Lap Grinder problem - WarmGlass.com

Lap Grinder problem

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Emily Will
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Joined: Fri Dec 14, 2012 1:08 am

Lap Grinder problem

Postby Emily Will » Mon Feb 03, 2014 3:17 pm

I have a new CrystaMaster 12" lap grinder, and accomplished a big goal by producing a
small bowl that is glossy both inside and out - thanks to the grinding and polishing of the
back of the bowl before slumping. BUT, on my first attempt I turned a very nice flat circle of
fused glass into 10 pendants when it flew out of my hand and hit the concrete floor. The problem
seems to be that with the 400 grit disc, it feels like there is water between the glass and the disc
that makes it sort of "hydroplane" and then sometimes the disc grabs it. So there is a constant
shifting of the amount of grab of the disc and it is very hard to hold on to it with my hand. Have
you experienced this, and how have you dealt with it? I wonder if there are suction cups that I could
apply that would give me a "handle" to hold on to while grinding. Any thoughts on this? How can
I improve my technique? I'm not having the problem with the 120 grit disc, or the nubby prepolising
or polishing discs. Just the 400 grit.

Thanks,
Emily
http://intenseglass.com

Marty
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Re: Lap Grinder problem

Postby Marty » Mon Feb 03, 2014 3:49 pm

I doubt you'll find suction cups strong enough in that small a size but if the back of the glass is smooth, a (new) toilet plunger is worth trying- get the cheap soft one with the flat lip (the one that doesn't work in toilets!) and cut the handle down.
You could try a ducktape handle but that'll be iffy too.
If the glass hydroplanes then you've probably got too much water. It'll be a problem getting the right amount between the 10" glass and the 12" plate. I'd go for a grit slurry on some plate glass, also with the ducktape handle.

Emily Will
Posts: 27
Joined: Fri Dec 14, 2012 1:08 am

Re: Lap Grinder problem

Postby Emily Will » Mon Feb 03, 2014 4:28 pm

Thanks, Marty

Actually, I neglected to say that my glass circle is only 5" in diameter. The disc is 12"

Emily

Marty
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Re: Lap Grinder problem

Postby Marty » Mon Feb 03, 2014 4:37 pm

I read too quickly and saw 10 pendants....

Still, 5" is a lot to ask from a 12" disc, especially if the water is not center fed (up through the middle of the plate). Try the ducktape- run a piece across the glass leaving a loop in the middle for a handle. Reinforce at right angles. Sometimes it'll give way when it gets wet, sometimes it'll be really tenacious. HIS glassworks has a very expensive version that people seem to like- I get the "contractor" stuff from HD. It works, mostly.

Pipwren
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Joined: Sat Feb 15, 2014 10:22 am

Re: Lap Grinder problem

Postby Pipwren » Sat Feb 15, 2014 8:16 pm

Another thought to keep in mind is if you have a new grinding disk it will take some time to wear down to a more manageable piece of equipment, in other words the more use the disk has the easier it is to control.

David Jenkins
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Location: Cypress, Texas

Re: Lap Grinder problem

Postby David Jenkins » Mon Feb 17, 2014 10:03 am

FWIW, I too made a Frisbee out of my first attempt at using a lap grinder I constructed. I subsequently got this tip here, I think:

Cut a piece of broom handle about 8" - 10" longer than the diameter of your bowl. Using 3M waterproof duct tape (I think I got mine from HIS - it's waterproof and will not come off as you do your lap grinder work), tape the broom handle to the back of the bowl. Now do your grinding - you'll find that the two "handles" you created give you complete control over the piece - no more unintended Frisbees. When you're done, GooGone will handily remove the sticky residue left when you remove the tape.

