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Last updated: January 8, 2026 at 9:57 PM

Following the sauna accident in Akasaka, I re-inspected the 42-year-old unit bath in my condominium and replaced the GOAL bathroom doorknob, which was rusted and showing signs of deterioration, with a DIY method.

Due to aging, the internal parts of this doorknob were severely rusted, and the latch sometimes did not work properly, so I had managed to trick it by injecting it with KURE 5-56.^{Note 1}

Therefore, as a precaution, we permanently installed an ``emergency escape hammer'' in the bathroom as shown below, so that even if you were trapped in the bathroom due to a malfunctioning doorknob, you could break the glass and escape.

However, due to the fatal sauna fire accident in Akasaka, the Small renovation of unit bath As part of this project, I decided to do a DIY job of replacing the door knob.

2026.01.06 Added
^{Note 1} The answer is provided by AI.It is best not to use penetrating lubricants such as "5-56" on doorknobs.It is said that Lubrication may temporarily make the movement smoother, but in the long run it is likely to cause problems such as the following.

・Adhesion of dust and dirt: Oil attracts dust and dirt, which hardens and becomes sticky inside, eventually causing malfunction.
・Occurrence of oil shortage: 5-56 has high permeability and evaporates quickly (runs out of oil), so its effects do not last long.

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The appropriate solution will vary depending on the cause of the doorknob malfunction.

1. Mild creaking or movement:
   If internal lubrication is required, consider using a lubricant spray that can also be used on keyholes. These are quick-drying and have a dust-resistant formula.
   Examples include KURE keyhole lubricant.
2. Failure of the doorknob body:
   If the problem does not improve even after applying oil, it may be due to aging or damage to internal parts. In that case, the entire doorknob body or lock case will need to be replaced.

Measure the existing doorknob

In order to replace the doorknob with a new one, we took the following measurements of the existing doorknob in order to confirm the manufacturer's name and identify the product number.

Order a replacement doorknob

As a result of the measurements above, it was determined that it was made by GOAL and the manufacturer's model number was ULW-4E BS70mm as shown below. Most of the doorknobs currently in circulation seem to have a backset of 50 to 60mm, and 70mm is considered a special case and is no longer seen.

Backset (BS) is the length measured from the edge of the door to the center of the base of the key cylinder, grip ball, and lever handle by placing a ruler on the surface of the door, and is an important dimension that must be measured when replacing a doorknob. If this distance does not match, you will not be able to install a new doorknob, so you will need to check the backset of your current product when replacing.

In the ULW-4E series, the back set 70mm (BS70mm) was discontinued by Monotaro, but fortunately it was on sale on Amazon for 3,900 yen (tax included).

Replacement doorknob (GOAL ULW-4E BS70mm) will arrive

I received a new doorknob (GOAL ULW-4E BS70mm) from Amazon, so I'm going to try replacing the doorknob right away!

GOAL ULW-4E BS70mm package contents

The package contents of GOAL ULW-4E BS70mm are as follows. The instruction manual was printed on the inside of the box, so I broke the box.

Advance preparation

As a preparation, remove the internal grip ball set in the ULW-4E (new). Use the included protrusion to push the ball into the hole in the inner ball stopper and pull out the ball.

2026.01.08 Added
We recommend that you have the following tools available for work.

• Phillips screwdriver (+2) and flathead screwdriver (blade tip 5.5mm) ⇒ VESSEL product information
• Shock driver or impact driver (if the screw won't turn using normal methods)
• Hammer (for shock driver)
• Pliers (for emergencies)
• Crowbar (for emergencies)
• Metal cutting saw (for emergencies)

Removal of existing doorknob

To replace with a new doorknob (GOAL ULW-4E BS70mm), first remove the existing doorknob by following the steps below.
As I will explain later, this existing doorknob was 42 years old, and due to aging, the internal mechanism was severely rusted, making it impossible to remove using normal methods, making the task extremely difficult. After 3 and a half hours of struggling, I managed to successfully remove it.

Removing the inner grip ball (Part 1)

The first phase of doorknob replacement is to remove the inner doorknob.
Other manufacturers have a special hook wrench that can be removed by hooking a special hook wrench into a small hole at the base of the doorknob and turning it counterclockwise, but GOAL doorknobs cannot be removed using that method.

Follow the steps below to firmly pull the grip ball inward while inserting a protrusion rod (one that we own) into the hole in the inner doorknob. However, the inside is rusted and does not move at all. Unavoidably, we resort to strong measures...

