Dimensions and Tolerances

[RussFairfield]

My previous posting on bushings turned into a discussion of dimensions and tolerance, and what we can see and feel. I am starting another topic because I am interested in how others handle the problems of wood movement with changes in humidity, moisture content, and temperature.

I have always believed that we have to keep the dimensions and tolerances in perspective and within reasonable limits when working with wood. One problem is that is that everything changes with changes in humidity and the resulting change in the moisture content of the wood. Finishes retard the rate of moisture and dimensional change, but they don't stop it. The pen whose joints I made to a perfect fit in January doesn't look and feel as good this summer.

The other problem is changes in dimension with temperature. Wood expands when it gets warmer and it shrinks as it cools, and some wood species move a lot. Sometimes that perfect fit I made while the wood was warm isn't as good the next day after the pen barrels have cooled back to room temperature.

Acrylics and stabilized wood don't solve the problems. While I have never detected any dimensional change with changes in humidity, they can move a lot with changes in temperature.

I do the things that have been suggested, like soften the edges of the wood, to make the dimensional differences between the wood and fittings less abrupt, and less noticeable. Even though I do this, I still have a problem when the wood shrinks to a smaller diameter than the metal fitting. I try to make an allowance for shrinkage, and sometimes I succeed and sometimes I don't. Either way, I seem to be the only person who knows the difference.

I solved the problem of fit at the tip by burying the metal tip fitting inside of the wood. Not only does it have a different appearance and "feel" good in the hand, it triples the price I can get from a SlimLine pen. I still have to measure the diameter of the wood at a couple critical locations to keep the pen from getting too large and still not cut through the wood at the tip. I have been surprized by how many people will tell me that a pen feels too large when it is only 1/32" larger.

Does anyone else consider the wood movement when making a pen, or is it inconsequential and not worth worrying about?

 

[Mudder]

Originally posted by RussFairfield
<br />Does anyone else consider the wood movement when making a pen, or is it inconsequential and not worth worrying about?

I consider wood movement and like you I'm sometimes successful and I'm sometimes disassembling the pen to reclaim the tubes. I have settled on making the wood .005†or so proud of the fitting and slightly chamfering the edges. It works for me.

One thing I have found is that acrylics don’t move and they sell 3 to 1 over my wood pens except in the Sierra. For reasons unknown to me the wood sierra sells very well for me.

 

[leehljp]

I am not experienced in wood movements in pens like you are because of the lack of experience so far. Maybe 50 pens so far, and I don't see them much after they are given away or sold.

However, in furniture and construction, I am well aware of wood movement and joints used to minimize the changes. I am also aware, from experience, of joints not to use in different circumstances strictly because of wood movement.

I welcome this discussion on wood movement in pens.

 

[Dario]

I know wood moves (shrink/expand) but never really had a chance to see it first hand on my pens since it is ALWATS HOT here in Texas!!! [][}][B)]

Kidding aside, I too try to let the wood stay a little proud of the (metal) kit parts when I can. I also try to round the edges a bit but faltered a lot...I'll try to remember this step more in the future. I am doing this with a 1000 grit sandpaper while on the lathe by loosening the mandrel bolt and inserting the sandpaper between the bushing and pen barrel and sand manually (lathe off). Maybe I need to buy that chamfering tool?

 

[its_virgil]

I think wood movement is more important to us as the penturner who wants the fit to be as nice as possible (and remain so) than it is to the customer. I ususlly turn a little proud, chamfer the edge to make the transition between wood and metal less noticeable. I seal the ends of the barrels with CA which I think helps reduce (maybe just a little)the wood movement. I just can't accept a pen where the barrel ends are smaller than the metal fittings. Those that shrink to that extreem are doomed to the dissassembly routine. There are lots of subtle factors to penturning than just selecting a wood and turning it to make a pen. We must continue to find ways to make the best pen we can, for personal satisfaction, and for our customers if we sell them.
Do a good turn daily!
Don

 

[angboy]

Originally posted by Mudder
<br />

Originally posted by RussFairfield
<br />Does anyone else consider the wood movement when making a pen, or is it inconsequential and not worth worrying about?

I consider wood movement and like you I'm sometimes successful and I'm sometimes disassembling the pen to reclaim the tubes. I have settled on making the wood .005†or so proud of the fitting and slightly chamfering the edges. It works for me.

