PG40 120×40 mm Eight Slot Heavy Aluminium Strut Profile for Machine Bases

OEM / ODM Available Free Sample Available ISO 9001:2015 EN 755-9 RoHS REACH

A 120 x 40 mm eight slot heavy PG40 aluminium strut profile with round M6 corner holes and an 11 mm web. For machine base rails that are anchored, tapped and subject to vibration.

Wholesale Price $6.20 - $10.40 / m per m

Material	Aluminium
Alloy Grade	6063-T5
Temper	T5
Section Size	120 x 40 mm
Slot	8 x 10.2 mm groove, 8 mm mouth, 40 mm pitch, outer pair 80 mm apart, M8
Length	6 m stock, cut to drawing to +/-0.5 mm
Tolerance	EN 755-9 / GB/T 6892, wall +/-0.15 mm
Surface	Mill finish / clear anodised / black anodised
MOQ	200
Lead Time	20-30 days after deposit for mill finish
Loading Port	Shanghai / Ningbo
Supply Ability	300 t per month
Payment Terms	T/T 30% deposit + 70% before shipment \| L/C at sight
Trade Terms	FOB \| CIF \| EXW
Certifications	ISO 9001:2015 \| EN 755-9 \| RoHS \| REACH

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Structural framing · PG40 heavy beam

A PG40 120 x 40 mm eight slot heavy aluminium strut profile is the heavy-wall version of the standard 120 x 40 mm beam. The envelope, the slot layout, the 40 mm pitch and the 10.2 mm groove are the same; the differences are the internal wall thickness and the corner holes, which are round 5 mm holes tapped M6 rather than the square 5 x 5 mm holes of the standard section. It weighs about 5.4 kg/m against about 4.6 kg/m for the standard version.

A machine base is the application that makes the heavy version necessary rather than merely nice to have, and the reason is not stiffness. A base rail has to do three things the rest of a frame does not: it has to hold anchor bolts that tie the machine to the floor, it has to survive vibration from the process without the joints fretting loose, and it has to carry the concentrated loads from levelling feet and anchor points. All three of those load the corner holes, and that is exactly where the round hole earns its place.

120 x 40 heavy section: thicker internal webs and round M6 corner holes, for tapped connections and anchored machine bases.

The three differences a round corner hole makes

The corner hole form is the detail that separates the two versions, and it changes three practical things. All three matter on a base rail and none of them shows up in a stiffness calculation.

Tapping is reliableA square hole interrupts the thread helix at its four corners, so the tap is loaded unevenly and the thread is thinner exactly where the load concentrates. A round hole takes a continuous, uniform thread all the way round.

Chips clear properlyWhen you tap a blind hole, swarf packs into the square corners and either jams the tap or stays behind in the thread. A round hole lets the chips fall clear, which matters when you are tapping a rail on site.

Stress concentration is lowerA round hole in a loaded section concentrates stress at its edge with a factor of about 3. A square hole concentrates the same load into four much smaller corner radii, and the peak factor is higher and its location less predictable.

Square corner holes are for clearance; round ones are for threads. That is the underlying rule. A square hole exists so that a square neck or a carriage bolt cannot rotate. A hole that is going to be tapped should be round, and on a machine base every corner hole is a candidate for tapping.

A machine base has three requirements

Take the three things a base rail has to do and check them against the two sections.

Requirement	What it loads	Standard version	Heavy version
Anchor bolts to the floor	Corner holes in tension and shear	Square hole, uneven thread, lower pull-out	Round hole, full thread, predictable pull-out
Vibration from the process	Joints in reversing load	Thinner web, more fretting at the joint	11 mm web, joint holds preload better
Levelling feet and jacking points	Concentrated bearing on the section	Thinner wall deforms under a foot load	Thicker wall spreads the load
Repeated re-levelling during commissioning	Threads cycled several times	Square-hole thread degrades quickly	Round-hole thread survives repeated use

Why not simply use a bigger section?

The obvious alternative to a heavy 120 x 40 mm base rail is a bigger beam. Sometimes that is right, but on a machine base it usually is not, for three reasons.

First, the envelope is often fixed. A base rail sits inside the machine’s footprint and under its guarding, and there is frequently no room to go deeper or wider. Second, the base rail’s job is not primarily to be stiff — it is to transfer the machine’s loads into the floor and to hold the anchor points, and a bigger beam does not hold a thread any better than a small one. Third, a bigger beam is heavier everywhere, including in the middle of the span where nothing is happening, whereas the heavy wall puts the material where the anchor points and the joints are.

Option	Effect on stiffness	Effect on the anchor joints	Verdict
Standard 120 x 40 mm	Reference	Square threads, lower reliability	Adequate for a light machine on a level floor
Heavy 120 x 40 mm	About 18 per cent more	Round threads, thicker web, holds preload	The base rail answer
Deeper beam, 160 x 40 mm	About 2.4 times more	Round corner holes on the heavy version	Use if the envelope allows
Larger square section	Much more	Round corner holes	Only if the footprint has room

Building a machine base

Set the anchor bolt positions from the floor, not from the machine Drill the floor first and make the base fit the anchors, rather than the other way round. Anchor bolts that do not line up cannot be adjusted afterwards.
Tap the corner holes before assembly Tapping is easier with the rail on the bench. Use the round corner holes and tap to a depth of at least 1.5 times the bolt diameter.
Keep the torque inside the aluminium thread limit About 15 N m for an M8 into an aluminium thread, and about 28 N m for an M10. The receiving thread strips before the bolt does.
Fit the levelling feet before the machine goes on Set the feet and level the base frame first, then lower the machine onto it. Trying to level a base with the machine already on top is much harder.
Re-torque the anchor points after the first week of running Most preload loss happens early. A scheduled re-torque catches it before it becomes a levelness problem.

Frequently asked questions

What is the difference between this and the standard 120 x 40 mm section?

Wall thickness and corner hole form. This version has round 5 mm corner holes tapped M6 and an 11 mm web; the standard version has square 5 x 5 mm holes. The envelope and slot layout are identical.

Why is a round hole better for tapping?

A round hole takes a continuous thread and clears swarf. A square hole cuts into the thread flank at its four corners and traps chips, so the thread is weaker exactly where the stress is highest.

Can I use the standard version for a machine base?

For a light machine on a level floor with the base bolted through rather than tapped, yes. For an anchored base that is tapped, re-levelled during commissioning and subject to vibration, use the heavy version.

Is aluminium a good material for a machine base?

It has better internal damping than welded steel, it does not need painting and it can be re-configured on site. It is less stiff per unit weight, so a long base rail has to be deeper than a steel one would be.

Do you supply the base as a finished frame?

Yes. Send the footprint, the anchor positions and the machine weight, and we will supply cut, faced and tapped rails, or a complete base frame with feet and anchor plates fitted.

Send the machine footprint and the anchor positions

Tell us the footprint, the anchor bolt positions and the machine weight. We will confirm the base rail, tap the round corner holes to your pattern and quote the frame with feet and anchor plates.

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