Why Blanks Go "BOOM"

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jttheclockman

jttheclockman

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Something that comes up so often and is talked about on a regular basis, and that is blanks going BOOM. Blowups. There are a few examples just recently here and people are talking about them. It probably happens way too often in the segmenting world. Just about all of us has had this happen and boy it is devistating when you have so many hours in a blank and it just blows up for one reason or other.

So what i propose we do is use this thread to list as many possible causes and if you have a remedy that has helped you over time, place that here as well.

What I am trying to do is have a reference point or thread that maybe helpful to avoid such pitfalls. Maybe it can be placed in the library or as a sticky pin in one of the forums.

What got me think about this is the topic came up when a member started doing segmenting work and he had the misfortune of being introduced to the dreaded "Blow Up" I mentioned to him though that no one person can tell you exactly why this happened. We were not there and watched every step of the way. As you will read there will be many many reasons why this occurs but hopefully the silver lining is we can learn what to look for and aids to help and maybe some of this can be helpful to others in the future. I feel segmenting is the future or blank making in general. The possibilities are endless.

I will start by listing a few of the obvious ones first and hopefully others we jump in and make this a meaningful post.

***Heat---Probably the number one enemy. It is imperative to control the amount of heat generated when drilling blanks and when turning. Heat will soften glue joints, melt plastics and all around play havoc with any kind of blank weather segmented or not. My remedies I use is to slow things down. slow the speed of the drill, slow the whole process, sharp tools and bits and I like to use DNA ( denatured alcohol) to cool my bits.

***Tools---Can not be stressed any more but sharp tools are a must. Never can a tool be too sharp. Know how to use the tool. Know how to present the tool to the workpice and keep it in that sweet cutting zone throughout the cut. use the proper tool for the job. Not all tools are made for each blank. Probably the most versatile tool is the skew. It is a tool I think everyone should learn to use. You read so many people are switching to carbide cutting tools but to me a skew will outshine any of them if properly used. Not that carbide tools do not have their place. yes they do.

***GluesThis gets subjective at times because we all have our favorites. To me when gluing wood to wood, I will always use Titebond II carpenters glue. When gluing metals to wood or acrylics I chose to use System 3 T88 epoxy. I will use CA on occassion to glue acrylics to acrylics. A couple key factors here in the glue area. Make sure the glue is not old. There is a shelf life to glues.It will lose its properties when gets old. Store glue in a cool dry place.

Make sure when using any glues that you let the glue cure and not just dry.

Also make sure your glue has enough open time or workable time before it starts to set up while you scramble to get your project assembled. Plan and layout your glueups and dry fit things. make sure you have enough clamps and a good way of clamping to insure success.

OK that is it for me for now. Lets have some more of your causes and cures for the dreaded blank "Booms" We all have had them but hopefully the one thing we learn is that we learn. Hopefully this thread can be used as intended.

Thanks for your input. :)
 
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Add to the Heat section; When drilling multi-part blanks, the blank must be supported from the end of the blank. No matter how you drill blanks, having the blank only clamped form the sides will break the glue joint.


Add to the Part about glues; Always scuff the brass tubes before gluing. They may have lacquer to prevent tarnish, or lubrication from the drawing process. This weakens the glue bond between the brass tube and blank.

John; this is a great idea.
 
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I always turn my segmented blanks between centers before try to drill them. I use a nova g3 with pin jaws. By turning them between centers all of the segments are at the same size so I can chuck them up it the G3 like this. The more of the blank that is supported the better as far as I am concerned. Now I don't turn them all the way to round I only knock off all 4 corners so I have something positive that is center. Hope this little tip helps. Nice post John T.
 
I would change the order for myself. I have learned to keep my tools sharp sometimes the hard way. This includes drill bits which are often over looked. But drilling a segmented blank, particularly with the segmenting at non-90-degree angles, with a less than sharp drill bit will cause a blowout.
 
Turning tips:
1) As you turn, stop and apply thin CA about every sixteenth of an inch.
2) Turn the ends, don't touch the middle--this way the middle continues to support your cuts "in" from the ends. Then, when the ends are nearly complete, stop. Use thin CA on the area you have turned and allow it to set (hours). You have many hours invested in MAKING this blank, don't try to rush turning!! When the glue is completely set, so your ends are near finished, THEN turn off the middle.

