drilling on lathe

[dachemist]

I've been having some difficulty drilling straight, constant diameter holes on my lathe (VS Jet mini, lowest speed). The drill bits keep flexing (bending in an up and down, kind of circular motion) as I drill leading to "oval" holes. It happens regardless of size or type, dull or sharp. I'm rather worried one is going to snap in half at some point. For pen blanks it's not such an issue (Gorilla glue to the rescue ) but there's still the safety aspect of it. I'd prefer not to have pieces of steel flying through the air at high speed. Any thoughts? Or should I go buy a drill press?

Thanks


Mike

 

[Dario]

Like turning, the culprit could be your drill mandrel, bent drill bit, improperly mounted bit, dirty MT2 taper or driver, etc.

 

[ed4copies]

Or your technique.

IF you hit the center of the spinning object with the center of the drill bit, WHERE will you get deviation?

Don't lock down the tailstock, bring it up by hand and hit the center of your blank. Ease the tailstock (and drill bit) forward by pushing ir forward along the ways. (rails) GENTLE. It WILL go straight.

[][][][]

If you get bored with pen blanks, try a pepper mill (6-9" long)!!!!!

 

[RONB]

Check the alignment of the tail stock to chuck for out of center condition. A little bit of play makes a big difference. I drill all of my blanks with the lathe. I don't own a drill press.

 

[ed4copies]

Originally posted by RONB
<br />Check the alignment of the tail stock to chuck for out of center condition. A little bit of play makes a big difference. I drill all of my blanks with the lathe. I don't own a drill press.

This could VERY WELL BE your problem, but if you don't LOCK it down, the problem goes away!!

 

[Rifleman1776]

I think Ed's first post may be the best guess as to the problem. Technique, bits flexing is not common. Nor is it easy to do. Without watching you work, I can only surmise you are putting way to great a pressure on the bit as you push it in. When I drill on the lathe I bring the tip of the bit to the work by sliding the tailstock the locking it. I then feed by turning the handle on the tailstock center for almost it's full length, then back out, clear chips, crank in the center, bring back up to work, insert bit into wood and repeat process. It is a very accurate way to drill. Slow but accurate. Let the bit do the work. Don't force.

 

[ed4copies]

You are absolutely correct, Frank.

However, with my old Delta, the front rail is worn slightly more than the back, so if I LOCK the tailstock without a shim on the front rail, it will be ever-so-slightly off. BUT, with the tailstock LOCKED in place, I could imagine some pretty interesting vibration resulting, as it tried to drill with the tailstock actually out of alignment.

This is what I am presuming is happening - not necessarily the ways are worn, but SOMETHING is putting the bit at a very slight angle to the center. By not LOCKING it, the drill WILL seek center.

Hope this helps!!

 

[Rifleman1776]

Originally posted by ed4copies
<br />You are absolutely correct, Frank.

However, with my old Delta, the front rail is worn slightly more than the back, so if I LOCK the tailstock without a shim on the front rail, it will be ever-so-slightly off. BUT, with the tailstock LOCKED in place, I could imagine some pretty interesting vibration resulting, as it tried to drill with the tailstock actually out of alignment.

This is what I am presuming is happening - not necessarily the ways are worn, but SOMETHING is putting the bit at a very slight angle to the center. By not LOCKING it, the drill WILL seek center.

Hope this helps!!

Accurate assessment, Ed. But with bits FLEXING, methinks something else comes into the picture.

 

[smoky10]

Another thing, make sure your blanks are square. If they're not square they will be off center in your chuck.

 

[Texatdurango]

My opinion…….. Long winded as usual!

I think it goes a little further than to just say tailstock locked or unlocked. In my case, my tailstock is loose on the bed and can easily be “cocked†while pushing along the bed. So to say I can get a straighter hole by pushing the tailstock “unclamped†by hand, really depends on where and how much pressure is applied on the tailstock.

Explanation:
In the photo, Fig C and D are the result of the position of the tailstock in Fig A and B.

My photography is poor but Fig C shows that the live center is off to the “right†(enough to cause a bad hole or out-of-round pen blank) while Fig D is centered and will give a good clean hole or a round turned blank.

Again, in the photo, fig A and B show the tailstock sitting loosely on the rail. In fig A, the tailstock is actually cocked to the right and even if pushed by hand in this position will continue to “skew†the hole because the tailstock is at a slight angle to the headstock and any resistance from the material being drilled will cause the bit to wobble back and forth between straight and cocked.

In Fig B, the tailstock is true to the center of the headstock and if I apply deliberate pressure to keep it in this position while drilling, the hole will come out a LOT more centered and clean. But… if I clamp the tailstock down while in this position, it even gives a truer hole.

I think that learning the characteristics of ones lathe goes a long way to learning what causes what, as each lathe is different and there is on one correct answer to a problem.

I didn’t realize how critical the position of the tailstock could be until I recently started drilling on the lathe and noticed slight variations on identical blanks.

That said, once I know what I’m doing, there is nothing in my shop that can equal the accuracy of drilling on the lathe.

I also drill as slow as I can get the lathe to go!

<br />

 

[gerryr]

One thing nobody asked is what kind of drill chuck do you have? Your description sounds a lot like the trouble I had with one I bought from Sears. It was the worst piece of junk I've ever encountered, well maybe tied with the tiny 3 jaw chuck from PSI for worst.[!]

 

[Randy_]

All of the suggestions sound like good things to look into. I've drilled a few blanks on my lather and never had a problem so I can't help with any first hand solutions.

