Turning Between Centers - PSI TBC Mandrel

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builtbybill

builtbybill

Member
Joined
Dec 17, 2014
Messages
265
Location
Clayton, NC
Hello,

So, I have been away from pen turning for a while, finishing up my Bachelor's and Master's degrees. When I was last making pens I had already given up on using 'traditional' mandrels, and have a few sets of kit specific TBC bushings. Now that I am getting back into turning I have been looking at TBC options other than replacing all bushings with TBC versions. I currently see two possible options: first is the PSI Turn Between Centers Mandrel System (~$35), or the Hurricane version (which looks like it is just a rebranded PSI system), and the other option is purchasing a set of 7mm TBC bushing adapters ( anywhere from$5 to $18). The adapters are the obvious economical choice, but there is a greater chance of producing OOR turnings, due to potential mating inconsistencies between the bushings and 60° centers. The PSI Turn Between Centers Mandrel System 'should' produce the best results and, for that reason, is the direction that I am leaning towards. Unfortunately, I have read many reviews where individuals are reporting problems with the bearings in the live center portion of the system. I know that statistically this is a very small portion of the total units that are being used, however it is still a concern.

Therefore, my question is: is it possible to replace these bearings if/when they go bad? Or is disassembly impossible? If the reviews conclusively indicated that the failures did not start until after hundreds of pens were produced then it would at least be a calculated risk, unfortunately some reviews state that the failures occurred almost immediately, which is a risk I would not want to take, unless at-home repairs could be completed.

TIA,

Bill
 
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In my experience the PSI TCB "mandrel" system is not really much better than a normal mandrel as far as non-concentricity issues go. I used one before I went to true TBC, and I really didn't feel I'd realized any benefit from it. The bearings are not that great, and it needs enough compression to stop the soft wobbly feeling it has that you then end up with too much pressure on the blank, which causes another set of problems.

I went TBC with bushings from TBCBushings.com for most things, and a few of the TBC+mandrel combo bushings from Turner's Warehouse (the combo bushings are pretty cool, although so far I've only used them between centers.) I don't regret the change. It is much better than any mandrel or the PSI TBC mandrel system. I find now that the quest is really for the best 60 degree centers (dead and live) that turn as true as possible, to eliminate that last bit of wobble...and, the wear on those centers from the TBC bushings themselves (ironically, the TBCBushings.com ones are so well engineered, that they seem to wear a lot more on the centers, than the centers wear on them...)

Due to the wearing issue, I started looking for ways to manage that. There is a member here, @mmayo that creates 3D printed TBC bushings. I have a couple sets...have not yet had a chance to try them out, but the idea definitely intrigues me. They are officially for finishing purposes, but I am going to give them a try for turning as well, to see how well they fare.
 
I use the PSI turn between centers mandrel system, have been using it since it came out and I have had zero issues with it. Mandrels, TBC, with or without bushings, tbc adapters, always a hot topic. I should amend my initial response, I use the PSI system until I'm about .020 from final size and then use a dead and live center, no bushings,to finish up. Works for me.
 
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Based on the input from here, as well as Facebook, I think I will just be going with TBC bushings. For bushings I already have I will either go with the 7mm TBC adapter or drilling them out with center bits.
 
I spent $18 on TBC adapter and had terrible results. 😟 Also, I contacted TBCBushings and they flat ignored my message. Complete trash.

TBC Converter Bushings

https://www.tbcbushings.com/index.php?route=product/product&path=61&product_id=58 I'm wondering if anyone has experience to share with this item. TBC bushings aren't available for some of the kits I have and the regular bushings are chewing up my live and dead centers...
www.penturners.org
 
Todd in PA said:
I spent $18 on TBC adapter and had terrible results. 😟 Also, I contacted TBCBushings and they flat ignored my message. Complete trash.

TBC Converter Bushings

https://www.tbcbushings.com/index.php?route=product/product&path=61&product_id=58 I'm wondering if anyone has experience to share with this item. TBC bushings aren't available for some of the kits I have and the regular bushings are chewing up my live and dead centers...
www.penturners.org
Click to expand...
I agree with Todd. My advice and I follow it, just buy real TBC bushings. There really is a difference and it is always better. Your mileage may vary.
 
