Cracking Resin Blanks

[cschimmel]

So I have only made a dozen or so pens from Resin and the last couple I cracked while drilling. I did one on the press and one on the lathe and I really want to figure out what I'm doing wrong. I had never cracked one before but its now mid summer here in AZ so my garage is easily over 100 at all times. Could it be that the bit and blank are starting hot so they are just over heating faster and cracking??

 

[seawolf]

Try putting them in the fridge untill your ready to drill?
Mark

 

[1080Wayne]

Cut blanks long , and dont drill all the way through . That is the commonest cause of cracking . Clear out the cuttings frequently , about every 1/8 inch . Try drilling with water in the hole . The friction created by drilling will often melt the plastic . As the cuttings rise up the bit , they may cool , resolidify , and jam the bit ( at least I think that`s what happens) . Make sure your drill bit is sharp .

Different plastic materials drill differently . There are also differences within one type , sometimes caused by pigments or fillers . Only guaranteed way to not have plastic occasionally break is to use wood . But it has been known to break too !

 

[bruce119]

Another thing I found that works good but you have to be careful. I blow air into the hole as I drill. Now wear eye protection and you don't have to blast it 25 psi is more than enough on difficult materials it keeps it cool and help clears the chips. But you still have to go slow and back out frequently to let cool. I have also had a tub of water nearby and drill a little stop the drill and with a wet rag grab the bit it cools it off fast. That method is real good for something that melts easy or heats the bit real fast and hot. And as was said make sure your bits are sharp you shouldn't have to put pressure on it let the bit do the cutting.

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[Willee]

Keep your bit cool and wet by drilling about a quarter inch, pulling out, and pressing an ice cube against the drill bit.
Mark the drill bit with a sharpie so you know when you are getting close to the end of the blank.
When you are about one quarter inch from the end ... slow the feed rate down.
Be sure you cut that last quarter inch with a clean cool bit.

 

[bruce119]

Keep your bit cool and wet by drilling about a quarter inch, pulling out, and pressing an ice cube against the drill bit.
Mark the drill bit with a sharpie so you know when you are getting close to the end of the blank.
When you are about one quarter inch from the end ... slow the feed rate down.
Be sure you cut that last quarter inch with a clean cool bit.

I love the ice cube. Two fold cool the bit fast and the dripping water falls into the drilled hole for coolant and lubrication.

Great tip thanks.

.

 

[TellicoTurning]

Cut blanks long , and dont drill all the way through . That is the commonest cause of cracking . Clear out the cuttings frequently , about every 1/8 inch . Try drilling with water in the hole . The friction created by drilling will often melt the plastic . As the cuttings rise up the bit , they may cool , resolidify , and jam the bit ( at least I think that`s what happens) . Make sure your drill bit is sharp .

Different plastic materials drill differently . There are also differences within one type , sometimes caused by pigments or fillers . Only guaranteed way to not have plastic occasionally break is to use wood . But it has been known to break too !

I concur with Wayne's suggestion.. I've had a couple of blanks that I didn't follow these suggestions and actually did get the drill bit stuck in a solid block of plastic as the shavings cooled and re solidified.. had to take a hammer and crack the blank off the bit... I don't use water as I drill on the lathe almost exclusively now and don't want to wet the ways because of the rust factor... I drill slow, back out often and leave the blank long.

When drilling a two piece pen, I always drill from the center where I cut the blank so I have a better chance of matching patterns.

 

[cschimmel]

Great tips I think some of these methods will help. It's crazy because of the temp in my shop(garage) I pick up a bit and it feels hot like I was already drilling but its just sitting there. Thanks again.