Control points for concrete

Yes, I really like them. We put a little epoxy on the underside of the disk to ensure that it stays put.

http://o-tags.com/m/

The O-Tags thingy looks very interesting. I wonder though how the freeze-thaw works when the countersink fills up with water. Supporter of this forum so they can't be all bad.

We use them frequently. Pre-drill the holes with a standard concrete bit before using the costly countersink bit to save wear on those and epoxy or grout them in. The plastic inserts work well also but the grout eliminates water infiltration for long term survival.

KScott, post: 386083, member: 1455 wrote: The plastic inserts work well also but the grout eliminates water infiltration for long term survival.

Have you seen a problem with the plastic inserts and freeze/thaw? I don't have to worry about that around here, but I've installed dozens of them with the plastic inserts and they've stayed put. When I had to remove two of them (an oops situation), I had to drill through the tops down to the stems to get the tops off, because a chisel wasn't getting me anywhere. (I didn't even try to remove the stems, they were in too tight -- I just grouted over the holes.)

Hammer drill, cement grout, PK nail. Be sure drill diameter is slightly larger than head of PK and drill the hole a bit longer than the length and you will have a point that lasts as long as the concrete around it.

2xcntr, post: 386086, member: 584 wrote: Hammer drill, cement grout, PK nail

Yes, but while you're still mixing grout I'm down the street drilling my next Berntsen hole.

I have found chisled crosses that were decades old, just saying. With the cordless tools available you could saw in a very neat cross with some depth.

These days I set them with the plastic inserts and the countersinking bits and everything seems to work fine. At a former employer we set them without countersinking and epoxied them in. I recently returned to a couple of those I'd set in 2011 and they were good as new, save for a little patina.

Like KScott I pre-drill with regular hammer drill bits to extend the life of the special countersink bit.

Mark Mayer, post: 386116, member: 424 wrote: Like KScott I pre-drill with regular hammer drill bits to extend the life of the special countersink bit.

I'm on my second Berntsen bit. The first one -- an older design -- failed after installing about 50 marks when one of the two carbide countersink teeth broke off. The stem portion of the bit didn't show much wear, though.

Jim Frame, post: 386089, member: 10 wrote: Yes, but while you're still mixing grout I'm down the street drilling my next Berntsen hole.

Yup it does add about 2 minutes per point.... but breaking a $125 bit after only 50 points ouch! Then you are screwed until they ship you another one. For another $125. Or maybe I got the price wrong? Anyway I would always spend more time picking out a good control point than actually setting one. For me and my clients a good location always would trump how fast we could set one.

As for chiseling cross cuts... even when done with a circular saw.. with todays tools available, why would you. I had a Ryobi gas hammer drill for many years before the electric ones came out. Still have it around here somewhere.

We had a local building we had to set control inside, went thru, used hammer drill to drill a hole the size of a PK, hole a bit deeper, used can of air to blow the dust out, put some mix as you squeeze epoxy in the hole, hammered the PK in. After a couple of years, the building had a fire, major damage. They came thru, used a machine to scrape the floor. rebuilt and re-opened the business. I can still go in and find the shanks of every PK nail, it just sheared the heads off them.

These seemed really awesome when I first used them... They look really slick countersunk into a concrete surface... But here in the midwest they do NOT stay put. And I have also only gotten about 50 holes drilled per bit...

It is much easier to use a 1/2" bit in your hammer drill and go slow to make a nice clean 1/4-1/2" deep drill hole for a CP or prop corner. Bosch bits make a nice dimple at the point, I have set probably a hundred CP's this way for stringless paving after realizing the brass monuments would easily pop up, even a bit ruining the vertical accuracy.

Fill the holes with silicone before putting in the pins and washers. It keeps water out, so it won't crack the cement when it freezes.

A 1/4" hole in the middle of a curb can spaul off the curb face if left to freeze.

-35 to -40, snow plows and salt make for tough competition.

It is around the corner, I worked in lined carharts yesterday (@ 9500' elevation) and was wishing I had thrown in a coat.)

bow season!

M

Monte, post: 386123, member: 11913 wrote: We had a local building we had to set control inside, went thru, used hammer drill to drill a hole the size of a PK, hole a bit deeper, used can of air to blow the dust out, put some mix as you squeeze epoxy in the hole, hammered the PK in. After a couple of years, the building had a fire, major damage. They came thru, used a machine to scrape the floor. rebuilt and re-opened the business. I can still go in and find the shanks of every PK nail, it just sheared the heads off them.

Yes, the can of air is essential... forgot that. I have used epoxy too just found grout to be cheaper and easier to clean up after.

2xcntr, post: 386135, member: 584 wrote: Yes, the can of air is essential.

A length of vinyl tubing works well, too (you supply the air).

I use a turkey baster.

I used a mess of them on seven Sonic Drive-In sites in Topeka, KS about 6 years ago. The CA on them was 3045. I'd be interested to know their longevity.

Does a schonstedt pick up the copper at all? Do you put the magnet in the hole below the BP marker?

Thanks!