help for newby

[gtrost]

I just started my first turn and have several questions. #1 Why does my blank turn? Is it because my end screw isn't tight enough. The pulley on my teigh lathe goes clockwise and does pulley speed have anything to do with it. Thanks for your time, Gary

 

[tomwojeck]

Gary,

I've had the problem with the blank spinning when I try to take too much wood off while it's still square. You really need to have a lighter touch when it's still square.

You can try to tighten the end screw a bit, but if you do it too tight, you can bend your mandrel and end up with an oval pen.

I'm not sure about the pulley question.

Welcome to the group!

 

[Fleabit]

If you take too much bite on the blank, it will spin on you as stated by Tom above. The end screw should only be tight enough to keep the bushings and blanks togather and than I just give it a slight tweak to snug everything.

 

[elody21]

Gary,
The problem could be the brass tube inside of your blank has come unglued. This can happen sometimes especially when you are turning hard wood or acrylic or corian. If you are having trouble with the tube spinning in acrylic or corian try this. After you rough up the tube with sand paper clean it with alcohol and clean the inside of the drilled blank with alcohol using a cotton ear swab. This also works very well on hard oily woods like cocobolo and ebony.
If it is not your tube maybe you are not getting your ends trued up well. This will cause less surface to be held by the nut.
Be very careful about tightening the nut too much. If you get it too tight it will cause your mandrel to bow and your pen will be oval.
Good luck and let us know how it goes. Alice
PS I agree about the too much bite at a time also!

 

[JimGo]

Gary,
I'll second what was said here; I had the same problem when I started (not that long ago!). My problem was that described by Alice (Elody21) above, and Alice has the right solution. The only caveats I would add are, you might want to use denatured alcohol (DNA), rather than regular alcohol, especially inside the blanks. I'll also strongly second her comment about using DNA, especially in oily woods; the oils tend to make for a poor joint when gluing, and the DNA helps get rid of the oil, at least temporarily. Oh, and try not to handle the body of the tube (or handle it as little as possible) since your body's oils may also cause the same problems.

If you're using CA to glue your blanks, make sure you're getting a nice, fairly tight fit between the tube and the blank, since most CA doesn't fill gaps all that well (requires surface-to-surface contact). Even thick CA, which is somewhat "gap filling" will not fill large gaps. By contrast, if there's a bit of a gap, the better choice might be Gorilla Glue or another polyurethane glue. The poly glues swell as they cure, which makes them more gap filling. The trick with the poly's is that they require water to cure properly. Some have suggested breathing inside the blank to add moisture. I used a cotton swab dipped in water inside the blank to just LIGHTLY moisten the joint. But be careful; too much water will cause the wood to swell, and may actually make the joint too tight. (do a search on Gorilla Glue for a lot of other tips)

Remember, though, that even with poly glue, you want to be careful not to drill TOO large of a hole. Most of the pens are turned to within 1/32-1/64 of an inch of the tube, which means you don't have a lot of room to play with.

You asked about tightening the knurled nut; see http://www.penturners.org/forum/topic.asp?TOPIC_ID=3740 for a discussion of why not to overtighten the nut.

Finally, Fleabit and Tom's comments about taking small bites at first is also very good advice; I have had some pieces that were glued properly, but that just REALLY wanted to spin on the mandrel. Had to barely touch the wood to them until they were closer to round, then they turned just fine.

Welcome to IAP and good luck! As everyone told me when I started, BE SURE TO POST PICTURES OF YOUR PENS!

 

[gtrost]

Thanks to all for the advice on the spinning blank. This is a great learning tool for the new ones. Thanks again Gary

 

[53Jim]

I would like to add another possible cause. Today I was turning a pen and the blank started to spin. I spent a few second at the slow spped grinder, and I was back at it. Sharp tools seem to keep the blank from turning.
Hope this helps
Jim

 

[elody21]

Hey JimGo,
I actually do use denatured alcohol. It is what I happened to have on hand when I started doing the inside of the blanks and outside of the tubes. I would be interested in knowing what the difference is and why denatured is better. Thanks!

 

[Fred in NC]

Alice, rubbing alcohol (isopropyl) has water in it, usually 10% or more. Drug store rubbing alcohol sometimes has other oily substances in it. DNA is closer to 100% pure alcohol, has mostly ethanol with some wood alcohol that makes it undrinkable.

Bottom line, works better and dries faster.

 

[elody21]

Thanks Fred for the info!

 

[swm6500]

I agree with the small bites. Those square corners just reach out and grab the tool.

 

[Rifleman1776]

Alice said, "Be very careful about tightening the nut too much. If you get it too tight it will cause your mandrel to bow and your pen will be oval."
That is the common thought on tightening. You will never see contrary advice, except from me. [] The truth is I have never understood that advice. The bushings and nut force the wood together while having a stretching effect on the mandrel. That would make it stiffer and straighter. In some kinds of engineering it is called stressing for strength. I really crank down on my tightening nut as the force is against the tubes and bushings. I do that so the blanks do not turn on the mandrel. My experience and opinion. For whatever it is worth, or worthless.

