Blanks cracking

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Hippie3180

Hippie3180

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I need your thoughts, I've had a small run of caps that are experiencing cracking, they go unnoticed until I go to press the cap/clip. I've noticed that my 27/64 bit is getting very hot, I try to allow time for it to cool, but still it's only seconds before it's very hot. I've tried experimenting with different speeds, I do drill for tubes on my lathe, our drill press isn't deep enough to hold a blank.

I spent half the day in the hot sweaty garage deliriously happy with how this box elder was looking only to discover a crack upon assembly. I'm not sure if the body has one or not because I chose to not waste components. I know the body was super hot upon drilling for the tubes, I did stop to allowed for cooling, I empty waste often and brush off my bit…..what could be going on?

I'll be giving things another go tomorrow as one does, but darn it's so disappointing. 😏

View attachment 355261
 
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Can happen if there is a little glue residue in the tube. Some pen kits are prone to very tight fitting, Triton comes to mind. I use a tubing expander, when I feel I need to. You can also file or sand the inside of the tubes to make a less tight fit. Drill bit getting excessively hot is usually due to it being dull.
 
Hmmm? Dull bits, that is a possibility as these were previously used on hemp that was extremely hard. Also, could be a tight tube. We did clean out the tube and lightly chamfered, so I think we were okay there. Things to think about and look into.
 
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Heat is the biggest enemy when it comes to drilling especially when the bit is deep inside the blank. I think you are right on target about your drill being dulled by drilling hemp. Sharpen it or in my case replace it. - Good Luck- Dave
 
Another thought is if your using barrel trimmers. Sometimes they will mushroom the tubes. I use a rat tail file to make sure the inside of the tubes are smooth and clean. It might be a few things causing the problem not just drilling. I've found that you might get by with an issue here and there but when there's more than one it causes thing to go wrong.
 
I picked up a new drill bit, going to rule a dull bit out first as it seems like a good possibility.
 
I agree with pretty much all of the above. I like to say that the most important thing in pen turning is patience (and, obviously, safety). Waiting for the bit to cool down feels like watching paint dry, but trashing a blank after you've spent the time and effort to get it just right... ugh. Sharp bits are an absolute must. I use a drill doctor to keep mine sharp.

I don't feel like the tubing diameter is consistent in the kits. Every now and then I'll get an order where the parts have a slightly different level of resistance when pressing as compared to the same kit in most other orders. Usually there's not a problem with wood, but the "plastics" are terrible for cracking. The more brittle ones polish up better, but crack much easier. You'll hear that crack when you are pressing and just cringe after working so hard to perfectly polish a barrel. 🤬 Also, consider that, if the parts start to go in at even the slightest angle when pressing, it will crack.

I also use a rat tail file when it seems there will be a problem, especially if I get a little glue in the tube. It pays to use the file on the blank before gluing the tube to make sure there is not much resistance. If I am cutting the tubing (such as for a replacement when a barrel cracks 😢), I always, always chamfer the end. I use a round cold chisel (by hand, not with a hammer) to get just a slight flare on the end; very, very slight mind you. If you are still using a standard barrel trimmer, consider the offset sanding jig in Rick's Custom Tools in our vendor forum.
 
Another possibility is shrinkage/expansion if the wood is not fully dried, or, if the wood/pen blank is allowed to sit by a window in which sun light hits it; extreme humidity swings such as 20% to 80+% over a few days.

Box elder is not notorious but does have a good bit of movement. (Most Woods Move with humidity and temp swings - a known fact). Any woodworker of mechanic with experience with wood handled hammers know that after 3 - 4 years, the wood handle gets loose: One Major cause: humidity swings expand the wood, crush the outer layer, it shrinks in dry times, and then expands again at the next high humidity swing. Over 2, 3, 4 years, loose handle.

This is not your specific problem at this time, but this does highlight that some wood movement becomes critical on pens.

Box Elder characteristics:
Shrinkage: Radial: 3.9%, Tangential: 7.4%, Volumetric: 14.8%, T/R Ratio: 1.9

Red Oak:
Shrinkage: Radial: 4%, Tangential: 8.6%,
Volumetric: 13.7%, T/R Ratio: 2.2

It is in the neighborhood of Red Oak but this aspect of box elder should not be a major problem to cause cracking unless it is green (uncured/unstabilized) wood or in an area where sunlight is hitting it for a few hours at a time.
 
I'm going to ask this because I had it happen to me a couple weeks ago.
do you face the blank and tube after all the finish work is complete to make sure you're still perfectly flush? A little finish in the wrong spot can crack the blanks too
 
You all have given me so much to think about.

I do sand instead of use a barrel trimmer. I do think that possibly my drill bit was dull, it's not really something that was on my radar. I purchased a new drill bit and of course the drill does still get hot. The body blank is longish on this pen, so a bit of a challenge to get through with no heat.The cap is where I've had the cracking though. These blanks were brand new, can't say what temps/humidity they've been exposed to.