One thing I have found is that acrylics don’t move and they sell 3 to 1 over my wood pens except in the Sierra. For reasons unknown to me the wood sierra sells very well for me.

So if you chamfer the edges, wouldn't that take some of your finish off the very ends of the blank? Does the chamfering bring the part of the blank that is up against the metal pen parts to exactly the same diameter as the metal parts, since you would have left them the 0.005" larger? Is there not a kind of slope with an empty sort of "v" space then down at the meeting part?

Please don't take that as critical in any way, I'm just trying to understand- this isn't something I'm doing, but am now wondering if I should, but I'd like to understand it first, otherwise I probably won't do it right!

 

[ed4copies]

I can't speak for the others (nor am I trying to), but on my final pass with the half-inch "straight skew" (has a very pronounced point), I roll over the edge (that means itsy-bitsy, not making a radius!!) that will meet the nib. On SOME kits, I also do this at other joints, depending on what I feel the user will be able to see and feel. This is done BEFORE the sanding and finishing. When sanding, ignore this until last few grits, so it will take a finish the same as the rest of the pen, but you won't accentuate the "roll over" so the eye can readily see it.

For me, this is a relatively new technique (last couple years), so I have sold hundreds of pens that did NOT have it-no one has EVER come back to complain (Does NOT mean it was never a problem, just never a problem about which I heard!!) But, I do think this makes a "better" pen.[][]

To be completely inconsistent, I only do this on SOME acrylics, when I think it will improve the fit (totally subjective!) [:0][:0]

 

[ilikewood]

I guess I fit in here really well too. I worry about shrinkage/growth and what is seen....even if the changes require a magnifying glass to see.

I am not sure if this can be solved. Expansion/contraction is something that everyone has to live with, but we can minimize the visual and mechanical effects. BTW- the expansion of brass is quite extreme when hot too. In engineering, two nonsimilar materials (metal/wood) with different expansion coefficients presents some real problems. The method that Russ is using is probably the best solution available (although I prefer just to make my tip totally out of wood instead of covering the metal, but that is just personal preference).

Woods that have extreme shrinkage/expansion I warn customers about (ebony, snakewood, etc) to keep them from getting too hot or dry. The shrinkage if too hot/dry in those cases can cause a catastrophic failure. One customer of mine left his ebony pen on the dash....split both barrels. I worry more about a customer mistreating their pen, so I caution the customer to take great care with their "treasure". I emphasize that these pens are something really special and care of them requires the right environment.

 

[its_virgil]

Good point Bill. I too caution customers about "mistreating" their new treasure. Dashboards are especially harmful as is anywhere inside the car in summertime.

Angie: What I call chamfering the ends may be a bit misleading. Ed's explaination is MUCH better. I use my skew and roll over the edge (just a tiny bit) on the last cut or use sandpaper on the edges to soften the "corner". The chamfer is ever so slight, but it helps. thanks Ed.

do a good turn daily!
Don

 

[bradh]

It is difficult to allow for the wood changes, since they could change either direction. If the pen goes to Florida it will swell as it gains humidity, if it goes to Arizona, it will shrink as the wood looses moisture. I just try to give stabalization time to any blank I buy or cut. I like to have the blank sit around for a couple weeks to stabalize before I use it. I do try and taper the wood so it transitions into the nib at the same angle that is on the nib. That seems to make any step in the wood less obvious.
I do find that I am much fusier than my customers. I see the .002" step beween the wood and nib, yet someone buys that pen and they are very happy with it.
Brad Harding
HardingPens.com

 

[Daniel]

