Saturday, July 26, 2008

We're Making Progress

When last we met, I had finished milling the stock for the 12 corner posts to thickness and had cut them to width. And we were leaving for Hershey, PA. That's mostly correct, as I finished these operations before July 4, and we actually left on the following Monday. I did get a little bit more done than that before leaving for Hershey.

I had decided that a 1/4" mortise looked minuscule on a 2" x 2" post, and I was worried that this joint might end up not being strong enough. I expect all kinds of people to be leaning on top of this pulpit as they deliver their sermons, and I know a 2" x 2" post will handle lots of weight, but my confidence in a 1/4" tenon under a load like that isn't there. So I decided to mill the rail & center stile stock to 7/8" thick & make the tenons 3/8" thick. But I could only do this if the stock for these elements was actually flat at 7/8" thick.

I had time to mill the stock for the rails & the center stile to thickness before we left, so I went ahead & did it. This changed the ordering of the steps in my "How Am I Going to Build a Pulpit?" post, but better safe than sorry. The stock was nice & straight before I got to 7/8", but not before it was less than 1" thick. So 7/8" is the thickest I could get. This is fine & I think everything will work out OK. Frankly, 1/4" mortise & tenons are probably fine, but I feel better at this stage.

When we got back from Hershey, I started to cut the joinery I had so carefully layed out on the posts. The first three kinds of cuts I needed to make were done with my DW 621 plunge router, the router's edge guide, and a 3/8" CMT solid carbide spiral up-cut router bit. I had to go out & buy this bit as I didn't have one in this size. And it turns out that it's a metric 3/8". That is, it's some metric size that is almost but not quite actually 3/8" in diameter. I didn't realize it wasn't a true 3/8" until much later.

I cut the mortises first. I set the router so it would plunge to 1 1/16", the depth of my mortises. The tenons are supposed to be 1" long & I wanted to leave a little room for the glue to go. I cut the mortises using a technique I had read about & it worked well. Instead of making multiple passes at progressively deeper settings, I essentially drilled a number of overlapping holes to full depth along the length of the mortise. When I had enough holes drilled, I then passed the router along the length of the mortise at full depth. This cleaned up the little triangles of stock left along the walls of the mortise.

The results were nice, clean mortises at full depth. Unfortunately, the mortises are not all uniformly long. I had my shop vac hooked up to the router, sucking up the chips as they were made. This meant that I had to look through a clear plastic ring that the bit passes through, as well as through the clear base. And the lighting wasn't that great -- the router body blocked a lot of light. The end result was I really couldn't see my layout lines very clearly, and some mortises are shorter than others. I need to rig up some kind of light on my router, or get a goose neck lamp I can use to illuminate the work. In any event, I was happy with the mortises. I would just have to cut the haunches in each tenon by hand & custom for the matching mortise. No big deal.

Next, I had to cut grooves along the length of the posts on the faces where the mortises were cut. I used the same router, bit, and edge guide, changing only the maximum depth of cut. In this case, the depth of cut was set to 1/2". I cut the grooves in two passes, one at 1/4" and the other at 1/2". This was working fine, until I was cutting the first pass on the last groove.

I still had the shop vac attached to the router & it was getting all the chips & dust, but I noticed that sometimes it wouldn't get everything. I realized that the filter in the shop vac was probably clogging, but I didn't want to stop just then to empty the vac & clean the filter. It was the last groove, after all. So what I did was to reverse the direction in which I was pushing the router so the vacuum could get another shot at picking up the chips. I had been doing this on the last couple of grooves & nothing had gone wrong.

In this case, it was a bad move. I think the bit must of started climb cutting & I didn't have a firm enough grip on the router. Next thing I know, the bit had cut through the 1/4" shoulder in the middle of the front face of the post. The post was now useless in that position, and I didn't have the stock to make a new post. The router got shut off, I stripped off my safety goggles, ear muffs, and dust mask, and went away to cool off & ponder what to do.

After thinking about it for an hour or two, I figured out what to do. The post that got damaged was the right front post on the right wing. Picture a square; the post was supposed to sit in the north-east corner on the right hand side of the finished pulpit. I decided to swap that post with the one for the left rear corner, or the south-west corner of the square. In that position, the damaged corner would get cut off in order to form a rabbet, so the damage would disappear. There was only one problem: I had cut mortises & a groove on the face that would face the user once the post was in its new position. I would have to fill in these no longer usable joinery cuts.

I still had some 1/2" thick cut-offs left over from forming these posts. I picked one & planed it to about 3/8" thick in my thickness planer. I then cut it to length & glued it into the groove. After the glue dried, I ripped off the extra material, leaving it a little proud of the surface. I then ran that face up through the planer and got it flush with the face of the post. The resulting patch is almost impossible to detect on the post face. This is one of the reasons why I say that God Himself is helping me with this project.

Here is a picture of the patch. You can see where the patch is on the top face of the post, and you can see how difficult it will be to locate the patch on the face after staining & maybe a little more stainable wood filler.

I had to go back & lay out & cut new mortises in the new post for the right front corner, and then cut the grooves. I also cleaned out the shop vac. There were no mistakes on this stick.

Next time: Making rails


neil said...

Hi your writing style. As I was reading, I'm thinking; is there another post. The grain match on the post-switcharoo came out really well.

Tony........I was right with you in routing the mortices, between getting older and needing more light to see, the fine work gets harder and harder. Just recently reading glasses and better lighting are now a necessity.

It's cool hang'in in "Tony's Woodshop"


Tony V said...


You flatterer you! ;-) LOL!

Thanks for the kind words. I had to get bifocals about three years ago. They're progressives. I find myself having to remove them to get a good look at the really find details. I'm afraid I'm going to need another new pair at my next exam.

I'll be making another posting soon, in the next couple of days. God willing.

Thanks again, Neil! It's nice to have a fan!