Yesterday, I completed the Front and Rear End Sills and attached them to the side sills. It was a pretty good day, but ended in frustration.
Chapter 4.2 – Front End Sill and Rear End SillThese will go on the front and back of the side sills to make a complete rectangle for the tender frame.
The Front End Sill and Rear End Sill both started as lengths of 5/8” square 12L14. Cut to length and squared up to size.
These are not really very remarkable in any way. They just have a few through holes and tapped holes.
So I set to work on the Front End Sill first. These are #3 clearance holes for the screws that will hold the Front End to the Side Sills. And this shot is just after completing the 82
o countersink in each of them.
There are a bunch of #3-48 tapped holes too, but apparently, I didn’t get a picture of those.
On to the Rear End Sill. This is very similar to the Front End Sill, but its 1/8” longer. The Rear End sill will stick out from the side sills by 1/16” on each side. The #3 countersink clearance holes are the same but the #3-48 tapped holes are all different.
There are also some holes for the rear coupler. These will need to be drilled when I get that assembly completed. But now that I have it all dialed in on the mill, I chose to leave a few marks on ‘about’ where they should go so that it's easier to position when I get to that point. I scribed these with a small engraving bit I have. It did the job nicely.
The Rear End Sill also has a couple of #8-36 tapped holes. These will be for rail posts down the line.
Here are the completed Front End and Rear End Sills.
Now for the fun! I hadn’t quite figured out yet how I was going to drill and tap the holes in the ends of the Side Sills. These things are over 15” long and even with my new big mill I don’t have the Z height to stand them up on end and still get the drill chuck and a bit in there. So, I worked out this method. I awkwardly clamped the two pieces together, like this. I had scrap pieces on the back and the side to help with alignment. You really can't make out what I did in this picture, can you? Well, it seemed to work regardless.
I used the clearance bit through the End Sill just to make a center hole. Then I switched to the correct size for taping and continued to use the End Sill as a guide to help me keep the hole straight. You can see the cordless drill sitting there on the vise waiting to do his job.
With the hole drilled, I took away all the fixturing, and making sure to clamp the piece at 90
o to the vice jaws, I used a tap guide to help me tap the hole. Again, this seemed to work pretty well. Notice that I clamped the guide in place for added stability.
Unfortunately, this is where calamity struck. On the LAST hole, I must have gotten a little careless, because I heard the dreaded crunching sound.
I don’t know exactly what happened. I’d swear I was doing exactly the same thing as the other 7 holes I’d done this way. But clearly, I did something wrong. Well, actually, I do know that I didn’t clamp the tapping guide in place. I’d stopped doing that for the last several holes, just depending on my other hand to hold it in place. That had worked for several holes. But then this. Clearly, I let it shift or did something wrong. Because here I am now with a two-piece tap, with one piece embedded firmly about 3/8” down in the hole.
There was no backing it out. It's still there:
I’m considering what to do. While the tap is HSS, the part is also steel. So I don’t think the Alum trick will work (though I’ve only had marginal success with that in the past anyway). I’m trying to think of a way to cut the tap out, but there’s so little material to work with. The hole is centred 1/8” away from the top edge. And to make it worse, I don’t really have a way to get it in the mill to work on it.
My top thought at the moment is to see if I can chip away enough of the end of the tap to get a few threads exposed, then I can just make a VERY short screw to go in on top of it.
I’m open to suggestions.
So, ignoring that issue for the time being, I assembled the frame:
I was very careful in setting up which end of which sill went together. But in the end, when I went to assemble it, I realized I’d completely forgotten to take into account that the Side Sills are NOT symmetrical. They middle bolsters are in different places from each end. And of course, I can never accidentally orient things correctly, so had done it backwards. But, on the bright side, my holes were uniform enough that even with turning things around, all the edges still line up beautifully! So that’s one positive!
Now I just need to deal with the half a tap that’s embedded in the frame there…
Thanks for taking a look at my trials and tribulations,
Kim