Out of round barrels

[Dan_F]

I seem to be having a problem with barrels ending up out of round, which I used to think was a mandrel problem, until it happened even using JohhnyCNC's bushings. Upon closer inspection of this last one with a 10x loupe, it appears that the brass tube is not centered in the blank. I used epoxy, which I thought would have centered the tube, but then laid it down flat. The epoxy seemed firm enough to keep the tube from settling, but I guess not.

The blank in question was acrylic, so the tube and blank were painted with model paint which I now realize might have settled as it was drying and contributed to the problem as well.

So the question is, how do you go about keeping your brass tubes centered after glue up?

Dan

 

[Texatdurango]

I don't know what size you drill your holes but it sounds like you have a lot of slop in your holes. Have you tried a smaller bit?

 

[Rifleman1776]

Search 'no mandrel' method of turning. Might help.

 

[Russianwolf]

it can be several things.

1)headstock and tailstock aren't aligned properly. With the dead center and live center in place the tips should come together perfectly. If they aren't, it can cause out of round when everything else is fine.

2)the blank ends are not milled square to the tube. The centers will reference the buskings correctly, but if the bushings are seating properly (due to the ends not being square) then it could lead to out of center turning.

that's the two biggies.

 

[jwoodwright]

You don't say what pen and a photo usually is best.

If 7mm kit, largest bit should be 9/32" ala Russ Fairfield and using poly.

Should have no slop. From the end, you should only see tube,ring of glue and material...

 

[johnnycnc]

Dan,
If your tube and blank were both painted with model paint,
and you glued together using epoxy(thicker than ca glue),
and still had room to float around,you may want to re-evaluate
your drill bit,and possibly your drilling technique.
Not all bits will leave a hole the size they are marked,
and many bits will do oversize holes in acrylic if things
get hot.
Also,I will ask;does the out of round happen EVERY pen,no matter what?

I'll strongly second Russianwolf's suggestions,
1.)head and tail stock alignment has to be there.
2.)blank end square to inside of tube</u>.(not outside of blank)
and I'll add:
3.)sharp tools.I mean scary sharp tools! I can turn out of
round pure garbage on my setup, with my bushings</u>[:0],
IF I let my tools go dull.Hey,it happens!
You're busy enjoying turning,sharpening is a hassle,....

These 3 things will solve most major out of round issues,
no matter what setup you're using,within limits.
Hope there is something in all the replies that helps!

 

[Firefyter-emt]

Dan, I understand what you are saying, but I can't see where it would be an issue. Your "rough turn" should round out the blank centered to the tube way before you get to the pen diameter. Unless you press so hard that the blank never becomes round, then that is not your problem. If your hole is too big, you have more of a problem of blow outs than out of round.

Have you "aligned your tips" to see if your headstock is in alingment to the tailstock? Use the dead center and the live center and see if the centers match. I like to "hold" a thin metal 6" ruler between the centers as well. It should stay straight, if it moves to one side then they are not in line.

 

[Dan_F]

First off, this happens even when turning between centers with the CNC bushings, so I'm sure it's not a mandrel problem. I will try to get a pic with a closeup big enough to show the problem. It is a matter of the brass tubes not fitting precisely in the holes in the blank.

Even with recommended drill sizes, there is often a slight amount of slop in the holes, especially at the top, and my brass tubes tend to find the extra space and migrate to one side, which throws off the barrel just that much. It is fairly sublte, hard to see on the finished pen, but easy to feel.

This is happening on Sierra and Carbera blanks. I haven't done any Slimlines.

Dan

 

[Texatdurango]

Originally posted by Dan_F

First off, this happens even when turning between centers with the CNC bushings, so I'm sure it's not a mandrel problem. I will try to get a pic with a closeup big enough to show the problem. It is a matter of the brass tubes not fitting precisely in the holes in the blank.

Even with recommended drill sizes, there is often a slight amount of slop in the holes, especially at the top, and my brass tubes tend to find the extra space and migrate to one side, which throws off the barrel just that much. It is fairly sublte, hard to see on the finished pen, but easy to feel.

Well, if you are satisfied that you are using the right drill bit, have you checked the bit to make sure it isn't bent or that your drill press is 90 degrees to the blank when drilling? If you can insert the bit into the blank after drilling and see a gap on one side or another, it is either a bad bit or misaligned drill press. Look at your tools.