Even if you pull it by hand, it won't budge, so put a flat head screwdriver into the groove of the ball and use the principle of leverage to force the ball out. I continued this process for 2 hours and was able to move it a little, but in the end I couldn't pull out the ball.

Removing the latch

The latch needs to be removed after the inner grip ball has been removed, but the metal behind the grip ball is rusted and cannot be removed using normal methods.

Therefore, I will give up on removing the grip ball for the time being and try removing the latch, although this will be an irregular procedure. This is not a regular procedure, but a method of destroying and extracting the internal parts.
By removing the latch first, you can prevent the doorknob from breaking and becoming trapped in the bathroom.

As shown below, I injected KURE 5-56 around the latch screws, removed the screws with a Phillips screwdriver, then inserted a flat head screwdriver into the gap at the front of the latch to force the latch out.

Removing the inner grip ball (Part 2)

Since I succeeded in removing the latch, I regained my composure and tried removing the inner grip ball again.
It seems that the only option is to cut the grip ball with an electric saw, but since I don't have such a tool at home, I will try to break it with a crowbar and pull out the grip ball.^{Note 2}

Wrap the crowbar's fulcrum with a towel to prevent damage, and place it on top of the aluminum frame, insert the point of action of the crowbar into the groove of the grip ball, and carefully pull out the grip ball.
Along the way, while pouring KURE 5-56 and repeating this process endlessly, I managed to successfully remove the grip ball😃

The internal parts were rusted and in a state of disrepair. From this state, I think you can understand that it can no longer be removed using normal methods.

2026.01.08 Added
^{Note 2} Electric cutters cannot be used indoors because they produce sparks. It will take some time, but you can cut it with a hacksaw.

Removal of round seat

Insert a flathead screwdriver into the notch of the round seat and remove the round seat. To remove it, use pliers to reshape the inner knob post that was deformed during the removal process.

Removal of the round seat back plate

Inject KURE 5-56 into the screws on the back plate of the round seat, remove the screws with a Phillips screwdriver, and remove the back plate of the round seat.

Removing the outer grip ball

Pull out the outer grip to remove the doorknob. The inside of the latch case is full of rust, so I will clean the inside of the latch case to prevent rust.

After a long struggle, I finished removing the existing doorknob. This was an extremely difficult task that took over 3 hours in total, and I almost gave up halfway through, but with patience and perseverance, I managed to successfully remove it.
The old doorknob in the bathroom was severely corroded and difficult to remove, so I realized that DIY work was extremely difficult.

Installation of new doorknob (GOAL ULW-4E BS70mm)

After removing the existing doorknob, install the new doorknob (GOAL ULW-4E BS70mm) received from Amazon using the following steps.

Installing the outer grip ball and latch

First, insert the latch, then turn the outer grip clockwise so that the retractor of the lock case catches on the tail of the latch, and then insert the doorknob.

Check from the indoor side that the tail of the latch is engaged with the retractor, turn the knob, and if the latch is interlocking, secure the front of the latch with a screw.

Installing the round seat back plate

Secure the inner round seat back plate for the ball with screws. The round seat back plate has a top and bottom, so check the orientation and install it.

Installing the round seat

Insert the round seat so that the notch at the bottom of the round seat is facing down.

Attaching the inner grip ball

Insert the inner grip ball. When you insert it all the way, the grip ball will be locked.

Doorknob replacement completed

It was a tough job, but we have successfully completed replacing the doorknob (GOAL ULW-4E BS70mm). Including installing the new doorknob, it was an extremely difficult job that took 4 hours, so I don't want to do this kind of replacement work again.

2026.01.08 Added

Replaced MIWA doorknobs in bedroom and bathroom

Although there were no particular problems, we also replaced the MIWA doorknobs in the bedroom and bathroom to alleviate future concerns.
The lifespan of a doorknob is approximately 10 to 15 years, depending on how often it is used and where it is installed, so it is a good idea to replace old doorknobs as much as possible to prevent accidents.

replace bedroom doorknob

In the bedroom, we replaced the MIWA doorknob ``MIWA BM (BS64/M type)'' with ``MIWA BM (BS64/D type)''. The M-shaped grip ball was small and difficult to grasp, so I chose the D-shaped one.

Removing the M-type doorknob

Installing a D-type doorknob

replace toilet doorknob

For the toilet, we replaced the MIWA doorknob ``MIWA BM (BS64/W type)'' with the same W type. The replacement procedure is the same as for type D described above. The gallery below shows the doorknob after replacement.