TBC--slimline???

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ed4copies

ed4copies

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I readily admit I am not a proponent of TBC (turning between centers without a mandrel). I believe an adjustable mandrel provides all the same advantages, but here are the points I have seen stated:

Bushings can be out of round
Therefore my pen becomes out of round

Can someone explain to me how this can apply to a slimline?? The 7mm tube fits snugly over the mandrel, which spins in a circle. TBC would be confined to one tube at a time, so use a short mandrel--one tube at a time and it seems there is no room for error.

What am I missing????

Thanks.
Ed
 
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Ed -

I tend to turn with TBC -- but because my big lathe has a movable bed, and I usually do not want to take the time to tune up the tail stock so it is a precise match to the headstock. The TBC bushings are more like a "universal joint" and accommodate minor alignment much like the drive/live centers do on spindles.

Once I take the few minutes to tune up the alignment, the differences are a matter of style as I use a ER 32 collet chuck to drive mandrels.

When making production runs, I am faster changing items with TBC as I can remove the turned product while the lathe is slowing down and have a new blank loaded quickly before it stops spinning
 
I don't even turn the lathe off...just retract the tailstock quill and the blank falls into your hand.

hold a new blank up with a bushing up against the livestock, then advance the quill into the headstock and the blank spins up.
 
Slim mandrel bushings wouldn't be a prob. A mandrel may or may not be straight.

It's mainly just a total different in tooling for me. I don't want to stitch back and forth. In go tbc pretty much all the time.

I happen to agree with you that a short adjustable mandrel can also be very accurate.

I think you can have big issues with tbc if your blanks aren't trimmed square.
 
The longer the distance...two segments of the barrel, the more pronounced the error becomes, this is where a mandrel can suck. Minimizing the distance, we minimize the extrapolation for error, which is why BTC should be more accurate. Since the bushings for BTC's stuff are custom machined to very high tolerance, the only variables left are alignment of the lathe and if the tube is straight or not. JMHO.
 
Dan Masshardt said:
Slim mandrel bushings wouldn't be a prob. A mandrel may or may not be straight.

It's mainly just a total different in tooling for me. I don't want to stitch back and forth. In go tbc pretty much all the time.

I happen to agree with you that a short adjustable mandrel can also be very accurate.

I think you can have big issues with tbc if your blanks aren't trimmed square.
Click to expand...

Which (squaring the blank) presents a high probability of ruining fragile blanks.
 
Jim Burr said:
The longer the distance...two segments of the barrel, the more pronounced the error becomes, this is where a mandrel can suck. Minimizing the distance, we minimize the extrapolation for error, which is why BTC should be more accurate. Since the bushings for BTC's stuff are custom machined to very high tolerance, the only variables left are alignment of the lathe and if the tube is straight or not. JMHO.
Click to expand...

Between centers, you will turn one tube at a time. Do the same on a short mandrel and you will achieve equally good results.

I am not "fanatic" about this, so I don't mean it as an "argument"---I see the logic for production, as stated above---but for accuracy I can't see where either is more accurate.
 
sschering said:
I don't own a mandrel.. It makes using one very difficult.
Click to expand...

If you BUY an adjustable mandrel, you spend $20ish once and $5 for every new pen design. (usually you get a set of slimline bushings WITH the mandrel). If you buy TBC bushings (as I understand it) you pay $20ish for each set.

This could be incorrect, but it appears the slimline bushings ($20) are about the same as the adjustable mandrel WITH slimline bushings.
 
Ed,
I am not a rocket scientist so I will keep it simple, I started off with using a mandrel an thought it was the only way to go (that was also when most of us used friction polish as a finish). I then saw the results of TBC with bushings and I switched to that method (along with using CA glue as a finish) I eventually got tired of having to cut the bushings off the blank after finishing so now I use TBC with out bushings. It takes me less time for a better product. But as we know everyone has their own style of turning, finishing etc.
 
ed4copies said:
Jim Burr said:
The longer the distance...two segments of the barrel, the more pronounced the error becomes, this is where a mandrel can suck. Minimizing the distance, we minimize the extrapolation for error, which is why BTC should be more accurate. Since the bushings for BTC's stuff are custom machined to very high tolerance, the only variables left are alignment of the lathe and if the tube is straight or not. JMHO.
Click to expand...

Between centers, you will turn one tube at a time. Do the same on a short mandrel and you will achieve equally good results.

I am not "fanatic" about this, so I don't mean it as an "argument"---I see the logic for production, as stated above---but for accuracy I can't see where either is more accurate.
Click to expand...

