Replacement Tie Bars — Machined From Your Broken One

Tie bar snapped at the thread, or the machine builder wants a five-figure sum and a three-month wait? We machine replacement tie bars and tie bar nuts for injection moulding, die casting and hydraulic presses from your broken original — thread form and pitch gauged, 42CrMo4 heat treated, nuts matched. No drawing needed, one piece up. Get a quote →

One bar, and the whole press stops earning

A tie bar is a simple part with an expensive job: four of them carry the entire clamping force, and they are the reason the platens stay parallel. When one breaks, the machine is not running at reduced capacity — it is out of production entirely, and every day it sits still is measured in lost mouldings.

What makes it worse is the supply route. Machine builders treat tie bars as captive spares, quote them accordingly, and for a press that is fifteen or twenty years old often cannot supply one at all. The bar is not complex to make — it is a heat-treated shaft with a thread at each end — but it is long, it is load-critical, and it has to match the original exactly. That is a machining job, not a spare-parts problem, and it is the one we take.

What we make

• 01
  Complete replacement tie bars — turned from solid alloy steel bar, heat treated, threads single-point cut, ground or polished on the running surfaces.
• 02
  Tie bar nuts — steel or aluminium bronze, matched to the bar, with spherical or tapered seats where the original had them.
• 03
  Matched bar-and-nut sets — the pair cut and gauged together, which is how you avoid inheriting the wear pattern that broke the first one.
• 04
  Sets of four — when one bar has already failed, the other three have seen the same cycles; a full set restores equal length and equal stretch across the platen.
• 05
  Hard chrome plated bars — where the original was plated, or where the bar runs through platen bushings and surface wear was the original failure mode.

Specification we work to

Feature	How it is made
Material	42CrMo4 / 4140 quenched & tempered as standard; C45 / 1045 stress-proof where the original specified it; hardness matched to the original, not raised arbitrarily
Thread form	Metric coarse & fine, ISO trapezoidal (Tr), UN / UNF imperial, Acme and non-standard pitches — single-point cut, so no tap or die has to exist
Thread run-out	Undercut and radius reproduced from the original — the detail that decides whether the new bar lasts
Shank	Turned and ground to your bushing fit; concentricity held so the bar does not wear the platen bushings one-sided
Surface	Polished, or industrial hard chrome plated where the original was
Nuts	Steel or aluminium bronze, cut to the same gauge as the bar, seat form as original
Documentation	Material certificate (EN 10204 3.1) and dimensional report on request; heat treatment record available

Repair or replace — the honest version

Plenty of shops will weld a broken tie bar and re-machine it, and for very large bars that is a legitimate route: a specialist repair typically runs around a third of new-part cost. But be clear about what it is. The break is at the thread, so the weld goes exactly where fatigue loading is highest, and the result depends entirely on the welder and the post-weld heat treatment.

Situation	Usually the better route
Very large bar, Ø200 mm and up	Weld repair worth pricing — material and freight dominate the cost of new
Small to mid-size bar	New bar — the price gap is small and you remove the fatigue risk
Second failure on the same machine	New bars and find the cause — repeat breaks are alignment or nut wear, not bad steel
Thread damaged, bar intact	Often re-machinable to a repair thread with a new matched nut
Original obsolete, builder cannot supply	New bar from your sample — no drawing needed

We will say so when repair is the better economics for you. Telling a customer not to buy the expensive option is cheaper than selling them a part they did not need and losing them afterwards.

Send the broken bar — we do the rest

Machines we make these for

• Injection moulding machines — from small tie-bar presses up to large tonnage clamps; the most common enquiry by far.
• Die casting machines — hot and cold chamber, where thermal cycling adds to the fatigue load.
• Hydraulic and mechanical presses — tie rods and column bolts on frame presses.
• Older and imported machines — where the builder has moved on, been absorbed, or simply will not supply a part for a twenty-year-old press. When the manufacturer is gone →

Capacity, and what we confirm before you commit

Our in-network turning capacity is Ø300 mm as standard, and long bars and larger diameters are arranged through partner facilities with the right bed length and heat-treatment capability. Rather than publish a number we cannot honour on every job, we confirm the exact envelope — diameter, length, weight and heat treatment — against your dimensions before you commit to anything. Send the sizes and you will get a straight answer, including a straight no if the bar is outside what we can do properly.

Related replacement & custom work

Frequently asked

Can you make a tie bar without the original drawing?

Yes - that is the normal case. Send the broken bar (both halves if you have them) or the surviving bar from the same machine, and we measure everything that matters: shank diameter, overall length, thread size and pitch at each end, thread length, the shoulder and undercut geometry, and the nut. Machine builders rarely release tie bar drawings, so reverse engineering from the part is the practical route. Photos plus measurements work when shipping a 3-metre bar is impractical.

Should I repair the broken tie bar or replace it?

It depends on where it broke. Tie bars almost always fail at the thread or at the thread run-out, and a weld repair in that zone puts a heat-affected weld directly where the fatigue load is highest. Specialist repair shops charge roughly a third of new-part cost and it can be the right call on a very large bar. On small and mid-size bars the cost gap narrows and a new bar with correct heat treatment removes the risk entirely. We will tell you honestly when repair is the better economics.

What material are replacement tie bars machined from?

Alloy steel 42CrMo4 (4140) quenched and tempered is the standard, and C45 (1045) stress-proof is used where the original specified it. Hard chrome plating is available where the original was plated or where the bar runs through bushings. We match the original material class rather than upgrading blindly - a bar harder than the platen bushings simply moves the wear somewhere more expensive. Aluminium alloys such as 6061 or 7075 are never used for tie bars; stainless 304 or 316 appears only on special corrosive-service presses.

Do you supply the tie bar nuts as well?

Yes, and we recommend replacing them together. The nut and the bar wear as a pair, and fitting a new bar into an old nut with a worn or bell-mouthed thread reproduces the same load concentration that broke the first bar. We machine matching nuts in steel or aluminium bronze, and can cut a spherical or tapered seat if the original used one.

Which thread forms and sizes can you produce?

Metric coarse and fine, ISO trapezoidal (Tr), UN and UNF imperial, plus Acme and non-standard pitches - single-point cut on the lathe, so an odd pitch that no tap or die exists for is not an obstacle. Our in-network turning capacity covers 300 mm diameter as standard; larger diameters and long bars are quoted case by case, so send the dimensions and we will confirm before you commit.

Why do tie bars break in the first place?

Almost always at the threaded section, and almost always from something other than the bar itself: uneven platen loading, a mould that is off-centre or mismatched in height, worn or bell-mouthed nuts, tapered washers that damaged the thread flanks, or original metallurgical defects. If you replace the bar without finding the cause, the new one usually breaks in the same place. A flat, beach-marked fatigue face means load distribution, not material.