Blowouts - Drilling on the lathe

[cbb007]

I am now using my new Nova chuck and jaws and am extremely happy with them. I was never able to drill a satisfactory hole with my drill press, but now my holes turn out great.

Now I have another problem when drilling my blanks ... When the bit exits the blank I get a blowout every time, to varying degrees. I try to exit slowly, but it still happens. So far, the bits I have used have been standard grind. Would a brad point fix the problem?

On a drill press, I can put a scrap piece of wood under the blank, what can I do on the lathe?

 

[Curly]

007 you can leave your blank long and stop short of drilling through. Then cut it a touch long and trim to length after you glue the tube in.

 

[jttheclockman]

You can do as Pete suggested if the blank is long enough to allow this. The other thing is to glue a small scrap piece to the end. Cut the size of the blank. You could then cut the scrap off using a bandsaw, table saw, hnd saw or whatever your choice. Or you can just turn it off. Good luck.

 

[Skie_M]

Brad points help with the softer woods, but harder woods and acrylics will give you headaches...

PSI sells an acrylic "bullet point" drill bit, that has a high degree of taper on it's tip to help gradually cut through the back of an acrylic blank, reducing the chances of a blowout (supposedly, I've never had the chance to try one yet).

I've found that a nice sharp 118 degree drill bit (standard jobber type) with a split point works well enough for me with hardwoods. I have a Drill Doctor, now, so I can sharpen and split my own drill bits ... This also means that my collection of dull drill bits has evaporated in a hurry.

Having very sharp bits on hand all the time is a pleasure ... since dull bits ALSO greatly increase the chance of a blowout.

 

[Ted iin Michigan]

Thinking Skie may have touched on a cause. Make sure your drill bit is sharp. It's something that's overlooked a lot. I need to resharpen a bit after 20 or so drillings. LOML got me a Drill Dr for Christmas a couple years ago and it really did make a difference. There's a learning curve, but it's not too steep.

On the std twist vs brad point issue, I absolutely prefer standard twist drills. I feed pretty slowly which helps with either style, but I always seemed to get blowouts in brittle acrylics with brad points. A LOT less with twist bits.

 

[magpens]

I always use standard twist, never brad point ... on wood, acrylics, everything.

Drill on my lathe.

Never had a blowout in 700+ pens.

Sorry, 007, can't offer any suggestions but you have a couple above.

 

[cbb007]

Thanks for the replies, everybody.

 

[CREID]

I always drill first into the blank, but not all the way through. Then I cut to length.

 

[MTViper]

Three suggestions: 1) slow down the lathe to 400 RPM or less; 2) clear the swarf every half-inch or so; and 3) feed your drill big in slowly.

If you try to go too fast (lathe or feed speed) or don't clear the chips and shavings out, you can create too much pressure at the exit end and it will blow out every time. Slow speed and clearing the swarf also allows you to drill with less heat build-up. You'll get a feel for how deep you are as you drill more and can make sure the last quarter inch is slow and smooth.

Steve

 

[dachshund1]

Another option is simply to: (1) cut the blank(s) to length; (2) carefully drill about halfway through; and (3) reverse the blank and repeat. Obviously, this involves stopping to remove/reseat the blank, but it's no great inconvenience.

I use pretty much only brad point bits (not by preference - this is just what I have available) and have never blown out a blank using this method. As others have suggested, slow and steady is the ticket (with sharp bits, of course).

As always, YMMV.

Terry

 

[thewishman]

I drill with different kinds bits (not brad point) aat about 800-1000rpm. When I get to the last 1/4" I take tiny bites and back off just enough to clear the chips from the front of the bit. I'm not too careful until that last part.

 

[leehljp]

Many ways and many methods for both safe drilling and for blowouts! :biggrin:

I have never had a blowout on the lathe with specialty blanks even with snakewood IN Drilling. I do NOT turn/drill slow, but I take small bites, and remove the bit on a regular basis - usually after no more than 1/2 inch feed. I turn at 800 to 1000 rpm but am not afraid of 1500 rpm. I have not had a blowout exiting that I can remember. I watch it exit by turning the tail stock wheel a smidgen at a time.