I do warn my customers about the danger of letting the pen get to hot. My primary concers about wood moving is cracking. which stabalizations does help. my next concern woudl be when combining woods in inlay or accent bands. various species of wood will have different rates of expansion, and even a tiny movment will ruin a tight joint like inlay requires. luckely the thicknesses we end up with would also help keep movement reduced as well.
also understanding how wood will expand will go a long way towrd being able to minimize the effect as well. a short explaination. take a typical board. it has a two "faces" two "Sides" and two ends. a typical board will have the growth rings running somewhat parallel withthe faces. when the wood expands it will move the most in the width of the face, it will move the next amount in it's thickness or width of the side. and finally it will move the least in length. knowing this you can at least shoot for the least problimatic orientation for the wood.
another note on how wood moves. as a board gets wet it will warp. this warp will happen in such a way that it looks like the growth rings as seen from the end grain are trying to straighten out. this can be usefull in selecting pieces of wood that will not move in this manner as much. the straighter the growth rings at the end of the board. the less it will warp with humidity changes.
thes and other movements of wood are relative wether the wood is 10 inches thick or only 1/10th inch as the movement is a ratio of the thickness, width or length. we have small pieces but also only small movement is noticable.
a final note. I am of the opinion that the brass tube itself causes move movement that the wood does in most cases. but some woods can have a really large ratio of expension as well. as an example trying to combine oak and pine woudl be a disaster. oak baraly moves while pine bloats up like a dry sponge being dropped in water. some combos are jsut begging to self destruct. knowing the expension ratios of the woods you are using allows you to choose combinations that will expand in close ralation with each other.
as for gettng wood to stay matched to the fittings. sadly the only suggestion I can think of is. don't use wood. wood is going to move. knowing how much might allow you to calculate a mid range allowance for it.
as for the short term cool down issue. this is simple. let your finished blanks rest for 24 hours and then touch them up again. they will not get nearly as warm from a final sanding etc. as they would from being worked from a turned to a rough fifnished condition.
one other trick to get wood to expend and loose a lot of its movment qualities. is to soak it in water. once dry it will have gotten a lot looser and lighter but has lost most of it's ability to change with humidity. you could end up wrecking a lot of wood this way as well so attempt it at your own risk.

 

[Blind_Squirrel]

Originally posted by RussFairfield
<br />I solved the problem of fit at the tip by burying the metal tip fitting inside of the wood.

Do you have a close-up picture example of this?

 

[RussFairfield]

How about 2 of them??

<br />

 

[Daniel]

Well now Russ, that photo is just loaded with ideas of how to deal with the wood meets metal issue. no nib, no center band, looks like the clip end was left proud in an intentional way (looks good at that).
looks like this pen wouldn't even have a brass tube in it.
it does raise one question in my mind. have you ever noticed a problem with the clearance at the center band, (due to expension of the wood)?
I know I've had problems in the past making the lower barrel even a bit to large and using the metal band.

 

[DCBluesman]

For those of you who would rather believe the myth that I know what I'm doing, stop reading here. The rest of the post falls under the category of "I'd rather be <b>lucky</b> than good."

For the first six months of my pen making, I figured "close enough" really was. I also figured that home made was the same as hand made. Consequently, I made a lot of home made pens...and it showed. After a while, I discovered that the "pretty pen, nice job" comments were not satisfying me, so I went on an acquisition binge, obtaining pens from Don Ward, Jim Lambert, Ed Davidson and numerous others.

I studied those pens carefully, examining and re-examining each one to determine what was so different between theirs and mine. The answer came down to one word...CARE. It was obvious from this dozen or so pens, that each crafter CARED about each step in the process and that the sum of the separate parts was greater than the whole. Interestingly enough, caring about my work was totally controllable by me. It's one of the few parts of any craft that is.

Armed with my new found knowledge, I set forth on a path to truly care about each step in the process. Without boring you with unrelated details, one of the "care" parts is fit. A subset of fit is tolerances. I have studied a fair number of kits when it comes to fit but will focus on the Baron since I tend to make a lot of those.

If you cut a Baron so it has straight barrels, the thickness of the wood ends up being approximately 1.050mm (0.041 inches). If I assume that I will not abuse the material by submersing it in water for long periods of time, storing it in a freezer or leaving it in a closed car on an summer afternoon, how much will the wood really move? 5%? (To put that in perspective, that would change a 2x4 from 3.500" x 1.5" to either 3.675"x1.575" or to 3.325"x1.425".) 5% change on the thickness of our Baron barrel equates to 0.53mm or 0.002". When you consider that the inside of our blanks is captured in glue and the outside is finished, those numbers are quite likely to be much smaller. If I've gotten the barrel to the correct fit with the hardware, I can live with that level of change. I just don't see how I can't guess whether my pen is going to Abu Dhabi or the Louisiana bayour...Greece or Greenland. Trying to predict what climattic conditions my pen will see is nearly impossible unless I only make pens to order...and even then, the user may move! (That's just as likely as the wood moving.)

