elect1960
Member
I have had a few pens out of round. Not by much but noticable. Me mandrel was bent so I bought a new one. This made it better but not perfect. The mandrel looks like it turns true. Any other sugesstions?
Pen out of round
- Thread starter elect1960
- Start date
Signed-In Members Don't See This Ad
- Status
Signed-In Members Don't See This Ad
ryannmphs
Member
my guess is that the mandrel is bent as well. A good way to test is to put the mandrel on the lathe with nothing on it (no blank or bushings), bring up the tailstock and position the tool rest next to the lathe. Turn on the lathe. Using a pencil, mark 3 - 4 lines on the mandrel (at each end and the middle). But do this very lightly, you should see, as well as hear, if the mandrel has a bend to it.
Ryan
Ryan
wdcav1952
Activities Manager Emeritus
Elect,
Interesting name, BTW. This tip helped me. After you do the majority of the turning, stop and loosen the nut on the mandrel. Make sure the tubes and bushings can move freely, turn them separately without the mandrel turning. Lightly re-tighten the nut on the mandrel. As you turn, the nut can tighten and cause the mandrel to flex slightly out of true. I know it sounds weird, but it happens. I hope this helps.
Interesting name, BTW. This tip helped me. After you do the majority of the turning, stop and loosen the nut on the mandrel. Make sure the tubes and bushings can move freely, turn them separately without the mandrel turning. Lightly re-tighten the nut on the mandrel. As you turn, the nut can tighten and cause the mandrel to flex slightly out of true. I know it sounds weird, but it happens. I hope this helps.
Fred in NC
Member
There are several reasons why barrels are off-center, and sometimes oval.
1. The tubed blanks are not square to the tube. When the nut in the mandrel is tightened, the angled ends of the barrels bows the mandrel. This is why they sell pen mills, although there are other ways to square a barrel to the tube.
Sanding against a 90 deg miter will not work, UNLESS you have managed to dril the hole absolutely straight thru the wood. That seldom happens!
2. The tailstock is overtightened, forcing a bow on the mandrel.
3. To some extent, this also can happen when the nut is tightened too much.
4. The mandrel is bent. Probably a result of any or all of the above.
5. The tailstock is out of alignment with the spindle.
6. The bushings are too loose on the mandrel. This can happen when you use a bushing with a hole much larger than the mandrel. For example, PSI mandrels have a smaller diameter than those from other sources. Their bushings are made to fit their mandrels. Berea, Woodcraft, Craft Supplies, and others are of a better diameter. PSI bushings usually fit them, because they are a loose fit on the PSI mandrels. A good mandrel is about .246" diameter, same diameter as a "D" drill bit.
7. The live center does not fit the end of the mandrel. The hole in the end is usually designed for a 60 deg included angle taper. Most woodworking live centers don't fit very well, and will get worn out.
This is what I would do:
1. Put the EMPTY mandrel in the spindle. That is, if you have one with a Morse taper. Otherwise just mount it whatever way it is supposed to. Push it all the way in BY HAND.
2. Bring the tailstock with the live center in it to about 1/16" from the end of the mandrel. You want a little clearance. Tighten the tailstock.
3. Rotate the spindle BY HAND, while looking at the end of the mandrel. You will be able to see whether it is properly aligned. If it is bent, you will be able to see the end of the mandrel going around in a circle. Straighten it if necessary, or get a good mandrel.
Proper way to mount a mandrel:
1. After squaring the barrels, mount them in the mandrel with the proper bushings. Snug the nut, but DO NOT TIGHTEN IT.
2. Mount the mandrel in the lathe.
3. Bring the tailstock in position with a little clearance. Tighten it.
4. Advance the live center with the wheel until it contacts the mandrel. If you are using a Morse taper, this will finish seating it in the spindle. DO NOT overtighten. Back it up a little, and then just advance it until it is seated inside the hole at the end of the mandrel, and there is no play.
5. Now that the mandrel is straight and secured, tighten the nut at the end of the mandrel. Finger tight is usually enough !!!! That is why it is round and knurled !!!
Make sure the tools are sharp, and that the tool rest is positioned properly.
Don't ask me how I know... been there, my friend !!!
Hope this helps !!
1. The tubed blanks are not square to the tube. When the nut in the mandrel is tightened, the angled ends of the barrels bows the mandrel. This is why they sell pen mills, although there are other ways to square a barrel to the tube.