 

[rlharding]

The only way the tube can be smaller than the hole in the blank (it doesn't necessarily make any difference of the hole is not drilled on centre)is that you hole is bigger. Sorry, not meaning to sound 'cute'.

If the hole is bigger you need to start from the beginning and every time you make any change to the blank (I'm leaving that broad)test the fit of the tube. You may find that you have the correct size drill but you also have significant drill wobble.

How did you decide which drill bit to use? Did you do a test by putting the bit next to the tube?
Did you have the instructions that provide the drill dimensions? I seem to recall a conversation a couple of months ago about a supplier listing the incorrect drill bit. Unfortunately I didn't pay any attention to it as I didn't make the pen in question.

Also, you say that you are using Johnny's CNC bushings and then talk about your mandrel. What people are referring to when they talk about Johnny's CNC parts is a dead & live centre at 60 degrees. when using this set up you don't use a mandrel at all.

Let us know what works.

 

[Russianwolf]

even if you allow a lot of slop and glue the tube in with GG. Once the blank is milled to square with the tube, it should come out round. You may have more wood on one side and more glue on the other, but the distance from the tube to the outside edge SHOULD be the same (meaning the turning is true).

 

[GBusardo]

Originally posted by Russianwolf

even if you allow a lot of slop and glue the tube in with GG. Once the blank is milled to square with the tube, it should come out round. You may have more wood on one side and more glue on the other, but the distance from the tube to the outside edge SHOULD be the same (meaning the turning is true).

I agree, even if your tube is not centered as it sets up, once the glue cures and the blank is milled square, it should turn round, not using a mandrel. Is it possible the bushings are slightly out of round? They are probably perfect, but you can check. I think maybe something is wobbling slightly. Could there be crud in the taper holes? There could be a lot of reasons your blanks are turning out of round, but I do not think how the tube sets up inthe blank is one of them.

 

[desert1pocket]

The bushings will cause the surface of the blank to be centered on the tube, and the hardware will also center on the tube, so it doesn't matter where the hole is in relation to everything else.

As other have said, it could be several things, faulty bushings, blanks not properly squared, lathe centers not lined up, deformed centers, etc., but it doesn't have anything to do with the tube being centered in the hole.

 

[Dan_F]

As for the drill press, the table is square to the drill, but I think there is a tiny bit of extra curricular (front to back) movement of the quill as it moves up and down, an artifact of the up and down mechanism. I have noticed that sometimes a hole will be tight in the middle of the blank, but show a little slack on both ends.

Drill bits are for the most part new, and all are well behaved as they roll across the table.

I do use a barrel trimmer to square the blank to the tube, however this may be the culprit. It's a Woodcraft kit, and the entire shaft tends to wobble a little in use. I think it's due to the construction of the shaft, where the flat that the set screw seat upon goes all the way to the end of the shaft, and makes difficult for the jaws of the drill to grab evenly. See picture below. The one on the left is the Woodcraft, the one on the right is from the recent group buy, but I haven't yet made the sleeves for the 7mm shafts that will let me use these on larger pens. Note how the one on the right goes back to round and the end, so that the jaws can capture the entire blank. Could a slight wobble of the cutter head casue this problem?

I checked the alignment of the centers, and they are as close to dead on as I can see with my loupe, though using Lee's ruler test, the ruler goes to about a five degrees off of perpendicular to the ways with the centers meeting. I don't know if that is significant or not.

I think my skew is sharp enough, it certainly had no trouble getting through the skin on my thumb the other day.[:0] I do sharpen or hone at least once per segment, but it's possible that I'm not getting it sharp enough.

There does seem to be some vibration from the lathe at around 1400-1550 rpm's, so I try to avoid that range when turning. It's a Powermatic 3520 B that I got new around Thanksgiving. I'm new enough to turning that I really have no idea of what tolerances should be, and how much effect such things might have on the finished product.

Dan

 

[Dan_F]

Originally posted by rlharding



Also, you say that you are using Johnny's CNC bushings and then talk about your mandrel. What people are referring to when they talk about Johnny's CNC parts is a dead & live centre at 60 degrees. when using this set up you don't use a mandrel at all.

Let us know what works.

I probably shouldn't have said anything about the mandrel, as the last pen I turned was between centers with John's bushings. I just meant that the problem persisted even after that change. I don't think it is any problem with the bushings, as the barrel was proud of the bushing on one side, just as it was in relation to the nib of the pen.

I tend to agree that the hole size is a red herring, I just latched on to that after seeing the gap filled with epoxy on the ill fitting end of the pen. Physics is not my forte.

