Lead Screws

Features of Ametric® Trapezoidal Screws and Nuts

Ametric® trapezoidal screws are precision rolled. Continuous search for improvement and many years of Ametric® experience in the development of the cold plastic deformation process which characterizes rolling allow us to offer our customers trapezoidal screws with excellent features.

Materials

Steel used in trapezoidal screws: Surface hardness after rolling

EN 10084 C15E - 1.1141 carbon steel App. 160/180 HB

EN 10083-2 1C45 - 1.0503 carbon steel App. 250 HB

Inox A2 - AISI 304 -1.4301 stainless steel App. 260 HB

Inox A4 - AISI 316 - 1.4401 stainless steel App. 280 HB

C45 and A2 stainless steel were chosen because in addition to their natural qualities as good construction materials, after rolling they give very good surface hardness and finish on the thread sides. A4 stainless steel also has excellent corrosion resistance. C15 is an excellent quality-price compromise. Roughness is less than 1 μm Ra for all.

These two features are decisive factors for qualitative appraisal of trapezoidal screws because they give very small friction coefficients, much lower than those obtainable with machined screws where other conditions such as speed, load and lubrication are equal.

Our trapezoidal screws coupled with bronze nuts give the opportunity to realize translation systems whose efficiency, flowability and quietness are much lower comparing to a coupling with machined screws.

Because of the low friction coefficient the amount of heat generated during movement is limited with resulting smaller nut heating. Nut life is also increased. We make nuts with 10 kinds of material to better meet the various requirements.

Steel used in nuts:

EN 10277-3 11SMnPb37 – 1.0737 steel with sulphur, manganese and lead

EN 10277-3 11SMn30 – 1.0715 steel with sulphur and manganese

INOX A1- AISI 303 – 1.4305 stainless steel

Brass used in nuts:

EN 12164 CW614N-M brass

Bronze used in nuts:

EN 1982 CuSn5Zn5Pb5-C – CC491K tin bronze with zinc and lead 60-70 HB

EN 1982 CuSn7Zn4Pb7-C – CC493K tin bronze with zinc and lead 65-75 HB

EN 1982 CuSn12-C – CC483K tin bronze 80-100 HB

EN 1982 CuAl11Fe6Ni6-C – CC483K aluminium bronze 160-220 HB

Plastic used in nuts:

PA 6 + Mo S2 DIN 7728 plastic

PA 6 + Mo S2 DIN 7728 + additives self-lubricating plastic

The nuts we make with length 3xTr: HDL, BIG and HAL deserve special attention.

These bronze nuts, thanks to their considerable length, distribute the load over a larger number of holding threads and thus limit surface contact pressure between screw and nut. This is decisive for long nut life.

By using the 3xTr long nuts compared with bronze nuts with conventional length (approximately 1.5xTr or 2xTr), higher loads can be born for equal traversing speed.

In particular, with HAL aluminum bronze nuts very high loads can be born and it is recommended to apply continuous steady lubrication. HAL nuts have to be coupled with screws in C45 or in stainless steel A2 or A4;

C15 screws are not recommended.

Where it is not desired to lubricate trapezoidal screws, self-lubricating plastic nuts are recommended.

It is not possible to couple plastic nuts with screws made by machining.