It’s been a while since I posted an update on my rocking chair project. I got busy with life and didn’t work on it for a while. However, I’m back at it full speed. Before I move forward with a full post, I figured that I’d show you a few of the mistakes I’ve made so far!
1. Don’t Use Construction Lumber for a Seat Blank Prototype
I thought that it made sense to use construction grade lumber for my seat blank prototype, but that was a bad idea since it cupped like crazy after I shaped the seat and made it thinner by 50% on one side. I experimented with pushing the cup out of it and it snapped.
My solution was to glue up some 8/4 cherry and derive the angles for the 20 spindle holes very carefully on the final seat blank.
At this point I also decided to make two rocking chairs in a batch production mode. I made jig templates for drilling the seat blank spindle holes and also for the top crest. I used the first seat blank to make the jig and successfully copied the holes in the second seat blank. More on that in a subsequent post.
2. Don’t Use 3/8” Tenons on Base Spindles for Chair Backs
I turned out 14 spindles from ash for the back of the rocking chair. They were a perfect tension and had nice, even tapers. However, I used 3/8” tenons that transitioned abruptly to an 11/16” diameter at the base of the spindle. This created a sharp point which caused the spindles to break at the base when I flexed them as I experimented with various angles of entry into the head crest.
This was a frustrating setback as I now have to turn 14 long, narrow spindles over again. I had already drilled 3/8” holes in the first seat blank. Thankfully, I was successful at re-boring these holes to 1/2” by working my way through some fractional bits. I was able to at least salvage the seat blank that way.
I will turn the spindles with 1/2” base tenons that transition gently to a 5/8” spindle diameter at the base. The set of weak spindles were still handy to experiment with the proper angles for the head crest. They give a good view of what the final chair might look like.
3. Be Sure You Have the Correct Prototype Piece When Making a Jig/Template
I used my final prototype for the top crest to build a jig that guides the drill bit for accurate, repeatable spindle holes in the crest. This picture tells the story well…
The technique is to drill through the top of the prototype crest into a piece of hardwood scrap. That scrap becomes the jig/template when you clamp it to the bottom of the final piece and drill from the bottom up into the piece. It perfectly duplicates the compound angle of the prototype crest. The mistake I made is that the final prototype was still connected to the spindles and I was using a bad prototype to make my jig! That only wasted a piece of scrap cherry.
I’ll try to catch up my blog posts to my project progress in the coming week…
-- Mark, Minnesota