Dan

 

[RussFairfield]

Are these pen barrels really not round, is their outside diameter eccentric with the inside diameter of the tube or do they just look that way??

This could be an optical illusion. The proof should be in how the barrels match the fittings, and not how they look from the open end of the tube. An illusion of being eccentric is created by the difference in thickness of the wood or plastic because the tube isn't in the center of the drilled hole. The ID of the brass tube can still be concentric with the OD of the barrel, even though it doesn't ;ool that way.

 

[Dan_F]

Russ---They are truly out of round, I can feel where they don't match up to the hardware on one side, but the other side matches fine. This is evident when they are still on the bushings. It's not a lot, but enough to feel easily.

Dan

 

[desert1pocket]

I'd say you have some run-out somewhere, or the bushings are bad, or your pen mill is not getting things perfectly square.

Is it happening on both the headstock and tailstock ends, or just one of them, or does it vary? Can you see or feel a slight wobble to the bushings or the centers when the lathe is spinning? Do you have a dial indicator? Is there any crud in the MT holes on either end, or on the shafts of the centers, or on the tips of the centers, or in the recesses on the bushings?

You could put your bushings in a spare tube and mount it between centers. If it spins true on both ends with no wobble, you aren't getting the ends square. If you feel any wobble, then you have some run-out that needs to be traced to it's origin.

 

[SuperDave]

Originally posted by Dan_F

I do use a barrel trimmer to square the blank to the tube, however this may be the culprit. It's a Woodcraft kit, and the entire shaft tends to wobble a little in use. I think it's due to the construction of the shaft, where the flat that the set screw seat upon goes all the way to the end of the shaft, and makes difficult for the jaws of the drill to grab evenly. See picture below. The one on the left is the Woodcraft, the one on the right is from the recent group buy, but I haven't yet made the sleeves for the 7mm shafts that will let me use these on larger pens. Note how the one on the right goes back to round and the end, so that the jaws can capture the entire blank. Could a slight wobble of the cutter head casue this problem?

I think you are correct in your assumption. I use the same trimmer and get a serious wobble in the cordless drill when seating one jaw on the flat. I have to make sure that the flat is "between" jaws and test it for running true before squaring the blank.

 

[Dan_F]

Even being really careful, I can't get all of the wobble out of the barrel trimmer. The good news is that I have a few heads and a bunch of shafts from the group buy, and tomorrow I will pick up some corian scraps and a 7mm drill bit, and make a bunch of custom bushings for the trimmer shafts so they fit in the various tubes.

I'll go try the bushing/tube combo without wood to check for any wobble.

I really appreciate the help in trying to get to the bottom of this.

Dan

 

[RMB]

For a newbie here, how do you adjust the headstock and tailstock to be alligned? hit it with a hammer?

 

[CharlesSharp]

Having your tailstock out of alignment won't cause an egg shape. When working as a machinist we used to move the tailstock out of alignment to cut a taper.

I think his mandrel is bowed/bent.
Assemble everything onto the mandrel to turn a pen then check the mandrel for runout. Hold a pencil against the tool rest with the point almost touching the mandrel and turn the spindle by hand slowly. If the gap between the pencil and bushing changes, something is wrong.

 

[Firefyter-emt]

The point is that he is not using a mandrel, but between centers. The bushings are known good, they are Johnny's and a dead center will never bend. If his centers are in line and the blank is milled properly, the only thing left is a bent headstock. Out of line headstock / tailstock will still mess with how the blank turns IMHO..

My money is on the pen mill. If it is not tight in the blank or the head wobbles they bushings will follow the end of the blank more than the inside of the tube.

 

[ed4copies]

Originally posted by Firefyter-emt

The point is that he is not using a mandrel, but between centers. The bushings are known good, they are Johnny's and a dead center will never bend. If his centers are in line and the blank is milled properly, the only thing left is a bent headstock. Out of line headstock / tailstock will still mess with how the blank turns IMHO..

My money is on the pen mill. If it is not tight in the blank or the head wobbles they bushings will follow the end of the blank more than the inside of the tube.

Lee,
This is NOT to pick on you, you're just the closest.

Picture the pen mill making the end 30 degrees instead of 90. Now, when we insert the bushings, the inside diameter allows it to move this much (why, who knows), so the tube is now WAY sloped (to the horizontal bed of the lathe). NOW, we attach the tailstock!!! Unless you know how to make the tailstock reach the other bushing, which is an inch above the tailstock at this point, it can't be done.

