After close inspection of the mixing cup and ball I found a couple of things that I didn't like. Firstly the mixing cups, which are plastic medicine cups, have six small reinforcing lugs in the bottom corners of the cup. Secondly the size a shape of the ball means there would be little or no mixing in the bottom corners. Combined with the ball not staying in the bottom of the cup are the most likely cause of the problem. Found myself a shot glass, which very appropriately has "Old Farts Shot Glass" written on it and a stainless steel bolt which have had the head and threads cut off. Added some masking tape to the shot glass so it sits snuggly in the mixer. The rod fits into the corners far better than the ball. I'll mix up a few different size batches and see how it goes, watching the rod very carefully to see where it sits. The epoxy won't be going anywhere near a rod until I'm certain that its all gone off. If part of it hasn't gone off then the rest of it hasn't got the right proportions and won't harden properly. I'll re read Tom's article more carefully and if anyone thinks there's anything else that I should look out for then please advise.
Just checked the speed of the motor and found it to be 33rpm which is far to fast according to Tom's article.
Also checked the speed of the microwave turntable which is 15 rpm which is a lot closer to what is needed. Do you think my wife will notice if it's not working?
ESFNEM Col
Port Kembla, NSW
Australia



Edited 2 time(s). Last edit at 05/28/2011 08:12AM by Col Chaseling.

When using my mixer I use a 1/2 wide strip cut from one of those phony credit cards that come in the mail, after its turning I use the strip to scrap the side of the cup down into the mix. I then move it to the bottom of the cup to clear the bottom. about 30 seconds or so is fine

33 RPM would have a lot to do with the ball not staying at or near the bottom of the cup.

.................

Col, I agree 100% about teh plastic mixing cups, I cannot believe almost everyone uses that to mix their finish. With all the lengths people go to for every single detail of the rod to be perfect, to mix in that thing with all the ridges > you'd think more people would be paranoid about what you posted. I use a shot glass for years and years, but I recently switched to a small wide candle holder which is much mor esturdy and has less of a chance of me knocking it over on teh bench, which I did a few times with teh shot glass. THE wider mixing thingy also allows the finish to spread out and bubbles release and doesn't set up as quick as the shot glass > not that I care or have problems with that.

Col ,
After a dozen variations of mixing speed, and mixing bolts on the inside of the cup, along with changing cups; I finally have the complete problem solved.

I slowly mix in a plastic cup with 1/2 a craft stick with rounded edges and frequent wiping of the stick, to clear any unmixed material.

0 defects, minimum bubbles.

Never have to wipe out any cups - one time use only. Never have to do any thing more than wipe the craft stick down with a paper towel to clean the craft stick.

Good luck for the folks who use the mixer and may it alwayws work to your satisfaction.

Take care
Roger

Billy I agree with you. I've been using a 100ml laboratory beaker when I mix by hand and it works fine but it's too big to fit in the mixer which is why I've gone to the shot glass. Looks like I've got to find a small 20 rpm motor if the changes I've made don't work and hopefully I can adapt it to what I've got. Should have built my own in the first place!!!!!

ESFNEM Col
Port Kembla, NSW
Australia

You will find that if you use a roller bearing instead of a ball bearing it will clean the edges a lot better and eliminate the majority of the problem

Ron Weber

Rons point is right on.
If you can't find a roller bearing you can just use a piece of the size drill rod you need. Cut to the length that you need with an abrasive grinding wheel. You can't saw these hardened steel rods.


[www.wttool.com]



These are polished perfectly round metal rods that can work well for the appication.

Although this type rod worked better than anything else that I used, I just didn't like the clean up of the rod afterward, as well as the wasted finish that tended to stay on the rod and was wiped off in the cleanup.

Good mixing.

REW

I guess this fits here too.

I had to bend the legs on the bottom of my PB mixer so the steel cylinder stayed at the bottom of the cup like it was supposed to. Out of the package the cup was held too flat and needed to be tilted up more. Now it mixes flawlessly.