You have a valid point Ed...but you still have the alignment of the mandrel, albeit short, to put into the equation plus the bushings...still used on a mandrel, the lathe alignment and square of the tube.
 
An adjustable mandrel would ALWAYS be my last choice for making ANY pen, but especially a 7mm slimline.

Generally, the slim leaves less "meat" around a tube. Because of this, any mistake is "amplified".

The best method, obviously, TBC with no bushings. The reason this is best is simply because there are fewer parts and joints involved, GREATLY reducing the chances of getting one piece wrong and turning off axis.

The second best method is TBC WITH 7MM stainless TBC slimline bushings. These bushings are fairly precise, and still use 60 degree points.

Years ago, I discovered that the head stocks on my lathes rendered MUCH MORE ACCURATE revolutions than the Morse Tapers could ever deliver. With this in mind, I had Rick Herrell make 3/4 60 degree dead centers to fit in a Beall collet chuck.

The third best choice is a regular piece of drill rod or a stainless mandrel inserted into a Beall collet chuck.this is VERY ACCURATE, uses just the amount of mandrel needed and DOESN'T rely on the "hit or miss" tolerances of a dirty or miss-bored Morse a Taper. With the Beall Collet setup, it is virtually impossible to bow a mandrel.

The next choice, in terms of accuracy would be an adjustable mandrel. While this is a set up that I would NEVER USE. many do use it. And are satisfied with the results they obtain. The adjustable mandrel IS a step up from a fixed length mandrel, but has too many variables to get the kind of accuracy I'm looking to achieve. I would not let my accuracy be compromised by a dirty or ill- seated taper or "sprung" collet of an adjustable mandrel.

The last and poorest quality is the fixed length mandrel. I won't discuss these as I feel that these also deliver unacceptable results for professional pen makers.

Respectfully submitted.
 
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While your answer sounds great and is well-written, Andy---it overlooks one important point.

Your "most accurate" is putting a 60 degree point into both ends of a small tube. IF the material is not faced completely to the brass, it is almost 100% certain it will crack with this pressure, when it nears final diameter.

If it IS faced absolutely perfectly, it could still crack if "squeezing" (tightening the tailstock) is used to achieve rotation while "not perfectly sharp" tools are used.

I think this is far more likely than the "crud in the morse taper" scenario---but I guess everyone has their own premise for "mostly likely to be overlooked" factors.
 
Oops! I should have mentioned that REGARDLESS of the setup I use, ANYTIME I use brass tubes it is ALWAYS 60 degree faced with my bullet reamer, THE ABSOLUTE MOST ESSENTIAL TOOL behind my Pen Wizard.
 
ed4copies said:
IF the material is not faced completely to the brass, it is almost 100% certain it will crack with this pressure, when it nears final diameter.

If it IS faced absolutely perfectly, it could still crack if "squeezing" (tightening the tailstock) is used to achieve rotation while "not perfectly sharp" tools are used.
Click to expand...

I'm probably flirting with disaster. I TBCed a few slims without cracking under pressure, and the pen didn't either! I mounted the blanks between 60° dead and live centers and hoped for the best.

I haven't turned enough pens to know whether I like the mandrel saver, TBC, or the new adjustable mandrel I bought from a certain vendor.

With TBC, I find it more convenient to "dismount" and measure with the calipers than if I use a mandrel.

I have noticed that TBC directly into the 7mm tube causes a chamfer in the tube, which I haven't decided is good or bad. I think it helps align the parts for assembly, but it makes the ends frighteningly thin and looking delicate.
 
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uh...I'd like to give the undeniably correct answer...but since there isn't one I'll refrain from further discussion that is and always will be an opinion...period.:confused: This is an art, not a quantum physics equation...once again...just mho
 
Brian G said:
ed4copies said:
IF the material is not faced completely to the brass, it is almost 100% certain it will crack with this pressure, when it nears final diameter.

If it IS faced absolutely perfectly, it could still crack if "squeezing" (tightening the tailstock) is used to achieve rotation while "not perfectly sharp" tools are used.
Click to expand...

I'm probably flirting with disaster. I TBCed a few slims without cracking under pressure, and the pen didn't either! I mounted the blanks between 60° dead and live centers and hoped for the best.

I haven't turned enough pens to know whether I like the mandrel saver, TBC, or the new adjustable mandrel I bought from a certain vendor.

With TBC, I find it more convenient to "dismount" and measure with the calipers than if I use a mandrel.

I have noticed that TBC directly into the 7mm tube causes a chamfer in the tube, which I haven't decided is good or bad. I think it helps align the parts for assembly, but it makes the ends frighteningly thin and looking delicate.
Click to expand...

