McCormick-Deering Primrose Cream Separator

McCormick-Deering Primrose Cream Separator

McCormick-Deering Primrose Cream Separator

Instructions for Adjusting and Operating

This McD Primrose Cream Separator manual is available in its entirety from Small Farmer’s Journal Farm Equipment Manual Reprints: No. 165

McCormick-Deering Primrose Cream Separator


  • No. 1 — 350 lbs. or 40.6 gallons per hour
  • No. 2 — 450 lbs. or 52.3 gallons per hour

McCormick-Deering Primrose Cream Separator

Setting and Leveling

Select a clean and convenient place which is free from dampness for operating the separator. When possible, cement foundation should be constructed.

Attach supply can bracket to frame with two cap screws. (See illustration No. 3.)

McCormick-Deering Primrose Cream Separator


Before securing frame to floor with lag screws, level machine by placing spirit level on the top of bowl housing, as illustrated; if not level, place cardboard or thin wedges under corners until level, then fasten frame securely with lag screws.

IMPORTANT: After setting and leveling, and before placing the bowl and tinware, fill the oil reservoir with Cream Separator oil and operate it for a few moments (without the bowl), then drain off this oil and close the drain cock. This will wash out any dirt that may have accumulated while separator was in transit. Oil reservoir should then be filled with new Cream Separator oil.

McCormick-Deering Primrose Cream Separator


It is important that light cream separator oil be used to lubricate the machine. Inferior oil, or oil that is too heavy, will not satisfactorily lubricate running parts.

Use only the Cream Separator lubricating oils recommended.

Spend a few moments each day in determining that the separator has sufficient oil and that, in operation, all running parts are being lubricated. It is worth while.

Before placing bowl and tinware, squirt a small amount of oil on top of the bowl spindle.

McCormick-Deering Primrose Cream Separator

Place bowl draining funnel in bowl housing as shown in illustration No. 4, and pour oil from sample can into oil reservoir until it begins to run over into drip cup below machine.

The oil in the reservoir must be kept up to the proper height at all times.

The separator should be filled with oil to the point of overflowing at least once a week.

Save all surplus clean oil which runs over into the drip cup. Every two or three months, remove the oil by opening the drain cock under center of frame (see illustration No. 1), and draining off all oil. Close drain cock and refill with fresh Cream Separator oil. The self-cleaning feature of the oil overflow lube will ensure the removal of liquids other than good clean oil.

McCormick-Deering Primrose Cream Separator


Bolt pail shelves to drip shelf. Put drip cup in place. Place crank on shaft and secure firmly with screw. (See illustration No. 7.)

The separator is then ready to receive the bowl and tinware. Before using the bowl it should be taken apart and all discs thoroughly washed. See special instructions and illustrations.

McCormick-Deering Primrose Cream Separator

Placing Bowl and Tinware

Before placing the bowl in position, be sure end of spindle is wiped perfectly clean; also see that the spindle socket in bowl is free from all dirt or grit. (See illustration No. 7.)

Caution: When placing bowl in position, be careful not to drop it. The driving pin on the spindle should be placed directly opposite the skim milk outlet.

McCormick-Deering Primrose Cream Separator

Place skim-milk cover over the top of bowl, pressing it down firmly so that it will rest evenly on the frame all the way around. Put the cream cover into the skim-milk cover and press it firmly down into place.

The spouts of these covers can be located to suit the convenience of the operator. Put on regulating cover, pressing it down firmly into cream cover. Put float into regulating cover.

McCormick-Deering Primrose Cream Separator

Before starting the Separator, fill the bowl with warm water.

McCormick-Deering Primrose Cream Separator

Supply Can

Place supply can on bracket: Note that notch in lower flange on supply can fits over finished portion on arm of bracket, bringing faucet into proper position.

The hook on bracket is for a cream pail or vessel into which the bowl may be drained after separating. Keep supply can faucet closed until bowl reaches its proper speed.


Principle of Construction

The mechanism of the Primrose is simple; the power applied to the crank drives the bowl through the medium of a non-slipping clutch, large spiral gear, spiral pinion and shaft, spindle drive gear and the bowl spindle.

Principle of the Separator

When the milk has been poured into the supply can, and machine has attained its speed, the faucet should be fully opened. The milk will then flow through the regulating cover, down the feed tube and into the bowl, where separation of cream from the milk takes place. The skim milk passes from bowl to skim-milk cover and out into receiver; the cream enters cream cover, thence to receiver. By adjusting milk regulating screw, any density of cream desirable can be obtained. The screw, acting on the skim milk in the bowl, leaves cream passage unrestricted. Milk screw regulating cream density, when turned OUT thickens the cream; when turned IN it thins the cream.

