# Drilling phenolic



## jschaben (Jun 21, 2009)

Went to make a copy of my Jasper 400 yesterday to incorporate guide bushings and.. when I finished drilling and flipped it over there was all kinds of blowout. Used brad point bits so I was more than a little surprised. Any suggestions other than drilling from both sides? The blowout doesn't hurt the function but isn't pretty. :wacko: The material is 1/4" phenolic. Not sure what the fiber in it is, probably paper. It's a recycled mouse tray from a computer desk.


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## bobj3 (Jan 17, 2006)

Hi John

It best to use a forstner bit and drill it out on both sides, and small 1/8" hole will keep in dead center..almost all drill bits will chip it out on the bottom side, just the way the drill bit is made..  takes out the center 1st. the forstner bit will cut the outside of the hole the same time it cuts the center hole out or to say just a little bit b/4 , most of the time when you use a forstner bit you will end up with a small washer that is stuck to the bit the norm..

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jschaben said:


> Went to make a copy of my Jasper 400 yesterday to incorporate guide bushings and.. when I finished drilling and flipped it over there was all kinds of blowout. Used brad point bits so I was more than a little surprised. Any suggestions other than drilling from both sides? The blowout doesn't hurt the function but isn't pretty. :wacko: The material is 1/4" phenolic. Not sure what the fiber in it is, probably paper. It's a recycled mouse tray from a computer desk.


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## CharleyL (Feb 28, 2009)

Phenolic machines much like plexiglass. It is very brittle and heats up easily. It's best to use a scraping cut at slow speed and use a scrap stock backer to prevent blowout. You can use a regular drill bit, but grind a small vertical flat on the end of each flute instead of sharpening it, so that it scrapes the hole rather than biting in and cutting it. Then run the drill slow enough that you don't get any melting. It will make a perfect hole. An alternative is to use glass cutting bits, which have flat, hard blades shaped to a curved point that scrape rather than cut, but again, run them slow enough not to melt the material. 

Putting a flat grind on a regular twist drill bit is a trick that I found for drilling laminate counter tops to keep from chipping the laminate around the hole.


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## jschaben (Jun 21, 2009)

I may try grinding a flat on a regular drill bit. As ALL the holes, except the center one, are 1/8" I was thinking the spurs on the brad points would do it but they obviously didn't. May just use it as is anyway as the blowout doesn't really cause any functional issue.


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## LMT Onsrud (Onsrud) (Jan 9, 2012)

*Drilling Phenolic*



jschaben said:


> I may try grinding a flat on a regular drill bit. As ALL the holes, except the center one, are 1/8" I was thinking the spurs on the brad points would do it but they obviously didn't. May just use it as is anyway as the blowout doesn't really cause any functional issue.



Hello John,

We actually make a bit that is specifically designed for composites and eliminates the delamination on both sides of the material.

The series number can be found here at the below link...

Series 85-800 | SC CFRP DRILL W/ DLC | Item Detail | LMT Onsrud 

The "W" point prevents the "creeping" which ensures hole diameter while the outside cutting edges shear the material producing a good clean hole. These tools are also coated in Diamond Like Coating (DLC) which increases performance. 

Let me know if you require further information...

Fred


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## LMT Onsrud (Onsrud) (Jan 9, 2012)

*Drilling Phenolic*



jschaben said:


> Went to make a copy of my Jasper 400 yesterday to incorporate guide bushings and.. when I finished drilling and flipped it over there was all kinds of blowout. Used brad point bits so I was more than a little surprised. Any suggestions other than drilling from both sides? The blowout doesn't hurt the function but isn't pretty. :wacko: The material is 1/4" phenolic. Not sure what the fiber in it is, probably paper. It's a recycled mouse tray from a computer desk.


These catalogs might assist...if not with this project, maybe one in the future for informational purposes...

The Drill I mentioned in a previous post can be found on page 22 of the OCComp-12 catalog - Milling and Drilling Tools.

Thanks!

Fred


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## bobj3 (Jan 17, 2006)

Hi John

What size hole are you drilling out ....1/2", 3/4",1" ,1 1/2" ???
That's why I suggested the forstner bit,anything bigger than 1/2" can be a hard one to do with the normal drill bit, not to say anything about the cost of the bit.

But if you are just drilling the holes for the 1/8" pin (pivot pin) the normal short stubby drill (135* ) bit works very well..

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## Quillman (Aug 16, 2010)

"Any suggestions other than drilling from both sides?"
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Drilling Phenolic is vaguely like drilling AC & PC.
Plexi drills will minimize the work climbing up the drill but don't necessarily make perfect holes in plastic laminate. And if you want to locate a series of holes on precise centers, other drills and drill shedules should be considered.
One hole for the day? Clamp the work on scrap plastic and use a 118 deg. drill; have a field day.
Perfect holes on precise centers, a bunch? Then counter sink with 82. deg CS, follow with plexi drill ~<1/64" of target hole diameter. Then ream.
Also, and cheaper, use 120 deg. CS followed x 118 deg. hss short drill, then ream.
The drill traction in phenolic is substantial so use a little solvent and slow the drill down.
Maybe 500 max for holes>5/16".


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## jschaben (Jun 21, 2009)

Hi Bob, center hole is 1/2", I did use a forstner bit for that. The rest are 1/8" and used a fairly new brad point for those. Could be the type of phenolic also. 
Fred - thanks for the link, I'm sure that would work. The "W" configuration is what I was trying to get to with the brad point. Unfortunately, a $70 drill bit isn't in the works just yet. I'll probably just use it as is because the issue is primarily cosmetic.


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## bobj3 (Jan 17, 2006)

Hi John

It's hard not to get blow out on the back side just like the MDF board below 

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jschaben said:


> Hi Bob, center hole is 1/2", I did use a forstner bit for that. The rest are 1/8" and used a fairly new brad point for those. Could be the type of phenolic also.
> Fred - thanks for the link, I'm sure that would work. The "W" configuration is what I was trying to get to with the brad point. Unfortunately, a $70 drill bit isn't in the works just yet. I'll probably just use it as is because the issue is primarily cosmetic.


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## Slomoe (Feb 14, 2011)

Use a flat backer board and you will not get blow out. It must be flat and tight as if it was one piece and there will be no blow out.


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