Tianjin OuNaiDa Transmissions Technology Co., Ltd. is one of the leading manufacturers and suppliers of hgw20cc linear guide block in China. If you're going to buy high quality hgw20cc linear guide block, welcome to get more information from our factory. Also, custom service is available.

HGW20CC Wide Linear Guide Block: 63 mm Width, 30 mm Height, 17.75 kN Dynamic Load

A customer building laser cutting tables asked us why his single-rail Y axis kept showing a few tenths of play at the far end of the cutting head arm. The rail was fine. The block was an HGH20CA - 44 mm wide, bolted to a 300 mm arm with the load hanging off the end. The moment arm was doing exactly what moment arms do.

He did not need a second rail. He needed a wider block. The HGW20CC runs on the same 20 mm rail and carries exactly the same bearing ratings as the HGH20CA - 17.75 kN dynamic, 0.20 kN-m yaw. What changes is the footprint bolted to his arm: 63 mm wide instead of 44 mm, with the mounting bolts 53 mm apart instead of 32 mm. The bearing was never the weak link. The bolt spread into his plate was.

Dimensions and ratings

Load ratings and moments are reproduced as published in the catalogue's kN and kN-m columns; no conversion has been applied. The catalogue notes 1 kgf = 9.81 N for the figures given in kgf elsewhere in the same document.

HGW20CC against HGH20CA: same bearing, different envelope

Both run on the same 20 mm rail. Both have identical load ratings. The difference is entirely in the block body.

The ratings are the same because the ball recirculation and raceway geometry are the same. What the HGW adds is 19 mm of extra width and 21 mm of extra bolt spread, plus a step up from M5 to M6 mounting bolts. You pay 0.1 kg per block for it.

That matters when the block bolts to a thin plate or an extruded profile. A wider bolt pattern spreads the reaction into the structure instead of concentrating it at two close-set threads. It does not change what the bearing can take; it changes what your plate can take.

The mistake: treating the block rating as the system rating

A 0.20 kN-m yaw rating on the data sheet is a static rated moment for the block. It is not a statement about your machine. Two things routinely undercut it.

First, the mounting surface. THK's installation instruction is to remove burr, dent and dust from the mounting surface before the guide goes on. That sounds obvious until you watch someone bolt a rail onto a plate with a weld spatter nib under it. The rail bends over that nib and the block runs against the resulting curvature for the rest of its life.

Second, bolt torque. THK publishes a recommended tightening torque table for LM rails, and the numbers differ sharply by the base material:

The M5×16 rail bolt on a HGW20 rail wants 882 N·cm (8.82 N·m) into steel but only 441 N·cm (4.41 N·m) into aluminium. Use the steel figure on an aluminium base and you pull the thread or dish the surface under the bolt head, which is a different way of bending the rail. THK adds that rails are ground and inspected with the bolts tightened, so the published accuracy assumes the bolts are actually at the recommended torque, not finger tight.

Tightening order matters too. THK's instruction is explicit: tighten from the centre of the rail toward the ends. Working end to end pushes any accumulated error into the last section.

Preload: pick a class, not a feeling

HIWIN's HG catalogue defines three preload classes against the basic dynamic load rating C: Z0 is 0 to 0.02C, ZA is 0.05C to 0.07C, ZB is 0.10C to 0.12C. On the HGW20CC with C = 17.75 kN that puts ZA roughly between 0.9 and 1.2 kN of internal preload.

The catalogue also ties preload to how straight your base has to be. Maximum parallelism tolerance for HG20 is listed as 25 µm for Z0, 20 µm for ZA and 18 µm for ZB. Heavier preload buys rigidity and costs you tolerance on the mounting surface - a ZB pair on a base machined to Z0 flatness will bind, run hot, and wear early. Note also that interchangeable guideways are offered in Z0 and ZA only; ZB is non-interchangeable, meaning matched block and rail.

If you are not sure which class you need, linear guideway preload and ball screw accuracy covers the interaction, and how to choose a linear guide and slider walks the sizing.

Installation: the reference side is not decorative

On a THK LM guide the block's reference surface is opposite the face carrying the logo, and the rail's reference surface is the one marked with a line. The procedure is to align the line-marked side of the rail against the side reference surface of the base, tighten set screws just enough to hold the rail in contact with that side face, then torque the mounting bolts.

Ignoring the reference side and bolting the rail on whichever way it came out of the box throws away the precision you paid for. If you need the reference surface or the grease nipple on the other side, that has to be specified at order time.

For the second rail in a pair, there are four documented alignment methods: a straight-edge with a dial gauge, using the parallelism of the table itself, letting the subsidiary rail follow the master rail through the table, or a purpose-made jig. Picking one and doing it properly is faster than iterating with shims.

Pairing and ordering

The HGW20CC runs on a 20 mm profile rail, 20 mm wide, 17.5 mm tall, 60 mm hole pitch, M5×16 mounting bolts. Our HG series linear guide and block listing covers the standard combinations, and customized length linear guide handles cut-to-length rails.

If your axis is longer than one rail section can be supplied, rails get jointed - read the joint rules on the rack side for the general principle, and ask us for the guide-rail joint fitting at order time rather than after delivery, because the rail has to be tapped for it.

What we need to quote

Rail length, number of blocks per rail, preload class, accuracy grade, base material (this sets the bolt torque and sometimes the preload choice), and whether the rails run in a dusty environment. HIWIN's own catalogue flags wood working machinery and glass or stone machining as the cases that need the high-dustproof seal options, and those add friction - 1.5 to 4.0 kgf for the ultra-high dustproof set against 0.6 to 1.2 kgf for the standard high-dustproof set - so it should be in the spec, not an afterthought.

Dimensional and load data come from the OND HGW-CC/HC and HGH-CA/HA tables. Tightening torques, reference-surface marking and mounting procedure are cited from THK published technical pages. Preload class, parallelism tolerance and dustproof accessory data are cited from the HIWIN HG series catalogue. Verify the final specification against the drawing supplied with your order.

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