Please Help! Pen proudness/Not Aligned

[Joe.B14]

Hi all, hoping you can help. I have made a few pens now using different kits (pictured is a Manager Rollerball) but also happens on a few Slim lines I have turned and whilst I’m quite happy with the results I am having an issue which seems to be quite regular no matter what kit…

The image shows the issue circled where essentially one half of the pen seems to have a proudness to just one side/edge against the bushing (Center bands) which means when the pen is together it looks miss-aligned! This is particularly visible on like a slim line profile pen.

Now a couple have not had this issue but many have. I know the lathe is 100% aligned at the centres, I drill on the lathe using a centre finder bit first and the hole seems to drill through the blank straight and I use a mandrel saver which is also straight.

With the above in mind, what could be causing this??

One thought I have had, was currently I am using a barrel trimmer with a hand drill… could this be causing uneven blank ends to the bushing? Should I also use/do this on the lathe?



Thanks in advance! :)

 

[alan morrison]

Mandrel could be over-tightened, causing some bowing.

 

[flexi]

This used to be very common not so much now...
Two things... 1..check the dia of the mandrel against your bushes... Yes they are not always the same size, if your using baggy bushes it will cause this.
2..as Alan has said if you have an adjustable mandrel with a locking wheel on the end, sometimes people get over zealous tightening the tail stock which will distort your mandrel.
The solution to 2 is either a lighter touch on the tail stock tightening , a mandrel saver ( hollow tail stock) or turning between centers 'TBC'....
Hopefully this helps

 

[MikeC]

It looks to me as though the top part where it meets the centre band is not 90 degrees to the tube.
I wouldn't use a barrel trimmer with a hand drill. I think that could well be your problem.
If it is not exactly 90 degrees to the hole and tube that would cause the misalignment.
Use the lathe with the trimmer in the tailstock, and line the tubed blank up accurately to centre with the revolving centre in the tailstock first before you tighten the blank in the headstock. You will see if the tube is lined up to the centre by eying it up with the lathe running before you draw the trimmer up to it to trim off the excess.
Also make sure that the blank is held tightly at the headstock end, otherwise it may wander off line during the trimming process.
Others will advise about their methods, but this is my preferred way of squaring off the blank.
Mike

 

[ValleyBoy]

Given that you have had this issue with different kits, assuming you’re using different bushes for each, then would indicate that it’s mandrel related as has already been mentioned.

You do need to get the ends of the blanks square, but assuming you have, then I would also suggest the mandrel is bending. I notice in the photo above there looks to be a slight split in the wood which may just be a feature, or it may be an indication of over tightening.

You can probably appreciate that if a mandrel is bent then it’s going to manifest in the finished pen more towards the centre than at the ends. This is because any bend in the mandrel is going to be more exaggerated at the mid point. And assuming you don’t have “baggy bushes” (love that phrase Mark) then you won’t notice it as the bushes will just follow the mandrel. So it all looks great when you’re shaping but it’s only when you assemble the pen that the concentricity issue becomes apparent.

So check the mandrel by rolling on a flat surface if possible, or against a straight edge, and if it is straight then try not to over tighten it on the lathe.

Alternatively try turning between centres instead. This will take any potential mandrel issues out of the equation. However you will need callipers to measure the end diameters if you use this method.

Cheers
Ash

 

[Joe.B14]

Mandrel could be over-tightened, causing some bowing.

This used to be very common not so much now...
Two things... 1..check the dia of the mandrel against your bushes... Yes they are not always the same size, if your using baggy bushes it will cause this.
2..as Alan has said if you have an adjustable mandrel with a locking wheel on the end, sometimes people get over zealous tightening the tail stock which will distort your mandrel.
The solution to 2 is either a lighter touch on the tail stock tightening , a mandrel saver ( hollow tail stock) or turning between centers 'TBC'....
Hopefully this helps

It looks to me as though the top part where it meets the centre band is not 90 degrees to the tube.
I wouldn't use a barrel trimmer with a hand drill. I think that could well be your problem.
If it is not exactly 90 degrees to the hole and tube that would cause the misalignment.
Use the lathe with the trimmer in the tailstock, and line the tubed blank up accurately to centre with the revolving centre in the tailstock first before you tighten the blank in the headstock. You will see if the tube is lined up to the centre by eying it up with the lathe running before you draw the trimmer up to it to trim off the excess.
Also make sure that the blank is held tightly at the headstock end, otherwise it may wander off line during the trimming process.
Others will advise about their methods, but this is my preferred way of squaring off the blank.
Mike

Given that you have had this issue with different kits, assuming you’re using different bushes for each, then would indicate that it’s mandrel related as has already been mentioned.

You do need to get the ends of the blanks square, but assuming you have, then I would also suggest the mandrel is bending. I notice in the photo above there looks to be a slight split in the wood which may just be a feature, or it may be an indication of over tightening.