McCormick-Deering Primrose Cream Separator

The Bowl in Principle

Separation takes place in bowl. The milk enters the bowl at “C”, the centrifugal force exerted by the speed of the bowl and interior bowl construction distributes the milk onto the discs, the cream traveling inward and is discharged at the center of the bowl, the skim milk traveling outward and is delivered at the outer edge of the bowl.

McCormick-Deering Primrose Cream Separator

Screw for Regulating Cream Density

The milk regulating screw is adjusted at the factory for a medium light cream, but it should be understood that the richness of the milk separated has a substantial influence as to what the cream will test. The bowl should therefore be used as received and after a trial run the milk screw changed to produce the desired density of cream. One-quarter turn IN of the screw will thin the cream approximately 7%, while one-quarter turn OUT will thicken the cream about 7%. One complete turn of the screw either in or out will change the cream test about 25%. Therefore, care should be exercised in setting the screw, and one-quarter turn at a time should be sufficient until the cream test desired is secured.


Taking Bowl Apart

McCormick-Deering Primrose Cream Separator

McCormick-Deering Primrose Cream Separator

The bowl is the most important part of the separator and should be handled carefully to avoid injury. To take apart, place bowl in bowl vise in center of supply can bracket as shown in illustration No. 13, so small hole in bottom of bowl drops over pin in bracket; then with bowl wrench remove nut by turning to the left as indicated by arrow on nut. (See illustration No. 14.) Then lift shell from tubular shaft with first and second fingers, at the same time pressing down on tubular shaft with your thumb.

McCormick-Deering Primrose Cream Separator

Washing Discs

Open bowl as instructed in preceding paragraph. Take off dividing disc, then remove discs from tubular shaft by inserting wire disc holder through holes at edge of discs, which will prevent discs becoming mixed.

McCormick-Deering Primrose Cream Separator

They should be washed by placing in a pail as illustrated, sousing first in tepid then in hot, soapy water, finally rinsing in clear scalding water and hung up to dry. They should remain on wire holder until required for use again. Separate them so that the air can circulate freely, or spots of rust may develop where discs touch. Discs should be frequently washed with brush and dried. (See illustrations No. 15 and No. 16.)

Washing Bowl

Bowl when unpacked, prior to placing in machine, should be washed thoroughly and all oil removed by washing in hot soapy water; also wash carefully immediately after each run; it should never be left filled with milk or water.

Drying Bowl

Do not place bowl or bowl parts in stove oven or on stove to dry, as this will injure tinning. Do not put parts together immediately after washing. Let them dry thoroughly and rapidly. In the daily use of the machine, all parts that come in contact with the milk should be kept thoroughly clean. Too much care cannot be taken in this respect, not only for the sake of the machine, but for the quality of the dairy products. If the separator is not to be used immediately, do not put the bowl together, but leave it open until just before using.

McCormick-Deering Primrose Cream Separator

Care of Rubber Ring

Before using, new rubber rings should be washed with clean water or good gasoline; do not use kerosene.

McCormick-Deering Primrose Cream Separator

Clean rubber ring carefully and place it in saucer of cold water and leave it there until you are ready to put bowl together again for next skimming operation. Do not hang rubber ring on a nail or peg, as it is apt to damage it and cause leakage. It should be laid flat. Keep oil away from ring, as oil destroys rubber.

McCormick-Deering Primrose Cream Separator

Assembling Bowl

To assemble the bowl, place the rubber ring (after dipping it in tepid water) in position as illustrated, “C”, then place discs on tubular shafts, making sure that they are in numerical order, beginning with number one marked “BOTTOM”. One of the three slots in the discs is made wider than the other two to correspond with one of the three wings on the tubular shaft, which is made with its edge turned to fit this wide slot in the disc, thus keeping discs in proper position on tubular shaft.

Be sure all discs are properly in place, then put on dividing disc and shell, being careful that the notch “A” in the bottom of shell fits over lug “B” on tubular shaft. After starting the nut on its thread, set the bowl in bowl seat and tighten with bowl wrench, until arrow mark on bowl nut (see illustration No. 14) is in line with notch in upper edge of tubular shaft and nut is tight.

McCormick-Deering Primrose Cream Separator

After the bowl is properly washed and assembled, it is strongly recommended that it be filled, just before using, with warm water, and when it reaches the proper speed the milk should be turned on as directed. The water so used will be discharged with the skim milk and not affect the cream density in any way.