Just an FYI: There is no reason you HAVE to "dismount". Stop the lathe and measure your blank on the mandrel. MAY have to move the tool rest, but if you approach from the back, even that is not really required.
 
No disagreement from me, Ed. :smile:

I have a Ryobi mini lathe. Once I get the tool rest set, I'm not moving it until I have no choice. Nice little lathe for $40 used, but I can understand why they stopped making them.

I don't contort quite like I used to, either.
 
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ed4copies said:
Which (squaring the blank) presents a high probability of ruining fragile blanks.
Click to expand...
Not really.

If you use a pen mill I suppose it could be probable. I rarely do.

I either use a sander and then sanding mill to perfect of trim the ends square in a chuck. As long as I'm not too aggressive with the tool here it's good.
 
Dan Masshardt said:
ed4copies said:
Which (squaring the blank) presents a high probability of ruining fragile blanks.
Click to expand...
Not really.

If you use a pen mill I suppose it could be probable. I rarely do.

I either use a sander and then sanding mill to perfect of trim the ends square in a chuck. As long as I'm not too aggressive with the tool here it's good.
Click to expand...

A pen mill is another tool that sits in a drawer in my shop. There are 15 or 20 much better and less destructive ways to square a blank that immediately come to mind.

Perhaps one of the quickest, most accurate way of blank squaring is to simply use a skew.

IMHO, a pen mill is to fine pen making what a wrecking bar is to fine, finish carpentry.
 
Dan Masshardt said:
ed4copies said:
Which (squaring the blank) presents a high probability of ruining fragile blanks.
Click to expand...
Not really.

If you use a pen mill I suppose it could be probable. I rarely do.

I either use a sander and then sanding mill to perfect of trim the ends square in a chuck. As long as I'm not too aggressive with the tool here it's good.
Click to expand...


Dan,

You and everyone else are precisely correct in the method you use----for YOU!

My point of contention is which way will be the easiest AND produce the most likely positive result. I deal with lots of people who don't spend a lot of time thinking through the logic, they just make pens.

So, CAN every way work?? YES, UNDOUBTEDLY!!

WILL every way work---only if every precaution is taken, which won't happen in a large percentage of cases.

I also believe we should look for BETTER solutions, when the EXISTING one has flaws. I think, for slimlines, the mandrel system has very few flaws and the TBC system offers more opportunity for additional flaws. YES, they can be overcome easily with planning and care---neither of which is "in vogue" with new turners.

I don't hope to convert YOU or anyone else, I was hoping to learn WHY some think TBC is better on 7mm. The production answers make sense. But the people who call me are NOT production turners.

THANKS to all---I sincerely appreciate your comments.

Ed
 
OOR pen discussions have been going on since the IAP and other pen turning forumns started. In May of 2010 Russ Fairfield and I both did pen turning demonstrations at the Utah Woodturning Symposium. During our downtime we spent several hours talking and comparing notes and relating experiences. One thing that we both had observed was how our drawer full of "bent" mandrels mysteriously became straight as soon as we started using a Beall collet chuck to hold them.
Do a good turn daily!
Don
 
its_virgil said:
OOR pen discussions have been going on since the IAP and other pen turning forumns started. In May of 2010 Russ Fairfield and I both did pen turning demonstrations at the Utah Woodturning Symposium. During our downtime we spent several hours talking and comparing notes and relating experiences. One thing that we both had observed was how our drawer full of "bent" mandrels mysteriously became straight as soon as we started using a Beall collet chuck to hold them.
Do a good turn daily!
Don
Click to expand...


It was EASY to bend a 7" long piece of quarter inch rod.

ANY method that changes that to 3" makes it a LOT harder to bend. I agree completely, Don---I bent LOTS of mandrels and had many OOR pens to show for it.
 
Mine got straight, too, Don. If I use a mandrel, a Beall is my method of choice. I have a drawer full of proof that the Beall method results in far fewer OOR issues than a MT mandrel apparatus.
 
edstreet said:
ed4copies said:
It was EASY to bend a 7" long piece of quarter inch rod.

ANY method that changes that to 3" makes it a LOT harder to bend. I agree completely, Don---I bent LOTS of mandrels and had many OOR pens to show for it.
Click to expand...


If it was a properly made rod it would not easily bend like that.
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This is why Berea introduced the "B" mandrel---to give it more "beef". Never caught on, but it was a good approach.