That being said, here's all the precaution I take. When I get a new set of bushings, I test fit them against the hardware on several kits. I test concentricity with a dial caliper. I adjust for any deviation by sanding the bushings to the correct dimensions. If that makes the bushings a tiny bit small, I can remember to leave the wood a little proud. At that point, if I finish to bushing size, I'm good to go. Yes, once in a while I go back and remeasure a couple of kits and the bushings. Manufacturing tolerances do change, but not often and not by a lot. What do I do when as I assemble a pen and I find the fit to be off? I either put it back on the lathe and sand/ refinish or I scrap the piece. At that point I will go through my re-calibrating.

In reading these posts, I should probably work a lot harder at this, but making pens is not rocket science. No one dies if a pen is .003" off at the wood/hardware junction. I just learn from the mistake, make corrections, and move forward. Fortunately, and here's where the <b>lucky</b> part comes in, I haven't had to do this very often.

 

[vick]

I try to get as close as I can on my fit and figure that will give me the best chances of it staying as close as possble. I do champher my edge just to barely knock of the hard corner with 350 to 400 grit sand paper. I have a tendecey to take off to much if I try to do it with lathe tools. Some times if the kit will allow I just skip that part so I do not have to worry about it.

<br />
Sometimes I think we might be to hard on our selves when it comes to pen making. If I have a pen with a small screw up (large screw ups never leave the house) that I would not sell I usually give it away at work or to a relative. I have never had anyone be able to tell what made the pen unsellable in my opinion. I am sure another pen maker or a pen collector would immediately be able to tell but the average person cannot. But we all have our own standards on what tollerance we consider acceptable.

 

[ilikewood]

I'm the guy who will spend 2 hours getting the right look. It still is never right in my eyes. So I guess 0.003" is way out of line.[:I][]

 

[RussFairfield]

Daniel asked about wood shrinkage at the center band of the pens in the photo. I don't know whether this is the answer he wanted, but there was a problem and this will describe how I solved it.

I had been making these pens with a butt joint between the two barrels, and someone asked why I wasn't recessing the lower barrel slightly into the end of the upper barrel. I hadn't though it necessary, and had always assumed that the butt joint was OK. But, the question nagged me, and I started looking more closely at the pens.

I discovered that I had a problem with the wood shrinking back from the ends of the brass tubes. Not only was there a gap between the barrels, I could see the shiny brass tube at the bottom of the gap.

Thinking about this, the shrinkage in the long direction of a piece of wood is small compared to that the radial and tangential directions, but it isn't "Zero". The number is something like 0.5% to 1% for most wood. Now, 0.5% of a 2.5" length is 0.012" or 1/64", and that is a significant gap that is visible. When the shrinkage is from two directions, the gap becomes twice as wide and a 1/32" gap is really visible.

When the pen is made with the wood at an angle or a full-cross grain, the larger shrinkage in the other directions becomes significant and the resulting gap can become large.

I could explain away the gap between the barrels because the burned rings on the upper barrel sort of disguised it. But, there was no forgivness for being able to see the brass tubes at the bottom of the gap.

The solution was simple. I now recess the lower barrel into the upper with a 3/32" taper joint. The gap disappears, and there is no way to see the brass tubes. The joint looks like this photo, and you can see the beginning of the taper on the lower barrel. It slides into a matching socket in the upper barrel.

<br />

All of this has made me aware of "gaps" and I starting seeing this shrinking of the wood away from the metal fittings on a lot of pens, particularly on those where the grain is at an angle or cross direction. It was easy to solve with this pen, but how do others solve the problem with pens with captured fittings, or is it small enough to be insignificant? Am I the only person who sees these gaps?

 

[ilikewood]

Russ, I noticed the exact same effect on my butt joint pens. I started recessing the lower into the upper barrel too. It solved my problems and I really think it is a cleaner look.

And no, you aren't the only one who sees this and worries about it. Maybe it is an Idaho thing![] Actually, there may be some truth to that as humidity here is extremely low, although I believe your area has some higher humidity.

 

[DCBluesman]

I make it a point to never kiss the brass. I leave a little room for breathing.

