Koken Barber Chair Parts Diagram

Working with a Koken Barber Chair Parts Diagram

I have spent more time than I care to admit rebuilding vintage hydraulic barber chairs. Koken is one of the brands you will run into most often in shop refurbishment work. The parts diagram for these chairs is not something you can just pull up on a modern website and have everything match perfectly. The company went through various ownership changes, rebranding, and the drawings themselves shifted over the decades. What follows is based on actual shop floor experience, not a glossy manual. If you are looking for a proper diagram, your best first move is to track down the chair's model plate. Koken chairs typically have a small metal tag riveted to the underside of the seat pan or the rear of the base column. It will list a model number like K-100, K-200, or variations like KSS-1 or KHD-5. That exact number determines which parts diagram applies. Without it, you are just guessing at bolt patterns and hydraulic connections, and that leads to ordering the wrong components. I once had a chair come in that was labeled simply as a "Koken Style." The previous owner had already torn it apart and thrown away the original diagram. The base was a four-star cast aluminum, the pump was a dual-action floor model, and the cylinder was a standard 3-inch stroke. I spent two hours cross-referencing parts from three different aftermarket suppliers before I realized the footrest bracket was a Koken-specific width that did not match any generic replacement. The workaround was to measure the original bracket, find a donor footrest from a scrap chair, and fabricate new mounting holes using a center punch and a drill press. That process took about forty minutes once I had the right donor part identified. The lesson is that "Koken style" is not a reliable enough identifier for ordering parts.

Here is what the main components look like across most Koken hydraulic models and what you need to pay attention to when you open a parts diagram:

Hydraulic System

The heart of the chair is the hydraulic unit. Koken typically used a floor-mounted dual-action pump connected to a single-acting hydraulic cylinder. The pump has two hoses: one for raising and one for lowering. On the parts diagram, you will see these labeled as the lift hose and the dump hose. A common mistake I see is people assuming both hoses are the same diameter. They are not. The lift hose is usually 3/8 inch and the dump hose is 1/4 inch. If you swap them or try to use universal fittings without checking the thread type, you will get leaks within days. The fittings on genuine Koken pumps use standard SAE flare connections, but cheap reproductions sometimes use NPT threads. That mismatch is the number one reason rebuilt chairs start dripping hydraulic fluid within the first week of use. The cylinder itself is a chrome-plated steel tube with a piston seal kit inside. The seal kit is what you replace when the chair sinks slowly under weight. Koken used a standard 3-inch bore cylinder on most of their mid-range chairs. The seal kit includes a U-cup seal, a wiper ring, and a piston O-ring. I usually replace the entire cylinder if the chrome on the rod is pitted. You cannot reliably rebuild a cylinder with scored chrome. A new cylinder runs about eighty to one hundred twenty dollars from a barber supply house and installs in roughly twenty minutes.

Base and Swivel Mechanism

The base is either a four-star or five-star cast aluminum or steel. The swivel mechanism sits between the base and the hydraulic cylinder. On the diagram you will see it labeled as the turntable or swivel plate. This part carries the entire load of the chair and rider. The bearing surface inside the turntable is a bronze or brass bushing that wears over time. When it wears, the chair develops a lateral wobble that feels like it is going to tip, even though the hydraulic system is fine. The fix is replacing the bushing or the entire turntable assembly. Generic replacements are available from companies like Global Industrial and Barber Supply Company, but the bolt pattern must match exactly. Koken used a six-bolt pattern on most models, but the diameter of the bolt circle varies between 6 inches and 7 inches depending on the model year. I learned this the hard way on a 1972 Koken K-200. I ordered a replacement turntable from a surplus supplier without measuring the bolt circle. It arrived with a 6-inch pattern, and the chair would not assemble. I ended up drilling out the old mounting holes and tapping new ones on the base to fit the 7-inch table. That added about an hour and a half to the job and required a drill press, tap set, and a good deal of patience.

