Alignment of Driver Mounting Holes

[David Carter]

I'm just about ready to drill driver mounting holes through the baffle and spacer of my first DR250. Never done this before. I just used screws to mount the drivers in my O10. I'm concerned about drilling the holes in exactly the right place so that my bolts aren't going in at an angle when I mount the driver. It's hard to mark them accurately when I lay the driver on the spacer because of the gap created by the gasket and also the fact that half the mounting hole in the driver frame is covered by the edges of the speaker cone fabric (see picture below).

Any tips on getting the holes lined up and drilled perfectly?

[WB]

Any tips on getting the holes lined up and drilled perfectly?

I used a transfer punch.

Transfer Punch Set

[LelandCrooks]

Grind, file, or shave a lead pencil to the size of the hole, long enough to reach the ply. Cut away the excess material in the way.

[Mark Coward]

The punch is best, and it will go through any gasket material blocking the hole. If you will be doing multiple cabinets a template is a good idea. To be the most precise, I will drill the holes with a small 1/8" bit first, then follow with the proper size. It is easier for me to align the small bit exactly on center, sometimes the large bits will "walk"a bit even with a punched indentation. Another reason for using the small bit first, when you drill with the full size bit you can go halfway through from each side, and prevent most or all of the splintering that can occur.

[Tim A]

For anyone doing woodworking, get a set of brad-point bits. No walking, perfect everytime.

No punches or pencils, stick a bit in that matches the the hole in the driver and push. It'll leave a perfect center mark, then remove the driver and drill with the right sized bit.

[DJ Big Ronn]

I'll make a hole on each side of the driver and lightly tighten them, so that I am assured that the driver does not move for the rest of the holes.

[WB]

Any tips on getting the holes lined up and drilled perfectly?

I was rushed earlier, but you did ask for "perfectly", so here's my take. Perfect bolt alignment is important on DR's because the bolts are so hard to reach.

First you want to mount driver using only two bolts (same as DJ Big Ronn does). I like to use transfer punches because (1) I already have them and (2) they leave a perfect dimple in the center, unlike a drill bit which leaves more of a line.

Place driver on baffle, hold firmly, and push proper size punch thru two opposite holes. Remove driver and deepen the indentation a little by using a center punch and small hammer. Next do as Mark Coward suggests and drill a 1/8" hole first, preferably using a drill press. Then open up hole to the required size for the Hurricane nut and install the two nuts.

Now by bolting the driver down, it absolutely can not move. Now transfer the remaining holes to the baffle using the above procedure and you'll end up with perfect hole alignment. Last step is to bolt the driver to baffle to seat all the nuts, and as a final check. Better now than when it's inside the DR. A few extra steps, but worth it. Also never use locktite, chances are you'll spin the nuts if you ever try to remove the bolts. At least that's been my experience.

[David Carter]

Thanks for all the great tips, guys. What I ended up doing (before all of your great responses came through) was to hold the driver down on the baffle and spacer and got each hole started by drilling directly through the hole in the driver frame with a 1/4" bit. Once I had the beginnings of each of the holes, I set the driver aside and finished the holes.

I will be trial mounting the driver soon, but I'm having trouble with my hurricane nuts. I pulled them into the holes by hand using the bolts, and I put some 5-minute epoxy on the shaft of the nut. Then I let everything sit for about 15-20 minutes and tried to tap each of the nuts, I think I've got a defective tap. The shaft seems to not be perfectly straight. Anyway, I spun the first three nuts I tried to tap. So, once I get those three nuts back in and secured, I'll be trial mounting the driver to see how well I aligned the holes.

Wish me luck!