made a mistake and drilled the hole too small in blanks

[Mike]

I thought I would turn 5 pens and be more efficient than one at a time. I didn't verify the tube size and drilled the holes with 7mm drill and they need to be 3/8".
Blanks are only about 1/8" longer than tubes.
Blanks are in the $5-7 range and I don't want to ruin them.
Will a brad point 3/8" bit self center?
I was thinking a twist drill might blow out the end.
Maybe drill most of the way with twist drill and switch to brad point for the final 1/4" or so?
I was thinking of trying it on a piece of scrap.

Anyone with tips or shared experience other than paying attention next time?

Thanks in advance for your help!!

 

[jttheclockman]

No on the brad point bit. I would step drill with twist bits. Nice and slow and there will be no blowout.

 

[Mike]

No on the brad point bit. I would step drill with twist bits. Nice and slow and there will be no blowout.

OK, I am going out now to give it a try.
This is procedure I am going with on the first one.
start with 7mm bit in tail stock chuck
slide blank on
move tail stock close to 4 jaw chuck and slide blank into it
clamp
remove 7mm bit
using 3/8" twist drill slowly
600 RPM is slowest speed for my Jet lathe

 

[monophoto]

Ah yes, the 'measure twice' rule. It's nailed me more than a few times.

A brad point bit will not center. Use a standard twist trill bit and let the bit enter the hole slowly. The key is that a typical twist drill bit has two bines - you want to make sure that both come into contact with the edges of the hole at the same time. If you get that right, the bit will center with minimal tear out at the other end.

 

[Mike]

Thanks for the tips, I will post later and let you know the outcome.

 

[Woodchipper]

Glaad i nevir made a misteak in drylling. OK, I put the blank in the vise with the original bit to line it up. Make sure the blank is secure and change to the proper bit to enlarge the hole while drilling slowly (except for acrylic which will bind and cause all sorts of problems). I have looked everywhere and can't find a drill bit to make a hole smaller.

 

[rherrell]

Drill it half way and then turn it around and drill the other half, that will prevent blowout. Use a regular 118 degree drill bit, NOT a brad point.

 

[Mike]

Thanks for the tips and advice.
OK, I opted for the drill press because it will run slower than my lathe.
I sharpened a 3/8" twist drill and used a 7mm drill to align the blank in the vise, then switched to the 3/8" bit.
I drilled all the way through slowly pulling the bit up a few times as I went.
All 5 came out with no blowout on either end.
On to the rest of the fun.

Mike

 

[Mike]

Glaad i nevir made a misteak in drylling. OK, I put the blank in the vise with the original bit to line it up. Make sure the blank is secure and change to the proper bit to enlarge the hole while drilling slowly (except for acrylic which will bind and cause all sorts of problems). I have looked everywhere and can't find a drill bit to make a hole smaller.

Yeah, my son had the same observation last night. Hard to make a hole smaller. We had a good laugh at the dinner table at my mistakes. Seems to happen a lot. You have to have a tough skin to hang out here. No snowflakes around.

 

[Monty]

Yeah, my son had the same observation last night. Hard to make a hole smaller. We had a good laugh at the dinner table at my mistakes. Seems to happen a lot. You have to have a tough skin to hang out here. No snowflakes around.

I've cut this blank 3 times and it's still too short.

 

[AllanS]

I've cut this blank 3 times and it's still too short.

the /real/ reason I started playing with segmentation.

 

[grpass]

Whenever I am going to use a large bit I always start with a 7mm. Then follow with the correct size bit. Makes it easier for me. Less issues. I always use a floor model drill press.

 

[Woodchipper]

Anyone who says they never made a mistake: 1. Is lying through their teeth. 2. Never did anything.

 

[jrista]

So, it seems most people have warned you away from a bradpoint bit. However...let me offer this. A standard drill bit has a 180 degree angle to a point in the CENTER of the bit. So, if you use such a bit, you will have to be very careful when you start the cut, to make sure you don't tear out the wood at the edges, and at the end of the cut to make sure you don't blow out any of the other side.

My opinion is this. A bradpoint drill bit cuts in two places...the point in the center...and at the EDGE of the bit! If you already have a hole, then the center does nothing for you. The bradpoint will simply cut open air through the center of your existing bore. HOWEVER, the fact that a bradpoint cuts at two points at the outer edge of the bit (where the two channels of the flutes start), IMO, gives you the best opportunity for cutting a larger hole without any concern of tearing or blowout.

I would use a bradpoint bit of the right size for your 3/8" tube. Drill on the lathe, with a self-centering set of pen jaws on your chuck. Start slow, yes, but you should have far less concern of tearing out the edges of the hole regardless. When you near the end of the blank, go slow again, let those two corners at the edge of the bit do their job, and just slowly slice your way out. I've drilled many hard resin and trustone (or similar) blanks with bradpoint bits, and never had any blowout issues. In fact, I've had many more blowout issues trying to cut the same materials with standard bits...so when it comes to drilling these harder materials, because of the way a bradpoint drill cuts, I generally prefer them.

There is sometimes the concern that the brandpoint point in the center can lead to the drill bit wandering through the blank at an angle. With woods, I have sometimes encountered this. However in your case, you have already drilled a smaller hole, so the risk of wander due to the point is nil.

 

[jttheclockman]

So, it seems most people have warned you away from a bradpoint bit. However...let me offer this. A standard drill bit has a 180 degree angle to a point in the CENTER of the bit. So, if you use such a bit, you will have to be very careful when you start the cut, to make sure you don't tear out the wood at the edges, and at the end of the cut to make sure you don't blow out any of the other side.

