McCormick-Deering Trailer Mower No 9
McCormick-Deering Trailer Mower No 9

McCormick-Deering Trailer Mower No. 9 (5’, 6’ and 7’)

During the 1940’s, McCormick-Deering retrofitted its basic horsedrawn mower design to be pulled by tractors and added infrastructure so that two could be pulled, one just behind and offset from the other. Some of our Amish friends prize these “Trail” mowers for horsedrawn use recognizing that they are built a tad bit heavier. What follows is the actual Instruction manual, including set up notes, for that model. There are some mechanical tid-bits hidden in here that will assist the more avid shade-tree tinkerers. SFJ


Remove all wires and arrange parts conveniently.

Lubricate all bearings and moving parts as you proceed, and see that they work freely.

Bolts must be used in the holes in which they are found, or in parts to which they are attached, unless otherwise shown.

Shaded portions in the illustrations show parts to be assembled; these must be placed on the machine in the order numbered.

Wherever the terms “left” and “right” are used, it should be understood to mean from a position behind and facing the machine.

We reserve the right to make changes or improvements in the design or construction of any part without incurring the obligation to install such changes on any machine previously delivered.

McCormick-Deering Trailer Mower No 9

Place main frame on wooden horses, slide washer (A) and sand cap (B) over axle with studs of sand cap toward end of axle. Slide wheel in place, assemble pawls and springs in pawl holder (C), slide pawl holder over axle and drive “Groov” pin in just enough to keep pawl holder in place. After both wheels are mounted, check for end play. Excessive end play (more than 1/16”) should be corrected by inserting washers (found in tool box) as needed at each end of main frame (A). Secure pawl holders to axle with keys and “Groov” pins.

McCormick-Deering Trailer Mower No 9
  1. Prop up frame so crankshaft is level.
  2. Remove hinge pins from inner shoe; scrape off the paint and oil them.
  3. Connect inner shoe to shoe hinge.
  4. Replace front pin first, but do not drive it in all the way.
  5. Replace rear pin and secure with cotter.
  6. Drive front pin to place and secure with cotter.
McCormick-Deering Trailer Mower No 9
  1. Put knife in place, oil and move back and forth until it runs freely.
  2. Attach pitman to wrist pin.
  3. Attach pitman to knife head.

The knife head connection of this pitman is entirely automatic. As fast as any wear develops, it is immediately taken up by the spring pressure without any attention on the operator’s part. This pitman may be easily and quickly attached to or removed from knife head without a wrench.

McCormick-Deering Trailer Mower No 9

To attach pitman: Press fork handle between straps and hold over knife head ball as shown in Illustration No. 3A. Press pitman down until straps partly close on ball, then fold handle back against pitman.

To remove pitman: Turn fork handle away from pitman with punch and then press on outer end of handle with foot. (See Illustrations Nos. 3B and 3C).

McCormick-Deering Trailer Mower No 9
  1. Attach the tilting lever quadrant (complete with tilting lever) to the right side of the lug on the main frame.
  2. Attach the lifting spring connection, rear, to the left side of the lug on the main frame.
  3. Hook the tilting rod into the shoe hinge and to the tilting lever, and secure with cotter pins.
  4. Remove the gag hinge pin from the gag lever hinge, scrape off the paint, and oil the pin. (See Illustration No. 5 also.)
  5. Connect the gag lever hinge to the lug on the inner shoe hinge by means of the pin removed from the hinge.
McCormick-Deering Trailer Mower No 9
McCormick-Deering Trailer Mower No 9
  1. Attach lifting lever with sector and lifting lever quadrant to main frame by means of a special shank-headed bolt inserted from right side of sector, with washer under head of bolt; at the same time, secure quadrant to frame by means of lower bolt.
  2. Hook lifting lever connection into sector from right side.
  3. Connect gag lever to hinge with pin found wired to inner shoe. (See Illustration No. 5 also.)
  4. Attach gag lever post to inner shoe with pin found in post (See Illustration No. 5A also.)
  5. Attach foot lever to lifting lever sector with pin found in sector.
McCormick-Deering Trailer Mower No 9
  1. Attach grass board to outer shoe.
  2. Attach grass stick to inner side of grass board.
McCormick-Deering Trailer Mower No 9
  1. Attach stub tongue to tongue socket with three x 4-5/8” machine bolts found in tool box; put large 1-3/4” x 12 ga. Washer under head of bolts.
  2. Attach cutter bar stay rod holder and rod to tongue.
  3. Attach inner shoe fender rod to shoe.
  4. Raise bar until latch pawl engages rear notch in quadrant. Hook lifting spring on hook and attach rear end to lifting spring connection, rear. Tighten spring until cutter bar rests lightly upon the ground and raises easily. Tension of spring should be such that cutter bar will float easily along the ground with just enough weight to hold it steady.
  5. Attach spring with seat to seat socket in frame with 5/8” x 1-5/8” machine bolt, found in tool box.
  6. Attach stub tongue pivot assembly to stub tongue.
McCormick-Deering Trailer Mower No 9


Keep your machine clean, and lubricate freely all bearings and moving parts.