The replacement box elder blank I started was very crooked, so my hole is closer to one edge than the other…will see how that pans out. I don't know if there is a possibility of a crack during drilling until I assemble, and yes there is the possibility I cause the crack during assembly and not drilling. Now I have so many more things to be aware of and consider, thank you for your input.
 
Hippie3180 said:
I picked up a new drill bit, going to rule a dull bit out first as it seems like a good possibility.
Click to expand...

It is probably not the bit going dull. (When they do, you can use something like a Drill Doctor to sharpen them up, too, and make them last a LOT longer.) It is just basic physics, really: friction. Every bit I have gets hot. Even at speeds of say 500-700rpm, which is not that fast for small diameter things, the cutting tip of the bit is in contact with another material, and being rotated. So there is a lot of friction involved, which generates heat. The bit being metal, sinks that heat, and increases in temperature. That increase in temperature, then, leads to the bit expanding in volume, which exerts outward pressure on the blank from the inside...which CAN (not necessarily always) lead to cracking.

My solution to heating is to keep the air compressor nozzle handy, and blow a lower pressure stream of air on the bit while I drill. This flow of air captures the heat and moves it off. An added bonus is that the air pressure helps blow the chips/curls being made by the bit, out of the flutes, keeping them clear, so I don't have to go through a ton of "back out the bit to clear the flutes" cycles.

Oh, that is another factor, too...you should be clearing the flutes. One way or another. If you allow the flutes to back up with chips and dust, then that creates even more surface area for friction. Normally, the design of a drill bit is that the edge of the flutes is just a tiny hair smaller than the cutting tip itself, but when the flutes back up with material, that material will expand and come into contact with the inside surface of the hole. That can create a LOT of friction, and since the bit is metal, that head will be sunk into the bit, heating it up even more.

So, I recommend keeping your air compressor nozzle close, and while you are drilling, just keep a lowish pressure stream of air on the bit (and aimed into one of the flutes, which will usually blast chips and curls out the other), and that should keep things cooler, which should avoid most of these problems. A good sign that the bit is expanding too much, is when you start to hear that screech.

A screeching bit, is an expanding bit. If you hear that screech, back the bit out, and use higher pressure air to cool it back down to room temp (or at least, not hot to the touch.) It also helps to measure the speed at which you drill. Too fast, and the higher pressure at the cutting end of the bit increases friction, heating things up that much faster. A measured speed of progression of the bit also helps ensure that the chips and curls actually clear out of the flute on their own...too much pressure/too fast, and the chips and curls will back up in the flute instead. Eventually, once you are deep enough, they have a harder time clearing the flutes on their own, which is where the air pressure helps keep them clear. Even with air pressure, periodic backing out of the bit, clearing the flutes, then cooling with higher pressure air before beginning again, should help you avoid most of the common problems with drilling.
 
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I've chased this problem endlessly. Here are some of the methods I've tried to minimize cracking.

IMG_8043.jpeg


  1. A drill doctor to keep bits sharp, and blanks cool.
  2. A rat file to clean the tube to remove any glue.
  3. A hand reamer to take a few shavings off the end of the tubes. I think this also might widen the tube a hair if used aggressively.
  4. A debur tool to chamfer the end of the tubes.
  5. A set of adjustable reamers to take off brass deeper into the tube when necessary.
  6. Rick Harrel's end sanding system for squaring, and re-squaring after the finish is applied.
  7. Lathe press kit that gives much better control at pressing parts slow, straight and square.
There are others like the tube expander that Ken mentioned. But I don't use them much. I'm not suggesting you need all of these to make good pens. I'm suggesting there are a lot of factors which may or may not solve your problem. Folks here are the best source of helpful suggestions.

My actual best advice to you— buy good quality kits. I'm a big fan of Berea kits and McKenzie among others. They're well made and fit out of the bag without a lot of cartwheels by me to make them work. I also have several kits/makers that I won't use anymore.
 
jrista said:
It is probably not the bit going dull. (When they do, you can use something like a Drill Doctor to sharpen them up, too, and make them last a LOT longer.) It is just basic physics, really: friction. Every bit I have gets hot. Even at speeds of say 500-700rpm, which is not that fast for small diameter things, the cutting tip of the bit is in contact with another material, and being rotated. So there is a lot of friction involved, which generates heat. The bit being metal, sinks that heat, and increases in temperature. That increase in temperature, then, leads to the bit expanding in volume, which exerts outward pressure on the blank from the inside...which CAN (not necessarily always) lead to cracking.

My solution to heating is to keep the air compressor nozzle handy, and blow a lower pressure stream of air on the bit while I drill. This flow of air captures the heat and moves it off. An added bonus is that the air pressure helps blow the chips/curls being made by the bit, out of the flutes, keeping them clear, so I don't have to go through a ton of "back out the bit to clear the flutes" cycles.