Sanding against a 90 deg miter will not work, UNLESS you have managed to dril the hole absolutely straight thru the wood. That seldom happens!
2. The tailstock is overtightened, forcing a bow on the mandrel.
3. To some extent, this also can happen when the nut is tightened too much.
4. The mandrel is bent. Probably a result of any or all of the above.
5. The tailstock is out of alignment with the spindle.
6. The bushings are too loose on the mandrel. This can happen when you use a bushing with a hole much larger than the mandrel. For example, PSI mandrels have a smaller diameter than those from other sources. Their bushings are made to fit their mandrels. Berea, Woodcraft, Craft Supplies, and others are of a better diameter. PSI bushings usually fit them, because they are a loose fit on the PSI mandrels. A good mandrel is about .246" diameter, same diameter as a "D" drill bit.
7. The live center does not fit the end of the mandrel. The hole in the end is usually designed for a 60 deg included angle taper. Most woodworking live centers don't fit very well, and will get worn out.
This is what I would do:
1. Put the EMPTY mandrel in the spindle. That is, if you have one with a Morse taper. Otherwise just mount it whatever way it is supposed to. Push it all the way in BY HAND.
2. Bring the tailstock with the live center in it to about 1/16" from the end of the mandrel. You want a little clearance. Tighten the tailstock.
3. Rotate the spindle BY HAND, while looking at the end of the mandrel. You will be able to see whether it is properly aligned. If it is bent, you will be able to see the end of the mandrel going around in a circle. Straighten it if necessary, or get a good mandrel.
Proper way to mount a mandrel:
1. After squaring the barrels, mount them in the mandrel with the proper bushings. Snug the nut, but DO NOT TIGHTEN IT.
2. Mount the mandrel in the lathe.
3. Bring the tailstock in position with a little clearance. Tighten it.
4. Advance the live center with the wheel until it contacts the mandrel. If you are using a Morse taper, this will finish seating it in the spindle. DO NOT overtighten. Back it up a little, and then just advance it until it is seated inside the hole at the end of the mandrel, and there is no play.
5. Now that the mandrel is straight and secured, tighten the nut at the end of the mandrel. Finger tight is usually enough !!!! That is why it is round and knurled !!!
Make sure the tools are sharp, and that the tool rest is positioned properly.
Don't ask me how I know... been there, my friend !!!
Hope this helps !!
woodscavenger
Member
DITTO
Thanks Fred, you beat me to the punch and saved my fingers a lot of typing.
Thanks Fred, you beat me to the punch and saved my fingers a lot of typing.
Fred in NC
Member
Maybe should be saved as an article, to save having to post it over and over.
elect1960
Member
Thanks for the info. I will try it this weekend and let you know how it works out.
Gary
Member
I agree, it is the kind of thing that would be helpful in the Articles Section.
its_virgil
Member
When I first started I noticed that after 6 or 8 pens they started to loose concentricity...looking at the end of the pens I could see that the thickness on one side of the tube was not equal to the thickness across from it. All things mentioned here checked out to be ok. Here is what I was doing...not keeping the tools sharp..I realized that as the tool dulled I would just push harder and by pen number 6 or 8 I was pushing so hard that the mandrel was bowing enough to make the pen out of round. A little touch up with a stone is all it takes to keep the tools sharp. They don't need to be ground on the grinder every time they get a little dull...just a touch up. I use the diamond hones with the plastic backs...a little tounch up between pens and even on the same pen if the wood is hard.
Do a good turn daily and ...keep 'em sharp!
Don
Do a good turn daily and ...keep 'em sharp!
Don
Fred in NC
Member
Don, I agree..... as a matter of fact, I said:
<b>"Make sure the tools are sharp, and that the tool rest is positioned properly."</b>
<b>"Make sure the tools are sharp, and that the tool rest is positioned properly."</b>
J. Fred Muggs
Member
All the above comments are real possibilities. But, one has not yet been mentioned. I have within the last 2 months had two sets of bushings that were not concentric. One was the Gentlemens/statesmens set, the other a cigar set. Each came from a different supplier. In both cases, it was the center bushing that was the problem. Obviously, this can only be a problem on pens where the tube is larger than the 7mm standard and the bushing fits inside the tube.
After doing what Fred suggests above to check the mandrel, put the bushings on the mandrel with plain tubes (no wood), and check to see if the tube is turning concentrically.
After doing what Fred suggests above to check the mandrel, put the bushings on the mandrel with plain tubes (no wood), and check to see if the tube is turning concentrically.