McCormick-Deering Primrose Cream Separator

Flushing (See illustration No. 21.)

Stop turning crank on Separator when milk level in supply can is down to top of faucet as illustrated. After all milk has passed out of supply can, close faucet and pour two to four quarts of tepid water in supply can (temperature of water should be from 100° to 110°). Wait one minute, then open faucet slowly, taking about ten seconds to secure full opening. Keep faucet opened until the first rush of cream passes out of cream spout (this will require from three to ten seconds); then close faucet until about half open, holding in this position until the flow from cream spout is reduced to a drip; then open faucet again, long enough to permit balance of cream to discharge from cream spout, when the bowl will be flushed. Time required for final flush will vary with the density of cream; only a few seconds are necessary to completely flush the bowl.

Let the bowl run down of its own accord until it comes to a stop before attempting to remove tinware.

To Clean After Flushing

Clean bowl after each skimming and flushing. In removing bowl from housing, care must be taken that milk remaining in bowl after skimming is not spilled over separator and on the floor. Set bowl in bowl vise in center of supply can bracket so small hole in bottom of bowl drops over pin in can bracket, in same manner as described earlier, but, instead of removing bowl nut entirely, loosen it just enough with bowl wrench so it can be taken off by hand.

McCormick-Deering Primrose Cream Separator

Draining Bowl (See illustration No. 22.)

The drain funnel in can bracket is to hold the bowl while draining and the bowl should be placed upside down in funnel and drained. Remove bowl nut and lift bowl shell, allowing the remaining skim milk to drain out of bowl into skim-milk bucket; put discs on disc holder and proceed to clean bowl and tinware as instructed. Give your separator a thorough cleaning every time it is used.


Speed Indicator

A uniform and proper speed must be maintained, to insure maximum efficiency in operating. A speed indicator attached to crank operates automatically, and indicates by a light tapping when machine is below speed. When machine has attained proper speed, tapping ceases, but the indicator will oscillate slightly when handle is in top part of circle (or revolution) as illustrated and if kept in this position will not run above normal speed.

McCormick-Deering Primrose Cream Separator

Keep up the speed of the bowl throughout the entire run.

A great deal of butter fat is lost by permitting the speed of the bowl to slacken.

Do not apply a brake to the bowl when the run is finished, as it may injure the bowl and is dangerous to the operator. Let the bowl run down of itself.


Bowl Spindle

The spindle is detachable from the bowl and is held in place by spindle stop screw. Spindle should remain in place when bowl is removed, thereby eliminating chances of damaging any part of spindle. The tempered steel point in the end, resting on a steel ball on top of the tempered steel point in lower spindle bearing, takes the thrust of bowl weight and reduces friction.

McCormick-Deering Primrose Cream Separator

To remove spindle, loosen stop screw at base of bowl housing and lift spindle from its place. Do not remove spindle except to replenish the oil supply, to renew points or to clean.

When putting the bowl spindle back in place, see that it turns freely and set the stop screw firmly against frame; this will prevent spindle from lifting out with the bowl. (See illustration No. 7.)

If bearings are removed for any reason, see that they are thoroughly cleaned with gasoline, and properly oiled before replacing.

McCormick-Deering Primrose Cream Separator

Upper Spindle Bearing

The upper spindle ball bearing is held in place by the steel spring.

To Remove or Replace Upper Spindle Bearing

Remove (1210C) bowl spindle stop screw, (1216CB) upper bearing cover, then pull up on spindle which will readily come out of bearings.

To remove the bowl spindle bearing upper after spindle is removed, insert finger in bore of bearing and simply pull bearing out of (1215C) upper spindle bearing spring.

To replace the upper bearing and spring, wrap spring around bearing and exert pressure enough to cause spring and bearing to seat into place.

McCormick-Deering Primrose Cream Separator

Removing Steel Points

To remove steel point, screw the wrench onto the threaded portion (as shown in illustration No. 26) until the point is started from its seat; it will then drop out of spindle end.

McCormick-Deering Primrose Cream Separator

Lower Spindle Bearing (See illustration No. 28.)

To remove steel point from lower spindle bearing, a hammer and a small punch are all that are required. The steel ball is held in place in the lower spindle bearing by a retainer ring. This retainer ring should not be pushed down tight against the ball. (See illustration No. 27.)

McCormick-Deering Primrose Cream Separator

In replacing clutch pawls (122C) note carefully “arrow marks” and see that they are inserted in exactly the same position as pawls removed.