I learned a lot from Eagle's blanks---this is one I have only shared with a half-dozen people. Once I started doing this, I did not blow up any more blanks!
 
randyrls said:
Add to the Heat section; When drilling multi-part blanks, the blank must be supported from the end of the blank. No matter how you drill blanks, having the blank only clamped form the sides will break the glue joint.
...
Click to expand...

I'm not sure if I understand what you mean by supporting the end of the blank while drilling. Can you elaborate?
 
Three tips. 1. Irregardless of your glue preference, use a small piece of craft foam to spread the glue over the entire surface of the tube before inserting it in the blank.
2. After trimming the blank, check each end for gaps between the blank and tube. Fill any gaps with sawdust and apply thin CA. 3. Irregardless of gaps, seal each end of a trimmed blank with thin CA before turning.
 
Just stopped back to check this post and I see some more great tips coming in. Such as turning the ends first, CA on the ends of a blank to seal it, applying ca as you turn the blank down, supporting the blank as it is turned or drilled. Great keep them coming.
 
I have attempted only 15 or so segmented pens with about 5 blowouts. Since some of the blowouts came at the drilling stage, I started drilling holes first and then glue up the segments. This may not work on complicated segmented pens but has worked for my simple segmented pens. I suppose this method is simply avoiding the heat created by drilling after the glue up.
 
-Glue coverage on the tube is more important than the type of glue used. All the blanks that I have had blow up, I can see the area that gave out first did not have full glue coverage between the blank and the tube. Twisting the glue-covered tube and pushing it in and out will work the glue into the blank. Always check the inside of the blank for a full glue coating before inserting the tube for the last time.
-Cut the ends of the blank from the outside in when turning the blank down, especially when getting close to final size. That way there is wood behind the cut to provide strength. When you cut inside out, the last outer section of the blank has no support behind it and is a prime area for blow out. This is important on burls, soft woods, as well as segmented blanks.
-When working with weaker woods or blank structure, I like to cut the blank down to about .100" oversize, stop and coat the blank in CA before proceeding. The CA coating provides a little more strength when you are cutting the wood while it is quite thin. The coating can also fill any gaps between segments that show up close to the tube.
 
Great thread guys, thanks for all the tips - I also turn all segmented blanks between center to a 3/4" diameter - then drill them on the lathe (840 rpm) while being held in a collet chuck for support. I have tried several brands of epoxy from the local hobby / craft store and always have fought the random failure. Since I started the more complex "V" segmenting with multiple materials, I have been using the Loctite HD epoxy and haven't had failure yet. Another good thing about this epoxy is it dries clear, not yellow. Every tip mentioned here is excellent, but HEAT buildup will kill a blank every time.

To repeat what has already been said;
- If using aluminum or brass in a segmentation; scuff it up - I even scuff up pic guard if I us it.
- Good glue coverage on segment pieces, tube and blank
- sharp bits
- drill slow
- back out often to clear sawdust (I back out every 1/8")
- make sure the bit is cool before re-entering - I cool it down with a wet paper towel.
 

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Great thread, John. You have given us a gift that keeps on giving. One question: I was intrigued by your use of DNA to cool down the drilling process. Easy, and no mess. Do you think there is any danger of the alcohol igniting from the heat? Russ
 
There are good points here but I don't see the state of mind of the turner. I have blown up more blanks being tense or when I have the "I have to get this done!" attitude.

I think a person who is more relaxed is more in tune to the needs of the segmented blank because they are not rushed.

Yeah, hippy point of view, but it is based on my experience.
 
One thing I do when drilling Snakewood is to freeze my drill bits before drilling. Seems to help out. This is particularly useful if you have several of the same size drill bit. Freeze them all and swap out often. When changing bits, insert a frozen tube in the drilled hole to cool it back down.
 
Russknan said:
Great thread, John. You have given us a gift that keeps on giving. One question: I was intrigued by your use of DNA to cool down the drilling process. Easy, and no mess. Do you think there is any danger of the alcohol igniting from the heat? Russ
Click to expand...

