Cleanup and check of a Mettler Instruments K4T single pan top loading balance.

After owning and using this K4T balance for over twelve years, I thought it was time for a full cleanup and accuracy check. When first purchased from Ebay it received a quick cleanup, function, and accuracy check, before I quickly put it to use.
I already owned several other Mettler K5 and K7 balances, and the K4T is basically an updated version of the K5T. According to Mettler’s website the K4 has been discontinued since: Jan, 1965.
Now that I am retired I thought the old K4T deserved some attention. I did a fairly extensive search of the internet, but did not find much information or photos of Mettler’s K4 balance, which replaced the Gram-atic 4000 series of balances.
So while cleaning I took the time to photograph the internals of the K4T.

The Mettler K4T balance is a single-pan balance, for rough weighing.
The weight readout is by graticule projected on to a ground-glass screen. It has a capacity of 4,000 grams with a precision of +/- 0.2 grams. The beam uses magnetic dampening with a stable readout in 2 to 5 seconds. The display has an optical range of 1,000 grams with 1 gram divisions. It has built-in substitution weights of 1 and 2 Kg, along with an adjustable spring type tare function of 500 grams. This unit was built in the late 1950“s.
Click on gallery images for larger view.
Mettler K4T 2 and 1 Kg weights Mettler K4T 2 and 1 Kg weights Mettler K4T 2 Kg weight Mettler K4T 1 Kg weight Mettler K4T Back Mettler K4T Left side view Mettler K4T 1 Kg weight Mettler K4T Arrested Mettler K4T Back no-load Mettler K4T Back loaded Mettler K4T Back lower Mettler K4T Front Mettler K4T Front lower Mettler K4T 2 Kg weight lifted Mettler K4T Knife edge Mettler K4T Knife edge assy Mettler K4T Left side angle Mettler K4T Tare and left front Mettler K4T Left side Mettler K4T Tare spring up Mettler K4T Tare spring down Mettler K4T Lower arm side Mettler K4T Lower arm angle Mettler K4T Lamp assembly Mettler K4T Right knife edge assy Mettler K4T Right side Mettler K4T Right side arrested Mettler K4T Right side zoom Mettler K4T Back counter-weights Mettler K4T Pan and 2 Kg weight platform Mettler K4T Rear mirrors Mettler K4T Graticule view of optical path Mettler K4T Pan base Mettler K4T Zero reading Mettler K4T with 400 gram test weight
- Some helpful notes for shipping Mettler K Series balances:
- First unplug the balance from power source.
- Remove the pan and pan base from the top of balance.
- Carefully remove the metal top cover section straight up, making sure not to put pressure on the front display bezel.
- Carefully remove the substitution weights from their holders and place on a clean soft surface such as a towel.
- Turn the “ARR.” knob on the lower back of the balance in the direction of the arrow to arrest the beam.
- Check that the knife edge pivots raise up, and the balance beam is secured and not loose.
- Using a flat blade screwdriver loosen the screw in the center of the weight range selection knob two turns. Gently pull straight out clearing the side pin from the case.
- Replace the metal top cover on the balance.
- If the balance has a tare knob on the left side, it is not removable and extra precautions will need to be taken in protecting it such as added padding on the left side around the knob. The knob will not survive a direct impact during shipping!
- The pan, pan base, substitution weights, and range selection knob should all be wrapped and packed separately from the balance. No loose items should be inside the balance case.
Mettler K Series PDF manual in English, French, and German, thanks to gmvv.org !
Dear Sir,
Do you have instructions on how to calibrate these? We have a K5 and would like to calibrate it. I test a 500 g standard, it shows just under 500 g.
Thank you.
Sorry no official instruction manual.
Some things to check though:
Balance must be stable and level, using the bubble level on the side of the balance.
Adjust zero with an empty pan.
Check the standard to verify it is within specifications, and has a recent cal check.
Check magnetic damper blade to verify it is not rubbing. This is a common problem if not shipped or stored properly.
If all of the above are good, then check accuracy using 50g, 100g, 250g, then 500g standards. If all readings are out of cal
and get progressively worse with increasing weight, then it most likely could benefit from an adjustment.
The fine adjust is a round weight on a small threaded rod. Recommend marking the original position before adjustment.
The course adjust is comprised of two knurled weights that must be loosened and then adjusted using a threaded screw.
Greg (Barbouri)
Dear sir,
I have a K5 . This week, the transformer short-circuited -> bulb lamp does not function anymore. Do you have the specs of the transformer (220V — 12V) and the bulb (Watts or ampere)?
Hi Ed,
Here are the specifications for the bulb in the K4:
Part# 1802‑L
Voltage: 6.5V, Amperage: 1.4A, 9 Watts
Maximum Overall Length: MOL 1.92″ / 49mm
Maximum Overall Diameter: MOD 1″ / 25.4mm
Base: BA15s, Single Contact Pin Bayonet
Glass: S‑8, Painted, Black with Small Side Opening
I am guessing that all the K series units use the same bulb.
There seems to be several different types of transformers used in the Mettler K series.
Most have been multi-tap type, but there are some that are single-voltage only.
My K4T, K5T, and K7T units all have four input voltage selections.
Greg (Barbouri)
Thank you, Greg, most helful.
My K5 has a multi-tap type 220V-transformer (220V supply). The bulb installed was a 21-Watt type; much too high I presume. A replacement transformer and bulb are hard to get, if not impossible.
Do you know a supplier?
Hi Ed,
I would try Ebay.com for a donor unit that has a good transformer and bulb, with possibly a spare bulb in the cover.
Greg (Barbouri)
After I posted this K4 balance blog, gmvv.org was kind enough to supply a use and calibration manual in multiple languages for the Mettler K‑series of balances
Greg (Barbouri)
Hello Greg,
Thank you very much for all your infos and the nice pictures!
I just bought one of this balances for a price of one Swiss franc.
could you post the solvent you use for the cleaning of the different parts? I guess you clean it not just dry. And did you see some oilpoints to lubricate (or is that maybe a no go on a balance?) 😉 best wishes from switzerland
Andi
Hi Andi,
For the external parts and case, I used an all purpose citrus cleaner with a distilled water final rinse.
For the mirrors and optics, Zanifer Pro-Lc Lens Cleaner.
For the internal non-lubricated balance parts and weights, I used 91% isopropyl alcohol.
No extra lubrication was added to existing lubricated parts, such as the tare mechanism.
Hi Greg,
Thank you very much for your fast and presize reply. I’l need to clean a lot here:-)
Did you know this site, it is specially interesting becouse of the prices they list there and the different tare functions: https://www2.humboldt.edu/scimus/Manufac/Mettler/MettlerCat.htm
Yes, I am familiar with the Humboldt University site.

Here is my collection of working Mettler K series balances: