Flat Lap vs Hand Held

[lbailey]

I've been fusing and finishing like crazy, learning a lot, very enjoyable. Really don't mind the coldworking and like the payoff when a piece really turns out well, but looking for the next logical step to power grinding/polishing the flat surfaces of the blanks. (Not the edges, have a table top Covington for that and understand I'll need to step up to a floor model later as needed). The flat laps w/discs are horribly expensive IMO and so looking for other power alternatives. Currently limited by kiln size to 12" square or 12"diameter blanks.

Assuming I prepare a suitable non-slip, no scratch work surface and can deal with the water spray would a 5" handheld wet grinder/polisher like the Flex be a good option? I'm thinking that careful use with the rigid backer pad and the velcro backed discs of the proper grit would make quick work of these flat surfaces.

Understand the sandblaster option but interested in having the option to really work these blanks up to a high polish.

Am I missing something? Didn't see many references to this option in search results here.

[Warren Weiss]

Ibailey,

I have successfully used the wet grinder that you mentioned. I was lucky to find a jig designed to hold an angle grinder with the disc held vertically. I put the work on a cheap "lazy susan" to finish a disc of any reasonable size. Worked well.

Warren

[Dick]

Taking to a high polish takes a lot of time, patience, and a feel for it with any equipment. Can be done with the handheld, but much harder to maintain the flat plane, and also the diamond swirls are much harder to deal with. Even on a flat lap this is tedious at best. The more steps you use, and alternative abrasives such as polpurs will help.

Dick

[Morganica]

I bought an Alpha maybe 9-10 years ago and in that time I've used it perhaps six times. It's great when the work is simply too big to take to the equipment, or when you're onsite somewhere (which is when I usually need it). Otherwise, I have to admit I don't even think to use it--I go to the flat lap instead. If I didn't have a flat lap, I might use it more.

Mine has 4-inch discs, though, and I've had trouble producing uniformly flat surfaces with them (as Dick mentions). That means it's harder to get to a full polish or even a uniform matte surface, something that comes naturally to a flat lap. You've also got to secure smaller pieces when you're grinding, or the action of the grinder will send them across the room. And it's extremely messy to use; after finishing I look like I've been caught in a huge storm.

I think I'm in the minority with this opinion--most of the people I know who have these, love them and use them frequently.

Either way, I tend to use diamond equipment to rough in the shapes and get me to a uniformish surface...then I finish by hand.

[lbailey]

Thanks guys. Guess I need to put a flat lap on my list, I assume the 12" Crystal Master will meet my needs for anything up to 10-11"?

How realistic is it to work larger pieces off the edge of the disc (through the brush, etc) and back again? Seems like it would be very easy to end up with wavy, uneven results......

Appreciate your patience with (another) new guy.

[Morganica]

You can certainly do bigger pieces on a 12-inch wheel (I'd remove the brush, myself). The bigger the piece, though, the more difficult it will be to keep it perfectly flat and even; you want to make sure that at least half the length of the surface being ground is on the wheel at all times (otherwise the glass tends to dip/tip/rise on the wheel).

One tip: I bought a flat lap with a center water feed, thinking it would be great for doing vessels (since it's difficult to get coolant inside a bowl if it's upside down on the grinder). Unfortunately, a center water feed also cuts the useful surface area of your flat lap exactly in half. And since I grind a bowl about once in a blue moon, I don't use the center water feed anyway--it has never even been hooked up. At some point I'm going to grind down the center spindle and replace my center-hole diamond discs with solid ones, a very expensive lesson. It'd (almost) be cheaper to get a new flat lap.

[Marty]

Thanks guys. Guess I need to put a flat lap on my list, I assume the 12" Crystal Master will meet my needs for anything up to 10-11"?

How realistic is it to work larger pieces off the edge of the disc (through the brush, etc) and back again? Seems like it would be very easy to end up with wavy, uneven results......

Appreciate your patience with (another) new guy.

One problem with working off the edge is that the diamond pads tend to curl a bit and you'll end up chipping glass (not a problem with grit laps). 12" is fine for small stuff, but if you're planning on 10-11" work, go for at least an 18" lap- you'll want the power and you'll need the area.

[JestersBaubles]

One problem with working off the edge is that the diamond pads tend to curl a bit and you'll end up chipping glass (not a problem with grit laps). 12" is fine for small stuff, but if you're planning on 10-11" work, go for at least an 18" lap- you'll want the power and you'll need the area.

Sadly, the cost gets exponentially higher. Even between the 8" and the 12", the price difference is significant.

Dana W.

[Marty]

The larger machines will expand your capabilities; think of them as investments.

Scrap plate glass and loose grit are cheap, what's your time worth?