Apex Slot & Other Seal Services

REC offers 2 types of apex slot machining. We can expand the apex slot to accomodate a 3mm apex seal on all rotors, but we can also perform a specific RX8 rotor modification to accept out in house 2mm REC apex seals. (For RX-8 see our RX-8 Rotor Section.)


REC In House Apex Seals

Rotary Custom Apex SealsREC apex seals are seals Rotaryengine.com have been manufacturing since 2004. Although we used to engrave then with our RX7 Specialties logo we dropped the logo after 3 years of production for 2 reasons.

1 - We felt it was best not to tamper with the strength of the material as engraving can leasd to stress risers which can lead to fractures.

2 - Most of the sales of this product are to shops who not only use them in their owwn builds, but race cars that owners work on or race themselves. Because there became a high demand for this product amoung racers, we felt they would like to protect the source of these seals. In other words, any distributor or racer who resold the seals wanted to keep the origin on the seals a secret so their competitotrs couldn't find out who was manufacturing them.


Once the logo was permancently removed we saw the seals being sold in much larger quantities to the shops who race or build the cars. The performance of these seals became very impressive and we were reminded frequently what a key infgredient they are to the racers success.


To date we offer 2 versions of our seals.
1 - Our standard tradtition "Black" seals. (Black in color with a silver tip)
2 - Our treated seals. (silver throughout in color)


Both versions of seals are equally as strong but the treated seals are less dependant on using premix in the fuel and they are also less harmful to the rotor housing chrome surface. However, both of these products are very gentle on the chrome surface as compared to the wear from many other seals that we have seen.
These days it seems there is a trend where other seal manufacturers are proving to be capable of designing a strong seal but it is difficult to obtain strength and gentle wear at the same time. REC seals have long since accomplished both and we know that our seals have stood the test of time.


REC seals are also one of the only aftermarket apex seals which use a factory shape end piece. Most other seals on the market use a long design end piece which in our opinion serves no purpose and if anything will disrupt the sealing quality. Since the very beginning Mazda has been designing ALL of their rotary engine apex seals with a perfect triangle shaped end. This was determined by Mazda to be the ideal design and it holds true to this day. Every Mazda apex seal uses this design and Rotaryengine.com does the same. We always have and always will. All our seals are sold with factory springs which are included in the price of each set.


To date REC seals are found in hundreds of street cars and track cars and are currently being used in 2 of the worlds fastest drag cars.


3mm Apex Slot

We offer 3 different types of 3mm machining services


3mm Apex Seal ModificationsThe first and least expensive process we offer is performed on an in-house custom machine which operates like a slitting saw. Attached to a special jig and fixture, the rotor is slowly manoeuvered on "air over hydraulic" tracks passed a small diameter cutting blade with a selected number of sharp carbide bits. This method provides no adjustment to select a desired clearance. The cutting blades are exactly 3 mm wide leaving a rotor with a seal clearance of approximately .0025 in. Although adequate and again, inexpensive, the finish is not a high enough quality to accept ceramic apex seals. This method is also not capable of cutting 93 up rotors or any other rotors with the induction hardened slots.

Cost per slot: $35.00


The second and still economical type of 3mm machining is performed using a special "end mill" attached to a milling machine. Unlike the slitting saw, the end mill bit does not complete the cut all in one pass. Using a 2mm wide end mill, we cut up one side of the slot and then back down the other. This process translates to conventional milling on the first pass and climb milling on the second pass creating a non-uniform finish. It is recommended to hand dress the slot with a stone or fining Emery paper to a finish of your liking. Specific rotor to seal clearances are available with this procedure. We can offer tolerances accurate from 2/10 to 3/10 thousandths of an inch.

Cost per slot: $55.00


The final but most expensive method of 3mm machining is done using a process referred to as EDM. This process uses a very thin wire that electro statically erodes away the material from within the slot. This provides one of the most impressive and accurate finishes and clearance tolerances. EDM is optimal for any high-performance or racing application. Providing tolerances accurate to one ten thousandths of an inch, the slots will now accept any material of apex seal desired including ceramics and carbon.

Cost per slot: $75.00


Corner Seal Hole Reaming

Rotary Corner Seal ReamingCorner seal reaming simply restorers all six corner holes on each rotor to their factory specifications. Some of you may own rotors which are perfectly good in all aspects with the exception of a couple of tight corner holes. Do not throw out these rotors as they can be put back into service simply by sending them to us and paying a small charge to repair them.


If you have a rotor whereby the material surrounding the corner whole (apex slot area) has folded in slightly due to damage in shipping or being dropped on the floor. REC might be able to repair these rotors for you. Again, do not throw them out until you contact us first.

Cost per rotor: $22.00


Rotor Repair

REC offers a unique method of repairing and reclaiming rotors to be reused. Using special customized tools and strategic methods we have proven to be very successful refurbishing rotors which would otherwise be too damaged for use. Outside of pressing in new bearings were milling apex slots we have the availability to refurbish corner seal bores and side seal slots. We also have other procedures to remove stuck or rusted side seals or corner seals. The amount of time spent on each rotor can vary from one part to another but a typical charge to refurbish a damaged or rusted rotor is approximately 1 to 2 hours. $80-$160


We can sometimes assess and quote a rotor by having the customer send us a photo. Please feel free to E-Mail Us to discuss any further concerns about obtaining the service.