Nine of ten federal workers are heading for a new performance appraisal system that will monitor their work constantly and determine how fast - or whether - they move up the pay and grade ladder.

This will be a multimillion dollar change, and a major pocketbook item for the one million federal civilians. The new system will spell out what it takes to keep getting regular 3 percent raises that now come almost automatically.

Federal agencies are getting the new guidelines from the Office of Personnel Management. OPM expects some agencies to begin the new ratings this year. All are expected to have the system in force by mid-1981. It will replace the present ratings of "unsatisfactory, satisfactory" or "outstanding" that determine eligibility for longevity raises.

Federal officials say that in the past, partly because of paperwork, management indifference and relunctance to withhold a longevity raise, 99 of every 100 employes got the raises when they came due. Raises come in one-, two- or three-year periods, depending on time in each pay grade.

The bottom-to-top pay spread in most of the first 15 grades (GS 1 through 15) represents about a 27 percent pay differential. In other words an employe entering one grade and staying there for 18 years would get the regular pay raises, usually without a hitch.

One of the chief goals of the new civil service reform law was to tighten up the "automatic" in-grade pay raises. Agencies will design their own programs on and occupation-by-occupation basis, subject to okay and review by the OPM. It is the successor to the old Civil Service Commission.

The new performance appraisal standards have yet to be detailed, but one key point keeps cropping up in each of the proposals. It is "politeness to the public." In future, if the system works the way it appears on the drawing board, employes who meet the public will have to meet minimum standards of courtesy and cordiality in their jobs, or be denied raises.

Workers who don't measure up to the particular performance appraisal standards may lose more than a regular longevity pay raise. They can also be reassigned, demoted or fired.

Officials say the key to the system will be enforcement by supervisors and managers. To make sure they do it the reform also sets up a new pay system for them. It will guarantee that managers in Grades 13 and 15 get only half the regular October pay raise for other federal workers. To get more, they must meet and exceed performance appraisals set for them - also to announced soon.

Linda Spell, field news editor for the National Federation of Federal Employees, is leaving the independent union today to live in Richmond. She's been field news editor for the past two years and deserves an "outstanding" rating, while they are still being given out.

Brown-Bag It: Federal workers who regularly eat in government cafeterias may have to do just that. Some 1,300 unionized cafeteria aides (in 45 eating establishments) may be heading for walkout. At issue are wages, health benefits and transfer rights. A strike vote is set for 5 p.m. today at the Mayflower Hotel.

Short Retirements: Two former top-notch bureaucrats are coming out of retirment to help the legislation and media campaign of the National Association of Retired Federal Employes. NARFE is battling administration proposals to whittle back federal pension benefits, and plans to offset social security benefits for future federal retirees.

To be special legislative representative, NARFE has recruited Smith Blair, former head of congressional relations for the General Accounting Office. During his tour with the audit agency Blair picked up valuable Capitol Hill contacts and how-to knowledge.

Joseph Oglesby, former public affairs chief of the Civil Service Commission will head the NARFE war against Social Security cutbacks, and any attempt to merge Civil Service retirement with Social Security. Oglesby's skill and credibility with the media won't hurt a bit.

New Faces: There will be lots of them on the House Post Office-Civil Service Committee this year.The unit that oversees federal pensions and other job benefits, and major portions of the Postal Service has lost five Democratic veterans and three longtime Republican members. The Democrats lose one member on the committee this year and the Republicans pick up a seat. The lineup will be 16 Democrats and nine Republicans.

New Democrats (with four more to come) are George T. Leyland (Tex.); Geraldine A. Ferraro (N.Y.) and Charles Stenholm (Tex.). New GOP members assigned to the committee include James A. Courter (N.J.); Charles Pashayan Jr. (Calif.); William E. Dannenmeyer (Calif.) and Daniel B. Crane (Ill.).