It might help if we knew what kind of bits you were using.....normal twist drills, brad/bullet point bits, split point bits? The fact that the bits are flexing is scary. That shouldn't happen when drilling wood unless you are using excessive pressure or the bits are of very cheap manufactures and have very thin webs. Are these bits relatively new and presumed to be sharp and correctly sharpened(not necessarily a good assumption) or are they well used?

It really shouldn't be necessary, but a center bit might help your drill bits get started off in the right direction.

I would cut some scrap pieces of 2x4 to blank size and experiment with the suggestions above until you figure out where the problem lies. There is no reason that you can't drill good holes with a lathe. Actually you should be able to do a better job than you could with a drill press. You just need to track down what you are doing wrong.

Do you have a Woodcraft or Rockler store close by or maybe a woodworking club. Chatting with a live body is frequently the best way to solve a problem.....although sometimes not all of the people in the stores are equally competent.

 

[Paul in OKC]

I said something about a center drill in a previous post about drill problems. (thanks for the pic, Randy). I think some or most of the problems with srilling are the same whether in the lathe or on a drill press. The squareness of the end being drilled can be one of the most, IMHO, problem areas either way. If not fairly square, you will get drill wobble. End grain and grain related things are up there too. Being a machinist, if I want a hole to start true in metal, I use a center drill. Same with wood, if I am concerned about the drill running out or not starting straight, I use a center drill as well. Just my 2 cents.

 

[dachemist]

First thanks everyone for all the replies. I posted the question at work during lunch so I tried to keep it short. I've been drilling as Ed and Frank described and it worked fine for a number of times and then suddenly I was concerned with having to dodge flying steel. The headstock is slightly off kilter (been meaning to try shimming it). I've tried all sorts of bits, new, sharp, dull, cheap, expensive, the various tips and all have had the wobble. I think I bought the drill chuck from the local WC before they went out of business [], not the greatest but not the cheapest either. I suspect Dario may be on to something with the dirty taper comment. The inside of the taper is kind of scary with tiny spots of rust. I've tried cleaning it but have had no sucess. I was contemplating getting a MT2 reamer from Enco ($35 isn't exactly cheap, but it could be worse, it beats trying to explain to the wife the need to buy a new lathe) but have some concern I may make things worse. The ends of the blanks are far from square as well though (been meaning to get a miter saw...hmmm...Christmas is coming up soon...)

Thanks again everyone.

 

[Dario]

Mike,

I learned about the dirty MT2 driver hole the hard way. The giveaway for me was all my MT2 tapers were getting a ring line/scratch around them at the same location. I did buy an MT2 reamer and that solved my problem.

 

[Rifleman1776]

Originally posted by Dario
<br />Mike,

I learned about the dirty MT2 driver hole the hard way. The giveaway for me was all my MT2 tapers were getting a ring line/scratch around them at the same location. I did buy an MT2 reamer and that solved my problem.

Dario, where did you get your reamer? I want one also but hate to pay the big prices I see.

 

[Jim in Oakville]

You have a lot of great advice here and you should start with the alignment issue first. Making sure your tail stock lines up with your head stock is the base that everything else and variation is stacked up on. I put a live centre in the head stock and a another one in the tail stock and bring them together...they need to be point to point, otherwise you need to investigate why. Using a pen mandrel as your alignment tool for the head stock assumes you have a straight mandrel, many are not straight.

I clean my MT with out a commercial reamer, I use a mix of Ajax on a shop towel that I pull through the MT on the HS to clean it out and I use a bottle brush and shop towel in a similar fashion on the TS every now and then.

I have a manual Jet Mini and it's been a steady performer now for 5+ years.

I gave up the drill press as part of my pen making routine 4 years ago and I will never go back. I use a Talon with spiggot jaws to hold my blanks and I use a Jacobs chuck in the TS to secure my drill.

I do like Ed4copies, bring the TS up and touch the blank, allow the drill to find it's centre and and then gently secure the TS and drill out my blank...I make about 300-350 pens a year and can think of two times in the last 4 years that I lost a blank...It's also the method I teach in my classes at LV.

Alignment of the TS and HS is your starting point, all other variation builds on it, and also having sharp tools helps too.

 

[Fred]

I believe that if you are getting the same troubling wobble with all the different bits that you say you have used, then it has to be the lathe. First do like Jim suggests, mount a center into the head stock (HS) and another into the tail stock (TS). Then bring the TS up to the HS and check that the two center points are in line with one another. Any deviation and you have found your problem right away. You will then need to 'fix' the deviation either by shimming one or the other. Since most HS are set in place I would try to eliminate the problem there. That way the shim remains in place. Shims applied to the TS may tend to pull out of place as the TS is moved. Check with the manufacturer of your lathe about the best way to shim the machine. Heck, they may be aware of this problem and have a solution for you ...

If the points of the two centers are aligned, then the problem is with the drill chuck. Try a different drill chuck and see if the problem persists. If it does then the problem is in the MT of one of the MT's. Clean the MT's with a rag and some WD-40. Examine the rag and look for tell tail signs of rust, dirt, etc. Examine the MT of the drill chuck and look for scratches. The shaft should be clean and scratch free. Clean the MT and use the WD-40 to coat it very lightly. If you find a ring around the MT of the drill chuck, then using a fine grit sand paper designed for use on metal, clean and polish the MT of the HS or TS, clean with WD-40, clean the MT of the drill chuck, remount and drill something. Check for the problem.

If the problem persists, go get a beer, sit down relax a bit, take a nap, etc. Get dressed, grab the checkbook, kiss the wife good-bye, tell her you will be right back, and go to the local WC, Rockler, etc., and take stock of your next lathe. Probable choice would be the big Powermatic (excellent lathe by the way) that has always caught your eye when you went into the store.

That's my idea's on this perplexing subject... Good luck! []