Help Please ! :)

[The_Bird_Man]

Good evening, hope all is well amongst the forum. Think I'll introduce myself a little first. My name is Eddie, 21 years old and from Lincolnshire. I have been wood turning for the past 7 years and enjoy everytime I'm on the lathe. I'm new to pen turning and have run into difficulty. Everytime I turn down a blank the outer edge of the brass tube to the outer edge of the blank isn't the same measurment 360. I have turned 10 of these so far and have the same problem with every one. It's only half a mm but that makes all the difference as you know and it is rather annoying me. If anyone could shed some light as to what is causing this or what I am doing wrong I would greatly appreciate it ! Many thanks, Eddie :)

 

[TaylorsMirfield.co.uk]

Sounds like possible bent mandrel or too much pressure from your tail stock causing your mandrel to whip

Sent from my HTC One using Tapatalk

 

[Grump]

Bent mandrel, out of round bushes, worn bearings. Tailstock not aligned.
Some pics would be helpful and welcome to the nuthouse init?

 

[The_Bird_Man]

Wow ! Thank-you both for the very quick responses !! Hmmm...... too much pressure from the tailatock sounds possible, although I only did it up enough to prevent any wobble from the mandrel. The mandrel is brand new. Worn bearings, could you elaborate please. Would that cause wobble on the mandrel ? I'll take some pictures now. And thank-you for the welcome ! :)

 

[rayf6604]

One other problem is the possibility that your bushes are not a snug fit on the mandrel bar. There are often differences in mandrel bar diameter and the hole in bushes. If the bushes aren't a snug fit then they can be out of true when the tail stock is tightened.

 

[Penpal]

Morning Eddie roll the mandrel on a flat surface will show if its round or not whenever I bought one I did this disconcerting to the dealer I can tell you. Check with a dead centre in the head and tail stock to see if the points line up, place a thin piece of metal or a feeler guage between the points using the tailstck gently bring the points up you will see clearly how your lathe lines up the rest is up to you.

Welcome to the forum from over here.

Peter,

 

[ni9eofse7en]

I had problems with worn bushes on the lathe causing vibration. Also the best advice was to turn between centres and do one blank at a time.

 

[Pierre]

Are you using a revolving point at the end of your mandrel or are you using a mandrel saver on the tailstock?

If you use a mandrel saver then it must go over the smooth metal and not just the thread else it will wobble. If you are using a revolving point then first check that the hole for the 1/2 MT is clean and sanded down then check for excessive pressure (it is the thread nut that should tighten up and not the tailstock) Equally, if on first use you pushed the revolving point too hard you could have created a secondary dimple in the cup of the mandrel!!

Finally, if it continues check with 2 drive spurs in the headstock and tailstock that their points are perfectly aligned ie 1 mm out is not allowed .

Then at the end of the day whilst turning your pens, if the same problem continues do a 'Walter' and just before finishing, turn the bushings in the tubes 1/4 turn on the final cuts until all is round (at least that's what he told me 3 years ago!!)

PG

 

[The_Bird_Man]

Thanks all again for your replies ! Will try all your suggestions tomorrow and see what conclusion I come up with. In the meantime here is a picture of what I've been ending up with. Many thanks, Eddie.

 

[Phil Dart]

Are you using bushes Eddie, or are you turning between centres? The tube itself looks mis-shapen which leads me to suppose you are not using bushes. Nothing wrong with that approach, and many people faovour it, but something is going wrong along the way, either in trimming your blank, or in mounting it on your lathe. Thanks for the photo, but a brief description of your method might also be useful.

 

[Grump]

All good advise above, try a kiss test.
Make sure the MT's are firmly inserted into clean sockets, clamp down the tailstock in it's natural landing position and wind it out to meet the drive in headstock.
Feel for any wobble in both sides, up down / sideways play on the headstock spindle will identify worn bearings if that's the problem.
Take pics if it's not perfectly aligned and tell us what and how you did it.

 

[Penpal]

Vex problem until fixed.

Peter.

 

[wm460]

Welcome to the forum Eddie, looks like everything has been covered.

 

[bluntchisel]

Hi, Eddie,

Welcome aboard, matey!
As you can see, there has been an excellent response to your problem and hopefully, by now, you've solved it. When you trim each end of your tube/blank are you using the appropriate sized barrel trimmer? Ideally, you should increase the diameter size of the staffs on these trimmers with each increase in the diameter of the brass tubes, so that they are a snug fit. Failure to do this often results in an off-centre trim.

Bob.

 

[Bill Mooney]

A lot to think about there Eddie, all the advice is good so just work your way through it. If your lathe has a swivel head I would start by checking your headstock/tailstock alignment as stated previously by using a dead centre in your headstock & bringing your tailstock with centre together until the points just kiss & see if the points line up. If they don't then adjust the headstock until they do. This is a good starting point before checking the other things suggested. Best of luck.

 

[Grump]

Good point Bill, I had muchly problems with my Charnwood lathe when I first received it.
It was only when I rebuilt it from putting the new bearings in that I found the swivel locating plate was assembled incorrectly and the pin was just a gnats cock out of alignment.
Perfick now init?

 

[Walter]

if the same problem continues do a 'Walter' and just before finishing, turn the bushings in the tubes 1/4 turn on the final cuts until all is round (at least that's what he told me 3 years ago!!)

I can't claim to be the originator of that. It is a tip I picked up from a Barry Gross video.

There has been some good advice already but here is a useful article here from the IAP website that lists some of the possible causes. It may help identify what is causing your problem:

http://content.penturners.org/library/general_reference/Why-are-my-pens-not-round.pdf

 

[The_Bird_Man]

Afternoon folks, hope everyone is good ! Would just like to say, what an awesome forum this is ! Certainly didn't expect this many replies, all greatly appreciated, thank-you ! :) Have been a little busy today so didn't get as much time in the man cave as I would of liked, but I have had a little play about. With the suggestions made, I did the kiss test. Both points matched up perfectly, bearings seem fine, no play in the headstock. Mandrel is turning true with no wobble. I had another go and unfortunately the problem still exsists. This is my method. I also make my own blanks.

1. Rip down timber to 20x20 mm
2. Cut to desired length ( length of brass tube plus a few mm )
3. Mark the center and put in the chuck. Line the X mark up with the tailstock spur.
4. Swap over to Jacobs chuck in tailstock and put in 4mm brad point bit. ( check if the point still matches the center of the X )
5. Turn lathe speed down, start the hole off with the skew chisel and commence drilling slow, cleaning out reguarly. Once complete, repeated with a 7mm brad point.
6. Rough up the brass tube to give it a good key.
7. Spray accelerator in the blank, glue up the brass tube, and slide into blank. ( goes in about 2mm from the surface.
8. Put 7mm barrel trimmer in pillar drill and square both blanks and ends till it just hits the brass tube.
9. Put madrel in headstock, slide on bushings and tighten up brass nut. ( not too tight, but tight enough)
10. Bring up talstock for support and lightly tighten to pick up the slack.
11. Turn to desired shape the dimensions.

 

[Penpal]

With the problem still there repeat carefully each check establish and eliminate one by one you will fix it.

Peter.

 

[Grump]

Sounds like oval or ill fitting bushes after all that lot init?
Next thing to try is between centers, first with bushes in then another go without bushes and using calipers.