leehljp
Member Liaison
Hard Facts on TBC, Mandrels Centers and 60°
There seems to be a constant confusion concerning TBC, (Turning Between Centers) and Mandrels as it concerns the live and dead centers and also bushings. I hope to clarify this and ask anyone to clarify if there are errors in my presentation here. AS people comment, I will edit in the changes.
(Premise for this: Constant mixing of information that is not technically correct and conveying erroneous perceptions, which causes some new people to have mixed emotions about the viability of TBC.)
1. Mandrels ARE metal and metal mandrels require a 60° Live Center (LC) to function properly.
Over the past several months, there have been posts here concerning vibration and Out Of Round/Eleptical pens. On several it takes the 2nd and 3rd page of replies before it is discovered that the person is NOT using a 60° live center.
2. 60° Live Centers are the industry standard for METAL, but NOT wood lathes.
Most people who buy their first wood lathe do not know the difference, and consequently run into problems as mentioned in number 1 above.
3. TBC, in contrast to using Mandrels - does not REQUIRE 60° LCs or 60° Dead Centers - when using the standard mandrel bushings.
It would be better to go to the same standard as used with mandrels (60°) but it is not necessary as an absolute for getting started.
4. COST: Except for Slimline series, getting started can be cheaper with TBC than with Mandrels - simply because most mandrels cost more than a Dead Center. Dead Centers can even be made at home on the lathe. Some wood lathe "centers" that cause problems on mandrels - can be used just fine for TBC. Check your lathe's stock "center" to see if it will work.
One advantage of TBC is the higher quality bushings available from JohnnyCNC, and while they cost a little more than standard, they are worth it. These do require a 60° LC-DC because the holes are chamfered to this. It only takes getting one or two sets of bad bushings from a commercial vendor to appreciate the bushings that John makes.
5. STANDARD MANDREL BUSHINGS OK for TBC in getting started. . . . UNLESS they are drilled Off Center. :hammer:
TBC began with many using the standard Mandrel Bushings, but due to some of these being drilled off center, John (JohnnyCNC) (and Paul in OKC for a short while I think) began to fill a void by offering custom precision bushings that once used, it is hard to go back to mandrel bushings again. Still, to get started, one can use what they have on hand. There may be (will be for most) some slippage due to the fact that the mandrel bushings do not have a chamfered shoulder for nesting in the DC and LC. But this it self will not hurt the precision unless the bushing is drilled Off Center.
6. SIMPLICITY IS AN ADVANTAGE of TBC
A. It uses LESS PARTS - eliminating the problems associated with the mandrel,
• Over tight tail stock,
• Flexing mandrel,
• Bent mandrel,
• Using wood lathe stock live center on mandrel;
B. It offers options of finishing without bushings . . . TO PREVENT:
• Bushing sanding dust,
• Glued in bushings,
• CA "lift" or "chipping" when separating the bushing from the blank
C. Using calipers to determine size extends the life of the bushings. On Mandrels, bushings are considered consumables (need to be replaced after sanding down or turned down with the skew/scraper.
If one were to check past problems that people have with vibration and OOR, a high percentage of those would be associated with mandrel usage. While long time lathe users do not have most of these problems (because their experience and skill have worked them out) new people often do.
When mentioning TBC to correct these problems, TWO PERCEPTIONS pop up regularly against the use of TBC: Cost and Complication! Both of these are more Perception Problems than real problems.
7. PERCEPTION VERSUS FACTS: TBC is not expensive to get started, but when it is mentioned that TBC Requires a 60° DC and LC, it does appear that it is going to cost more. When chamfered bushings are mentioned to beginners, Cost again comes to mind as well as complicated set ups for which most people are not ready. This is the PERCEPTION that people get . . . even though most people already have bushings and a wood stock live center and some kind of drive center on hand - that can be used.
NOT ADDRESSING THE FACTS when these perceptions pop up - as people refer to TBC - unintentionally leads to and spreads misinformation. That is what Perception does! I tried to address this with a fellow member who said he wanted to move to TBC. I thought he was speaking of it from a complicated point of view and wished to eliminate any complications. He took it in a straight forward way in which it was intended and not as criticism. In my trying to correct that perception, another veteran member took it as a remark against him, which it wasn't. Perception, Context, Facts. Dangerous but necessary!
The above is for Getting Started, Making The Transition from Mandrels to TBC. Below is for "moving on up".
CREAM RISES TO THE TOP! After getting started, and the speed and simplicity are discovered, many people will want to make modifications, buy more durable products such as carbide tipped/hardened centers, along with Johnny's bushings along with his and others delrin bushings.
TBC can start inexpensively enough, but there are plenty of options to climb to the top of precision turning with durable lasting products. TBC is what will help move to the $100, $250, $500, $1000 and more quality pen. To be sure, these can be accomplished with mandrels for sure but TBC can make the transition to this quality much faster for those just starting out. It is not a panacea, but it is huge.
