Another Sad Lesson Learned Today

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egnald

egnald

Member
Joined
Jun 9, 2017
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Location
Columbus, Nebraska, USA
Greetings fellow IAP members,

My PSI Big Grabber mandrel arrived last week and so today I figured it was finally time to try it out. I've had a blank glued up for more than a week already, just waiting for this.

First of all, the nut on the back of the mandrel that is used to tighten the mandrel (by squeezing a bladder inside the tube) is too big for the through hole in my headstock - just slightly so the morse taper wouldn't go in far enough to stay tight. I cobbled something to make it work for now, but I need to come up with a better solution.

Having very little experience with this sort of thing, I had painted the inside of my blank white, which would have worked out OK, not the best, but at least OK for any standard tubed blank, but not for the material I chose to use for the closed end. It was a tortoise shell blank that I've been saving for quite some time. Anyhow, I turned it and realized I should have probably painted it black (or maybe dark brown). The picture really tells the story. I'm not even going to turn the lower tube. Time to figure out a new blank and cut some new brass tubes I guess. Argh!

Regards,
Dave

PS Once I got it to fit, the Big Grabber mandrel worked really - really good for what I was doing!

IMG_3699 Cropped.jpg
 
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Ugh! It was going to be so good, it makes me feel better about some of the struggles I have.
 
Dave...is there a tube in there, or is it just resin? I'm wondering, if its just the resin and no tube, if you are very careful, if you could use a simple tool (maybe even a repurposed flathead screwdriver properly shaped and sharpened) to clean off the paint, without messing with the resin, and re-paint it?

If there IS a tube...well, maybe the paint might be just what you need to extract the tube and try again? The paint doesn't prevent a glue bond, but in my experience it does weaken it. I am not sure of an exact mechanism off the top of my head, but, I do wonder if you might somehow be able to twist the tube to break the bond (technically, it would be the bond between paint and resin that would be breaking) and extract it. Then you might be able to try again...
 
jrista said:
Dave...is there a tube in there, or is it just resin? I'm wondering, if its just the resin and no tube, if you are very careful, if you could use a simple tool (maybe even a repurposed flathead screwdriver properly shaped and sharpened) to clean off the paint, without messing with the resin, and re-paint it?

If there IS a tube...well, maybe the paint might be just what you need to extract the tube and try again? The paint doesn't prevent a glue bond, but in my experience it does weaken it. I am not sure of an exact mechanism off the top of my head, but, I do wonder if you might somehow be able to twist the tube to break the bond (technically, it would be the bond between paint and resin that would be breaking) and extract it. Then you might be able to try again...
Click to expand...
Yes there are tubes. They were glued in with white epoxy. I thought about trying to drill them back out, but that's for another day. - Dave
 
I was amused a moment ago. I looked at a customer photo of a finished pen where I got the blanks and it was obvious that whoever made it had either left the tube unpainted or had painted the inside of the blank white. It has the same yellow color as mine did.

Blank.JPG Customer Photo.JPG

In the meanwhile I took the a leftover piece of the blank and sliced off a few thin slices - about the thickness around the turned cap - and painted them on one side with an assortment of colors that I have. After the paint dries I will compare them with an unpainted, thicker, blank to see which one matches up the best. Then I'm going to give it another go with new blanks.

As for the blanks I already have painted and tubed, I think I am just going to cut off the closed ends, square the blanks to the tubes, and finish them as a regular Diamond Knurl pen.

Dave
 
egnald said:
Yes there are tubes. They were glued in with white epoxy. I thought about trying to drill them back out, but that's for another day. - Dave
Click to expand...
Ah, white epoxy...Well, that might increase the challenge a bit.
 
egnald said:
First of all, the nut on the back of the mandrel that is used to tighten the mandrel (by squeezing a bladder inside the tube) is too big for the through hole in my headstock - just slightly so the morse taper wouldn't go in far enough to stay tight. I cobbled something to make it work for now, but I need to come up with a better solution.
Click to expand...

David; That is unusual. If you can find out the thread of the rod, you could get another coupler nut (used to join two threaded rods together). Put it on a bolt and grind a taper into the end of the nut. Make sure you leave enough flat for a wrench to grip the nut. I have made closed end pens but only in wood using a mandrel like this one. I also have made my own where I could not get one to fit the tubes I wanted to use. They look similar to this one.
https://www.arizonasilhouette.com/product/CE2.html
 
David

What lathe do your have, and what is the diameter of the headstock bore?

From the image, it appears that the lock nut is larger than the long nut used to position the rod and compress the bladder. What is the dimension across the corners of that locknut?



PSI is usually very good about making sure that their tooling works on their lathes. The product description clearly states that it is designed for MT2 machines. I have a PSI Turncrafter lathe (MT2) , and the headstock bore accommodates a 3/8" draw bar. My first lathe was MT1 and had a 1/4" bore - is it possible that your lathe has an MT2 spindle, but the bore is only 1/4"?

Randy's suggestion is one solution. Another is that if the problem is in fact that the mandrel was designed on the assumption that any lathe with an MT2 spindle will have a 3/8" bore, and yours is the exception, another possibility would be to file/grind the corners off the lock nut so that it fits in the smaller bore.
 

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monophoto said:
David

What lathe do your have, and what is the diameter of the headstock bore?

From the image, it appears that the lock nut is larger than the long nut used to position the rod and compress the bladder. What is the dimension across the corners of that locknut?



PSI is usually very good about making sure that their tooling works on their lathes. The product description clearly states that it is designed for MT2 machines. I have a PSI Turncrafter lathe (MT2) , and the headstock bore accommodates a 3/8" draw bar. My first lathe was MT1 and had a 1/4" bore - is it possible that your lathe has an MT2 spindle, but the bore is only 1/4"?

Randy's suggestion is one solution. Another is that if the problem is in fact that the mandrel was designed on the assumption that any lathe with an MT2 spindle will have a 3/8" bore, and yours is the exception, another possibility would be to file/grind the corners off the lock nut so that it fits in the smaller bore.
Click to expand...

I have a Jet lathe and I use a 3/8 drawbar all the time, so the through hole is 3/8 (0.375). You hit the nail on the head though, PSI used a M6 thread and both the compression nut and lock nut on a M6-1 measure 0.446 across. To fix it I bought an extra M6-1 hex coupler and a couple of nuts. I mounted them on a piece of M6-1 rod and then sanded them down so they would fit. I then filed flats on them to accomodate a 3/16 wrench for tightening. It worked pretty good so I think that will be my permanent solution. - Dave
 
egnald said:
I have a Jet lathe and I use a 3/8 drawbar all the time, so the through hole is 3/8 (0.375). You hit the nail on the head though, PSI used a M6 thread and both the compression nut and lock nut on a M6-1 measure 0.446 across. To fix it I bought an extra M6-1 hex coupler and a couple of nuts. I mounted them on a piece of M6-1 rod and then sanded them down so they would fit. I then filed flats on them to accomodate a 3/16 wrench for tightening. It worked pretty good so I think that will be my permanent solution. - Dave
Click to expand...
I read somewhere that a drawbar can potentially do damage by scoring the inside of the headstock bore if the rod is too large. So when I made my drawbar, I opted to put some heat-shrink tubing over the portion of the bar that actually fits inside the bore - I left about 3/8" uncovered at the 'right' end to screw into whatever fixing I was using it with. I also left the 'left' end uncovered enough to be able to screw the holding nut onto the end with the bar in use. But the portion of the bar that is actually freely exposed inside the headstock is covered in that plastic material.

I wonder if it might be prudent to put some tubing over the sanded coupler to prevent it from damaging the inside of the bore.
 
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