nightowl
Member
There are videos here for alot of things but is there one for turning pens between centers? I am curious about how it is done and considering giving it a try.
Mandreless turning?
- Thread starter nightowl
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JDenney
Member
Not sure about videos but this post helped me understand the process. I just got some of JohnnyCNC's bushings on Monday, and what a difference! Turning between centers with factory bushings made a big step up in the quality of my pens, in terms of roundness and the ability to get the ends matched to the mating pieces on the kits. Now, using Johnny's bushings, I'm getting another level of smoothness and performance from my lathe. Eliminating the wobble enabled me to turn down to about .005" or so of the proper diameter, then take the bushings off, and finish w/sandpaper to get within .003" or less of the measured diameter of the kit. It does require a small investment in a dead center for the head stock and a live center for the tail stock, but for me, getting rid of the mandrel was the best thing I've done for the quality of my pen making. I purchased my 60 degree centers from the littlemachineshop.com, but Johnny is now selling them as well, and I have no doubt his are of the highest quality.
leehljp
Member Liaison
In the link that Joe D. refers to above, Frank mentioned that it was much easier to just do than to try to conceive of on a computer. It is so true.
Simply do this:
Place two bushings - one on each end of a tubed blank (squared with a trimmer of course)
Place that between the live center and dead center.
Tighten tail stock,
Turn!
Simply do this:
Place two bushings - one on each end of a tubed blank (squared with a trimmer of course)
Place that between the live center and dead center.
Tighten tail stock,
Turn!
GaryMadore
Member
J
jackrichington
Guest
yes it is that easy..I got my carbide dead center at Grizzly
davinci27
Member
Actually you could skip the bushings, I do.:biggrin:
Oh come ON! It can't possibly be that easy!
Cheers!
Gary
arw01
Member
I had trouble getting it all in line
Tried just using the dead center and my livecenter, but had trouble getting the bushings to line up exactly straight so that I didn't end up with an eccentric turning.
On that pen I ended up using a collett to hold the mandrel as my morse taper that came with the mandrel is not threaded deep enough. This allowed some wobble in the mandrel and always resulted in slightly out of round pen pieces.
Once I go the collett, that went away 100%. I bought a set of Johnycnc bushings in both steel and delrin, but have not made up that particular kit since they came in.
Tried just using the dead center and my livecenter, but had trouble getting the bushings to line up exactly straight so that I didn't end up with an eccentric turning.
On that pen I ended up using a collett to hold the mandrel as my morse taper that came with the mandrel is not threaded deep enough. This allowed some wobble in the mandrel and always resulted in slightly out of round pen pieces.
Once I go the collett, that went away 100%. I bought a set of Johnycnc bushings in both steel and delrin, but have not made up that particular kit since they came in.
leehljp
Member Liaison
Having trouble aligning the dead center and live center is probably not the fault of the LC & DC but something on your lathe. I would look for the cause.
JDenney
Member
You might try again w/John's bushings, as the factory bushings I had were sometimes out of round. If you can have the tips of the centers line up when you slide them together, the problem is most likely the bushings. If the tips of the centers don't exactly meet, then you might need to look at your lathe.
arw01
Member
I think the issue was my aligning the Wall Street II bushings on to the drives. I was not trying to be terribly careful about it as I figured, obviously incorrectly, that hole would be self centering with a 60 degree center tip.
Mr Vic
Member
I couldn't find dead center to save my life so I took a block of UHMW (plastic), chucked it up, turned round and then put a point on one end...Works like a charm...Now everwhere I look I see an offering for the dead centers.....Go figure!
jhudson1977
Member
I'm getting ready to try this as well as my mandrel has a terrible wobble. I replaced the bearings thinking that I had a problem in there (which I did) and the wobble got less, but there is still a wobble.
So, to troubleshoot the issue, I put a center in and mounted a piece of tiger maple. Started to turn that down and as soon as it was round, no more wobble. Now I'm at the point of purchasing a new mandrel set (I've already replaced the rod) or trying this. Since I have everything I need already, I'm going to try this.