So, if the tailstock lines up, all "slop" should be eliminated from any "misfacings", shouldn't it??? I don't have a good answer, I just haven't read one yet that made sense to me. Sloppy bushing fit (bigger hole than mandrel or smaller "nibs" than the tubes) seems to me to be the ONLY viable answer.

BTW, I have this problem sometimes and I change EVERYTHING - mandrel and bushings and it goes away. So, it is NOT NECESSARILLY the lathe alignment - tho that would be my FIRST guess.

Because the head and tail line up at the headstock does NOT eliminate the possibility of the ways being worn, so the tailstock goes out of alignment as it travels away from the headstock. But, I don't see how THIS would make the pen out of round - on the headstock end.

I'm so confused[8)][8)][8)][8)][8)]

 

[loglugger]

The alignment of a wood lathe is not a critical point, as your truning tools are not attached to the lathe as in a metal lathe where the tooling is attached to a stright line as it moves along the work.
With a wood lathe if you are not useing a mandrel and the lathe is out a little it should not make a difference as with a metal lathe if it is out of alignment it will make it into a cone shape. If the wood lathe is out and you are useing a mandrel then every revolution the mandrel will bend. I hope you can make sense out of this better than I can type it.
Bob

 

[Firefyter-emt]

I will give you the worn ways, but this is pretty rare on wood lathes. Metal lathes suffer from this much more because of the material that is turned.

Now if the blank is not 90 degrees to the tube, it can very well make a "Z" even if the centers are perfectly lined up.

Given the fact that Dan is turning between centers, with a dead center and John's bushings, leads me to believe that it's either the blank is not true to the tube, or the centers are out of line.

The reason out of line centers screws up pen tubes is because the bushings don't want to keep the line of the offset, but want to make that Z shape, even more so with a proper 60 degree center bore. Because the tube is "crooked" in the span between centers, there weill be a high spot and a low spot when compared to the tube.

 

[Dan_F]

Hi folks, stay tuned for more information about runout and such. No time now, but I received Lee's barrel end sanding mill today, and am on my way to pick up some corian to make the sleeves with.

Dan

 

[DCBluesman]

This is where I came in. In the opening post,

it appears that the brass tube is not centered in the blank.

If the tube is not concentric with the drilled hole, but is canted within the hole, the resultant blank will be overturned on one side and proud on the other. This will result in the blank being underturned relative to the hardware on one side and proud of the hardware on the opposite side. The solution is to use a drill bit that is closer to the correct size for the tube. thus better insuring that the tube is concentric with the hole. Ignore the suggested drill sizes in the instructions. Mic the tubes.

 

[ed4copies]

Lee,

The "Z" was a good way to say it. I now have a mental picture. STill not sure I BELIEVE it, but I'm certainly willing to entertain the possibility.

Thanks for responding.

 

[alamocdc]

Originally posted by Dan_F

... tomorrow I will pick up some corian scraps and a 7mm drill bit, and make a bunch of custom bushings for the trimmer shafts ...

Dan, if you use a 7mm bit you will drill a hole larger than the dia of the mill shaft. The shaft sold to fit 7mm pens is not 7mm, bit is made to fit "inside" the 7mm tubes. I use a 1/4" bit for my trimmer bushings and they all fit the shaft for 7mm pens just fine.

 

[ed4copies]

Originally posted by DCBluesman

This is where I came in. In the opening post,

it appears that the brass tube is not centered in the blank.

If the tube is not concentric with the drilled hole, but is canted within the hole, the resultant blank will be overturned on one side and proud on the other. This will result in the blank being underturned relative to the hardware on one side and proud of the hardware on the opposite side. The solution is to use a drill bit that is closer to the correct size for the tube. thus better insuring that the tube is concentric with the hole. Ignore the suggested drill sizes in the instructions. Mic the tubes.

Remember YESTERDAY - I'M HERE TO TROUNCE ON YOUR TOES!!!

IF the tube is not centered, and you turn the OUTSIDE, the amount of plastic left will be greater on one side than the other. HOWEVER, the resulting pen parts will fit FINE. The outside of the pen is circular, the tube is circular. The distance to the OUTSIDE of the material is UNIFORM. This is accomplished because the BUSHINGS are holding the TUBE and allowing you to remove only an EQUAL amount all the way around the TUBE. On one side you may have a ton of material, while the other side is nearly all glue space, but the BUSHING has not allowed you to turn off more on one side than the other, relative to the TUBE.