Seat and Backrest Assembly

The seat and back are mounted to a metal frame that bolts to the hydraulic cylinder top plate. The frame on Koken chairs is typically 1-1/2 inch square tubing with gusseted corners. The cushion is held on by straps or a perimeter channel. When replacing the cushion, you need to match the underside channel width. Koken used a 10-inch wide seat channel on most models and a 9-inch channel on narrower barber styles. If you put a 10-inch cushion on a 9-inch channel, it will slide around and the stitching will wear through within months. I always measure the channel before ordering a replacement cushion. Foam density matters too. Standard upholstery foam at 1.8 density will bottom out in a year. Go for 2.5 density minimum if you want the cushion to last beyond two years of daily use. The armrests bolt to the side of the seat frame. Koken used a variety of arm styles over the years: fixed vinyl pads, adjustable chrome arms, and the later wrap-around style. The mounting bracket has a single 3/8 inch bolt hole. Replacement arms from aftermarket suppliers are hit or miss. The bolt hole alignment is often off by a millimeter or two, which means you end up widening the hole with a file. The footrest is mounted on a swing-arm bracket that pivots on a pin. That pin is a common failure point. It works loose over time and the footrest drops into an upright position while the chair is in use. The fix is replacing the pin and adding a small C-clip to retain it. The original Koken pin does not have a clip, which is a design flaw I have seen cause injuries. Adding the clip takes thirty seconds and prevents the footrest from becoming a projectile. Genuine Koken parts diagrams are scarce online. The company as it existed in its prime is no longer operating as an independent manufacturer. Most diagrams you find on forums and eBay are scans from old service bulletins or photocopies made by previous owners. They are often blurry and missing part numbers. For accurate reference, I recommend taking the chair apart, photographing each component, and measuring everything before you order anything. Keep a notebook with the measurements. That notebook becomes your personal parts diagram and it will save you more trouble than any scanned PDF.

Several suppliers still carry reproduction parts for Koken chairs. Barber Supply Company in Pennsylvania and Vintage Barber Supply in California both stock hydraulic cylinders, seal kits, turntables, and cushions. Neither of them carries every part for every model year, so you will sometimes need to fabricate or source from a scrap chair. The scrap chair market is your safety net. There are warehouses full of dead Koken chairs that are being stripped for parts. Buying a non-running chair for fifty to one hundred dollars and pulling what you need is often cheaper and faster than waiting on back-ordered reproductions.

Common Problems and What the Diagrams Do Not Tell You

The parts diagram will show you what each component is called and where it goes. It will not tell you about the problems that actually show up in the field. Here are a few that come up repeatedly: The hydraulic pump seal kit is the most frequently replaced item. The diaphragm inside the pump wears out and the chair stops pumping up. The seal kit costs about fifteen dollars and the replacement takes ten minutes with a socket set. But if you do not bleed the system properly after the repair, air gets trapped in the cylinder and the chair pulses instead of rising smoothly. Bleeding means operating the pump through its full range of motion with the dump valve open until all fluid flows without bubbles. Skipping this step leaves the chair feeling spongy and unprofessional. The gas strut on adjustable backrests fails on roughly half of all Koken chairs older than fifteen years. The back will not stay in position and slides down under the barber's weight. The replacement strut is a standard 12-inch furniture gas spring available from any hardware store for eight to twelve dollars. The challenge is removing the old one. It is press-fit into a bracket and requires a careful prying motion with a flat blade screwdriver. Break the bracket and you create a new problem.

The most dangerous failure point is the base-to-turntable connection. The bolts that secure the swivel mechanism to the star base can work loose from vibration. I have seen chairs tilt at an angle because a single bolt backed out completely. Check these bolts every time you service a chair. Torque them to forty foot-pounds and apply a drop of thread locker. This takes two minutes and prevents a chair from collapsing during a haircut. When working with any Koken barber chair parts diagram, treat it as a starting reference rather than a complete guide. The diagrams are outdated, parts are inconsistently reproduced, and the real details are in the measurements you take yourself. Build your own reference from the physical chair. It will be more accurate than anything printed, and it will be useful the next time you pick apart another one of these heavy steel machines.