 

[JimGo]

Interesting point, Frank. I never really thought about it. I'm an EE, so I don't know much about mechanics, but from what I can figure it should depend on whether the force from the knurled nut pushes the mandrel into the headstock, or whether it actually pulls it out of the headstock. If the nut pushes the mandrel in, then you'd likely induce bowing, which would be exacerbated by the centrifugal force as the lathe turns. If it pulls the mandrel out, then you might be pulling the mandrel straighter. However, this assumes that the ends of the bushings are perpendicular to the mandrel's axis of rotation; if they are crooked, and the nut is sitting tightly against them, then wouldn't the bushings make the nut crooked too, thereby causing bowing?

I'm not trying to start an argument...It's just the technical side of me is curious to figure out what the best approach is. I mean, heck, you make some GREAT looking pens! Do you notice any of them being out of round? For example, if you make a slimline without a centerband, can you rotate either half and not notice any changes in the fit between the pieces?

 

[lkorn]

Jim,
I think your intuition is right on! The flimsy brass nut is NOT going to either straighten OR Bow the STEEL Mandrel no matter how much you tighten it. It WILL however create an out-of-round barrel because of the little bit of play in the bushings. They have to be oversized in order to slide easily onto the mandrel. ANY play in the fit of the bushings will show up in the turning and will be exacerbated by overtightening the brass nut.

 

[Old Griz]

The most common cause of bowing the mandrel is actually not the brass nut, but over tightening the tail stock center... that will definately cause the mandrel to bow...
You want to touch the tail stock center to the mandrel, turn the lathe on to low speed and just tighten the tailstock until the center turns freely and no more... I tighten the brass nut just enough to keep the blanks from moving freely...

 

[Rifleman1776]

Jim, as they say, first things first. Being an old-timer and a writer, I may be one of the few left who doesn't view the word 'argument' as bad or negative. It is simply an exchange of ideas in a give and take discussion, whether in person or e-wise. And that is, as I understand it, the purpose of the forum. Discuss viewpoints, if we all thought alike there would be no need for the fourm. I digress, this should be in casual conversation. You said, "I mean, heck, you make some GREAT looking pens! Do you notice any of them being out of round? For example, if you make a slimline without a centerband, can you rotate either half and not notice any changes in the fit between the pieces?" I am flattered by your comments. No, my pens are round and and ends fit fine, with or without centerband. I do believe, however, that it is ESSENTIAL that blanks be squared properly before being placed on mandrel for turning. I use small brass washers between spacers or bushings before putting the nut on mandrel. That minimizes chances of pressure on the blank, all stresses are then on the tubes. I think, I hope. [] It works for me.

 

[jdavis]

Griz is right, the tailstock causes the bow in the mandrel. Tightening the brass nut only secures the bushings and wood together. Keep tools sharp and light cuts on square stock.

 

[JimGo]

Frank,
Thanks for the feedback. I like the idea of the washers; may have to steal that for myself!

I'm still pretty new to this, so my comments should be taken from that perspective. However, when I first started I would tighten the nut pretty well, and I wound up with blanks that were pretty significantly out of round. I then switched to a looser nut and tighter tail stock, and found that I still had the same problem. I now do what Jack and Tom mention above, as was suggested by Lou (DCBluesMan) when I met with him. That is, I keep the nut loose, and bring the tail stock up until it sits at the end of the mandrel without touching (I double-check the alignment at this point, too). Then I turn the lathe on and slowly turn the hand wheel on the tailstock until it starts to spin with the mandrel. Then I turn the lathe off and hand-tighten the knurled nut.

In my older turnings, like I mentioned, I could see the "oval" shape to the blanks, especially where the wood met the different pen parts. I recently made some Jr. Gent's and a slimline using this new technique, and the results have been MUCH better. On one of the Jr. Gent's (the one I carry every day), I can feel a SLIGHT difference on one end (maybe a couple 100'ths), but it's the kind of thing that you have to really be looking for to see/feel, and I think I can chalk that up to a slightly bent mandrel. One of these days I'll sit down and make sure everything is truly square.

 

[Ryan]

I know that the bushings play a BIG part in the final out come of the pen. I can turn 4 different styles of pens and if one of them is a statesman I can count on the first 3 being round and the statesman being slightly oval. There seems to be a problem with these bushings. CSUSA is looking into it further since I and one other person have brought it to their attn. I can take a TON of time making sure the blanks are square and the mandel is straight. as soon as I put the bushings and blanks on even the slightest twist of the brass nut sends everything out of wack. It has been frusterating since I sell a lot of these pens.

I don't want to be long winded but the only fix I have been able to come up with for the statesmans is below.

1. For the smallest diamiter bushing I use one of the cap bushings from a jr statesman. This seemed to help a lot.

2when I am getting close to the final thickness, I loosen the brass nut and rotate JUST THE BLANK 90'. You need to make sure bushings DO NOT rotate.

I still end up with a slight bow but the above seems to help some.

Ryan

 

[DCBluesman]

I'm pretty much with Frank and Tom on this. Square, square, square. If anything isn't, tightening the knurl nut or the tailstock will cause lateral pressure on the spindle and bowing.

 

[Ron in Drums PA]

I think what "MAY" happen when the brass nut is to tight is that the wood my be compressed by the bushing. And if one side of the wood is "Softer" the opposite side you will bow the shaft.