out of round

[hazard]

I have been struggling to keep my pens round. I have a new jet variable mini lathe. It seems I get a wobble in the mandral. I try not to tighten the tail stock to much. I have worn the tip on the live center so this might contribute. Probably a little to lose a few times. I switched to the live center from my grizzly lathe. Same taper. I noticed I am getting alittle wear on this also. I tighten the nut on the mandrel to keep the rough blank sold and find that if I loose the nut some after I have the blank round this helps but I still get some wobble. I bought a few extra shafts and have switch them around. Sometimes it helps. Sometimes not. I have pushed out the mandrel to reseat itself. This has helped. Something else I have noticed is the wood pushing me out on the hard grain. It could be a combination if I don't get all of these right I get the wobble or could be turning technique. Just kind of frustration.

I have the $10 mandral from woodcraft. The mandral seems to flex fairly easy. I did buy a pro mandrel from csusa. It looks the same as the woodcraft mandral but is 1" less and costs $10 more.

What is a recommended live center. Is wearing down the tips on the live center caused by the mandral common?

Chris

 

[cowchaser]

I can tell you the recommended live center is the 60 degree live center from www.littlemachineshop.com. It is the part# 1189. I can't help you on the other question.

 

[gwilki]

Chris

The live centre that comes with the Jet mini is not good for pen turning. As Dustin said, you need to go with a 60 degree centre. The small A mandrel is easily bent, too. A couple of ways to avoid the flex is to get rid of it and turn between centres, or get one of the adjustable mandrels and turn one blank at a time. That way, you only have a couple of inches of mandrel hanging out to flex. You can do the same thing by chucking up the mandrel rod in a Beall chuck.

 

[GBusardo]

Hi, I think almost everyone has had this problem at one time or another, some (me included) more than most. A few tips gathered here have helped me quite a bit. When ever I can, I use the dead center method, as shown on our home page. I also got the live center from the Little Machine shop shown in the link above. Also, clean the end of the mandrel and tip of the center, I bet you find a little gunk there. Lastly, If I need to use a mandrel and I can see my blanks turning out of round, I turn my blanks on the madrel 90 degrees, that has helped me too. If all else fails, you can always use your 100 grit paper gouge [] I think there are actually more help tips on this topic, but these stick out in my mind the most.

 

[Malainse]

Originally posted by cowchaser
<br />I can tell you the recommended live center is the 60 degree live center from www.littlemachineshop.com. It is the part# 1189. I can't help you on the other question.

Live center from Little Machine Shop, great investment !!!!...

 

[hazard]

Thanks for the info

I will be placing an order with the little machine shop tonight or tomorrow.

Chris

 

[ed4copies]

Chris,

Are you using a roughing gouge?

 

[ahoiberg]

also chris, is the out of roundness happening on a particular end of the pen? if your bushings are at all on the threaded part of the mandrel, that can cause out of roundness. also, do a search on 'out of round' and you might find some old threads dealing with this, i know i started one up a while ago and there were some good tips in there outside the 60 deg live center.

 

[its_virgil]

Several have suggested the 60 degree live center but I didn't see a reason given to you. Here it is: Look at the tail stock end of your mandrel. There is a dimple bored into it. This dimple is cone shaped and the vertex of the cone, the tip, is 60 degrees. Unless the live center you are using has a 60 degree point they don't match...the cone shaped dimple and the cone shaped live center tip. That is the reason the live center that came with your lathe is wearing the groove around the tip. This wearing will cause the end of the mandrel to wobble or travel in a circular path as it follows the groove. Purchasing a 60 degree live center will take your penturning a notch above what you are doing now. And, the purchase will be one of the best investments you can make to improve your pens. Good luck.
Do a good turn daily!
Don

 

[Firefyter-emt]

And you know, between centres does not require a new live center until you buy "custom made" bushings that have been drilled with a 60 degree center bit.

Still, for about $5.00 the dead center and BCB turning is one of the cheapest ways to seriously improve your turning (and CA finish!)

 

[johnnycnc]

Chris,a new live center,60 degree as others
have said will help,especially over a chewed up one.
It does mate in your mandrel end,and can have an affect.
A big cause of out-of-round for me was tools that
were not truly sharp.A dull tool makes us push to cut,
and the pushing can lead to flexing the mandrel.
It only goes downhill from there.
Try touching up your tool frequently,see if that helps.[]

 

[hazard]

The tools I am using are a Rex-Kip Deep Fluted Fingernail Gouge
I just got from csusa, 1/2" shallow gouge, 1" sorby skew and 1/2" marples skew. I sharpen before every pen I turn. I have learned from bowl turning that when you push and force the chisels everything gets out of round in a hurry so I try not to push at all.

Where can the between center bushing be purchased? I have not seen these for sale anywhere.

"Lastly, If I need to use a mandrel and I can see my blanks turning out of round, I turn my blanks on the madrel 90 degrees" I have tried this with some success.

Last night when I was turning a cigar pen the bushing closest to the head stock was messed up. I was turning bloodwood. Not a difficult wood to turn from my limited experience.

I order two of the live centers from the Little Machine Shop last night so hopefully this will help some.

thanks again for the inputs
Chris

 

[jrc]

I got this live center over 3 years and turned thousands of pens with it. I wore out the one that came with the Jet mini before a year and 3 more after that. This one should last for years.
I had to take off the very tip to fit the mandrell.http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=38573

 

[Firefyter-emt]

Chris, lookup johnnycnc here at IAP he was making the best one on the site, but may be busy for a bit.

 

[THarvey]

The dead center would be the first place I would check.

However, also check your bushings. If the inside diameter has begun to wear, this could cause some bouncing on your mandrel.

The results would be similar.

 

[johnnycnc]

Chris,if you are interested in some between center bushings,
steel AND delrin(saw your other post)check this out
http://www.penturners.org/forum/topic.asp?TOPIC_ID=27934
topic is closed,but I have been a very busy guy,and am set to
open another round up for sale probably this weekend.
If interested,you can PM me before then.

 

[bradh]

I had an out of round issue and I found it was my turning technique. I was so focused on riding the bevel that I failed to notice that I was lifting the tool off the rest. To keep the piece round, the tool needs to stay in contact with the rest.
Hope this helps.