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NY 855400

Sept. 11, 1990

CLA-2-84:S:N:N1:102 855400


TARIFF NO.: 8483.40.5010

Mr. Philip Kwok
NNR Aircargo Service (USA) Inc.
Hook Creek Blvd. & 145th Avenue
Unit B-3 East
Valley Stream, NY 11581

RE: The tariff classification of a series of harmonic drive gears from Japan, South Korea and Taiwan

Dear Mr. Kwok:

In your letter dated August 14, 1990, on behalf of your client, H D Systems Inc., you requested a tariff classification ruling.

Harmonic drive gears are a unique group of fixed ratio speed changers which incorporate an even more unusual ball bearing called a "Wave Generator" bearing. The basic harmonic drive is made up of three main parts: a circular spline, a flexspline, and a wave generator bearing. The wave generator is in the center of the assembly and resembles a radial ball bearing. The primary difference is that the wave generator has a thin, flexible outer ring which distorts in an elliptical pattern as the oval shaped inner race (plug) is rotated inside it. The wave generator in turn is mounted inside the flexspline, a non-rigid thin cylindrical cup with external gear teeth. As the wave generator rotates it causes the flexspline to distort elastically in the same elliptical pattern as the generator. This assembly is inserted inside of the circular spline, a rigid ring which has internal gear teeth. Due to the way that the wave generator causes the flexspline to distort, the gear teeth on the flexspline move counter-clockwise relative to the teeth on the circular spline, thereby creating a clockwise rotation of the circular spline.

The harmonic drive gears in question, series HDUR, HDUC and HDUF, are very precise speed changers used to power sensitive equipment. They are available in ratios (wave generator revolutions to circular spline revolutions) of from 50-1 to 240- 1.

The applicable subheading for the harmonic drive gears will be 8483.40.5010, Harmonized Tariff Schedule of the United States (HTS), which provides for fixed ratio speed changers. The rate of duty will be 2.5 percent ad valorem.

This ruling is being issued under the provisions of Section 177 of the Customs Regulations (19 C.F.R. 177).

A copy of this ruling letter should be attached to the entry documents filed at the time this merchandise is imported. If the documents have been filed without a copy, this ruling should be brought to the attention of the Customs officer handling the transaction.


Jean F. Maguire
Area Director

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