Mica Pearl Blanks

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bigcountry7

bigcountry7

Member
Joined
Dec 30, 2022
Messages
59
Location
Missouri, USA
These are mica pearl blanks from psi. I had my first explosion today while drilling. I wound up setting the depth stop so I left 1/8th and then sized to length.
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It really doesn't like being worked. They also chip out a ton while turning, but the chipout is pretty controlled, so you can manage.

The results are pretty nice though
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Brad point bits have cutting surfaces that are far to aggressive and grabby especially for plastic blanks and especially when breaking through on the bottom of the hole.

I use standard twist drills and drill slowly in a kind of pecking motion to clear the flutes of the bit very frequently and to help reduce heat buildup - heat is one of the real culprits when it comes to blowouts on blanks. On some especially brittle plastics like Inlace Acrylester and on some hard and brittle woods like Ebony, I leave the blank long, mark the drill, and avoid drilling through, then I cut the blank off to expose the hole. (The drill pecking rule of thumb is to not exceed 3 times the drill diameter before withdrawing the bit on each peck).

At some point, I wound up buying a few drill bits that are made specifically for drilling plastics. Instead of the typical 118 & 135-degree point drills, the bits made specifically for plastics are ground to a steeper, 60-degree point angles. This allows for more gradual penetration and significantly less friction (heating) when drilling. They are also less aggressive (grabby) in how they cut. Although it is probably overkill I have for the most part acquired a considerable set of these special 60-degree drill bits in the common pen tube sizes.

Regardless of the equipment and drill bits you use, remember, heat buildup from friction during drilling (packed flutes, etc.) is the primary cause of problems. Drill slow, use sharp bits, use the pecking method, etc. and I'm sure you will get satisfactory results.

Regards,
Dave

PS The pens are gorgeous!
 
Drilling is certainly my least favorite and least successful part of pen making. The advice every gives here is top notch and I appreciate it.

It looks like my dp was set to 800rpm. I slowed that down to 390.

I was clearing chips every 1/8-1/4" and I was using some paraffin on the bit to reduce friction.

I saw some references to fisch bits and I plan to invest in the 7mm and 3/8" bits from them. I do find it easier to line up the bit in the center using the long brad point spur. That's partly because I use this tip hold the blanks:
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Comments on that are welcome. I wasn't sure I'd like making pens or not, but I'm now 80 or 90 pens in since Thanksgiving and I am now open to getting a pen drilling vise.
 
I would give serious consideration to drilling on your lathe. You would need pen jaws for your headstock, and a drill chuck for your tail stock, but the accuracy of drilling (the headstock and tailstock are already in alignment), and the ease of advancing and retracting the drill bit is, in my opinion, far superior to using a drill press with a vice holding the blank. I did that for a couple years, with more than occasional blowouts through the sides. Getting perfect alignment of the blank and drill bit on a drill press is not as reliable as on the lathe. Since I have been using my lathe for drilling, I have not had a single blowout.
 
KMCloonan said:
I would give serious consideration to drilling on your lathe. You would need pen jaws for your headstock, and a drill chuck for your tail stock, but the accuracy of drilling (the headstock and tailstock are already in alignment), and the ease of advancing and retracting the drill bit is, in my opinion, far superior to using a drill press with a vice holding the blank. I did that for a couple years, with more than occasional blowouts through the sides. Getting perfect alignment of the blank and drill bit on a drill press is not as reliable as on the lathe. Since I have been using my lathe for drilling, I have not had a single blowout.
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I have considered drilling on the lathe.
I have a oneway scroll chuck and a Jacob's chuck. I would need a pair of spigot jaws or a new dedicated chuck. I have been trying not to collect too much junk for the lathe. I have the means to purchase what I need, but I fight the urge to buy things I won't use.

Is drilling on the lathe slower?
 
KMCloonan said:
What RPM are you drilling at? And what type of drill bit? Brad point drill bits are notorious for causing blowouts.
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I actually disagree with this. :p I find that with certain materials, bradpoints, because they cut at the edge, actually can give you a much cleaner exit hole. I have had more blowouts in brittle materials with normal bits myself.
 
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For me, I have an okay set of metric brad point bits, so that's what I use.

For my 3/8" blanks, i have cheap twist bits from HF and nice fisch brad points. The brad points wander less, but they seem to heat up faster. I haven't developed a preference yet.

I've never used a sharp angle 60 degree twist bit.
 
