# Drilling metal parts for bed rail and center beam #2: Thirty marks

 Blog entry by MrLaughingbrook posted 04-07-2017 10:16 PM 1027 reads 0 times favorited 0 comments
 « Part 1: up to now Part 2 of Drilling metal parts for bed rail and center beam series Part 3: Parallels and x/y vise »

Today I made the last of the thirty marks needed on the center beams.

Objective 1: mark for joining the two angle irons together to form a T with a centered series of equally spaced 6-32×1/4” flat screws.
Objective 2: mark for joining center T beam to wood cap.

I’m very happy with my learnings and results, so thought I’d share.

With advice from others, thanks theart, Gil, and the internet I put together this kit and procedure.

1. Calculate fastener interval as length minus two times minimum desired distance from the end, divide by four (for five fasteners or some other even number for more or less). 72 – 2 / 4 = 17.5.
2. Calculate divider setting, 17.5 / 3 = 5.833. Round down slightly if desired (will increase distance of last fastener from the end)
3. Set divider using caliper micrometer or ruler with indented markings matching rounded down value which may be better for repeatability.
4. Blue dye the area and mark a center point using tape measure and scribe dot, strengthen the mark with a square scribed line.
5. Mark a parallel line offset from the edge using 5/8” set on the combination square and scribe as sliding the square down the length of the iron. Since I’m now using magnifier glasses then I realize this line does not have to cut deeply into the surface, a light line is sufficient.
6. Prick punch the center point (Gil suggested the fine auto punch instead of my big center punch). And, again the magnifier glasses are a great improvement. I realize I was trying to scribe lines deep enough to catch/position the punch, now lighter is better with a visual positioning of the auto punch.
7. Use divider to lightly scribe a step out from center, prick punch, repeat until end of beam.
8. Add light center punch on top of prick punch at hole locations. Circle hole locations with silver to reduce chance that I’ll drill at a step mark.

All new marks seem satisfactory like this:

I’d like to descale the hot rolled steel before marking on the next project. However, I plan to pay for that at the powder coating shop on this one, so will mark on top of the scale.

Next up is to drill successfully on these excellent marks.

-- MrLaughingbrook