Help needed

[Alan008]

Well after reading loads of threads about resin casting,watching u tube,loads of people showing how to make pen blanks I tried,I followed the instructions and tried what other people try,still I get bubbles in my blanks,they look good and about half way down machining I hit the bubbles and they are spoiled,I'm very gentle with my chisels so it's not as if I dig in and take lumps out,so it must be something I'm doing wrong,any advice that I haven't tried would be great,thanks in advance.

 

[Lancastrian pens]

Hi
You will need either a vacuum or pressure chamber to remove all your air bubbles plus I always de gass prior to pouring the resin, when it comes to turning your blank get it as round as you can on a belt sander etc so dont try and turn a square blank and use sharp tools and take your time.

 

[Bammer]

1st ... what resin are you using ?

Can't give you a proper answer without knowing that first.

If it's PR, then it's likely they are not bubbles but chip out. You do not need a vacuum or a pressure pot with PR

If it's PU or Epoxy, then you will need a pressure pot.

 

[Penpal]

Brad covered,its a huge subject ,go seek on U Tube and libraries of forums for guidance,but heck living in Durham you are semi surrounded by members of this forum personally.

Peter.

 

[Lancastrian pens]

Regardles of the resin type you need to de gass and use a vacuum/pressure pot if you want quality castings every time, you will introduce air into the resin when mixing in the catalyst and leaving it to luck for all the air bubles to escape will give you a high failure rate.

 

[wm460]

Might be some help in here.

http://www.penturners.co.uk/misc/tutorials.php#tabs-2

 

[Alan008]

Thank you for the information and I have read there is a difference between a pressure and vacuum pot,what do you all recommend,thanks

 

[Paul hd]

Thank you for the information and I have read there is a difference between a pressure and vacuum pot,what do you all recommend,thanks

For resin casting you should go for a pressure pot. Vacuum is only needed to stabilise delicate wood.

 

[Bammer]

Regardles of the resin type you need to de gass and use a vacuum/pressure pot if you want quality castings every time, you will introduce air into the resin when mixing in the catalyst and leaving it to luck for all the air bubles to escape will give you a high failure rate.

Chris you do not need any additional equipment if you use PR. You do need it if you use epoxy, pu, or any of the stuff called alumlite

PR has a low viscosity which allows the bubbles to rise. Warming the pr can increase the flow of bubbles, warming the mold can do this also, vibration such as putting it on a running scroll saw bed can help. Temperature during curing will help also. I have poured then sat in the sun and got perfect casts. I don't even worry about adding bubbles to pr when mixing.

 

[Bammer]

Thank you for the information and I have read there is a difference between a pressure and vacuum pot,what do you all recommend,thanks

Alan

Still need to know what resin you are using ?

 

[Lancastrian pens]

Chris you do not need any additional equipment if you use PR. You do need it if you use epoxy, pu, or any of the stuff called alumlite

PR has a low viscosity which allows the bubbles to rise. Warming the pr can increase the flow of bubbles, warming the mold can do this also, vibration such as putting it on a running scroll saw bed can help. Temperature during curing will help also. I have poured then sat in the sun and got perfect casts. I don't even worry about adding bubbles to pr when mixing.

I always cast under vacuum and most of my casting is done using clear PR or epoxy,more often than not I am casting it around brass tubes with carbon and watch parts attached and without using a vacuum air bubbles can trap on the underside of the tube or behind the watch parts. Having spent hours preparing a blank and have to throw it away is disapointing to say the least.

 

[Bammer]

I always cast under vacuum and most of my casting is done using clear PR or epoxy,more often than not I am casting it around brass tubes with carbon and watch parts attached and without using a vacuum air bubbles can trap on the underside of the tube or behind the watch parts. Having spent hours preparing a blank and have to throw it away is disapointing to say the least.

Oh, sorry I should have explained it a bit better. You do not need vacuum or pressure pot with PR, you can use it if you want, but vacummimg a mold with PR in it will make a bit of a mess. Not saying you can't use one, but I am saying you do not need one.

No Vacuum used on these

 

[Ray7756]

Hi guys
Lots of mention of PR and PU can someone tell me what PR & PU stands for, think PU is Poly Urethene????
Cheers
Ray

 

[Paul hd]

Hi guys
Lots of mention of PR and PU can someone tell me what PR & PU stands for, think PU is Poly Urethene????
Cheers
Ray

I think it stands for Polyester resin.

 

[Alan008]

Sorry about the delay in answering,I use clear cast polyester resin,not sure if it's bubbles or bits braking while on the lathe,it seems to cut ok then suddenly it sounds like sandpaper and when I stop and have a look it's rough and bitty if you know what I mean,I have carried on slowly and steady and it seems to get a bit better then goes again,could this be the way I mix or something else,thanks in advance.

 

[Bammer]

Ok that is normal for PR, called chatter.
Full speed after you’ve got it round.
Skew chisel will work well, make sure it’s sharp. Lot of people can’t use it and resort to carbide tips

They aren’t bubble, just chip outs

 

[Bammer]

I will add take light cuts

 

[Alan008]

Thanks Brad,I will try that,I have used carbine tips but will try with what you say,will let you know how I get on.

 

[Penpal]

You have been hiding these Brad they are outstanding mate.

Peter.

 

[wm460]

They are beauties Brad.