However, everything I've read involves placing the bushings into the blanks. How is this accomplished with the Slimlines in which the bushing sits directly against the wood and brass tubes? Is it nothing more than friction force keeping them together or am I missing a step here somewhere?
So, to troubleshoot the issue, I put a center in and mounted a piece of tiger maple. Started to turn that down and as soon as it was round, no more wobble. Now I'm at the point of purchasing a new mandrel set (I've already replaced the rod) or trying this. Since I have everything I need already, I'm going to try this.
However, everything I've read involves placing the bushings into the blanks. How is this accomplished with the Slimlines in which the bushing sits directly against the wood and brass tubes? Is it nothing more than friction force keeping them together or am I missing a step here somewhere?
JDenney
Member
Simply put the centers into the tubes and snug them up. Just be careful not to get them so tight you flare the ends of the tubes. This is how I do my final sanding/cutting to size and how I finish my acrylic blanks. Trying this is much easier than explaining it. 
leehljp
Member Liaison
Unless the bushing holes were drilled off center, (and that does occur with commercially available bushings on occasion) the bushings and 60° center tips are self centering. I've been doing mandrel-less for 2 years and never gave this part a thought. It always self-centers when I pull it up just snug.
When the bushings fit tight into the brass tubes and the blanks are squared, self-centering is a natural event.
johnnycnc
Member
For slimlines/7mm pens it is kinda tough. I am not trying to sell you stuff,
please don't take it that way.
But there are these available;
http://penturnersproducts.com/index.php?main_page=product_info&cPath=2_3&products_id=73
I make other 7mm bushings also for between centers.
Already buying new centers to do the same...after damaging a soft steel live center from PSI. Called them to find out how hard the steel was in their live centers, they said they sell so cheap they cannot use hardened steel. Guess that says it all....don't buy PSI.
So what about the clearance between the bushings and the brass tubes causing OOR? Even the CS bushings for Statesman etc have some clearance it seems. If bushings are not used, will the tubes deform on the centers? I see how you can sand etc with the centers and no bushings, but when turning, is there not too much load to eliminate the bushings? Really hope this works...I really, really dislike (h__e) mandrels.
So what about the clearance between the bushings and the brass tubes causing OOR? Even the CS bushings for Statesman etc have some clearance it seems. If bushings are not used, will the tubes deform on the centers? I see how you can sand etc with the centers and no bushings, but when turning, is there not too much load to eliminate the bushings? Really hope this works...I really, really dislike (h__e) mandrels.
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johnnycnc
Member
Good centers with hardened steel are out there, and not that expensive.
Yes, clearance, or "really poor, sloppy fit" of bushings in tubes can cause OOR. Some are worse than others. I found this out along the road of no mandrel.The technique is good, but the tools have to be good, also.
If you use no bushings,just centers,good luck turning anything.Never worked for me. Just an exercise in frustration.And yes, you can flare tubes and crack brittle materials by cranking centers in tubes;they are a 60° wedge, afterall!
jhudson1977
Member
For slimlines/7mm pens it is kinda tough. I am not trying to sell you stuff,
please don't take it that way.
But there are these available;
http://penturnersproducts.com/index.php?main_page=product_info&cPath=2_3&products_id=73
I make other 7mm bushings also for between centers.
You have recommendations all over this forum so I decided I would give it a try. Now, if I could only find someone that makes a nice high quality spindle to replace the Chinese made one in my TurnCrafter Pro, I would be all set.
Anyone know of anyone that does this?
J
jackrichington
Guest
I'm late, but here's another Idea...check you bushings & make sure they are clean..if they aren't you will get OOR DAMHIKT
Rifleman1776
Member
Oh come ON! It can't possibly be that easy!
Cheers!
Gary
Yes, it is that easy. For all pens, other than 7mm, that is the only way I will make a pen now.
BTW, I get my centers from Grizzly. Wherever you buy them, make sure you get centers for machine tools. Those are hardened, centers specifically for wood are soft steel, probably just to keep cost down.