Todd in PA said:
I spent $18 on TBC adapter and had terrible results. 😟 Also, I contacted TBCBushings and they flat ignored my message. Complete trash.

TBC Converter Bushings

https://www.tbcbushings.com/index.php?route=product/product&path=61&product_id=58 I'm wondering if anyone has experience to share with this item. TBC bushings aren't available for some of the kits I have and the regular bushings are chewing up my live and dead centers...
www.penturners.org
Click to expand...
Todd,
I haven't seen a message from you. If you want to, let me figure out what the problem is. If you have issues with any of my bushings I will try everything I can to resolve your problems. I don't get on here much at all so best to email me directly bsnikitas@cox.net. Or you can call or text me @ 757-848-8806
Brian
TBCbushings.com
 
When it comes to final diameter, I don't use bushings at all. You have your pen kit, which provides the exact dimensions you need. Spend your money on a good dead center, 60 degree live center, and calipers and get your measurement off the actual pen parts, then turn to those dimensions.

I do use bushings (if I have them...I don't buy them anymore when I get a new pen kit) on a mandrel saver to get close to final diameter, but even then I stop a good 16th of an inch proud of the bushings.

The problem with bushings in the world of penturning is that there are too many "perfect world" assumptions. You have to assume that the bushings are manufactured to the correct dimension, with the correct tolerance, and are themselves perfectly round and concentric. Then you have to assume that whatever interface you have between the bushing and the pen runs true in all directions. Finally, you have to assume that the pen kit you're using actually meets the advertized specs with little to no variation; you could have perfect bushings, but if your pen kit is a few thousandths above the advertized diameter, turning to the bushing means you've removed too much material. And moving forward, you have to assume that there's consistency from individual kit to individual kit, even if you always buy from the same source. On top of all that, unless you're using a brand new set of bushings, you have to assume you have sanded material off, or at least that you've sanded evenly and you still have a round bushing.

Much better (IMO) to rely on relative measurements from your calipers. That removes issues related to the bushings themselves and addresses inconsistency between individual kits. It also cuts down on the number of parts sitting between headstock and tailstock.
 
Todd in PA said:
I spent $18 on TBC adapter and had terrible results. 😟 Also, I contacted TBCBushings and they flat ignored my message. Complete trash.

TBC Converter Bushings

https://www.tbcbushings.com/index.php?route=product/product&path=61&product_id=58 I'm wondering if anyone has experience to share with this item. TBC bushings aren't available for some of the kits I have and the regular bushings are chewing up my live and dead centers...
www.penturners.org
Click to expand...

** I need to amend my earlier statement. I just got off the phone with Brian from TBCBushings.com. My original message to him requesting a return/refund was not received. But he saw this message and is absolutely a conscientious and caring parts maker. After discussion, he is going to send me a new set because we believe my set must have been in some way misformed. My experience was not typical among his customers. I can't *yet* endorse the TBC CONVERTER product, but I can at least retract my experience about being ignored.

I very much want the product to work as described, and hope I'll be back here in some days to report a more positive experience.
 
UPDATE - 11/16/2022

I received a replacement set of converter bushings from Brian, and also separately purchased a new pair of 60 degree centers to try for a better result.

My findings are that I still get a slightly out-of-round barrel when using these converters. However, the non-concentric issue smaller. I have compensated for this by stopping a but short of final dimension, and then removing the bushings altogether to finish directly between centers. This strategy was recommended by people on IAP. It saves me from accidentally cutting the bushings as well.

Using non-TBC bushings was wearing grooves into my centers. My hope is that the TBC-converter bushings will significantly reduce wear on my new centers.

Todd in PA
 
I had the same issue: slightly out of round. Noting wrong with the bushings. I just pressed to hard, or I need to sharpen my skew. This and scraping the last 0.1 mm was the solution.
 
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