Editing Juki Maintenance Notes


== Counter Knife ==

* '''Description'''
The Juki 5550-6 has a stationary knife, a moving knife, and a thread guide. If they get dull, you will find that the thread does not cut and a rat's nest can build up in the needle plate. The stationary knife may be resharpened once, but I don't think we have a sharpening stone. Its easiest to replace all three at once. I found our thread guide was broken too. If sewing heavy thread, the knife will only last 3 months. It takes under an hour to replace these parts. Keep the knife area clean by removing the needle plate and using the cleaning brush to remove lint, fuzzy or dirt from the knives. If there is a large amount, use the vacuum. This helps a lot.

Page 7, Section 20 of the manual has a lame description of this part of the machine. Manual: [[Media:Juki-ddl-5550-6.pdf]]

[[Image:undertrimmer.jpg|thumb|right|Thread guide on left, movable knife top, stationary knife bottom.]]


* '''Buying'''
I bought a pack of all three parts for $18 on eBay. They are Strong H brand and may not be as good as Juki brand parts, but so far (after one day) they are better than the dull knives we had. I searched ebay for Juki 5550-6. Its listed as an 'Undertrimmer Knife Set'. Original Juki parts would cost $38+tax and a trip to Apparel City (I couldn't find Juki brand parts online).


* '''Instructions'''
Caution! Unplug the machine! 

You need a #3 allen wrench and [https://www.noisebridge.net/wiki/File:Knifewrench.jpg this 1/4 wrench with a 4.5 flathead bit.] and a can of compressed air. The small flathead screwdriver used for needle changes (in the grey drawer beneath the Juki) is useful too.

Remove needle plate.

Clean the area with the cleaning brush or a vacuum.

Note current adjustment position of the stationary knife... This is how we probably want the new one installed.

Remove stationary knife first, then remove the tiny thread guide screw and remove the thread guide, then loosen the allen screw and slide the moving knife toward you.

The wrench pictured above makes it possible to loosen and tighten these small screws at the tough angle. I found the tools in the dirty shop in the top right drawer. The small wrench was in with the ratchets.

Dab a drop of sewing machine oil on the moving knife with a cotton swab. (I'm not sure if this is needed. It may just attract dirt. Considering the abuse it takes, it's probably a good idea).

Replace all three parts in the reverse order that you removed them. A dab of something sticky (I used solder rosin) on the needle replacement flathead screwdriver can keep the tiny screw captive as you replace it into it's hole. 


* '''Last Replaced''' (log replacement date here)
May 1, 2011 - Chris Murphy

== Needle Bar ==

* '''Description'''
The Juki 5550-6 has a polished rod that holds the needle with a set screw. The hole that holds the set screw that holds the needle got stripped and then someone made some improvisations instead of fixing the problem by ordering and replacing the part. That wasn't good because we lost the thread guides in the process.


* '''Buying'''
Be sure the new needle bar comes with the set screw as well... or reuse the old one.
Needle Bar, Juki #22906002 


* '''Instructions'''
Caution! Unplug the machine! 

You need a large-ish phillips screw driver and several medium and small slotted screw drivers. You also need an egg carton or tray to hold the various parts. 

Remove the needle, the set screw that holds the needle, and the thread guides (Juki part numbers #229-06309 and #110-18801)

Remove the small rubber cap on the top of the machine. Its about 6mm in diameter.

Unscrew the three phillips head screws that hold the large, black face plate on the left side of the machine. They are the screws around the perimeter.

Once the needle bar mechanism is visible... Inside the faceplate, remove the black plate that covers the upper half of the needle bar. Remove the screw that holds the needle bar to the rotating crank arm mechanism that moves the bar up and down. Use the correct size driver for this last screw, its stiff and can be stripped if you use the incorrect size driver.

The needle bar slides straight up and out of the top of the machine. 

Note that the needle bar has score marks several centimeters above the screw holes. They are visible if you enlarge the image on the right. These are for Needle to Bobbin Hook alignment described in page 6, section 18, of the Manual: [[Media:Juki-ddl-5550-6.pdf]]

Insert the new needle bar with the faceted side facing you and the set screw hole facing right of the sewing machine operator.

Tighten the screw on the rotating crank arm mechanism. As noted two steps above, you will have to adjust the Needle to Hook relationship as described in the manual section 18.

Replace the black plate. 

Replace the thread guides (Juki part numbers #229-06309 and #110-18801). 

Replace the needle (notch facing to the right of the operator). 

Replace the set screw that holds the needle. 

Replace the big black faceplate on the side of the machine and the three phillips screws that hold it on.

Its probably a good idea to change the sewing machine oil. This can be a very messy process if you overfill it. It will spill on the floor, so don't overfill it! Use new oil because used oil may contain a tiny amount of water which will eventually rust the mechanism.

* '''Last Replaced''' (log replacement date here)
June 21, 2013 - Chris Murphy