a bit in a drill chuck. These fit right in the tailstock quill andeliminate distance and some possible sources of deflection. Unfortunately I don'thave them in every size. The same diameter bit in a jacobs chuck: JKJ

All three of the jacobs chucks are in good shape; two ofthem are less than 2 months old. I have no taper bits...

Does your quill have an adjustment to takeup play? Mine has a set screw on the far side. Is the lathe old, maybe partsworn? (Hey, Christmas is coming, a new lathe would look great under the tree! ) JKJ

The only adjustment on the tailstock is the locking handle for the quill. Iagree a new lathe would look purty under the tree; but I have to justify thatto SWMBO first <LOL>

Do youknow another turner with a similar lathe you can try using with your chuck anddrill bit and everything? If it shows the same problem, substituting things oneat a time might narrow down the problem. If they have the same lathe, you mighteven try your tailstock on their lathe to make sure that's not the problem.

That's all I can think of at the moment. JKJ

Unfortunately I don’t know any other turners in town,although I’m sure there are several. I want to say thanks for all yoursuggestions – There’s some food for thought there and I’ll keep digging intothis problem.

Art

[Clint Bach]

Screw machine drill bits may help. They aren't as easy to find though. They are shorter and stiffer than jobber drill bits. They just might solve your problem.

C

[John K Jordan]

Screw machine drill bits may help. They aren't as easy to find though. They are shorter and stiffer than jobber drill bits. They just might solve your problem.

Are they long enough to drill through a typical pen blank? The bits in the set I have seem too short. The flute on a 7mm screw machine bit is only 34mm.

[Clint Bach]

I'm not sure about the length but by clearing the flutes by backing them out occasionally you can drill as deep as the amount of the bit sticking out of the chuck. Once you get that deep you could change to a regular bit and it should drill straight the rest of the way. I seem to have to clear the flutes on regular bits to get them that deep anyway. The stiffness of a screw machine bit will probably get the hole started properly... I haven't tried this.

[Leo Van Der Loo]

I have a cheap HF 10X18 lathe that I use for turning pens and small spindles. It has developed a shake when drilling pen blanks - but only wooden ones. With acrylic it's solid as a rock. I've cleaned the belt and pulleys, have retightened all the bolts, and have tried making a starter dimple with a center drill. So far, no luck in getting rid of the shake. I've taken all the side to side slop out of the quill, but it still has a very small amount of upward deflection - so small that trying to use a single piece of masking tape as a shim is too much to allow the quill to retract into the tail stock (which is tight when locked down).

Does anyone have a suggestion on where to go next? I've got to be missing something!!

Rather than just make a dimple with the center drill bit, drill deeper with the center drill bit, and use a lager centering drill bit, so your drilling bit can start right in the drilled opening, that should keep the drill from wandering.

[Michael Costa]

Intersting,I I've always used my drill press with a 7mm bit for pens.

[Dan Hunkele]

Using the tip of your skew to put a dimple in the end of the blank will automatically find center for you.

[John K Jordan]

...The stiffness of a screw machine bit will probably get the hole started properly... I haven't tried this.

I've used the screw machine bits a lot on the lathe for shorter holes. Ruth Niles even sells them sized for tapping the 3/8" thread on her stainless bottle stopper hardware, handy to keep with the supplies rather than hunt for the right bit in a set.

I have drilled short holes with these without a starter hole in some woods (like ebony) but out of habit (and a few bad experiences) I almost always make a starter hole/dimple.

I keep a center drill bit in a spare jacobs chuck so it's very quick. If that chuck is in use for something else I use a parting or other tool to make a starting cone. I haven't tried starting with the S/M bit then switching to a longer bit but it makes sense for problem cases.

BTW, a spotting bit made for CNC use also works well to start a hole. These are also short, sturdy bits. More expensive than the center bits.

None of this may work, of course, if Art's lathe is misalligned as he suspects!

JKJ