Thursday, January 11, 2024

Bernina 900 Foot Pedal Fix Request

I had some family hand me an old Bernina sewing machine (a Nova, looks like a 900 but I cannot confirm this).  It's not working.  The pedal is simply not allowing it to function.  Apparently, they had taken the pedal to a repair shop, and the shop turned them away, because it was only used for a short time, and the parts stopped being made a long time ago.

Granted, they have a few extra sewing machines, but they REALLY like this light weight machine, and were hoping I could get the pedal fixed.  It's called an "air pedal".  It seems to function just like other sewing machine pedals, but it "floats", or at least, it is supposed to.  This one just floated without connection.  So, I took it home, and promptly took the thing apart.

 First thing I noticed is that there is a barbell of sorts used to connect the pedal to the actual hinge hardware, and it is not in position.  Problem?

Perhaps.  The blue circle is around the barbell.  The green circles are two concave holes where the two ends of the barbell are supposed to go (think of a hip joint - one round ball and one socket).

 Here are some more views of the two halves.

Let's put it back together in what we'd call "the Right Way" (trademarked?) and see what happens.

Here we can see the ball joint in it's natural habitat, with the actual pedal ready for installation.

So, was it the actual problem?  Yes. The machine actually started up this time.  It immediately stopped, which sent me home with the whole machine for some electrical tests.

I flipped it over, and a pin fell out (one you might see holding sleeves on a brand new dress shirt that is being opened, not machinists pins or internal pins).  I paused, flipped the machine upright, plugged everything in, and hit the pedal.


While holding the pedal, I rotated the manual crank wheel, and it started working.  That's it - a pin held the whole thing hostage.  It's back online.

Small Parts Sled

In the process of building the tool chests, I have encountered the need to do some small parts.  Since I do not desire to lose any fingers, and since I didn't want to use my big panel sled used to cut the sides, it was time to tackle yet another sled.  I've seen a Rockler sled listed on Amazon for $90, and it was severely tempting. However, I thought I could save a couple bucks and do it myself, since that sled likely had to be built for my specific table saw, anyway.  So, let's see.

Now, if I filter out the costs of the stuff that wouldn't be included in the Rockler kit, we're looking at the melamine ($20), UHWM ($29), t-track ($36), and a couple of screws that you likely have sitting around for a grand total of $85.

Hold on - I ONLY saved $4?  [sigh].  But, the parts would let me build a second jig if I needed to, say for instance that I was going to build a jig for my router (which IS on the docket).

Anyway, I added t-track folding stops ($28), two t-track hold down clamps (I got mine from Rockler for $8 a piece on sale, but $25 on Amazon for two), an aluminum angle bar for some custom jigging on this thing for $21.  All this, with enough to make a second jig, for $150, and that included stuff the Rockler kit did not for only $60 more.  Off to the build (which you'd have to do with the Rockler kit, too, but most parts are pre-cut).

First, mark up the melamine board for the parts.

The usual cutting of those parts out (yes, I have quite a bit of left over material - I could build a slightly larger sled, or [again] a sled for possibly cutting some custom grooves on the router) went pretty quietly.

With parts cut out, it was time to install the UHMW (again, slicker than HDPE, and the stuff I ordered came pre-drilled).  Note that in my case, my table saw miter slots are NOT 3/4", so I had to use the table saw to trim the width down - and that was a bit harrowing because the blade wanted to grab that material BADLY and throw it at me.  Please take note of your own table saw slot dimensions!

The first bar went on relatively straight forward.  I used a 90-degree square (a carpenters square will work, too - pretty much anything that will get you close) and simply attached it to the bottom.  It didn't have to be on the table saw to get it set into the right position.  I actually set it on the left side when looking at the bottom, about an inch away from the side.  This would become the right side of the jig when flipped over.

The second bar was where I was a little more careful.  It needed to be parallel with the first (the board itself did not need to be exactly perpendicular).  I used some super glue (it won't stick very well to melamine, so be gentle until it's screwed on).  With the UHMW set properly in the left miter slot on the saw, and some super glue/cyanoacrylate set on top, I dropped the previously-attached board and miter into the other slot, and slowly dropped the board onto this new one.  Give it a minute to set up.  It should hold just long enough to pull the board and the two miter bars out, flip it over, and screw the second bar down.

Now is when we get a LITTLE more careful with getting everything square.

Raise the saw blade on your table saw to be just above the top of the melamine board when it is in the slots properly.  Yes, we're going to cut into it (not all the way through, yet).  Start the table saw, and feed your sled base into the blade until we have the top being cut by 1/4".  We will then back the sled base out, and set it to the top and pull back to do the same for the other side of the board.  In this case, we want to cut 1" on the top surface of the sled base (1/4" more than our melamine material that will be used for the sides of the sled).

Now, drill all the holes to hold the fences/sides, and countersink for the screws.  Use a square to make sure the fence/side is at 90-degrees, and then put the first screw in (pick the hole farthest away from the cuts on the sled base - it will be less finicky on the next step).

Now, use a right angle (I used a drafting triangle) to square up the fence to the two marks from the saw blade.  If you are going to use this as a reference for your parts, make sure this is accurate.

Clamp that fence into final position.  I used a 90-degree clamp I'd made for my tool chest drawers, just to make sure.  Then, flip it, and drive the screws into position for the first side/fence.

The second is a little easier.  Find a length of material that will set between them.  Square the fence up to the sled base, and drive one screw.  Move your material height block to the other end, square it, and drive that screw.  Now you can drive the screws in that will hold those sides/fences in position.  Make sure you have at least two screws on each fence/side ON EACH side of where the cut marks are to ensure it is secured.  I ended up with 6 screws on each fence to attach the sides/fences to the sled base.

Flip the sled, and install your t-track slot onto the tops of the fences.  Now, raise the saw to where you will likely have it (I raised it about a half inch above the sled base), and make one final cut through the entire base.

You can use those fences to cut a perpendicular groove with a 3/4" straight flute router bit (parallel to your sides) for the hold down clamps.  Rockler has this going parallel to the saw cut, I have two of them perpendicular so I have a little more range.

Then you can install the final bits of t-track onto the sled base.

Now, with potential hardware installed, you have a very solid, manipulable jig to hold small parts on.  The angle block can use the t-track hold down to give me a 90-degree surface for clamping, too, so I am very versatile with this little jig.