Ok, don't shoot!!!! I'm only repeating what some one else recommended.
No, I don't think there is an easier way if you don't have the industrial equipment designed to press out 100's of rafts a day.
Perhaps, mark out a raft on top of the next raft. Make sure you are using an extra long bit instead of the standard bit that comes in the hole saw so that when you drill half way through the first layer of raft, it is marking the next layer for you. Flip the first layer and finish drilling then go on to the next layer and drill from the "pre-marked" holes which will hopefully mark the next layer down too. Drilling half way and flipping makes it easier to remove the plug from the hole saw rather than having to take it apart each time to remove the foam, you can just pull it off by hand.
Wear a dust mask and have a shop vac and ear plugs handy for clean up?
Sorry, good luck
I figured that would be the case. I guess I will just suck it up and start drilling.
I have drilled thousands of holes in rafts. I have drilled so many that I have actually dulled a hole saw bit from drilling foam. The best method I have found is to use a Rigid hole saw dit instead of Milwalkee for 2" foam. The Rigid bit is beeper than the other allowing a deeper drill. I prefer to use a light cordless drill and use a 35 gallon trash can for a table.I sink the bit from the top side only and pull back when the pilot drill holder just touches the foam on the inside of the bit. This will leave about 1/8 of foam still attached on the bottom side of the 2" cut. Then the hole can simply popped through the raft by pushing a finger down in the center of the cut. The cuts and most of the dust will fall into the trash can. This method has saves HUGE ammounts of time because if done correctly you NEVER have to stop the drill to clear the bit of foam. When you pop the hole out the 1/8 remaining foam will pop out in a way that leaves a beveled edge on the bottom side of the raft which helps prevent roots from getting snagged on a sharp edge.
The Milwaukee bit is shallower and will leave 3/8 of foam at the bottom of the cut. This makes it MUCH more difficult to pop through.
I pre-paint the rafts as a 4x8 sheet then cut to size. I carefully lay out and drill the first raft being sure not to pop out any holes. When the first raft that is drilled it becomes my template to mark all the remaining rafts. The template raft is placed over the next raft and a pencil can be used through the pilot hole to mark the new raft.
My seedling rafts are 2x2 and hold 61 net pots. I can mark,drill, and pop out one of these rafts in less than 3 minutes
I know of others that have devised special bits and used drill presses to achieve the same beveled hole results as my method. I have also seen the sheets drilled from the top and then finish drilled from the bottom. These other methods work but are substantially slower than my method.
I keep some of the drilled out holes to temporarily fill unused holes while the rafts are growing produce(reduces algae growth on surrounding roots). The bulk of the drill outs I donate to my daughters preschool where they use them for a range of crafts.
I think that will work for me also. The only problem I run into is finding 2" foam. I have only found the 3/4" stuff locally and have to double it up to get the desired thickness. I will keep searching for two inch and may have to order it in.
Yea, you probably will need to have it special ordered.
I've never really done well with the traditional rafts with holes.
The rafts I've done I don't make holes in them, I simply lay capillary matting over them and place my plants on top. (this works best for micro-greens and baby lettuce and shoots, all things that are light and fast. and I've done them on 1/2"-3/4" or 1/2" doubled up.
When sourcing blue foam on the mainland I found the best prices from White Cap building supply. They are a national chain likely in your area.
Unfortunately I live at the end of the earth and our choices are limited to what ever showed up on the truck. I will do some looking though. Surely some one around here carries it.
Well if you need to order it and can't find anyplace.
As far as the template is concerned, John Tramell who is on this site told me about using a 2'x4' piece of 1/4" ply where he marked his circles and put a small nail through the center he then takes that sheet and presses it on the 2'x4' styro which leaves holes showing where to place his drill. I use a 1 7/8 hole saw allowing the pilot bit to pierce the underside then flip the sheet over and drill using the holes from the pilot bit and the piece pops straight out without sticking in the hole saw.