Friday, March 23, 2018

Dark Chocolate and Sponge Cake (8)

Yesterday I found myself deep into my milling machine - well, not so much, but this is the most apart I've had it so far:

The motor was quite a lump and way too heavy to lift physically.

Once the motor was off with the aid of a come-along, I could remove the drive pulleys and the drive pulley housing:

Getting the drive pulley off was quite a chore, as the M35 fine threads were a bit chewed up:

The above picture is after I had cleaned things off with a feather file.

The cause of the damaged threads was found, the obvious clue being the tip shape of each of the two set screws which fixed the locknut in position:

It looks like these set screws had been modified by a previous owner of the machine. It makes no sense from an engineering perspective to drive hardened points into fine threads if you have any future plans of disassembly. Many German craftsmen are skilled and fastidious workers, however the person who did the above should reconsider his career path perhaps. Maybe I'm too grumpy!

The reason for all of this malarky was to get at the machine's brake mechanism, which lay under the drive pulley. It had been making noises for a while now, and as I was in between tasks on the milling machine, it seemed like an opportunity for a 'quick' (hah-hah!) look-see. Besides the noises, which were obvious but not too alarming, there had been the odd piece of fibrous brake shoe material eject from under the pulley, so I knew at a minimum that the fiber needed replacement.

When I got the pulley off, I found that one of the cast aluminum shoes had broken in half:

I considered for a bit making a new one with the mill from some 1/2" 6061T-6 plate I had kicking around, but decided to investigate another angle first, just in case. Parts for old Zimmermann mills are non-existent for the most part, however it just so happens that the model of mill that I own was licensed for manufacture in the Czech Republic-  now called Czechia on the maps - by TOS Kurim, who made a metal milling version called the FNK-25a.

I located the North American distributor for TOS milling machines, in Ontario, and lo and behold they even had the brake shoes in stock, with shoe lining already affixed:

Though the parts were not cheap, it made sense to order them rather than futz about. It would have been fun to make one, but not the best use of shop time, and I was unsure about dealing with the linings anyhow.


Back to the work on the upper frame. In order to trim off the remaining joint portions on the shaper, I made up a sacrificial backing piece, a mirror of the molding profile - here, I'm checking the fit to the stock:

Once that was fitting suitably, I could finish off the trimming work. Here's one of the completed corners, and bear in mind that the view is of the underside of the connection:

Work then turned to trimming trenches for the locking pins, or shachi sen, on the half laps:

Some opportunity was there for trimming on of the sloped ramp ways with a shoulder plane, so I took it:

This joint half is pretty much there:

An assembled corner:

The joinery was completed then through the other corners, with just the sen themselves to be fabricated. I'll save that for later on.

Next task was to fabricate the battens which span across the panel of the top. I had rough cut the parts several weeks back, and boy oh boy this 'special' mahogany just does not move at all! No twist, no bow.

Nevertheless, I jointed, planed, and finish planed the pieces to final dimension, cross cut to dimension, and then formed the tenons, which are slightly off-center of the vertical axis:

These tenons will be formed into half-dovetails, something I should get to shortly.

Thanks for dropping by the Carpentry Way.