Turn Between Centers Question

[Pens By Scott]

Hi everyone,
I've been looking and experimenting. My question on TBC is:

Do you need special Bushings to do all TBC?

With bushings like the ones from PSI for, example, the Majestic, they have 3 parts for the two barrels, not really good to use for TBC (I think)

But for say, an Executive, Polaris, Zen or other ones with two bushings for each barrel, do you still need special bushings for TBC?

I've tried it, it seems to work, but am I setting myself up for injury, or replacement costs for Centers and bushings?

Thanks in advance!

 

[KenV]

John Goodin sells bushings that are specific for turning between centers and some specialty situations such as shell casing pens. These are well made in my experience.

But are not a requirement.

I often use regular bushings with the dead/live centers. I have on occasions, put the bushings into the ER-32 Collets and used a center drill with the lathe to achieve a tapered transition for better fit and easier mounting.

Note that TBC with bushings will not improve on the bushings -- and a couple of times I have noted when the bushing was mounted in the collets that the hole was not as well centered as it should be (the circle was going around in a circle -- the center of the bushing was offset compared to the portion that inserts into the tube).

Bushings are always a replacable consumable.....

 

[ssajn]

I turn almost everything between centers without using bushings. Takes a little longer because you have to measure a lot but I feel I get better results. I've found too many sets of bushings with the thru hole off center not to mention kits from different manufacturer being a little different.

 

[Texatdurango]

Here is something to consider in your evaluation.......

Personally I have used the bushings as supplied by the kit maker which are designed to slide over a mandrel and they DO WORK mounted between centers BUT.......they could be improved! I have also drilled the ends of the kit bushings myself with a 60 degree center drill and have also purchased specialized bushings pre drilled with 60 degree ends.

Try this.... take a kit bushing with just a hole designed to fit over a 1/4" mandrel and place it on the end of a 60 degree center. Move it around on the point and you will readily see that the bushing hole moves around freely on the point but only makes contact on a very thin ring. Then imagine if the bushing had a 60 degree countersink it would fit SNUGLY on the center making for a much more accurate coupling as there is more surface contact to keep the blank aligned.

So, my answer would be that if you want to turn with the bushings you have, knock your socks off, you'll be fine! If you are comfortable with drilling the kit bushings yourself with a center drill, again, knock your socks off, you'll do fine and finally, if you have the money and want to buy the after market pre-drilled bushings they'll work just fine as well so the choice comes down to personal preference.

Just one opinion from one who has done a LOT of center to center turning!

 

[EricJS]

I agree with the above posts; you can use regular bushings, but you'll like the TBC Bushings better.

Once I decide to stay with a certain kit, I generally buy the TBC Bushings from JohnnyCNC. If you use a certain set of bushings very often they are well worth it. If you only use them a few times, you may want to use regular bushings.

 

[PenMan1]

JohnnyCNC makes these little "dodads" that fit into the ends of standard "a" mandrel bushings and converts them to true 60 degree points.

I think he actually sells these as 7 mm TBC bushings, but they work great on my standard "a" mandrel bushings.

At some point, I will replace all my bushings with TBC models, but for now, I like the little converters.

 

[toddlajoie]

I think he actually sells these as 7 mm TBC bushings, but they work great on my standard "a" mandrel bushings.

THAT is a great idea, and I am ashamed that I never thought of even trying it...

I initially tried the standard mandrel bushings with the 2 60deg centers, but found them to be no more, in fact, sometimes less accurate than they were on the mandrel. Using the 7mm TBC bushings would solve that problem and make them at least as accurate as they could possibly be ( being standard mass produced, unchecked bushings after all...)

I use both the TBC bushings and turn some with no bushings at all ( for pen kits that I don't do often enough to warrant buying the TBCs, and kits that Johnny doesn't make bushing for ...) but TBC bushings for not, the bushings are only used to get close to final size, and final sizing, sanding and finishing is always done without bushings between centers, which for me gives a better end result ( to get a good tapered end, you need to be able to go below the final measurement beyond the blank....)

 

[PenMan1]

Todd:
I started looking to see what these things are actually called. I can't find it the invoice anywhere, but I am almost certain that Johnny (possibly Rick Harrell) made them for me.

 

[johnnycnc]

Scott,
You do not need special bushings. I started with the factory bushings when I went to turning between centers in '06.
They were somewhat of an improvement over the mandrel, and got away from the mandrel associated issues.
This did not solve everything for me, as I am a pretty picky guy.
The fit in the tubes and the center hole being off center at times( and even if you 60° it..it's still off center) held me away from MY goals.
My goal was concentric (roundness, whatever you wish to call it)
barrel to kit fitting parts. The specialty bushings I make were purpose driven in their design, and got me where I wanted to go. My goals and anyone else' s may or may not coincide, so find what makes you happy.
I always say...if you are happy with your current results; no need to change a thing.
The 7mm pens are a bit tough without specialty bushes. And those double factory bushes would be a pain, i would think.

Andy; yes, it is likely my 7mm TBC bushings you are using.

 

[azamiryou]

JohnnyCNC makes these little "dodads" that fit into the ends of standard "a" mandrel bushings and converts them to true 60 degree points.

I think he actually sells these as 7 mm TBC bushings, but they work great on my standard "a" mandrel bushings.

Fuh, fuh, fuh... I *have* these, and never thought of using them like this. I think my TBC skillz just leveled up.

 

[johnnycnc]

JohnnyCNC makes these little "dodads" that fit into the ends of standard "a" mandrel bushings and converts them to true 60 degree points.

I think he actually sells these as 7 mm TBC bushings, but they work great on my standard "a" mandrel bushings.

Fuh, fuh, fuh... I *have* these, and never thought of using them like this. I think my TBC skillz just leveled up.

This was discussed by someone here in early April of this year. I uploaded a shot of what it looks like back then.:neutral:
http://www.penturners.org/photos/index.php?n=18038

I put my thoughts in the photo comments then, but won't repeat them here, as they are there!



John

 

[PenMan1]

John:
I thought it was your product. I bought as a special package under a name I can't find on your website. It consisted of the 7 mm "cone" bushings, a comfort? bushing, European set up.

It is a GREAT setup and you should publish it's name and part number here as I am getting too old to even remember where I bought stuff!

 

[PenMan1]

Matthew:
One word of advice. As good as John's 7mm TBC bushings are, if your kit bushings have off center holes, you will still be out of concentric.

The good news is that John's 7mm will show misfit bushing holes as soon as you flip the switch on the lathe.

They really were a good TBC start for me, as I was dead broke at the time. Eventually, I'll own one set of all John's bushings.

 

[leehljp]

I have and use John's bushing on many. I also have some of the cheaper consumer bushings and rarely use them unless I don't have a set of the good ones from John.

Ken Vaughn wrote this: "I often use regular bushings with the dead/live centers. I have on occasions, put the bushings into the ER-32 Collets and used a center drill with the lathe to achieve a tapered transition for better fit and easier mounting."

What this does is eliminates the problem with the hole drilled off center in bushings! Great idea, and I have a full set of collets too. I should have thought of that a long time ago. The down side to that is two fold: 1. the cost if you don't already have the collets, and 2. so many of the commercial/consumer bushings have quite a bit of "play" between them and the tubes, which can affect the outcome regardless if the bushings are perfectly round.