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Drilling metal parts for bed rail and center beam #1: up to now

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Blog entry by MrLaughingbrook posted 04-03-2017 08:25 PM 650 reads 0 times favorited 1 comment Add to Favorites Watch
no previous part Part 1 of Drilling metal parts for bed rail and center beam series Part 2: Thirty marks »

First time blogging… But, the activity I’m on now seems like a good topic.

I’m building two beds. I need to join angle irons to wood for bed rails and center beam re-enforcement. I need to join angle iron to angle iron to form a T beam.

Now, I’ve drilled into metal more than a few times… Often I’m disappointed with the results. Knowing that the inside of the bed rails will not be on display, I decided to use it as a learning opportunity and for skills development. It has been a fun journey so far, so I’ve decided to blog about what has happened up to now and then post updates as I progress further.

To make it interesting I planned to far exceed the requirements of the project on accuracy and beauty.

Objectives:
1. Join angle iron to wood of rails with a centered series of equally spaced #8×3/4” screws properly countersunk into the metal.
2. Join two angle irons together to form a T with a centered series of equally spaced 6-32×1/4” flat screws.

Here’s my sketch up :)

I started with scrap pieces and learned some things:
1. It is nearly impossible to reposition a previously drilled through hole for adding a countersink at the drill press. Using the bit to “find” the center, then clamp down piece and drill did not work well for me. It was better to use a hand drill and let it find the center using a light touch. A friend suggested I use Keo – 1/2 Inch Head Diameter, 82° Included Angle, 0 Flute, Cobalt Countersink instead of the five flute version I had. So, ordered that.

2. After drilling holes in first piece, using a transfer punch to locate matching holes in a second is possible, but it seemed better to clamp the two together and drill a pilot hole through both. I tried both. I drilled the tap size through both, separated them, tapped one and enlarged the other for clearance then countersunk with hand drill. Next time I’ll use a smaller pilot bit as I found that the cut from tap size to clearance size is too small and risky.

3. Tapping the threads by hand may be fine for 1/8 inch steel, I could see it would be problematic if the piece were much thicker and required 90 degree tap. Next time I’ll start the tap square using the drill press to start it.

4. 3 in 1 household oil is not the best cutting fluid. Ordered some Tap Magic for next time.

5. Positioning a piece on the drill press to enlarge an existing hole by using the drill bit to center and pin the piece to the table for clamping kind of works. But, they have a center finder pin for this, ordered that for $6 from Lee Valley.

Feeling confident enough to use the project pieces for the bed rails… They need a centered series of equally spaced countersunk holes for #8 screws. I calculated then marked using a tape measure from one end using a silver Sharpie, a scribe/square and center punch. Mounted on the drill press and drilled through holes of 11/64”.

Here all twenty holes are complete and the irons are resting on the wood part of the bed rails.

I learned some more things:
1. Placing a center punch at the intersection of two scribed lines is difficult. You can see in the above pictures that I did not always hit the crosshairs. It seems to me that the off center holes are mostly due to center punch, not the drilling.
2. Using a tape measure to layout series of holes is inaccurate.
3. The zero flute bit is very nice. Thanks Gil.

I planned some improvements and decided to move ahead with the markup of the center beam pieces:
1. Use Dykem blue layout fluid and magnifying glasses to improve accuracy of my center punch placement (more advice from Gil).
2. Establish a center point using tape measure and scribe dot. A small inaccuracy here will show up as unequal end segments I’m thinking. Square scribe a line from the midpoint. Scribe a line parallel to the edge over entire length of iron. Use a divider to step off the intervals out from center point on the parallel to edge line. Scribing a crosshair at each hole location.

Using zoom lens photography to check my accuracy reveals that I’m improving but still need more practice locating the center punch. Here is a composite image of the five marks in the first rail:

Next I hope to accomplish improved accuracy using sharper scribe, divider (it tended to skate as I attempted to walk off the segments), and center punch along with closer scrutiny through the magnifying glasses.

-- MrLaughingbrook



1 comment so far

View theart's profile

theart

13 posts in 365 days


#1 posted 04-04-2017 12:50 PM

I haven’t done anything like that in a while, but from what I recall:
- Easy with the hammer. Steel work hardens, and if you go too heavy with the center punch the drill bit will try to go around the hard spot.
- Instead of trying to layout all of the spots in one go with the dividers, center punch them one at a time.
- De-scale the stock before the layout dye. You’ll get much sharper scribe lines.

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