Blanks keep busting

[scjohnson243]

So this has happened more than a few times to me - I did not take any pictures, but I should have... My after I'm griding down my blanks and I get it close to the right size the end of the blank cracks off...

I kept making sure my tools were sharp but it happened to me 3 different times yesterday...

Is this something others have experienced? I do have the "cheap" tool set from harbor freight, and I have been using nothing buy my spindle roughing gouge to shape pens... I just ordered a HSS SRG from Sorby, so I dont know if that will matter... Maybe not enough glue on the tube?

I dont really know, just looking for help wasting blanks.

Thanks!!

 

[Swagopenturner]

It's possible you have tightened your mandrel nut too tight. Even with a Mandrel saver this can happen with the tail stock tightened down too much. Is it happening with wood, acrylic, or some other material? I know Tru-Stone really hates thin areas, like the nib ends.
It is possible you may not have spread the glue evenly all over the tube and/or not waited until it is completely cured. I always wait at least several hours if not overnight, before turning a blank to let the glue completely set, no matter what glue I use.
Also, don't forget to roughen the tube before gluing. This gives the glue a better surface to adhere to.
And the last thing; Go Slow! Don't rush a work of art.

 

[sbell111]

It's possible you have tightened your mandrel nut too tight. Even with a Mandrel saver this can happen with the tail stock tightened down too much. Is it happening with wood, acrylic, or some other material? I know Tru-Stone really hates thin areas, like the nib ends.
It is possible you may not have spread the glue evenly all over the tube and/or not waited until it is completely cured. I always wait at least several hours if not overnight, before turning a blank to let the glue completely set, no matter what glue I use.
Also, don't forget to roughen the tube before gluing. This gives the glue a better surface to adhere to.
And the last thing; Go Slow! Don't rush a work of art.

I have two suggestions to add to Mark's:

• Make sure that you are drilling with the correct-sized bit. The kit instructions do not always get this right. If your bit is too large, then the glue will not adequately bridge the gap (while maintaining strength). If the bit is two small, you're basically squeegeeing the glue off the tube as you insert it.
• If you are not milling the blank all the way to the tube, then the mandrel is putting pressure on the blank instead of the tuber. This will cause failures as you describe.

 

[ed4copies]

Show a couple pictures of your blanks, ready to turn.

From the end, showing the brass tube.

Thanks,
Ed

 

[scjohnson243]

Thanks all - When I get home I'll post some pictures, I do tighten my mandrel nut very tight - that could be a problem..

It has happened mostly with Acrylic, I dont have as much of the problem with woods.. I have been roughing the tubes with 50 Sandpaper a bit before I glue it in, but I did notice yesterday that I may not be putting enough glue on - So I will re-glue a few more tonight and see if I can see a difference tomorrow when I turn it.

Thank you for the help... Will post pictures tonight and see if I can figure it out.

 

[edstreet]

To many factors that comes into this and so far good info but several things missing that would help greatly.

Type of material? Direction of cut? Type of cut being made? Speed of the lathe? Type of glue used? How rough, uneven was the material before it exploded? State of the chisel (force, speed, direction) when the explosion happened? Is this always the entry hole or exit hole from the drill bit?

 

[Tim'sTurnings]

Thanks all - When I get home I'll post some pictures, I do tighten my mandrel nut very tight - that could be a problem..

It has happened mostly with Acrylic, I dont have as much of the problem with woods.. I have been roughing the tubes with 50 Sandpaper a bit before I glue it in, but I did notice yesterday that I may not be putting enough glue on - So I will re-glue a few more tonight and see if I can see a difference tomorrow when I turn it.

Thank you for the help... Will post pictures tonight and see if I can figure it out.

When I have broken blanks, most acrylic, I found that I was trying to take too big of a bite with the gouge. Take small cuts with your gouge and do no press real hard. Pressing hard or "jamming" the gouge into the blank will break it every time, especially near the ends of the blank. JMHO.
Tim.

 

[lwalper]

If you're using thick CA to glue the tubes, you may have rubbed it off as you slid the tube in leaving the bottom end without adequate glue. After gluing I frequently add a drop of the thin CA on the end to perhaps wick down into any little gaps remaining.

 

[Kendallqn]

All these suggestions are helpful I prefer epoxy to ca and I use a hanger wire to coat the inside of the drilled blank completely then roll the tube in it so both surfaces are covered before inserting. I also use a skew to turn acrylic not a gouge.

 

[PSNCO]

I don't know if it will help. My son is the turner, I'm more of the enabler. He was blowing out blanks left and right. After talking to another member here, we solved the blown blanks problem with the tool approach. My son was turning above the centerline. It was recommended that he try turning below the centerline. Since changing his approach with the tool to the blank....no more blowouts.

It drove him nuts as he was blowing out the blanks towards the end. It was driving me nuts because he was blowing out a number of blanks that I cast only one or two of.