NOTE: In localities where the soil is sandy or full of grit, knife guides, wearing plates, and knife clips should not be lubricated; in other localities, where these conditions do not exist, lubricate frequently.

Important: The gears of this mower must run in oil!

Before using the machine, remove the front bolt from the gear case cover and pour four quarts of motor oil (S.A.E. 20) into the gear case. This will bring the oil level above the top of crankshaft when the pole is at working height. Maintain this level by adding fresh oil as needed. Never use heavy transmission oil.

Lubricate the pitman box and lower end frequently.

Lubricate at least once a day:

  • Clutch shifter.
  • Shoe hinge pins and bearings.
  • Joints for lifting mechanism, also gag lever and cam.
  • Lever bearing and pivots.
  • Shoe hinge on coupling bar.
  • Main wheels.
McCormick-Deering Trailer Mower No 9
McCormick-Deering Trailer Mower No 9
McCormick-Deering Trailer Mower No 9
McCormick-Deering Trailer Mower No 9
McCormick-Deering Trailer Mower No 9



See that your machine is properly set up, adjusted and lubricated as instructed, before going into the field.

Be sure that all nuts and set screws are tight. Spread all cotters to keep them from falling out.


Knife clips should be set to hold sections down against ledger plates on guards, but must allow knife to run freely.

McCormick-Deering Trailer Mower No 9


Keep the cutting apparatus in perfect condition. Always have knife sharp. There should be perfect shearing between sections and ledger plates, that is, the tip of every section should lie smoothly on ledger plate. Sometimes, in rough cutting, knife may be bent. It is then necessary to remove knife and straighten same. The knife may be straightened by squinting along the edge, noting where it has been bent and pounding same on a flat block with a hammer, then again lining it up with the eye and giving it a light tap where necessary until same is perfectly straight. Replace knife and see that it slides freely. The steel wearing plates are designed to hold knife sections in a correct cutting position. If, after long service, they become worn enough to allow the points of the sections to rise from ledger plates, they should be replaced by new wearing plates.

McCormick-Deering Trailer Mower No 9


These parts are properly adjusted at the factory and require no attention.

If any replacements of gears or clutch are made, mesh and bevel gear and bevel pinion are controlled by shims on bearing cap located at “A”.

When mower is in gear the clutch lever is toward the rear. In this position clutch fork “B” should work freely in groove of clutch to prevent wear when mower is running. This can be controlled with clutch washer adjustment nut “C” on clutch shaft.


To throw mower into gear, shift clutch shifter toward rear.

To throw mower out of gear, shift clutch shifter forward.


If outer end of bar sags behind the inner end in raising, shorten the adjustment; if outer end is too light, especially on short bars, lengthen the adjustment.

McCormick-Deering Trailer Mower No 9


Latch pawl on lifting lever is adjustable to take up wear. Lower round portion on pawl, when in engagement with notch in quadrant, should be about in line with front edge of lever. (See Illustration No. 16) Bolts must be kept tight.

McCormick-Deering Trailer Mower No 9


To tilt guards, use tilting lever (near right wheel).


To regulate height of cut, raise or lower soles under inner and outer shoes; cutter bar should be the same height at both ends. In rough ground, shoe soles should be adjusted and front of bar tilted up enough to keep knife out of ground.


In cutting very close to the ground, adjust height of cut and tilt cutter bar forward. However, this should be done only in down grass and smooth ground; otherwise, knife may be injured.


Do not hammer or bend down the lips of guards. This practice will result in choking knife and causing mower to run hard.


Excessive draft is usually due to the following:

  • A dull knife.
  • Poor lubrication
  • Non-alignment of cutter bar.
  • Poor adjustment of cutter bar parts.
McCormick-Deering Trailer Mower No 9
McCormick-Deering Trailer Mower No 9


For passing over stones, stumps, etc., and for turning corners, cutter bar can be raised high enough for ordinary conditions by means of foot lever; both inner and outer ends of bar are thus raised at the same time. Cutter bar can also be raised by means of the hand lifting lever. (See Illustrations Nos. 18 and 19.)

McCormick-Deering Trailer Mower No 9


To fold cutter bar for transporting, see that the pitman wrist pin is at highest or lowest point (if this is not done, breakage of pitman or knife head may result); then raise cutter bar to an upright position with hand lever and foot lever (pull hand lever down to last notch in quadrant). Insert hold-up rod through hole in cutter bar and secure with nut. (See Illustration No. 20.)

Important! Be sure mower is out of gear before folding the cutter bar.


If cutter bar is too light upon the ground, slacken lifting spring; if too heavy, tighten spring. This is done by adjusting the bolt in lifting spring. The lifting spring, when properly adjusted, reduces the friction of cutter bar on the ground, thus lessening the tendency toward side draft; the weight is also taken off the frame and transferred to the main wheels, giving the maximum traction.


Connection of grass board may be tightened to any extend, or board may be made rigid, if preferred. To lay a good swath, the position of grass stick may be changed by using the various holes in grass board. For tall grass, raise rear end of stick; for short grass, lower rear end. (See Illustration No. 7.)

McCormick-Deering Trailer Mower No 9


Remove “Groov” pin from pawl holder and use a wheel puller as shown in Illustration No. 21.