I'd like to start a discussion on various methods for doing this. I've only done 4 myself and what I do is place the engine in its correct position, clamp it down, and scrape some coloured chalk into the holes. Then I remove it and drill away.

I don't know if this is the best method, I have made a booboo or two and I would be great to see if there is a method most people use or a tool that is quite common.

Got this from my LHS. Works great for engine AND servo screw holes.

http://www2.towerhobbies.com/cgi-bin...?&I=LXK378&P=7

I've used two with success: clamp engine in plance then i) the use a Great Planes dead center tool ii) heat a screw with a torch and push it in the hole to mark the center. Both worked perfectly. The dead center locator is easy and accurate.

flatfour, is right. Self centering and it gives you a cenetr punch mark to work with. :thumbup: :thumbup:

I have had no more of the "Screwed up the motor mount blues" since I purchased a "Dead Center" Drill.

This is a must have IMHO

ZB

I just clamp the engine in position, then take drill bit that is 0.1 mm smaller than the holes in the engine mounting lugs and mark the engine mount. The same goes for control horns, servos, canopy's... well anything basically.

If the surface to be marked is too hard or dull so it's hard to get a good mark, I just put a small piece of tape on the hole area and mark the tape...

Consider getting a set of transfer punches from Harbor Freight for $8.99. Cheap, lots of sizes and VERY handy to have around the shop!

http://www.harborfreight.com/cpi/cta...temnumber=3577

All good ideas. I clamp the engine but mark only one hole with the centering tool, drill and tap, secure the engine through the one hole, mark and drill a second hole, use it to secure the engine along with the first hole then mark the last two and drill them. If I try to mark all four then drill, I always end up with one or two that are off enough so that they can't be tapped and used. I guess I'm just not good enough at it.

I drill clearance holes, then use 6-32 socket head cap screws with matching ny-lock nuts with locktite to boot. Works great! The clearance holes allow for a little more imperfection. Don't get carried away with the size of the clearance holes though otherwise things get sloppy. They should be just big enough for the bolt to drop through.

Reid