For a tutorial, Here is a link to the most superb Tutorial on TBC to date:
http://www.penturners.org/forum/showthread.php?t=54760
There seems to be a constant confusion concerning TBC, (Turning Between Centers) and Mandrels as it concerns the live and dead centers and also bushings. I hope to clarify this and ask anyone to clarify if there are errors in my presentation here. AS people comment, I will edit in the changes.
(Premise for this: Constant mixing of information that is not technically correct and conveying erroneous perceptions, which causes some new people to have mixed emotions about the viability of TBC.)
1. Mandrels ARE metal and metal mandrels require a 60° Live Center (LC) to function properly.
Over the past several months, there have been posts here concerning vibration and Out Of Round/Eleptical pens. On several it takes the 2nd and 3rd page of replies before it is discovered that the person is NOT using a 60° live center.
2. 60° Live Centers are the industry standard for METAL, but NOT wood lathes.
Most people who buy their first wood lathe do not know the difference, and consequently run into problems as mentioned in number 1 above.
3. TBC, in contrast to using Mandrels - does not REQUIRE 60° LCs or 60° Dead Centers - when using the standard mandrel bushings.
It would be better to go to the same standard as used with mandrels (60°) but it is not necessary as an absolute for getting started.
4. COST: Except for Slimline series, getting started can be cheaper with TBC than with Mandrels - simply because most mandrels cost more than a Dead Center. Dead Centers can even be made at home on the lathe. Some wood lathe "centers" that cause problems on mandrels - can be used just fine for TBC. Check your lathe's stock "center" to see if it will work.
One advantage of TBC is the higher quality bushings available from JohnnyCNC, and while they cost a little more than standard, they are worth it. These do require a 60° LC-DC because the holes are chamfered to this. It only takes getting one or two sets of bad bushings from a commercial vendor to appreciate the bushings that John makes.
5. STANDARD MANDREL BUSHINGS OK for TBC in getting started. . . . UNLESS they are drilled Off Center. :hammer:
TBC began with many using the standard Mandrel Bushings, but due to some of these being drilled off center, John (JohnnyCNC) (and Paul in OKC for a short while I think) began to fill a void by offering custom precision bushings that once used, it is hard to go back to mandrel bushings again. Still, to get started, one can use what they have on hand. There may be (will be for most) some slippage due to the fact that the mandrel bushings do not have a chamfered shoulder for nesting in the DC and LC. But this it self will not hurt the precision unless the bushing is drilled Off Center.
6. SIMPLICITY IS AN ADVANTAGE of TBC
A. It uses LESS PARTS - eliminating the problems associated with the mandrel,
• Over tight tail stock,
• Flexing mandrel,
• Bent mandrel,
• Using wood lathe stock live center on mandrel;
B. It offers options of finishing without bushings . . . TO PREVENT:
• Bushing sanding dust,
• Glued in bushings,
• CA "lift" or "chipping" when separating the bushing from the blank
C. Using calipers to determine size extends the life of the bushings. On Mandrels, bushings are considered consumables (need to be replaced after sanding down or turned down with the skew/scraper.
If one were to check past problems that people have with vibration and OOR, a high percentage of those would be associated with mandrel usage. While long time lathe users do not have most of these problems (because their experience and skill have worked them out) new people often do.
When mentioning TBC to correct these problems, TWO PERCEPTIONS pop up regularly against the use of TBC: Cost and Complication! Both of these are more Perception Problems than real problems.
7. PERCEPTION VERSUS FACTS: TBC is not expensive to get started, but when it is mentioned that TBC Requires a 60° DC and LC, it does appear that it is going to cost more. When chamfered bushings are mentioned to beginners, Cost again comes to mind as well as complicated set ups for which most people are not ready. This is the PERCEPTION that people get . . . even though most people already have bushings and a wood stock live center and some kind of drive center on hand - that can be used.
NOT ADDRESSING THE FACTS when these perceptions pop up - as people refer to TBC - unintentionally leads to and spreads misinformation. That is what Perception does! I tried to address this with a fellow member who said he wanted to move to TBC. I thought he was speaking of it from a complicated point of view and wished to eliminate any complications. He took it in a straight forward way in which it was intended and not as criticism. In my trying to correct that perception, another veteran member took it as a remark against him, which it wasn't. Perception, Context, Facts. Dangerous but necessary!
The above is for Getting Started, Making The Transition from Mandrels to TBC. Below is for "moving on up".
CREAM RISES TO THE TOP! After getting started, and the speed and simplicity are discovered, many people will want to make modifications, buy more durable products such as carbide tipped/hardened centers, along with Johnny's bushings along with his and others delrin bushings.
TBC can start inexpensively enough, but there are plenty of options to climb to the top of precision turning with durable lasting products. TBC is what will help move to the $100, $250, $500, $1000 and more quality pen. To be sure, these can be accomplished with mandrels for sure but TBC can make the transition to this quality much faster for those just starting out. It is not a panacea, but it is huge.
For a tutorial, Here is a link to the most superb Tutorial on TBC to date:
http://www.penturners.org/forum/showthread.php?t=54760