HTH
Dave Jenkins
Glass at Harbor Gates
Cypress, TX

Morganica
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Re: Lap Grinder problem

Postby Morganica » Mon Feb 17, 2014 3:16 pm

I've still got the scars from my first "frisbee." Instead of sailing across the room and breaking somewhere else, it slammed against the wall and bounced back to attack my thumb. (nearly severed it, too)

Marty taught me the duct tape loop method--you make a closed loop of duct tape that sticks straight up, perpendicular to the piece, and stick it on with about a gazillion layers of tape on the surface. The broom handle method works too. What I've found, though, is that what really holds well on the grinder will be a pain to get off the glass afterwards--keep your Goo Gone handy--and prepare to spend some time making sure ALL traces of the stuff are gone. It will leave marks if you fuse it into the glass.

If your grinder has variable speed control, slow it down to the lowest setting, and don't push so hard, especially with the coarser discs. Usually the frisbee thing is happening because you've got a lot of downward force and excessive wheel speed at the same time. When your fingers get tired or you shift position slightly you change the direction of force and...wham. And as Marty said, some pieces are simply safer done by hand.
Cynthia Morgan
Marketeer, Webbist, Glassist
http://www.morganica.com/bloggery
http://www.cynthiamorgan.com

"I wrote, therefore I was." (me)

David Jenkins
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Location: Cypress, Texas

Re: Lap Grinder problem

Postby David Jenkins » Tue Feb 18, 2014 1:16 pm

I'd just reiterate (whether you use a loop of tape or a taped-down handle) - make sure you invest in the correct type of duct tape. The normal stuff you get at Lowes/HD will very quickly lose it stick when subjected to the water you're using on the lap grinder. Spend the extra bucks and get this 3M Water Resistant tape:

http://www.hisglassworks.com/cart/3M_393_Water_Resistant_Cloth_Duct_Tape_p701.html#.UwOPZfm7zxE
Dave Jenkins
Glass at Harbor Gates
Cypress, TX

The Hobbyist
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Re: Lap Grinder problem

Postby The Hobbyist » Wed Feb 19, 2014 11:59 am

I swallowed hard a couple years ago and bought some of that tape from HIS. It has worked flawlessly since. Its use is reserved for lap grinder work and thus has lasted quite awhile.

I can't praise the folks at HIS enough. Their products are great as is their customer service.

Jim "The Hobbyist"
"With or without religion, good people can behave well and bad people can do evil; but for good people to do evil—that takes religion. " Steven Weinberg

Morganica
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Re: Lap Grinder problem

Postby Morganica » Wed Feb 19, 2014 7:00 pm

I love HIS, too....but I've never had a problem with plain-old hardware store duct tape coming loose. I degrease the glass and make sure it's very clean before I tape it down, and I use a lot of tape...but I haven't had problems and I do this a fair amount. Generally I have to apply Goo Gone and a lot of razor blades and elbow grease to get it off the glass.
Cynthia Morgan
Marketeer, Webbist, Glassist
http://www.morganica.com/bloggery
http://www.cynthiamorgan.com

"I wrote, therefore I was." (me)

Jeanne
Posts: 75
Joined: Wed Aug 20, 2003 8:16 am
Location: NJ

Re: Lap Grinder problem

Postby Jeanne » Thu Feb 20, 2014 12:06 am

Anyone ever try one of those suction/glass/dent remover tools? Like this one?

http://www.amazon.com/Tooluxe-Single-Ha ... KRC3QP61SZ

Lynn Perry
Posts: 108
Joined: Sun Jun 08, 2003 5:27 pm
Location: East Tennessee

Re: Lap Grinder problem

Postby Lynn Perry » Thu Feb 20, 2014 11:48 am

I have one that looks just like it. It will only hold on a perfectly flat surface and for only a very short while when it loses suction completely. I tried Gorilla duct tape which works great for me for most applications. Once it got wet, it also lost adhesion. I finally bought a roll of the $50 wet duct tape from HIS as well as a less expensive roll of duct tape from HIS which removes cleanly without the need for solvents and razon blades, at least that is the description. I will be using both later when spring arrives.


Jeanne wrote:Anyone ever try one of those suction/glass/dent remover tools? Like this one?

http://www.amazon.com/Tooluxe-Single-Ha ... KRC3QP61SZ
Lynn Perry


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