McCormick-Deering Primrose Cream Separator

Place spiral gear guard (928CB) over gear and secure with bolts.

McCormick-Deering Primrose Cream Separator

Removing and Replacing Spindle Drive Gear and Bearing

McCormick-Deering Primrose Cream Separator

1. Remove crank holding screw and crank. Remove bolts and spiral gear guard. Open gear case cover as illustrated. Tighten upper screw lightly to hold cover in position. (See illustration No. 31.)

McCormick-Deering Primrose Cream Separator

2. Turn spindle drive gear until small end of taper pin appears and remove by tapping lightly with hammer and punch. Be careful that pin is not injured in removing. (See illustration No. 32.)

McCormick-Deering Primrose Cream Separator

3. Pull out spiral pinion and shaft and remove spindle drive gear and washer. (See illustration No. 33.) If spindle drive gear is tight on pinion shaft, it can be loosened by holding spindle gear firmly after taper pin has been removed and turning the crank which should be replaced for this purpose.

McCormick-Deering Primrose Cream Separator

4. To remove spiral pinion bearings, loosen set screw on inside of frame for left bearing (see illustration No. 34) and on outside of frame for right bearing, with screw driver, and then force bearing out, using driving bar.

5. To replace bearing in frame, use mallet and driving bar. Care must be taken to adjust bearing so that it will not bind on spindle drive gear.

6. In replacing spindle drive gear, great care must be taken that large hole in the hub lines with the hole in pinion shaft. Taper pin should then be inserted and secured firmly with a light tap of hammer on punch. If the hole in spindle drive gear and in pinion shaft do not line up so that taper pin will drop into place without binding, the right hand bearing (from front of machine) should be adjusted by loosening set screw on outside of frame with screw driver (see illustration No. 34) and driving bearing in or out, as may be necessary to line up the spindle drive gear taper pin hole, with the hole in pinion shaft. (NOTE: By driving the right hand bearing in, it loosens the spindle drive gear on the pinion shaft and by driving it out will tighten it. The adjustment should be carefully made that the gear is not loose when properly assembled.)

7. Washer must be placed on spiral pinion shaft and located next to the right hand spiral pinion shaft bearing (from front of machine) and on inside of the frame.

8. When replacing the pinion shaft bearings, left or right, the oil hole at the extreme end of the bearing should be inserted so that it will be inside the frame and the groove down.

McCormick-Deering Primrose Cream Separator

Adjusting Height of Bowl

If it is found necessary at any time to adjust the height of bowl, remove lower spindle bearing oil cap, loosen lock nut (see illustration No. 35) with open end of bowl wrench, and with small flat wrench raise or lower the bowl as required until groove around bowl neck is flush with top of cream cover, taking care to tighten lock nut and replace oil cap after adjustment. (See illustration No. 36.)

McCormick-Deering Primrose Cream Separator

The lower spindle bearing should never be removed unless it must be replaced.


Operators should at all times most carefully observe the following IMPORTANT points.

  1. That the machine is set level and remains so in use.
  2. That the machine runs steadily and smoothly at all times, except for slight vibration of the bowl in starting or stopping.
  3. That the discs are placed on tubular shaft in proper rotation, never forced on shaft wrong, and that the bowl locking nut is screwed down to mark.
  4. That bowl is kept to its proper height.
  5. That bowl is not dropped in putting it into machine.
  6. That no attempt is made to regulate the density of the cream by changing the speed of the bowl. This method is wasteful of cream.
  7. That the milk should be at a temperature of 85 to 95 degrees for skimming. Milk can be skimmed but not efficiently at a lower temperature, and is better for feeding when warm.
  8. That the rubber ring is properly cared for and is renewed when necessary.
  9. That extra bowl rings, steel points and brushes for cleaning be kept on hand for use in emergency.
  10. That the oil used is of good quality, but not too heavy.
  11. That if milk is accidentally spilled into the gears or bearings, flush out at once with oil and to avoid rusting follow up with a thorough oiling.
  12. That all parts which come in contact with milk are kept thoroughly clean and are washed and scalded after each operation. The machine should be carefully wiped off and kept covered when not in use.
  13. To replace tubular shaft nut, the bowl must be locked tightly and a new mark nicked in the end of the tubular shaft, corresponding to the mark on the nut. The old mark in the tubular shaft must be effaced.

McCormick-Deering Primrose Cream Separator

McCormick-Deering Primrose Cream Separator