"7 MM" or "A" mandrels were economical, and EASY to bend. As a brand new turner, I also knew nothing about sharpening. So, push hard enough on a 1" roughing gouge and you could take off enough wood to shape a pen-----AND bend the rod, in the middle. SO, many pens were OOR, but ONLY in the middle. Both ends still turned true where they were held in place by the "straight part" of the rod. (Was many years before I figured this out----not a BRIGHT boy!!)
 
I actually like the "B" mandrel and have reamed several bushing sets to fit onto one. I also make my own mandrels with letter D drill rod (for "A" mandrels) and letter L drill rod(for the "B") mandrel. This way I can get several mandrels (using drill rod)for the price of just one(retail).
Do a good turn daily!
Don
 
I too have been experiencing OOR and I decided to take some measurements to come up with the best solution.

With a dead drive inserted in the headstock I get a deviation of .0015 if the dead drive is inserted to give me the best reading. If not oriented properly the dead drive deviation can be as much as .005.

The adjustable mandrel gives a deviation of less than .001, again if it is inserted with the right orientation. With the mandrel saver set at about a pen blank's distance that end of the mandrel whips around at about .008.

The Beall collet chuck gives a deviation of .005 at the chuck with a quarter inch drill bit inserted. I don't understand this because the Beall collet chuck "should" provide less deviation.
 
ed4copies said:
sschering said:
I don't own a mandrel.. It makes using one very difficult.
Click to expand...

If you BUY an adjustable mandrel, you spend $20ish once and $5 for every new pen design. (usually you get a set of slimline bushings WITH the mandrel). If you buy TBC bushings (as I understand it) you pay $20ish for each set.

This could be incorrect, but it appears the slimline bushings ($20) are about the same as the adjustable mandrel WITH slimline bushings.
Click to expand...

But with a good 60 degree drive and revolving center, the bushing that you bought with the kits will work and the only "custom" bushing you actually need will be for the 7mm pens... slims, euro's etc... the cigar and larger pens already have bushing that fit inside the tubes and only need to be held with the drive and revolving centers.
 
larryc said:
I too have been experiencing OOR and I decided to take some measurements to come up with the best solution. With a dead drive inserted in the headstock I get a deviation of .0015 if the dead drive is inserted to give me the best reading. If not oriented properly the dead drive deviation can be as much as .005. The adjustable mandrel gives a deviation of less than .001, again if it is inserted with the right orientation. With the mandrel saver set at about a pen blank's distance that end of the mandrel whips around at about .008. The Beall collet chuck gives a deviation of .005 at the chuck with a quarter inch drill bit inserted. I don't understand this because the Beall collet chuck "should" provide less deviation.
Click to expand...


Isn't it obvious where where it's at? The deviation that is.

Sent from my iPhone using Forum Runner
 
edstreet said:
larryc said:
I too have been experiencing OOR and I decided to take some measurements to come up with the best solution. With a dead drive inserted in the headstock I get a deviation of .0015 if the dead drive is inserted to give me the best reading. If not oriented properly the dead drive deviation can be as much as .005. The adjustable mandrel gives a deviation of less than .001, again if it is inserted with the right orientation. With the mandrel saver set at about a pen blank's distance that end of the mandrel whips around at about .008. The Beall collet chuck gives a deviation of .005 at the chuck with a quarter inch drill bit inserted. I don't understand this because the Beall collet chuck "should" provide less deviation.
Click to expand...


Isn't it obvious where where it's at? The deviation that is.

Sent from my iPhone using Forum Runner
Click to expand...


Enlighten me.
 
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larryc said:
I too have been experiencing OOR and I decided to take some measurements to come up with the best solution.

With a dead drive inserted in the headstock I get a deviation of .0015 if the dead drive is inserted to give me the best reading. If not oriented properly the dead drive deviation can be as much as .005.

The adjustable mandrel gives a deviation of less than .001, again if it is inserted with the right orientation. With the mandrel saver set at about a pen blank's distance that end of the mandrel whips around at about .008.

The Beall collet chuck gives a deviation of .005 at the chuck with a quarter inch drill bit inserted. I don't understand this because the Beall collet chuck "should" provide less deviation.
Click to expand...

Larry, after reading this thru several times it appears that you have a situation similar to mine.
I won't go into great detail but basically it comes down to marking the dead center to get the least amount of runout, called the 'sweet spot'.
In my case I have determined that the MT2 was bored off center and the dead center I have also has a slight off-axis cut. If positioned correctly, the runout on the tip of the dead center is just under .002" so that is what I deal with. I have used a small file and marked the headstock drive and the dead center so it is easily positioned correctly each time.
If you have a problem with runout on anything that threads onto the headstock, and there is a runout on the headstock itself, there isn't much you can do about it since you cannot easily change the position of the chuck on the threads.
 
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