You can probably appreciate that if a mandrel is bent then it’s going to manifest in the finished pen more towards the centre than at the ends. This is because any bend in the mandrel is going to be more exaggerated at the mid point. And assuming you don’t have “baggy bushes” (love that phrase Mark) then you won’t notice it as the bushes will just follow the mandrel. So it all looks great when you’re shaping but it’s only when you assemble the pen that the concentricity issue becomes apparent.

So check the mandrel by rolling on a flat surface if possible, or against a straight edge, and if it is straight then try not to over tighten it on the lathe.

Alternatively try turning between centres instead. This will take any potential mandrel issues out of the equation. However you will need callipers to measure the end diameters if you use this method.

Cheers
Ash

Thank you so much everyone for your help and support with this! Really appreciate your tips and lots for me to think about & try; which I will do this weekend!

I think key takeaways for me to consider as a start then is triple check my mandrel and tbh I may get another this weekend anyways to help with elimination, change how I square the blanks, I.e not by hand & look at the bushings!

Honestly thanks again everyone, really appreciate your time :)

 

[silver]

Some great answers above, few things that I would add to the pot.

If you are using a mandrel saver then only tighten enough to enable the blanks to be turned down, I guess that you may be over tightening due to the ends of the blank not being totally square. It bites on the side that touches first so there isn't enough friction to get the blanks turned.

Even with a hand drill you should be able to get the blanks square! are the end mill inserts the right size? they need to be the right fit so that they don't wobble inside the tube when squaring off.

One thing to watch out for even if you find it to be a mandrell bent then you will need to replace the bushes as they will be worn off set and will cause you problem in the future.

As for the small crack at the clip end, that could be a red herring! that may have happened when pressing the parts together.

Don't forget to let us know how you progress and any problems you find.

 

[Phil Dart]

Some more thoughts to add to the pot Joe.

A hand drilled barrel trimmer should, as Eamonn says, still result in a squared end. Even if it doesn't, that is not the cause of your problem - bushes, assuming thay are a good fit in the tube, have no choice but to go in, in line with the tube. If the end isn't squared, that is an aesthettic issue, not an turning problem.

It is difficult to "over tighten" a mandrel saver to the extent that it would affect alignment. The old fashioned nut-on-the-end mandrels used to sufffer from over tightening and the result was a bent mandrel shaft. However, an overtightened mandrel saver simply puts undue pressure on the bits ON the mandrel, not the madrel shaft itself, so overtightening isn't the cause of your problem either, although if you can't fairly easily move the bits by hand with the lathe stopped, it IS too tight.

Therefore, assuming your centres are lined up in ALL planes, and you have negligable runout, (both aspecsts worth double checking), you are left with three things and you can discount all the others. Two have already been mentioned - a bent mandrel shaft and baggy bushes. The third is too much pressure from the tool whilst turning, which is more oven than not a result of the tool not being sharp enough.

 

[Hallelujahal]

Think you've all nailed it! Phil's final comment rings a bell of familiarity with me

 

[Nicholas Andrews]

Hi all, hoping you can help. I have made a few pens now using different kits (pictured is a Manager Rollerball) but also happens on a few Slim lines I have turned and whilst I’m quite happy with the results I am having an issue which seems to be quite regular no matter what kit…

The image shows the issue circled where essentially one half of the pen seems to have a proudness to just one side/edge against the bushing (Center bands) which means when the pen is together it looks miss-aligned! This is particularly visible on like a slim line profile pen.

Now a couple have not had this issue but many have. I know the lathe is 100% aligned at the centres, I drill on the lathe using a centre finder bit first and the hole seems to drill through the blank straight and I use a mandrel saver which is also straight.

With the above in mind, what could be causing this??

One thought I have had, was currently I am using a barrel trimmer with a hand drill… could this be causing uneven blank ends to the bushing? Should I also use/do this on the lathe?

View attachment 50380

Thanks in advance! :)

In my experience it is very easy to bend a standard length pen mandrel by over tightening of the tail stock. The metal is not the strongest and even taking care not to over tighten, in time mandrels go out of alignment. As has been suggested, turning between centres (TBC) should avoid this problem. Penn State Industries have an excellent TBC system with short mandrels for both the head and tail stock which are just long enough to accommodate the required pen bushings. (They come in both 1 and 2 Morse taper.) This does mean the distance between head and tail stocks is minimal so watch your fingers! It is also possible to turn only one barrel at a time (if the pen kit demands two barrels) thereby increasing slightly the overall time to complete a pen. A small price to pay though for ensuring all parts are in alignment.

 

[Dalboy]

Something that may also help is when turning a double barrel pen like yours is to turn each end separately, this will mean having a shorter mandril and less chance of pushing the centres of centre