My opinion is this. A bradpoint drill bit cuts in two places...the point in the center...and at the EDGE of the bit! If you already have a hole, then the center does nothing for you. The bradpoint will simply cut open air through the center of your existing bore. HOWEVER, the fact that a bradpoint cuts at two points at the outer edge of the bit (where the two channels of the flutes start), IMO, gives you the best opportunity for cutting a larger hole without any concern of tearing or blowout.

I would use a bradpoint bit of the right size for your 3/8" tube. Drill on the lathe, with a self-centering set of pen jaws on your chuck. Start slow, yes, but you should have far less concern of tearing out the edges of the hole regardless. When you near the end of the blank, go slow again, let those two corners at the edge of the bit do their job, and just slowly slice your way out. I've drilled many hard resin and trustone (or similar) blanks with bradpoint bits, and never had any blowout issues. In fact, I've had many more blowout issues trying to cut the same materials with standard bits...so when it comes to drilling these harder materials, because of the way a bradpoint drill cuts, I generally prefer them.

There is sometimes the concern that the brandpoint point in the center can lead to the drill bit wandering through the blank at an angle. With woods, I have sometimes encountered this. However in your case, you have already drilled a smaller hole, so the risk of wander due to the point is nil.

Just a counter point on this thought. A twist bit has a conical front point which helps centering the bit within an existing hole. Its sharp edges will cut from the center to the outside edge of the bit as with a brad point bit the sharp outside edges cut straight down putting more force on the grain of the thin wood and could rip these as opposed to cutting especially if bit is not sharp. Yes to both bits needing to be sharp and drilled at a slow speed to let the bit do the work. Brad point bits are designed to drill using that center point to accurately align the bit for a hole. You are eliminating this feature when drilling in air and now relying on the drilling device be it a lathe or drill press to be dead on center with blank. Just my point of view and why I said do not use brad point bits to enlarge a hole. It is like using a spade bit to enlarge a hole.

 

[pssherman]

To eliminate the tearout, use a backer board. You can do this by gluing a small block of wood to th end of the blank and cutting it off after drilling. That way any tearout will be in the backer board not your blank.

 

[Mike]

Wow, I didn't expect this many replies. Thanks to everyone.
I have probably drilled about 100 blanks, around 35 about 2008-2009 and the rest over the last year or so. Life got in the way for 10 or 11 years there.
I drilled all of them with the colt pen blank bits. I have only had blowout a couple times and one poorly stabilized spalted maple blank just disintegrated.
My concern here was drilling with a smaller hole already there.
The different opinions are interesting and I am going to have to think about them.

 

[jrista]

Just a counter point on this thought. A twist bit has a conical front point which helps centering the bit within an existing hole. Its sharp edges will cut from the center to the outside edge of the bit as with a brad point bit the sharp outside edges cut straight down putting more force on the grain of the thin wood and could rip these as opposed to cutting especially if bit is not sharp. Yes to both bits needing to be sharp and drilled at a slow speed to let the bit do the work. Brad point bits are designed to drill using that center point to accurately align the bit for a hole. You are eliminating this feature when drilling in air and now relying on the drilling device be it a lathe or drill press to be dead on center with blank. Just my point of view and why I said do not use brad point bits to enlarge a hole. It is like using a spade bit to enlarge a hole.

Yes, the bit would need to be centered "externally" for sure. I'm not disputing that. Just saying, if you put the blank in a pen vise chuck on the lathe, then it will be centered...so you shouldn't even need anything on the bit itself to center. It just will be centered. I guess I should have said, I do not recommend trying this on a drill press, as I think centering properly on a press would be much harder.

On a lathe, the way a bradpoint cuts should greatly limit the chances of tearout or blowout. I've had to do this myself when I've accidentally used the a too-small bit, and I have sets of both bradpoint and standard bits, and I always get better results with the way a bradpoint cuts from the edge. You are correct that you need to be careful about speed. I also am quite careful about the moment of contact...control that, so you lightly start the cut and get a good groove in place before you really get going, and you should be fine, with super-clean edges to the hole.

I just saw the comment about a backer board...and I like that, too. When you have enough blank length (I know that is not the case here), you can also cut the blank longer than necessary, drill to but not through the end of the blank, then saw the blank down to the right size and reveal the hole as well. That, too, can prevent blowout, and is sometimes how I drill blanks with harder materials.

 

[PenPal]

My preferred drill bits have a full drill point followed by fairly flat lands that serve me well over the last 40 rs. There are infinite answers to your query,everything depends on the shape of your blank. I also highly value the final jaws in my drill vice that have a horizontal and vertical vees that allow me to accomodate out of square etc. When cutting burl to follow the grain. My drill vice weighs incredible with micro adjustments in the two main directions gifted me so many years ago. Topped it off with a 4 inch vice and these jaws.

 

[penicillin]

Thanks to everyone for their helpful posts above. I learned a few hints that I had not known before.

All I can add is that I have had poor results from enlarging holes in pen blanks. All of my successes were redrilling wood pen blanks, although not all wood pen blank redrilling was successful. Every one of my plastic (acrylic) pen blank redrilling attempts were failures. They blew out or blew apart near the start. The next time I have that problem, I have a few new ideas (from above) to try ... so .... Thanks!

 

[grpass]

Thanks to everyone for their helpful posts above. I learned a few hints that I had not known before.

All I can add is that I have had poor results from enlarging holes in pen blanks. All of my successes were redrilling wood pen blanks, although not all wood pen blank redrilling was successful. Every one of my plastic (acrylic) pen blank redrilling attempts were failures. They blew out or blew apart near the start. The next time I have that problem, I have a few new ideas (from above) to try ... so .... Thanks!

One more thought. When I enlarge them as I said before, I usually start with a smaller bit about half the size of what the final size is going to be. Always works, At least for me.