If you are getting your bits hot enough to set DNA on fire we need to talk.:)

No I never let the bits get too hot and it cools them down very quickly. I keep the rag soaked. DNA will not raise the grain as water does so it is a good substitute. I drill billiard balls out all the time using a carbide forstner bit and I cool the drilling process out with DNA. Have been doing this for years now.

I am also not sure of the chemical makeup of DNA used in the woodworking industry and that used for burning for cooking. May not be the same chemical breakdown. DNA is widely used in woodworking products and cleaning use. Maybe a chemist here can tell you that. I do not know the flash point of each DNA product.
 
Haynie said:
There are good points here but I don't see the state of mind of the turner. I have blown up more blanks being tense or when I have the "I have to get this done!" attitude.

I think a person who is more relaxed is more in tune to the needs of the segmented blank because they are not rushed.

Yeah, hippy point of view, but it is based on my experience.
Click to expand...

Well I would like to make a comment about this comment. In my opinion if you are not in the right state of mind when using power tools you better put them down and walk away. If your mind is not in the correct place that is when accidents happen.

Being tense while turning can lead to misuse of the tool so relax it is only a material piece of wood.
 
"Attitude" or "confidence" is built up over time and experience.

When I started turning plastics, there was a trepidation that led to "blowups".

Now, I am totally confident that I can turn any material. The problem then is lack of attention. I ruin an occasional blank that is almost finished. I ruin it, because my skew touches the spinning blank as I am "finished with" a cut. TOTALLY a lack of attention!!
 
I agree with Ed. If you can't pay attention to what the blank and/or tool is telling you during your turning process, take a step away and regroup. Knock on wood, of the few blow ups I've ever had, looking back they all gave me plenty of warning that I was putting too much stress on the cut or that some other attention was needed on the blank to solidify it.

For those REALLY sensitive blanks, a layer of gauze and thin CA when drilling is a good option along with frequent time out for a thin ca flood while turning.

Oh yeah, and as someone else already mentioned, stay far away from brad point bits when drilling mixed-media or even in my personal experience any acrylics. They are good on wood and wood only from my point of view, everything else gets a standard ground bit.
 
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BURLMAN said:
One thing I do when drilling Snakewood is to freeze my drill bits before drilling. Seems to help out. This is particularly useful if you have several of the same size drill bit. Freeze them all and swap out often. When changing bits, insert a frozen tube in the drilled hole to cool it back down.
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1st off, let me say that I've never done this, so I'm not speaking from experience. But I'm wondering if the sudden change in temp (going from very hot to very cold) might cause a sudden movement in the wood/resin and cause it to crack. Kind of like putting an ice cube in a hot glass can sometimes cause the glass to break.

EDIT: I agree with Ed and Carl. Most of the times I've had blowouts, I had some warnings that either I ignored, or realized after the fact. When in doubt, slow down, or stop completely, and take a break.
 
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If you have a blank that is made up of many small parts, with many metal and non metal inserts, try gluing thin plywood strip to the four sides before you drill the blank. These will give the blank a lot of support, holding all the parts together while drilling. Plywood turns away very easily on the lathe. I did this on a blank that had 20 plus different parts and it worked perfectly. The first blank made at the same time, without the extra exterior reinforcement, failed twice in drilling. Scrap plywood is cheap and lends a lot of extra strength.
 
airborne_r6 said:
randyrls said:
Add to the Heat section; When drilling multi-part blanks, the blank must be supported from the end of the blank. No matter how you drill blanks, having the blank only clamped form the sides will break the glue joint.
...
Click to expand...

I'm not sure if I understand what you mean by supporting the end of the blank while drilling. Can you elaborate?
Click to expand...

Wayne; I use a Support Block under the blank for the drill bit to press against. If you drill on the lathe, you can insert a block between the jaws. A picture is worth a thousand words.
 
randyrls said:
airborne_r6 said:
randyrls said:
Add to the Heat section; When drilling multi-part blanks, the blank must be supported from the end of the blank. No matter how you drill blanks, having the blank only clamped form the sides will break the glue joint.
...
Click to expand...

I'm not sure if I understand what you mean by supporting the end of the blank while drilling. Can you elaborate?
Click to expand...

