Fauxstone blanks keep failing again and again and again!

[ndep]

I am having a large number of failed fauxstone blanks. I'm attempting to drill out the bigger bore on the majestic pen kits. So this leaves less margin for error because the walls are relatively thin.

Here's what I have tried:

(a) with and without popsicle stick splints to support the blank; when splinted, I tightly wrap the full length of the blank with duct tape. Splinting does not protect the blank --- I have had two blanks fail when splinted. Because the wood grain on the splints run the length of the splint, they have little ability to resist a blank that wants to crumble.

(b) I have been drilling on the lathe at 100rpm, 300rpm and 550 rpm. 300 rpm appears to have a lower risk of blank failure.

(c) I apply moderate pressure advancing the drill bit using the tail stock wheel. I'll advance it a 1/8th to 1/4 turn at a time and then pause. Less pressure is better, but it starts to take up a lot of time if I proceed too slowly.

(d) I have tried with and without spritzing. My spritzing is very aggressive. I do it at least twice a minute, with several squirts each time down the drill bit flutes. I use a spray bottle on stream (not mist) and I squirt directly into the bore hole. Without spritzing the temperature rises to 130 degrees (F) which greatly increases the risk of blank failure. Spritzing generally keeps the temperature at about 80-90 degrees. I think this helps.

The blanks are failing in a few ways. Most of the time, a large chunk blows out with the splint flexing outwards. A few times a hairline fracture will develop along the blank marbling.

I have also noticed that some of the blanks have hairline fractures, cracks, missing chips or other "features" that may or may not compromise the structural integrity of a blank. But even working with the most flawless blanks, they still crumble.

I would appreciate any thoughts on how to improve my abysmal results. The following come to mind as potential avenues for exploration:

(a) should blanks with hairline fractures, cracks, missing chips, etc be discarded or returned due to high risk of failure?

(b) are hairline fractures repairable in some way (my guess is they explode when turned)?

(c) should I splint with 12 or 16 gauge steel plate rather than popsicle sticks?

Thanks!

 

[Bats]

I haven't worked with fauxstone and haven't tried this trick with anything else, so be warned that I'm sorta talking out of my bats here, but a lot of times when I've seen people talk about splinting fragile or segmented (or fragile segmented) blanks they'll wrap it in gauze and then douse the whole mess in CA, so it makes the entire assembly nice and rigid. With duct tape and popsicle sticks, I imagine there's still a lot of room for flexing, and it only takes a tiny bit to allow for a crack or blowout.

As for fixing the hairline fractures, have you tried thin CA? as long as it bonds with the fauxstone (and I have no idea whether it will) then it may be able to penetrate into the cracks.

 

[jttheclockman]

Use smaller kits or a different blank for those large kits.

 

[Curly]

What kind of drill bit are you using? Brad point or standard 118º jobber drills? Cheap or high quality? Sharpe or a little dull??

I suggest you try new regular jobber bits purchased from a supplier like MSC, KBC (I think the US site will show up for you) or any machining tool supplier in the nearest big city.

It has been recommended in the past. Wrap the blank tightly with string and saturate with CA glue. Do it a little at a time as cotton in the string can help kick it off fast and it gets hot. It will turn off when you get to that stage.

 

[carlmorrell]

I made one Fauxstone, was no where near as nice as Trustone. But it was what the customer commissioned. I also almost never use my lathe to drill with.

I would GUESS it is heat and/or too much pressure. I think I get a better feel for how much pressure I apply with a drill press. YMMV. When I drill, I only drill for 10-15 seconds. I always keep vacuum close to the drill bit to help evacuate chips, and get some airflow over the drill bit. After 15 seconds of drilling, I stop and turn my attention to something else for another 15-30 seconds. I never start drilling if the drill bit is hot to the touch. It takes 5 minutes to drill sometimes, but what's the hurry?

I also believe in scary sharp tools. I don't use brad points, because I have no idea how to sharpen them. I use twist drills, and a drill doctor.

Good luck.

 

[KMCloonan]

I just completed a couple of Black & Gold Matrix Tru-Stone pens. I followed advice I saw here, and started with a small drill bit, and progressively worked up to larger and larger bits. This way, the larger bits are removing a lot less material, therefore not heating up near as much. All of the bits were new and sharp. I think I used 5 bits to get to 33/64".

 

[Alchemist]

Have you tried starting with a smaller bit and moving up? Even with larger bores, I will start with smaller bits and move up. I do use my lathe to drill. I use jobbers at anywhere between 500 to 750 rpms… short bursts, no more than a quarter inch deep. Once the bit is inside a good amount, it stops leaving the blank and stays just inside the hole. I use tool blast which is a Teflon spray for cutting tools. I haven't tried the faux stone or trust stones, but know that true stones are like 80-something percent stone and the rest resin.

 

[pshrynk]

No experience with FauxStone, but I use the masonry bits with TrueStone. Start at 7 mm and move up as Alchemist suggested. When you run out of sizes for the masonry bits, then use wicked sharp regular bits and go S L O W L Y.

 

[pewitmer]

Heat build up during drilling can be a cause. Try slowing the process with the big drills. Seems like the resins start to melt when the drill bit gets hot. That happened a couple of times to me in the past. The blank starts to crack then turn to dust.

Paul