Granite Pavers

[Randy Walker]

Granite Pavers

I have been asked to engrave some brick sized, black granite pavers that are part of a memorial. The existing pavers are engraved about an eighth of an inch or so deep. Obviously my little 30 watt laser won’t do that. I am guessing that previous engraver (now retired to another state) used a sandblaster to get the depth, and because all of the corners are sharp points not radiuses.

I have read a few of the sandblasting threads and am now researching all of them. I remember somewhere there was some advice on a laserable rubber membrane that could be used for masking. Could someone point me in that direction, or to some other good laserable masking material?

I also need some advice, on sand blasting cabinets and a good media to do granite with. I am leaning strongly toward the Harbor freight mid size cabinet, with the light in it.

Lastly I could use some help on pricing. I will be doing names on two lines on the pavers, first name, middle initial on the first line, last name below no color fill.

This is something new for me so any help, suggestions, information, advice, or guidance anyone can give me would be greatly appreciated.

Many thanks
Randy Walker

[Gary Hair]

Randy,
I have done lots of pavers, granite and others. I use Anchor 116, it's polyester based so it is laserable. It's high tack so it sticks well to almost anything. If the pavers are polished though you don't want to use it, it is too aggressive and will give you nightmares removing it, you are better off with their 117 instead (I think that's the number for the medium tack). Get the $199 cabinet from Harbor Freight along with their 90# top load pressure pot. You can also buy 70 grit aluminum oxide from them for much less than you can buy anywhere else. You'll want a better nozzle than what comes with the pressure pot but you can use it in the mean time. Your biggest expense will be the compressor - you need to have something that will put out 90 psi at 25cfm if you want to do granite, at least in any kind of reasonable time that is. A typical home compressor, 30 gal, 3hp, will not work! As for pricing, you should be getting at least $25-$35 each for them in quantities less than 50 or so. That may sound high but granite takes a long time to blast and you'll regret not getting at least that much for them. Clay bricks you can do for half that much but they take less than half the time to blast.

Check out cuttingedgesandcarving dot com, it's the best sandcarving site you'll find.

Gary

[Mike Null]

Silicon carbide costs more but is a superior medium. Aluminum oxide has an inherent static electricity problem that's really a nuisance. I like a finer grit than 70 but 70 is certainly efficient for that job.

Gary is 100 per correct about the pressure pot. Don't expect the cabinet light to be of much help. You'll need a way to capture used media for re-use and an exhaust hook up--some type of vacuum.

[Larry Bratton]

Gary is also right about the air compressor. All that other stuff is useless without an adequate compressor and they are not cheap.
The most important thing to be aware of when buying an air compressor for blasting is the CFM rating. All that other is just hype if the compressor doesn't give you the cfm you need. Gary says 90psi at 25cfm which is probably adequate for the job. Look at the Home Depot and Lowes compressors and you will see what I mean about the price when your talking CFM.

[Randy Walker]

Sorry about being so long in getting back for your responses. Things just got busy for a while.

Thank you so much Garry, Mike, and Larry these were exactly the kind of answers I was hoping for. I think I’m looking at the same HF sandblast cabinet you are suggesting. I looked at their site but I couldn’t find the pressure pot. I’m sure when I get there they will be able to point me to it. I think the think the thing that’s going to hurt me is that my compressor only puts out about 6cfm at 90 psi. The initial order is for 110 bricks, if they will pay $25+ per brick I may just take this opportunity to up-grade my compressor too. For dust collection I was hoping one of my old shop-vac’s (from before I got my central dust collection unit) would be good enough.

You didn’t mention where you get the anchor masking. Is it available one line? How expensive is it?

Mike you mentioned finer grit and silicone carbide and a finer grit. How fine would you use on something like this, and is the silicone carbide really worth the extra expense?


Many Thanks
Randy Walker

[Mike Null]

Randy

Because I do mostly glass and crystal with mine I use a very fine grit (150). If I were doing lots of pavers I would buy a separate pressure pot just for that grit and i would use something like Gary has recommended or a little higher.

Silicone carbide will last longer though you'll probably never need to worry about aluminum oxide as far as that goes but the static electricity thing was a real problem for me. I tried to ground my equipment in every way I could think of to no avail.