A couple of times (or maybe more) I wrapped delicate blanks tightly in string and CA'ed the stuffings out of them, then drilled.

Part of the "blowout" cause, which many people don't understand or acknowledge is not the speed or temp at all but the thin wood. I can force drill a pine 2x4 and nothing more than an unsmooth hole. IF I cut a section down to 3/4 by 3/4 and decide to drill that, it will cause a blowout. It is the lack of mass and natural reinforcement that allows the blowout to take place. Wood's structural strength is in its mass. Take away the mass, and alternatives to keeping the wood's integrity must be used.

I personally (for myself) have been a proponent for higher speeds and smaller bites, and reinforcing the integrity of weak woods; and almost micro slow exits.

This is not the first time I have posted the picture below, done by our resident engineer on a woodworking forum to show the effects of slow speed vs faster speed in pine:


View in Gallery

Faster speeds take smaller bites at a given feed rate; slower bites can kinda "chew" at the same given rate. Slower has more of a tendency to "grab" rather than slice. Slower does require sharper edges to prevent them from "catching" and tearing.

 

[GDGeorge]

The other thing with brad point vs plain 118 degree is that the drill doctor doesn't do brad points. At least I haven't figured out how. To me a sharp bit is more important. I use a drill press. I start the blank with an automatic center-punch and then drill with a sharp bit. I don't make an effort to be excessively slow because the bit and the blank will heat up. This can get messy, especially with non-wood or gummy blanks.

Best,
Jerry

 

[magpens]

Thanks for the pic, Hank .... interesting !!!!

 

[farmer]

Drilling wood

Many ways and many methods for both safe drilling and for blowouts! :biggrin:

I have never had a blowout on the lathe with specialty blanks even with snakewood IN Drilling. I do NOT turn/drill slow, but I take small bites, and remove the bit on a regular basis - usually after no more than 1/2 inch feed. I turn at 800 to 1000 rpm but am not afraid of 1500 rpm. I have not had a blowout exiting that I can remember. I watch it exit by turning the tail stock wheel a smidgen at a time.

A couple of times (or maybe more) I wrapped delicate blanks tightly in string and CA'ed the stuffings out of them, then drilled.

Part of the "blowout" cause, which many people don't understand or acknowledge is not the speed or temp at all but the thin wood. I can force drill a pine 2x4 and nothing more than an unsmooth hole. IF I cut a section down to 3/4 by 3/4 and decide to drill that, it will cause a blowout. It is the lack of mass and natural reinforcement that allows the blowout to take place. Wood's structural strength is in its mass. Take away the mass, and alternatives to keeping the wood's integrity must be used.

I personally (for myself) have been a proponent for higher speeds and smaller bites, and reinforcing the integrity of weak woods; and almost micro slow exits.

This is not the first time I have posted the picture below, done by our resident engineer on a woodworking forum to show the effects of slow speed vs faster speed in pine:


View in Gallery

Faster speeds take smaller bites at a given feed rate; slower bites can kinda "chew" at the same given rate. Slower has more of a tendency to "grab" rather than slice. Slower does require sharper edges to prevent them from "catching" and tearing.

There are so many different drill bits that one can use its insane.
But is you really want to drill wood fast use a gun drill bit or a coring bit .
https://www.cuesmith.com/coring-drill-312-x-18.html

 

[skiprat]

Couple more things you can try.
A drill bit is like a screw, it wants to move forward and bite into the material. As it starts to come out the other end, the backlash in your lathe tailstock quill allows the bit to jump forward as it exits the material. Try holding the chuck back with your left hand while advancing the quill with your right hand. You can also snug up the quill travel locking lever a bit
On hard plastics, a freshly sharpened drill can be a nightmare. Drill a hole in a chunk of metal before using it particularly on plastic.
Like Hank, I use higher speed, slower feeds on everything but metal. :wink:

 

[leehljp]

There are so many different drill bits that one can use its insane.
But is you really want to drill wood fast use a gun drill bit or a coring bit .
https://www.cuesmith.com/coring-drill-312-x-18.html

The things I learn here make it WELL worth the price of admission! :biggrin: Air cooled drilling! I like that!