Wayne; I use a Support Block under the blank for the drill bit to press against. If you drill on the lathe, you can insert a block between the jaws. A picture is worth a thousand words.
Click to expand...

Perfect, thank you. I do it on the drill press but hadn't thought of doing it on the lathe.
 
I am not sure how I would accomplish this on a lathe either. I suppose you could glue one on then part it off afterward? Makes great sense on the drill press.
 
A few years ago I put together a tutorial for a pen that I made that I think will help new segmentors with the problem of blow-ups. Since I have started using this method, I have not blown up any more blanks. If you follow the tutorial, you might not ever blow up another blank! I have posted this link before but it was years ago and most people don't look that far back. Hope you enjoy it. Here's the link: Brass & Ebony II - A Penturner's Paradise
 
Roy_Quast said:
A few years ago I put together a tutorial for a pen that I made that I think will help new segmentors with the problem of blow-ups. Since I have started using this method, I have not blown up any more blanks. If you follow the tutorial, you might not ever blow up another blank! I have posted this link before but it was years ago and most people don't look that far back. Hope you enjoy it. Here's the link: Brass & Ebony II - A Penturner's Paradise
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Roy I do remember those pens and they still have not been matched in excellence and thought process. As far as gluing the extra pieces to the sides has been talked about by many here before and the use of sandpaper is also a good idea if need be. Those pens are some of the finest segmenting i have ever seen presented. There are a couple others out there but these rank very high.

Have you been doing anything else exciting as this and if so where can we see it?? Thanks for the reminder.
 
John T.
Thanks for asking, but I have not made many pens since then. My time at the job has been very restricting along with home matters. I wish I could get back into turning a few. I have some vacation time coming up.....maybe then. I'll see you on the segmenting threads when I can.
Roy

PS... I still think that if you add wood...LUMBER to all 4 sides, the blank can not blow up when drilling. Not just popsicle sticks, but 1 inch thick maple!!!! Also, if you have thick metal... only use sandpaper. I don't care how sharp you think you have your skew or gouge, the first time it hits metal, the sharpness is history. Which would you rather have, a blank that never blows up which I agree, takes a little bit longer to sand down, or blanks that are finished faster, but half of them blow up?
 
A Good Refresher Thread!

Just browsing and came on this and copied a full page of excellent suggestions for my interest in trying segmenting.

Oh, the tutorial follows a few links, but is AMAZING!!!

Roy: You need to teach us more!!!
 
Roy, I remember reading that, written 2 years before I started turning - I did a LOT of research since I didn't have turners around to teach me. Thanks for reviving it. Amazing piece of work that I filed away in my "future" copy :rolleyes: folder! It did start me using popsicle splits plus heavy twine and CA for drilling support - didn't have that much of a metal load to deal with. Even the work required to build the fixture was daunting! Wow!
 
Ialways knock off the corners of my blank with a belt or disc sander. never had one blow up starting out. I have had to add thin CA to fill areas that did not glue during glue up. Just watch the joints of your segment. JMHO Dennis
 
Roy_Quast said:
A few years ago I put together a tutorial for a pen that I made that I think will help new segmentors with the problem of blow-ups. Since I have started using this method, I have not blown up any more blanks. If you follow the tutorial, you might not ever blow up another blank! I have posted this link before but it was years ago and most people don't look that far back. Hope you enjoy it. Here's the link: Brass & Ebony II - A Penturner's Paradise
Click to expand...

ROY:
Going to the post, it's not showing up. How about reposting for us.
Thanks

Charlie
 
Dieseldoc said:
Roy_Quast said:
A few years ago I put together a tutorial for a pen that I made that I think will help new segmentors with the problem of blow-ups. Since I have started using this method, I have not blown up any more blanks. If you follow the tutorial, you might not ever blow up another blank! I have posted this link before but it was years ago and most people don't look that far back. Hope you enjoy it. Here's the link: Brass & Ebony II - A Penturner's Paradise
Click to expand...

ROY:
Going to the post, it's not showing up. How about reposting for us.
Thanks

Charlie
Click to expand...


Penturner's Paradise is a site not active now, try this: http://www.penturners.org/forum/f13/brass-ebony-54029/
 
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