<br /> [8D]

 

[ilikewood]

This is coming from a guy who lives in an area where a dry day is 75% humidity![] I actually recess mine a bit too, but only on woods that are extremely hard. Softer woods present a bit of a problem if you need to put a bit of nut pressure on the mandrel to keep em from spinning on ya.

 

[Max]

Lou,

Do you do that on all your pens, or just some styles?? Just the bottom barrel, or both?? Sorry, maybe I'm not quite following this...

Max

 

[DCBluesman]

You're right, Bill. But I solve the problem even for softer woods by coating the inside of the barrels with thin CA. And Max, I do this for all of my pens, both barrels, except the ones where I don't use a brass tube at all. If the barrel length is a critical dimension, I cut the tube.

 

[clem]

i want to turn a churchhill pen but i'm having trouble fitting the bushings they are a little to big for the tube size i probible could getthe bushings in if i drove the in but would more than likely split the wood any suggestions clem

 

[DCBluesman]

The bushings should be snug, but should not have to be driven in. Try chamfering the ends of the tube and cleaning out any manufacturing burrs or stray glue.

 

[Randy_]

Originally posted by clem
<br />.....but i'm having trouble fitting the bushings they are a little to big for the tube size.....any suggestions....

600 grit sandpaper!!

 

[its_virgil]

I've been doing the very same thing with my slimline kits for awhile now. I like the fit much better and the look is so much more clean. I realized the butt joints were good when the pen was first made but deteriorated over time due to wood movement.
Do a good turn daily!
Don

Originally posted by RussFairfield
<br />
The solution was simple. I now recess the lower barrel into the upper with a 3/32" taper joint. The gap disappears, and there is no way to see the brass tubes. The joint looks like this photo, and you can see the beginning of the taper on the lower barrel. It slides into a matching socket in the upper barrel.

 

[Randy_]

Interesting discussion and some good suggestions offered. Anybody out there have actual figures on the amount of movement that we can expect in the woods that are commonly used for pencrafting??

 

[joeatact]

Sorry for a dumb question but what is the easiest way to cut the tapered hole in the upper barrel? What type of bit?javascript:insertsmilie('[:I]')
Blush [:I]

 

[DCBluesman]

Originally posted by Randy_
<br />Interesting discussion and some good suggestions offered. Anybody out there have actual figures on the amount of movement that we can expect in the woods that are commonly used for pencrafting??

No actual figures are shown, but an interesting article nonetheless. http://www.morlanwoodgifts.com/MM011.ASP?pageno=82 mid-way down the page.

 

[RussFairfield]

It isn't the easiest way, but I have made a lot of the pens by turning the barrels to 1/2" diameter, and then holding them in a chuck to turn and fit the ends. A scroll chuck will work, but a collet chuck is more accurate. I make the socket with a small parting tool, and the bottom of the recess is the same diameter as the smallest 7mm bushing that I had. Then I sand the inside of the taper with 400 grit, wipe on a coat of thin CA glue, wipe off the encess before it dries, and the socket is finished. Then I put the lower barrel in the collet and turn a taper on the end to fit the socket. Now I can put the barrels back on the mandrel and proceeded to make the pen.

Then I got smarter and made an end trimming tool that would cut the tapered socket when I was trimming the ends of the blanks. I made this cutter by turning a taper on the end of a 1/2" diameter barrel trimmer. This is where a metal lathe is a handy tool to have in the shop, but it could also be made by holding the trimmer in a drill, and spinning it against a grinding wheel.

The tapered trimming tool works fine, but I still prefer to turn and fit the ends separately because I have better control, there is less chance for tear-out in the socket, it only takes a couple minutes to do, and I can finish the inside of the socket while it is still in the collet.

I will close with a plug for a collet chuck. It isn't a requirement, but it sure makes the job easier and more accurate when we get into these techniques where we are doing turning off the mandrel. It is also the most accurate way to hold a mandrel in a lathe. I don't know about anyone else, but any problems I may have had with eccentric barrels, and barrels that weren't round, disappeared when I started holding the mandrel in a collet.

