Question about drilling on the lathe

[jkeithrussell]

I've been doing more and more of my drilling on the lathe. I've noticed that often the hole ends up being a little larger than it would be if I had drilled on the drill press. Is this normal, or am I doing something wrong? I mostly use the long jaws on a Barracuda2 chuck with the blank square.

 

[DurocShark]

What kind and age is your lathe?

I found that there is just enough slop in my tailstock to occasionally expand a hole, though it is mostly in really hard materials like aluminum.

Another thing is using cheap bits and drilling too aggressively will cause the bit to flex and vibrate causing an out of round, or even oversized, hole.

 

[jkeithrussell]

The lathe is less than a year old, but I have found it necessary to tighten up the bolt under the tailstock to keep it snug. I might be drilling too quickly.

 

[Greg O'Sherwood]

First, make sure your headstock and tailstock are aligned by seeing if your centers touch points when pushed together.

2nd, when drilling using a mini lathe, I've found that the further out you extend your quill (wrong term?), the more inaccurate it can run out, so do this in short amounts, then move in your tailstock, repeat...

I've been drilling on my Jet mini for a few months and have decided to go back to using a drill press since I got my Huffman vise and new 16 speed floor drill press for Father's Day (stealth gloat). Virtually Zero runout is nice.

.

 

[mickr]

greg is on the mark..short drill depths..move tailstock, repeat

 

[jkeithrussell]

The headstock and tailstock are in aligment, I think. The 2 points of the centers are in alignment when the tailstock lock in engaged.

I am probably just working too quickly.

 

[Greg O'Sherwood]

Also make sure the taper in your tailstock is VERY clean. If the taper isn't sitting perfectly, then you can get micro-wobble (I just invented that word) that is magnified at the end of the bit. Same goes for the headstock.

 

[RichB]

One other thing which can drill a hole a little big is the length of the cutting (Flute) edge on the tip of the drill. Each length must be the same. I would sharpen one a little longer to make a bigger hole.

 

[fafow]

I had this exact same problem. I did two things and now rarely have this happen. One was to buy a set of center drills. You should be able to find a set for under $10 including shipping. The second was that I was leaving the lathe running when I backed out the drill bit. I now stop the lathe before backing out the drill bit, clean out the shavings in the flutes of the bit, run it back into the wood, then turn the lathe back on. There is an excellent tutorial on this at http://syzygypens.com/blog/2009/06/01/drilling-a-pen-blank-on-the-lathe/ He uses a collet chuck, but it works fine with a set of jaws.

Now that I am drilling on the lathe instead of a drill press I have "discovered" that the short pieces of wood are no longer a problem with the barrel trimmer. On the lathe the pilot can go as far beyond the end of the wood/tube as you want since it can go into the headstock with no problem. On my drill press I was using the pen press from Rockler and for the short pieces where the trimmer pilot is longer than the wood/tube I had to put something under the wood that was not wider than what I was trimming. It got to be a real pain at times. Drilling on the lathe, I can now see where the drill is starting the hole, and can be pretty darn sure that it will come out the center of the back end of the wood. I've been told once you get this working you won't go back to a drill press and I see now why this is so.

 

[aggromere]

I think all that is good advice. I have never drilled a square blank on the lathe. I always round it first. Although doing it square might be helpful, unless that is part of the problem, but I don't know. I do remember a post from Hank Lee about having a tiny piece of CA on the lathe bed that was messing him up. Any little thing that gets under the tailstock could be causing a problem.

 

[shull]

Make sure that you clean out both the underside of the tailstock and the lathe ways. The goal is to make sure that there is no buildup of sawdust or glue to get in the way of tightening down the tailstock for the drilling operation. Rub your finger along the contact areas and check for a smooth finish. A putty knife or a LIGHT touch with a fine file will smooth the rough spots.

Stopping the lathe before backing out the drill bit is an excellent idea and will avoid a lot of issues. Also do not run the quill out too far as already mentioned.

Good Luck
Steve

 

[rherrell]

Long jobber length drill bits tend to wobble a bit and that will result in an oversized hole. I use screw machine length drill bits whenever I can. If you don't have any, shorten up on the bit so you have just enough length for the job. Some 1/2" chucks aren't very "deep" and won't allow for it, so another option is a 5/8" chuck. That's the drill chuck I use most.:wink:

 

[jkeithrussell]

Thanks for all the tips. I'm going to break down and clean up the lathe tonight and incorporate these suggestions. I'm certain after reading all of these tips that I'm working too fast and the drill bit is getting extended too far (part of working too fast).

 

[workinforwood]

Or....use a smaller bit and when it makes an oversize hole, it will be just right! :smile-big:

 

[W.Y.]

I have not drilled on a centering device for several years since I found out how much easier and more accurate it is by doing it on the lathe. .
Unless I missed it, I don't think anyone here mentioned speed when drilling .
Here is the way I do it (sorry for the bad pictures) but even bad a picture is worth a thousand words.

http://wmyoung.proboards.com/index.cgi?board=turning&action=display&thread=6063

After the first 50 or so blanks I drilled like that I liked it so much that I sold my self centering vice for half price rather than have it sitting around in the way and collecting dust.

I even drill curved deer antlers accurately on my lathe (slightly different procedure) and that is something that is difficult to do with a centering device on a drill press.

 

[j.d.sackett]

all lathes have runout in the headstock. the higher end the lathe, the less runout. that by itself could cause the problem. add cheap drill bits, and that makes it worse. i make pens on a mini metal lathe and the runout at the chuck is about .003. doesnt seem like much, but it is. you might want to try using a slightly smaller bit than actually needed and buy a reamer the diameter you need. unlike drill bits, reamers are round, and the specified diameter. just depends on what kind of accuracy you can live with. reamer should solve most of the problem, not very expensive. good luck. regards, j.d.

 

[Randy_]

.....Here is the way I do it (sorry for the bad pictures) but even bad a picture is worth a thousand words.

http://wmyoung.proboards.com/index.cgi?board=turning&action=display&thread=6063 .....

That link doesn't work unless you are a member of the forum.

 

[W.Y.]

That link doesn't work unless you are a member of the forum.

It should now.
Let me know if it doesn't

 

[titan2]

It should now.
Let me know if it doesn't

Nope.....still have to join........


Barney

 

[W.Y.]

Nope.....still have to join........


Barney

Thanks for the heads up. I thought I had it set for members only some time back to get rid of some spammers but since then opened it to the public. I will re-check my settings .

 

[txbob]

Well, I didn't know it was so difficult and had to be so precise. I turned a wooden handle about 1" diameter and 4" long, drilled a 7mm hole in it, and glued in a 7 mm bit. To drill a blank I use the point of my skew to make a dimple in the end of the spinning blank, then I just hand hold the drill bit, by its handle, as I drill the hole through the blank, backing out several times to clear the chips. I've drilled maybe 400 or 500 blanks that way. I'm glad you guys told me it won't work, or I would have kept on doing it that way.
txbob

 

[W.Y.]

Nope.....still have to join........


Barney

Thanks Barney.
It should work now

http://wmyoung.proboards.com/index.cgi?board=turning&action=display&thread=6063

Sorry for the inconvenience.