Grrrr I had a blowout!

[egnald]

Hi all,

I just had a blowout on a nice Black and White Ebony blank from Laos. I drilled the body OK, but when I was drilling the cap I had a blowout when my drill was exiting the blank. Since this wood is hard and is prone to cracking, normally I would have cut the blank long and stopped drilling before breaking through, then saw it to the final length, but I was being greedy with the material so I could use the little cutoff nub to turn a custom cabochon for a cap insert (Jr. Gent Kit).

Oh well, I will just have to try again with a new blank tomorrow. - Dave

 

[WriteON]

Wood can have a nasty attitude. Sorry to see that.

 

[Gary Beasley]

A split like that, next time I would wrap it in tape. Looks like it had a weak section in it. Might be a good project to see if it will glue back together.

 

[Penchant 4]

Perhaps this would work...or some variation. Glue the pieces to the tube, wrap the whole in tape/rubber bands and then saturate with thin CA such as Glueboost's Ultra thin.

However it is done, hope you are able to retrieve this from its path to the scrap pile.

Good luck!

 

[leehljp]

It looks like you used brad points, and generally brad points are more prone to cause blowouts. It doesn't look like a total loss though. As mentioned by others, and since the wood striations vary in color, it looks doable to CA it together, if done carefully. I would use thick CA or 5 minute epoxy to allow time to get alignments correct.

 

[egnald]

To all: Thank you for your comments and suggestions. Unfortunately the blank was splintered and cracked a bunch along the sides where it blew out so gluing it back together just isn't going to be successful. Next time I might try gluing on some splints before I drill as the cap on the Jr. uses a pretty large hole (not much material left to turn away). And as Hank pointed out, I was using a brad point since I don't have any standard HSS bits for the Jr. series (yet that is).

I'm going to start over this morning with a nice, easy, Olive blank. After all, my objective was to make a custom insert (finial button?) for the cap - my very first attempt. I already knocked the black plastic one out and was ready to go.

Dave

 

[wmillman]

It looks like you used brad points, and generally brad points are more prone to cause blowouts. It doesn't look like a total loss though. As mentioned by others, and since the wood striations vary in color, it looks doable to CA it together, if done carefully. I would use thick CA or 5 minute epoxy to allow time to get alignments correct.

Hank I suspect it's experience that you say brads can cause blow outs like this, I am curious what exactly on the brad do you think is causing this? reason I ask is I have been buying just brads and if there is a good reason not too I would appreciate knowing.

 

[Gary Beasley]

The wing tips on the brad points are bad about grabbing when they start to penetrate the end. The standart point bit on the other hand penetrate as a tiny hole at the bottom and expand the hole as it works through. That presents lower torque on the material. It still must have a backer in tight contact underneath to cut cleanly through. Wrapping the blank or gluing reinforcements will still give much greater chance of success. Also be sure to allow the bit some cooling time as you drill. A hot bit expands a tiny amount and will also cause problems with grabbing plastic blanks of any kind.

 

[Gary Beasley]

Something like this is a good thing to have for any shop and using a drill bit chart to match to the closest letter bit or match a metric size can get you nearly any size hole you need.

Ironton Titanium Drill Bit Set 327-Pc. | Northern Tool

This Ironton® 327-Pc. Titanium Drill Bit Set is a must for all well-stocked garages or workshops! You get a standa...

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[KenB259]

Hank I suspect it's experience that you say brads can cause blow outs like this, I am curious what exactly on the brad do you think is causing this? reason I ask is I have been buying just brads and if there is a good reason not too I would appreciate knowing.

I stick with jobber type bits as much as I can, for the following reasons. Brad points work great across grain, but tend to follow the grain when drilling into end grain. If you're just using a plain wood or plastic blank, not a huge issue. If you are using a segmented blank, straight and true holes become a major concern. If you have any type of metal in a segmented blank, that brad point bit will destroy it in a heartbeat. Also, jobber bits are easily sharpened. I'm sure brad points can be sharpened, I don't know how that's done though.

 

[SteveG]

My approach to drilling blanks that I suspect may blow out is similar to Bill's rubber band solution is to do a continuous wrap using cotton twine, followed by thin CA. Works very well...makes it so you really have to work at it to achieve a blow out.

My experience with brad points tells me to avoid for pen blank drilling for the reasons already mentioned: tendency to go off center when drilling end grain AND likelihood of the "wings" to catch the grain and cause a blow out. Also, you can step drill with standard bits, when you are drilling vulnerable wood. Brad points are not good for the step drill technique.

 

[NGLJ]

To avoid blowouts I drill from both end on my lathe. I start with 4 flute carbide end mills which give a clean hole and don't usually cause a problem. Depending on the size of hole that I need I start with 6mm (good for 7mm tubes) then 8mm and finally 10mm (good for Sierra). I finish off with very sharp brad point bits which now have little to remove and I can drill right through with no problem.

 

[leehljp]

Gary and Ken gave good explanations, and that explanation has been somewhat of a standard for several years here when the subject of "drill bits" are brought up. Ken mentioned when brad points can be used, and in general most experienced pen turners stay away from them for the reasons that Gary said, and from experience.

 

[NGLJ]

Regardless of the drill bit type quality makes a huge difference. Buying less than the best available is a mistake. When I see drill bits for a few $'s I stay away. I only use drill bits from Lee Valley. Their HSS brad point bits are razer sharp and have a specially designed fluting which gives very clean entries and exits. Of course they aren't cheap but quality costs! Recently I have been making stave blanks and I have had no problem with my method as stated in my previous post. Regardless of whether brad point or twist I would never try to drill straight through a blank. There are too many things that can go wrong. I believe a stepped approach gives the best results. It takes a little longer but patience is a virtue in all things.