On my last two builds I've noticed that my turned synthetic grips aren't quite as round as my reel seats. In other words when I measure and sand to meet reel seat diameters I get one 'axis' that meets level and the other axis is off by just a hair. ie it's like I'm turning off center. Is it possible that my lathe isn't level from front center to back center? Is there anything I can do to fix this? I'm using 1/4" mandrels in a 4 jaw Barracuda chuck with 60 degree rear. Thanks in advance!

TJB

It might be the reel seat isn't perfectly coencentric to teh blank, and ot teh grip. WHat you can do is sand close on teh lathe, glue everything up, then finish sanding on teh blank an dmake sure everything is perfect. I hand sand every rod I build to make sure its' all perfect.

1/4" mandrels are prone to flexing under pressure, this could be your problem.



Edited 1 time(s). Last edit at 03/07/2012 09:07PM by Phil Erickson.

Thomas,
You can do a short test on your grip.
Take a caliper and measure the handle.
Measure each side, as you rotate the grip in your hand.

Then, also measure from each side to the bored out part of your handle - i.e. the thickness of each side of the handle.

a. If you find that you have equal measurements on each side of the grip as you rotate it in your hand, you have completed a perfect handle on your lathe.
If, however you find that the handle is thicker on one side than another side, that means that you have not turned a perfectly round grip. Of course you need to check each end of the handle.

b. Now, when you have measured the thickness of the handle wall from the outside of the grip to the bored hole, you will discover if you have a perfectly centered hole.

A very frequent cause of the issue that you are having is that the turning of the grip has been done well.
But, then, when the handle was reamed to the final size, the reaming was not done uniformly - i.e. the blank will be closer to the outside edge of the handle on one side than the other side.

I find that if I am reaming a grip, I hold the grip in my hand when using the reamer, but as I ream, I let the handle rotate a bit from time to time in my hand, so that I am getting a uniformly centered hole in the grip.

If, you find that you have a centered grip on one end but not the other end, you can slightly increase the size of the reamed hole on the non centered end of the grip. Then, you can use thin strips of masking tape to get the handle centered. When the handle is glued up, the handle will be rock solid and perfectly centered.

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If you are finding that when measuring the handle you find that the handle is not round; i.e. one side thicker than the other side. you need to take more care when turning the handle.
The best way to achieve this perfect roundness, is to use a good tool holder and a shaper, so that the handle will have a perfect uniform distance from the tool holder as the handle rotates. Then, when doing the final finish with sandpaper, don't be so heavy handed, that you sand the handle out of round. As you sand, it is a good idea to stop from time to time to double check the concentricity of the handle. If you do find that you are getting out of round, lock up the handle and sand material off of the thick side. Then resume the final finish work.

Billy's comment on leaving a touch of extra material on the handle and then doing the final sanding after glue up will also work. But, of course doing the final sanding on a non turning handle will take a greater amount of time, than if you can do a perfect job on the lathe first.

Good luck and may all of your handles be perfect.

Roger

Bill, that's what I thought at first but the second time was matching up with firm fitting Fuji ECMS exposed blank trigger seat (rear of seat to front of back grip).

Phil, I tend to tighten the mandrel, knuckle bustingly / tool chippingly close the the jaws. I figure the minimum exposed mandrel method would help keep the 'noise' vibration to a minimum.

Could the barracuda jaws not be tightening square?

My centers don't perfectly match up tip to tip when placed close up. They are off just a tad. Is there a shim in my future?

TJB

Thomas,
On your lathe, if you chuck in a 2 inch piece of round stock- pipe, rod or similar and tighten it down and then spin the chuck, is there any runout or wobble in the end of the short length of pipe.

If you have any runout at all when you chuck in a piece of perfectly round stock, you have a chuck issue that needs to be addressed.

Also, if you look at either the front or back edge of the chuck as the chuck is rotated, is there any wobble or runout on the chuck itself which would be indicative of a bad lathe head stock to chuck mount.

Good luck
Roger

Are you sanding or cutting? Sandpaper floats on the item's surface. It will not create a perfectly concentric shape.

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Thomas, it is not just the exposed mandrel that flexes, a 1/4" mandrel will flex within the turning grip material. I do not turn EVA , but do turn cork, cork composites and many types of wood and I have quit using a 1/4" due to the flexing issue. I go up in diameter of mandrel as close to the blank size as I can.

I've always chalked it up to the rate at which end or side (my terms) grain sands away. One faster/easier than the other.

Jeff

Lots of great suggestions here.

1. Check your headstock to tailstock alignment. If you install a chuck on the headstock, and close it all the way, then advance the tailstock until it just touches the chuck, the tip of the tailstock should line up perfectly with the hole in the chuck. If not, then you need to adjust your alignment.
2. The suggestions on mandrel flex and size, and reaming are probably the more likely candidates. I also avoid using the 1/4 inch mandrel for this reason.
3. Initial shaping should also be done with some sort of a tool on a tool rest. Either a rasp, stanley surform or a gouge should be used to achieve initial roundness with respect to the mandrel/hole.

When I turn rear grips for spey and switch rods, I do this on a larger mandrel with the butt end of the grip unsupported. This gives me a clean end that I don't have to plug, but I also had to step up my mandrel size and shorten it to help with the roundness issue. I made one from 1/2" drill rod, but just long enough to work a 4" or 5" grip. It seems to work well. I first tried this with a 17" mandrel just hanging the grip off the end and it allowed too much wobble and made an off-center grip. The shorter mandrel did the trick.

Good luck and let us know how it goes.

Terry

Over tightening tailstock center (live or dead) in the mandrel will cause osolation in the mandrel.

Thanks for all the replies!
I gouge first, then wallpaper sander (black with the big holes - forgot what it's called) then sandpaper up to 320. This is all on composite cork.

My chuck does not have any wobble, but a larger mandrel wobbles just a tad if not supported by tailstock.
I did have to file off some of the headstock where it tightens down on the frame when I got this lathe a couple years ago. My headstock and tailstock centers did not match up, leading to the discovery of some metal that should have been removed at manufacturing. Once I removed that the centers were much better but I may have to check again. Hope that made sense. Is there a way to adjust if the centers don't match up perfect?

I do tighten the tailstock pretty hard as it tends to move back a little when I work.

I would like to maintain the use of 1/4 inch mandrels for turning cork as drilling to larger would add a step, but I will do so if it would solve this problem.

TJB

You will continue to have problems with the 1/4" mandrel, they are just too flexible, and the longer the more so! Every mandrel needs to be supported at both ends! You might get away with a big very sort mandrel, but barely! Tightening a 1/4" mandrel strongly with the tail stock will put a bow in the mandrel before you ever turn it on. If your tail-stock tends to loosen at start up, just tighten it a little as you go.

After reading this thread for a couple of days, I'm pretty convinced it is the small diameter mandrel that is the cause of your problem.

As for the "added step", don't you eventually have to enlarge the bore anyway?

Shorten your mandrel. That will immediately equate to a more rigid mandrel. If you can't shorten your mandrel to a more manageable length, turn your grip with the raw grip blank located as close to the head stock as possible. I would also try to bore the material to turn on the largest diameter mandrel that you can possibly get away with. If possible, use lathe "cutting" tools to bring the raw form to a uniformly round cylinder first, then move to sanding. Smaller cuts with less pressure and higher speeds generally create a more uniformly concentric cylinder than trying to remove too much material at once at lower speeds.