 

[its_virgil]

I have a collet chuck and will never go back to holding mandrels any other way. I also use the collets for holding some of our kit parts to modify them, such as shortening some of the couplers and or CBs in some kits. Stick a dowel into a small piece of wood and hold it with a collet to make a wooden finial. With the full set of collets, I've been able to hold any thing I've needed to and the surface is not marred as it is with a Jacob's chuck.
Do a good turn daily!
Don

Originally posted by RussFairfield
<br />
I will close with a plug for a collet chuck. It isn't a requirement, but it sure makes the job easier and more accurate when we get into these techniques where we are doing turning off the mandrel. It is also the most accurate way to hold a mandrel in a lathe. I don't know about anyone else, but any problems I may have had with eccentric barrels, and barrels that weren't round, disappeared when I started holding the mandrel in a collet.

 

[its_virgil]

I also solve this problem by turninig a small tennon on the transmission end of the lower barrel and fitting it inside the matting end of the upper barrel. There may be other ways of solving this same problem mentioned by Russ.

<br />

Do a good turn daily!
Don

Originally posted by RussFairfield
<br />
The solution was simple. I now recess the lower barrel into the upper with a 3/32" taper joint. The gap disappears, and there is no way to see the brass tubes. The joint looks like this photo, and you can see the beginning of the taper on the lower barrel. It slides into a matching socket in the upper barrel.

 

[Daniel]

Russ, you understood my question quite well. good answer for it as well. I to have had problems in the past with beiing able to see the brass tube.
two reactions I have had when it comes to this type of failure, and I consider a pen marred this badly a failure. is to allow my wood blanks to dry on a shelf for a long time, actually months. this is easy at this point as I have lots of blanks and don't turn all that many pens right now. I also have a great urge to use only stabalized woods. A moisture meter woudl be a great help in keeping the blanks to a standard dryness. Right now I have to use feel.
as for the question about info on how wood will move. I don't have any links for them but there are charts out there that list them along with far more info that you would ever want to know. I'll see if I can find any of the links I bookmarked while searching for information a couple of years ago. I will tell you every species of wood is different.
I really like this topic. it is this sort of detail that will lead you from being a penturner to being a master penturner.
you can really know every type of wood you use, you can even goas far as knowing what finish works best for that particualar wood. It may be good for one style of pen better than others. and what other woods it is compatable with as far as how much it shrinks. the same wood from one location could very well be different than from other locations. and solutions that really solve problems inherent with wood are always good.
wood is going to be wood and it is up to us to work with it.
to do so you really need to understand the piece of wood you have in your hand at the time. how much you want to understand it is for each person to decide.
Maybe we should post soem pictures fo the types of failures we are discussing. I know it is hard to show the bad stuff, but we all have some. and then solutions can be offered for them.
I know I have several pens that cracked along the length of the barrel even a couple of years after they where made. this problem has bothered me so much I have even thought of giving up making pens, at least wood ones. I do have a strong tendance to shy away from light, straight grained, unstabalized woods. and I stress that pens I sold two years ago are out there giving me a bad name.
even buffalo horn is headed for the won't use it pile for this reason.

 

[RussFairfield]

I chose to use a tapered socket because of the burned rings in the end of the cap. There isn't much wood left between the bottom of the burned ring and the inside of a straight socket, and I was losing too many pen barrels.

 

[Randy_]

Originally posted by DCBluesman
<br />.....No actual figures are shown, but an interesting article nonetheless. http://www.morlanwoodgifts.com/MM011.ASP?pageno=82 mid-way down the page.....

Lou: Interesting, indeed!! And there were some other worthy articles as well. Thanks for posting that link. Wonder if Don knows this guy?? They aren't exactly neighbors; but are in the same neck of the woods if you have a long neck!![][]

 

[clem]

thanks for all the replys will try the sugestions clem

 

[its_virgil]

Don't know this guy. Lubbock is 250 miles from Wichita Falls, but he is now on my list to visit next time I'm in Lubock.
Do a good turn daily!
Don

Originally posted by Randy_
<br />

Originally posted by DCBluesman
<br />.....No actual figures are shown, but an interesting article nonetheless. http://www.morlanwoodgifts.com/MM011.ASP?pageno=82 mid-way down the page.....

Lou: Interesting, indeed!! And there were some other worthy articles as well. Thanks for posting that link. Wonder if Don knows this guy?? They aren't exactly neighbors; but are in the same neck of the woods if you have a long neck!![][]