KMCloonan said:
I would give serious consideration to drilling on your lathe. You would need pen jaws for your headstock, and a drill chuck for your tail stock, but the accuracy of drilling (the headstock and tailstock are already in alignment), and the ease of advancing and retracting the drill bit is, in my opinion, far superior to using a drill press with a vice holding the blank. I did that for a couple years, with more than occasional blowouts through the sides. Getting perfect alignment of the blank and drill bit on a drill press is not as reliable as on the lathe. Since I have been using my lathe for drilling, I have not had a single blowout.
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This is what I have been doing and have had great luck with no blowouts. I have also been using standard drill bits.

I did have an issue this evening using round blanks. One half drilled perfectly fine. The other half somehow ended up crooked. All I can figure is the chuck wasn't tightened correctly. Still enough material to make it work. But it's the first time I've seen that.

My only real issue is that on my Shop Fox there isn't a standard wheel / - it's much smaller and there is not pin to grab to speed up the insert/withdraw process. It's on my list to make a wheel for it.

Michael
 
As you can see from the replies above , there are several different ways to skin the cat . I`ve used brad points (not always sharp) on the drill press almost exclusively since I started this game . You like them because it is easier to find the blank center . I like them because it is easier to drill off center when my read of the blank tells me that I will get a more attractive pen that way .

Drilling in 1/4 inch pecks to keep the flutes from clogging , leaving the blank long by the an amount equal to the drill point , stopping drilling as the point just starts to come through , then cutting or grinding the excess away , works on all materials .

As others have said , frictional heat buidup is the principal enemy . On low melting point plastics and hard dense woods , I add lubricant to my regime , specifically water . Messy , yes , but the most effective coolant . Oil as a lubricant has some potential for adhesion problems . As a general rule , if the bit is too hot to hold your hand on after a peck , trouble is lurking .
 
Yeah...I definitely had to account for cooling while drilling multiple blanks.

When you clear the chips (the "pecking method" as it seems to be called here), do you pull the bit all the way out of the material or only part way? I usually pull it all the way out.
 
bigcountry7 said:
Yeah...I definitely had to account for cooling while drilling multiple blanks.

When you clear the chips (the "pecking method" as it seems to be called here), do you pull the bit all the way out of the material or only part way? I usually pull it all the way out.
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All the way , every time , and I try to prevent cuttings from falling back in , not always successfully . When using water , the swarf may stick to the flutes , which is a pain , but ***
 
Hello all, let me apologize in advance for my OCD related to terminology. It is a result of 40+ years as a teaching engineer.

Peck Drilling is the standard name in the machining industry for an intermittent feed method which is used to improve chip (swarf) removal and tool (drill bit) cooling. Regardless of the material, it is recommended for all deep drilling as defined by a hole depth 3 or more times the diameter of the hole.

In the more modern world of CNC machining (Computer Numerical Control), the two most common cycles related to Peck Drilling are G73 and G83. The main difference is that in G73 the pecks do not return the tool above the face of the material for each peck, but instead simply backs off the cutting face to break the swarf chips before reapplying pressure to continue the cut. This is most common when using a Coolant Fed Twist Drill and a pressurized coolant system. For G83 the tool is backed all of the way out of the face of the material for each peck as there is no pressurized coolant used to cool the material and tool and to clear the swarf.

Dave
 
egnald said:
Hello all, let me apologize in advance for my OCD related to terminology. It is a result of 40+ years as a teaching engineer.

Peck Drilling is the standard name in the machining industry for an intermittent feed method which is used to improve chip (swarf) removal and tool (drill bit) cooling. Regardless of the material, it is recommended for all deep drilling as defined by a hole depth 3 or more times the diameter of the hole.

In the more modern world of CNC machining (Computer Numerical Control), the two most common cycles related to Peck Drilling are G73 and G83. The main difference is that in G73 the pecks do not return the tool above the face of the material for each peck, but instead simply backs off the cutting face to break the swarf chips before reapplying pressure to continue the cut. This is most common when using a Coolant Fed Twist Drill and a pressurized coolant system. For G83 the tool is backed all of the way out of the face of the material for each peck as there is no pressurized coolant used to cool the material and tool and to clear the swarf.

Dave
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I didn't even know Gregory peck was a woodworker...
🙂

It makes sense to describe the process, but I don't think I've ever heard it before. I was enrolled in a design school that tended more towards the "fruits and nuts" as opposed to the "nuts and bolts" of design and construction.
 
Tom,
I always drill on the lathe. Have you tried starting with a centre bit to give the other drill bits a starting point?
I also follow up the centre bit with a drill bit which is about half the size of the final hole you want. That means that the final drill bit does not have much more material to remove and it already has a guide hole. There is less chance of any blow out on the exit, because there is not as much pressure on the exit hole area.
On a really difficult material or hard wood I would use more than one starter drill before drilling the final diameter.

As they say -"works for me".

Mike
 
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