Oh, that is another factor, too...you should be clearing the flutes. One way or another. If you allow the flutes to back up with chips and dust, then that creates even more surface area for friction. Normally, the design of a drill bit is that the edge of the flutes is just a tiny hair smaller than the cutting tip itself, but when the flutes back up with material, that material will expand and come into contact with the inside surface of the hole. That can create a LOT of friction, and since the bit is metal, that head will be sunk into the bit, heating it up even more.

So, I recommend keeping your air compressor nozzle close, and while you are drilling, just keep a lowish pressure stream of air on the bit (and aimed into one of the flutes, which will usually blast chips and curls out the other), and that should keep things cooler, which should avoid most of these problems. A good sign that the bit is expanding too much, is when you start to hear that screech.

A screeching bit, is an expanding bit. If you hear that screech, back the bit out, and use higher pressure air to cool it back down to room temp (or at least, not hot to the touch.) It also helps to measure the speed at which you drill. Too fast, and the higher pressure at the cutting end of the bit increases friction, heating things up that much faster. A measured speed of progression of the bit also helps ensure that the chips and curls actually clear out of the flute on their own...too much pressure/too fast, and the chips and curls will back up in the flute instead. Eventually, once you are deep enough, they have a harder time clearing the flutes on their own, which is where the air pressure helps keep them clear. Even with air pressure, periodic backing out of the bit, clearing the flutes, then cooling with higher pressure air before beginning again, should help you avoid most of the common problems with drilling.
Click to expand...
Very informative, I have experienced screeching for sure.
 
Todd in PA said:
I've chased this problem endlessly. Here are some of the methods I've tried to minimize cracking.

View attachment 355307

  1. A drill doctor to keep bits sharp, and blanks cool.
  2. A rat file to clean the tube to remove any glue.
  3. A hand reamer to take a few shavings off the end of the tubes. I think this also might widen the tube a hair if used aggressively.
  4. A debur tool to chamfer the end of the tubes.
  5. A set of adjustable reamers to take off brass deeper into the tube when necessary.
  6. Rick Harrel's end sanding system for squaring, and re-squaring after the finish is applied.
  7. Lathe press kit that gives much better control at pressing parts slow, straight and square.
There are others like the tube expander that Ken mentioned. But I don't use them much. I'm not suggesting you need all of these to make good pens. I'm suggesting there are a lot of factors which may or may not solve your problem. Folks here are the best source of helpful suggestions.

My actual best advice to you— buy good quality kits. I'm a big fan of Berea kits and McKenzie among others. They're well made and fit out of the bag without a lot of cartwheels by me to make them work. I also have several kits/makers that I won't use anymore.
Click to expand...
Also very helpful. I have experienced a variance in kits even within the same line of kits.

What lathe press do you recommend? I do know that I don't feel like I have the best control when using my press..it does sometimes go father than I mean for it to, and yes sometimes parts get wonky.
 
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bugradx2 said:
I'm going to ask this because I had it happen to me a couple weeks ago.
do you face the blank and tube after all the finish work is complete to make sure you're still perfectly flush? A little finish in the wrong spot can crack the blanks too
Click to expand...
I use a very fine sandpaper and by hand sand any ca fingernails off, but that's it.
 
Todd in PA said:
I've chased this problem endlessly. Here are some of the methods I've tried to minimize cracking.

View attachment 355307

  1. A drill doctor to keep bits sharp, and blanks cool.
  2. A rat file to clean the tube to remove any glue.
  3. A hand reamer to take a few shavings off the end of the tubes. I think this also might widen the tube a hair if used aggressively.
  4. A debur tool to chamfer the end of the tubes.
  5. A set of adjustable reamers to take off brass deeper into the tube when necessary.
  6. Rick Harrel's end sanding system for squaring, and re-squaring after the finish is applied.
  7. Lathe press kit that gives much better control at pressing parts slow, straight and square.
There are others like the tube expander that Ken mentioned. But I don't use them much. I'm not suggesting you need all of these to make good pens. I'm suggesting there are a lot of factors which may or may not solve your problem. Folks here are the best source of helpful suggestions.

My actual best advice to you— buy good quality kits. I'm a big fan of Berea kits and McKenzie among others. They're well made and fit out of the bag without a lot of cartwheels by me to make them work. I also have several kits/makers that I won't use anymore.
Click to expand...
Also, I've already had the realization that all kits are not made equal. Good advice, spend money on quality kits.
 
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Wow - Gorgeous Blank - too bad it is cracked. I suppose you could turn about 1/4-inch or so off - down to the brass tube and then glue on and turn a contrasting color like Walnut or something. Then it becomes a segmented pen! - Dave
 
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