IF you rotate your pen blank on the bushing, NOTHING will change, so the OUTSIDE of the pen is ROUND compared with the fittings.

UNLESS the bushing was sloppy somewhere.

 

[Paul in OKC]

I get amazed every time the out of round blank thing comes up. You can't turn something out of round without an eccentric chuck. No matter how wobbly your set up, your blanks will be round! Out of concentricity, but ROUND. Now, my opinion on the matter is that something is out of 'true'. In my mind, no matter how oversized the hole is, when trimmed and turned, it will be round. Might be thicker on one side than the other,(the 'gap' will be full of glue on the thin side) but if everything else is TRUE, the diameter will still match the hardware, and it will be round. I have turned some loose tubed pens, and if the barrells are thick enough when finished (not slim line) Every thing is good. If I had time I would do some over kill on a couple of pieces and do a non-scientific professional machinist test just to prove it . So, my thoughts are that something is ****-eyed, or bent. Or you are using the wrong size shaft for the tube on your pen mill.

 

[Paul in OKC]

Just read your post, Ed. Go, man, go!!

 

[jhs494]

Well stated Paul!
The only time I have ever came across a turned pen that came out not round, was from my sanding it, and in this case it was a segmented blank and the hardness of the various woods caused them to sand unevenly.

 

[jtate]

Could it be out of round if you turned a balnk that was out of concentricity and then rotated the blank a little way on the mandrel and turned it some more? Would this make it oval?

Could it be out of round if you had the nut screwed down too tightly and the mandrell was bent in a sort of bow?

 

[Firefyter-emt]

One more time.... THERE IS NO MANDREL TO BE BENT! I HIGHLY dobut that you can bend a dead center. The bushings are good, better fit than any thing that ever touched a mandrel before so it is not in the blank holding method!

Paul.. exactly my thoughts!

 

[Paul in OKC]

Originally posted by jtate

Could it be out of round if you turned a balnk that was out of concentricity and then rotated the blank a little way on the mandrel and turned it some more? Would this make it oval?

Could it be out of round if you had the nut screwed down too tightly and the mandrell was bent in a sort of bow?

If you rotated the blank on the mandrel and it only cut on one side, yes, that would make it a bit oval. But if it is doing that, something else is not true, whether mandrel, the face of the bushings, something. I am one that does not believe that tightening the nut bows the mandrel. My logic says that the nut is pulling the mandrel out from the headstock as it is tightened against the bushing/blanks. I do think that over tightening is not a good thing, but for other reasons.

 

[Paul in OKC]

Originally posted by Firefyter-emt

One more time.... THERE IS NO MANDREL TO BE BENT! I HIGHLY dobut that you can bend a dead center. The bushings are good, better fit than any thing that ever touched a mandrel before so it is not in the blank holding method!

Paul.. exactly my thoughts!

Turning between centers I would think would eliminate the issue, like you said. If using a dead center in the head stock, I would check the run out there. Make sure you are not using too much pressure, any slight issue could be magnified by that.

 

[Russianwolf]

Take a 1" square spindle blank and point it between centers. Turn it round. Now loosen the tailstock and offset it from the original point by .1 inches. And again turn it "round". Will the resulting spindle be round?

I have a lathe with a cracked bed making alignment of the tailstock nearly impossible. You can't turn a round pen on it.

Since the centers don't seat in the bushing correctly they push the pen out of line a little bit. like this &gt;______&lt;. So as it turns one side will be slightly closer to the tool as it spins, resulting in a barrel that is flush on one side and proud on the other when the hardward is pressed in.

 

[Dan_F]

Here is a little more info. Run out at the dead center is .0005; here is how it was measured...

https://i98.photobucket.com/albums/l279/T-Caster/P1010790.jpg[/IMG

What is an acceptable amount of run out for a lathe?

Here is Lee's ruler method of checking alignment of head and tail stock. This is about 5 degrees off of perpendicular to the center's axis, as measured with a protractor. I have no idea how to fine tune the alignment, it's not mentioned in the owner's manual.

[IMG]https://i98.photobucket.com/albums/l279/T-Caster/P1010794.jpg

I'm now off to make some sleeves for Lee's sanding mill which arrived earlier today.

I sent some readings from the bushings off to John to see what he had to say. I Should hear back tomorrow.

Dan