You can find the pressure pots here. http://www.harborfreight.com/catalog...rasive+blaster

[Larry Bratton]

Randy:
Your going to have to go somewhere besides HF, Lowes or Home Depot to get a compressor that has that much cfm capacity. Grainger would carry some that will do the job, but get out your credit card. Your talking Ingersol Rand etc. You will just have to do some shopping. However, if you get one with that much capacity, you will be all set to handle most anything that comes your way sandblasting wise. It can be pretty lucrative, make wood and foam signs, glass, etc. Good luck with it.

[Mike Null]

I have been using a $300 Craftsman for years with no problem and no lack of pressure. If I'm doing a large job the compressor will kick on once or twice but unless you anticipate substantial volume a compressor like this will work just fine.

I also use it for air brushing cermark and for my heat press.

[Larry Bratton]

I have been using a $300 Craftsman for years with no problem and no lack of pressure. If I'm doing a large job the compressor will kick on once or twice but unless you anticipate substantial volume a compressor like this will work just fine.

I also use it for air brushing cermark and for my heat press.

To sandblast granite pavers????

[Mike Null]

Larry

Yes, but not very many. Keep in mind that a coarser grit and higher pressure will speed up the blasting time.

In my business where not more than 10% of my business is sand blasting a large compressor is a waste of money. For Gary, whose sandblasting business is substantial, it's another matter.

[Larry Bratton]

Yes Mike, agreed. However, the point I was making was that if you make that investment his capability would be greatly enhanced. From my experience a low cfm compressor just is sooooo slow it can get really frustrating trying to work with it. I sold all my sandblasting stuff, as I migrated to CNC and laser a long time ago, but I still remember the frustration with it.

[Gary Hair]

I have been using a $300 Craftsman for years with no problem and no lack of pressure. If I'm doing a large job the compressor will kick on once or twice but unless you anticipate substantial volume a compressor like this will work just fine.

I also use it for air brushing cermark and for my heat press.

It's not often that I completely, absolutely, wholeheartedly disagree with you Mike. I have a 5hp, 60gal, 15cfm @ 90psi compressor and it's barely adequate for doing anything other than glass. I have a 12.5hp, 175psi, 26.2cfm compressor that I am rebuilding and it will keep up with me for almost anything I want to do. Plus, being gas powered, it's portable so I can take it anywhere I need to go. Unless you plan on blasting with a tiny nozzle, 1/16" or less, at low pressure, 25psi or less, you just can't get away with a $300 compressor.

Here is a good budget for the most basic items:
Compressor - $2,500 (EatonPP10V120Y1)
Cabinet - $220 (HF number 93608)
Pressure pot - $150 (HF part number 93889)
Dust collector - $130 (HF 31810)
Nozzle - $40 (granitecitytool.com 3501-0002)
Nozzle holder - $40 (parts list on cuttingedgesandcarving.com)
Blast media - $40.00 (HF 99945 - on sale now for $40, otherwise $50)
Stencil - $113 (pacificcoastpaint.com Anchor #116, #117 - same price but medium tack)

There are other misc. bits and pieces you will need, but this list would get you started.

You'll notice that I put the compressor FIRST - it is the most important thing to spend money on and not go cheap. The rest of the equipment isn't that expensive and can be upgraded if you need to later, but you don't want to buy a cheap compressor, burn it out, and have to buy another one.

Gary

[Larry Bratton]

Like I said "Get out your credit card"

[Randy Walker]

Yea….Gary, as much as I would love to have a $2500 dollar compressor, I just don’t see that in my budget for this job. I talked to a friend of mine that sprays foam from a 55 gallon drum. He hooked 2, 8.5cfm compressors in tandem. He says he rarely runs out of air and when he does, its usually a good time for a break. I think I will try it out with my current compressor and if I have too much down time I will try adding another compressor that will fit in my budget. Everything else is pretty much what I was expecting.

I checked out the site for masking and it seems quite reasonable. Thanks for the link.

Randy Walker

[Larry Bratton]

Randy,
You might find somebody to sub it out to. I used to use a monument company when I needed something I couldn't do. They have the equipment and if you got them to do it for $12 and you got $25 what would be wrong with that?