Fred in NC
Member
Ah bad bushings !!! Never ran into that one, but a definite possibility, especially if only some types of pens have the preoblem. Thanks, other Fred !!
joeyh
Member
Fred in NC,
You said something about straitening a mandrel. I've heard something about this in the past on this site. The poster said to look at Russ's website ( I think that the discussion was about bushings ca glued to a mandrel). I looked and couldn't find it. Can you tell me how to save my bent mandrels, or does anyone else know where I can get this information?
Thanks,
Michael
You said something about straitening a mandrel. I've heard something about this in the past on this site. The poster said to look at Russ's website ( I think that the discussion was about bushings ca glued to a mandrel). I looked and couldn't find it. Can you tell me how to save my bent mandrels, or does anyone else know where I can get this information?
Thanks,
Michael
Fred in NC
Member
It is here:
http://www.woodturnerruss.com/Pen12b.html
http://www.woodturnerruss.com/Pen12b.html
joeyh
Member
Fred in NC,
Thank you for your help. This should alow me to repair my rods that are slightly out of allignment.
Michael
Thank you for your help. This should alow me to repair my rods that are slightly out of allignment.
Michael
Rifleman1776
Member
"As you turn, the nut can tighten and cause the mandrel to flex slightly out of true."
I have seen this advice repeatedly here and elsewhere. But, to me, it defies logic. I tighten my nut fairly hard. My reasoning is that I don't want my work to slip while I am turning and that is the purpose of the locking nut. And, the nut (I use a brass washer between the nut and the blank) holds against the tube, not the blank. This puts a stretching stress on the mandrel helping to assure that it is straight and reduces the tendancy to flex.
My tailstock is only gently pressed against the mandrel as overtightening would cause a bend.
My penturning experience falls far short of those here who have made maybe thousands. But, so far, this works for me.
I just don't understand why a less than tight retaining nut would be reccomended. 'Tis a puzzlement, indeed.
I have seen this advice repeatedly here and elsewhere. But, to me, it defies logic. I tighten my nut fairly hard. My reasoning is that I don't want my work to slip while I am turning and that is the purpose of the locking nut. And, the nut (I use a brass washer between the nut and the blank) holds against the tube, not the blank. This puts a stretching stress on the mandrel helping to assure that it is straight and reduces the tendancy to flex.
My tailstock is only gently pressed against the mandrel as overtightening would cause a bend.
My penturning experience falls far short of those here who have made maybe thousands. But, so far, this works for me.
I just don't understand why a less than tight retaining nut would be reccomended. 'Tis a puzzlement, indeed.
Fred in NC
Member
OK....
First of all, if the barrels are not square, you will have problems when you tighten the nut. You will create a bow in the mandrel. If you don't believe me, cut a couple barrells with an exagerated angle at the end, and see what happens. Mount the mandrel on the lathe with the live center just off the end of the mandrel, and tighten the nut. You can see the end of the barrel move away from being centered.
Second, "finger tight" might not mean the same to everyone. To me it means not using a 15" wrench to tighten it. Just tighten by hand with the knurled nut. I have never experienced the nut tightening by itself when turning. A few times it came loose because it was not tight enough.
Just my own experience, OK ? Yours might be different ......
First of all, if the barrels are not square, you will have problems when you tighten the nut. You will create a bow in the mandrel. If you don't believe me, cut a couple barrells with an exagerated angle at the end, and see what happens. Mount the mandrel on the lathe with the live center just off the end of the mandrel, and tighten the nut. You can see the end of the barrel move away from being centered.
Second, "finger tight" might not mean the same to everyone. To me it means not using a 15" wrench to tighten it. Just tighten by hand with the knurled nut. I have never experienced the nut tightening by itself when turning. A few times it came loose because it was not tight enough.
Just my own experience, OK ? Yours might be different ......
Rifleman1776
Member
Fred said, "First of all, if the barrels are not square, you will have problems when you tighten the nut. You will create a bow in the mandrel."
That makes sense. But then the problem is out of square work stock, not a tight nut. Some folks may have techniques that allow turning without squaring the ends of the blanks, I dunno. I square everything before turning. And a well (finger) tightened nut holds the work and seems to do O.K. for me.
That makes sense. But then the problem is out of square work stock, not a tight nut. Some folks may have techniques that allow turning without squaring the ends of the blanks, I dunno. I square everything before turning. And a well (finger) tightened nut holds the work and seems to do O.K. for me.
- Status