Thread: Full blind mitered dovetail case
13th Jul 2019, 06:41 PM #16
Not discouraged yet Luke! Today I moved on to the sockets. First I knocked up a simply jig to help align the boards so I could mark the sockets from the pins. I also found the sides bowed ever so slightly so had to cramp up the sides to make sure the pins were marked aligned to the line.
I proceeded to cut the first row of sockets to the scribed lines
But unfortunately have found the pins don't fit the sockets straight off the saw.
I'm trying to work out what I did wrong. I think it looks like I cut on the wrong side of the line.
I'll rest and revisit things tomorrow.Franklin
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13th Jul 2019, 07:51 PM #17
I tend to cut my first set a bit proud when doing wide D/Ts, it's a reasonable precaution. As you proceed to the next couple, you'll gt a bit more confident & cut closer. As my old cabinetmaker mentor used to say "split the line!" ......
14th Jul 2019, 09:21 AM #18
Hi Ian, After a good dinner (roast pork and apple strudel) and a good nights sleep I think I did cut on the right side of the line, they are just a very tight fit. If they were through dovetails in pine I think I might just 'persuade' them into place. As you suggest, I think I should put the sides back in my marking jig and reknife the lines. Given the difficulty of actually getting the knife alongside the pins in the jig, I guess the knife could have laid over too far and undercut the pins a bit when marking out. Previously I have usually cut sockets first. I might use a pencil line this time and I'll then shave a few sockets and recheck the fit.
14th Jul 2019, 01:54 PM #19
The reknife just made the original lines all look good. I decided instead to shave the ends of the tails a tad, allowing the pins to seat further in and the pins then started to fit the sockets with just a couple of the sockets requiring extra attention. Now the pieces fit together, albeit quite tight. A full dry fit will probably be a challenge as I think knocking the sections apart again might cause some damage. I'll see how the other sides go before trimming any more off these dovetails.Franklin
14th Jul 2019, 06:39 PM #20
Yep, it's tricky transferring your marks when there's so little room & you can't see what you are doing clearly,
& easy to get your lines off a bit. It doesn't take much, as you've discovered...
I have a long, thin scratch-awl that I use for situations like this. A typical scratch-awl has a round shaft, but that doesn't make a precise mark against a face, so this one is ground from an old triangular file. I made a 'diamond' point, bevelled on one side, so it's really a very long, thin-bladed marking knife. It gets into tight places much better than a typical marking knife, and the long blade helps me to keep it aligned square to the face I'm scribing from. Looks a bit odd compared to a 'standard' scratch-awl, but it certainly does the job: Scratch awls.jpg
The bling is entirely unnecessary, of course - I just like to play with my metal lathe...
19th Jul 2019, 03:22 PM #21
After the sockets were chopped out I proceeded to attack the mitres. I cut a jig to help chisel down the leading corners and then proceeded to pare off the bulk of the waste from the edges by eye with the intention of following up with a rebate plane to cleanup down to the line.
The planing idea didn't work. I had cut a 45 batten to run the plane against, but I had trouble keeping the plane from digging in to both the batten face and the ends of the pins. In the end I abandoned the idea of planing and used the 45 batten to guide the widest, longest chisel I had to pare the bevels down to the line by hand.
Then came the fun of dry fitting. The joints were tight and I'm worried about getting the parts separated again without damage, but eventually got things looking OK. It is a real challenge to the senses to get all the walls in the joints square and perpendicular! The layout I used didn't allow for any slack in fitting and it was hard to tell where the binding points were. I eventually chose to shave a smidgen off the length of both the pins and tails to assit with fitting. I now have a very small gap along the edges when fitting the sides together and I'm assuming it will mostly close up when I eventually cramp the whole carcase together.
I'm pondering whether I should try a full dry cramp up to make sure the joints do close up and that there are are no hidden hangups before final glueup, but I'm worried about damaging things breaking it all down again.Franklin
19th Jul 2019, 06:24 PM #22
The way I get two bits like that apart after a dry fit when they are too tight is to lay a length of scrap pine against the inside of the carcase & tap it off, going backwards & forwards along the caul so the joint comes away evenly & doesn't twist too much. If things are as tight as you say, you may be able to see some bruising & crushing where the tight bits are & tidy those up to get a nicer fit on the next try..
20th Jul 2019, 12:24 PM #23
Clearly my judgment of vertical and horizontal when paring by chisel leaves something to be desired. No surprises there really.
Prior to proceeding to a full dry fit it occurred to me to ensure the bottom of the sockets were all good by using the #71 to level them. I was surprised that although I had thought I might have been mostly undercutting, there were indeed a few that weren't deep enough and actually all of the end sockets need shaving a bit as well as a few along the middle. The fit is starting to look better now.
Next time I'll ensure the #71 comes out earlier and I'll need to source a narrower pointy tooth blade as well to get through the small socket openings.
28th Jul 2019, 01:28 PM #24
Finally at a full dry fit stage. Trying to juggle the drawer dividers into place would be easier with about eight hands. I think the dividers on the left need to have about half a mm taken off to help jockey the center divider into place and take pressure off the dovetails seating down. 0.5mm doesn't sound much but I think when it finally comes time for the final glueup it might just make a difference to the clamping pressure required. Beveling the edges of the boards going into grooves a smidgen should also ease locating them.
30th Jul 2019, 04:57 PM #25
All glued up.
I clamped some scraps below the trenches to help locate the drawer dividers and they went in OK. I did have a small problem with the rear dust panels. I had made them out of some wide scraps of thin NGR which has been lying around for a while. They were a wee bit warped but seemed springy enough to force into the grooves during the dry fit, however when I gave one a bit of a firm tap to get it to seat during the glueup it split on me. Not to worry it's only the back.
I hope I ended up using enough glue in the dovetails. I was concerned about getting squeeze out along the joints inside and out. Everything seemed to seat well and the seams look OK now they have been fully clamped down (really for the first time). There are only slight gaps visible on the front mitres. All in all I'm pretty happy with the fit and look for a first effort using slightly wonky boards! I measured the diagonals and they are just about spot on, just as well as I don't know how I would have gone about trying to crank the case square!
glueup1.jpg glueup2.jpg glueup3.jpgFranklin
2nd Aug 2019, 01:08 PM #26
I started fitting the drawer sides and found one set wouldn't go in all the way. When I looked in the slot I could see a scrap I had used to hold the shelf in place during glue up was still in the cavity. That particular scrap piece happened to be a cutoff of the shelf above and fitted exactly into the width of the drawer space. Unfortunately it is binding trying to pull it out. At this stage it appears the only way to release it will be to get in the hole and make a through cut.
New SNAFU to me.
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