Members of Congress usually speak politely to each other on the floor, because the punishment for harsh language is the cruelest that can be inflicted on a politician: He must sit down and shut up.

But about once a year, in the heat of debate, something snaps in a member with a short fuse. And so it happened yesterday to Sen. Lowell Weicker (R-Conn.) in debate with a fellow Republican moderate, H. John Heinz (Pa.).

Weicker had offered an amendment to a supplemental appropriations bill that would trim $13 million in loan guarantees for construction of a steel plant in Heinz's home state.Heinz suggested that Weicker was acting in the interests of a company headquartered in Connecticut.

That did it. Weicker retorted that anyone who would make such a statement was "either an idiot or devious" and that Heinz probably qualified on both counts.

Heinz rose on a a "point of personal privilege" but was ignored by Weicker and the presiding officer until he found a Senate rule book and cited Rule 19.

This forbids senators to "impute to another senator any conduct or motive unworthy or unbecoming a senator." If in the opinion of the presiding officer a senator violates this rule, the chair shall order the senator to take his seat "and he may not proceed without leave of the Senate."

This brought Senate proceedings to a half. Weicker was asked to take his seat. The next step would have been for the official reporter to read back Weicker's words and for the presiding officer to decide whether or not they violated the rule.

But the reporter who had taken down Weicker's words had left the floor to transcribe his notes. As the Senate waited, Majority Leader Robert C. Byrd (D-W.Va.) intervened and eventually got unanimous consent to strike Weicker's remarks from the record.

It took a bit of doing, however, Byrd tried being soothing, saying he could understand why Heinz took "umbrage," and adding that "many times we say in heated debate what later we wish had not been said."

"I take considerable objection to is characterization," said Heinz of Weicker, "I see no willingness on his part to have the remarks stricken from the record."

Weicker, after getting permission to speak, said he would consider agreeing to striking his remarks from the record "if the senator takes umbrage, and I would if I was him . . .."

Heinz offered to apologize if Weicker felt his intergrity had been impugned by Heinz's remarks. Weicker wasn't willing to go so far as to apologize, but he did agree to wipe his statement from the record. Then they shook hands and none of this will appear in the Congressional Record's account of yesterday's Senate debate.

Weicker's amendment was defeated, 59 to 29. CAPTION: Picture, Weicker: He's sorry if Heinz takes offense, "and I would if I was him . . ." AP