300mm or 350mm disc cutter: pick the correct wheel

The two saws are already on the van, the engines look close enough, and someone reaches for the larger disc because the kerb looks deep. That is the moment a 300mm or 350mm disc cutter choice goes wrong. Stihl UK lists the TS 410 as a 300 mm saw, the 12 inch size, and the TS 420 as a 350 mm saw. The wheels are a different diameter, and the guards stay with the saw they were built for.

This page uses the Stihl UK pages for the TS 410 and TS 420, plus UK dealer specifications from Builders Equipment, CMT and Seddon. We did not run a lab test. Those pages give no UK street price for the machines. The blade price below is the amazon.co.uk figure from our 350 mm diamond blade comparison in October 2026. A qualifying purchase can earn us a commission at no extra cost to you.

In short

Choose the TS 410 when a 300 mm, 12 inch wheel is the disc you already run and the cut sits inside that saw's own reach. Choose the TS 420 when you need the 350 mm, 14 inch wheel, including the 125 mm maximum cutting depth UK dealers publish for that model, and a blade with a 20 mm bore. The guards do not swap, so one diamond blade cannot serve both saws.

Same family, different wheel

Stihl sells the TS 410 and the TS 420 in the same petrol cut-off range, so they get treated as one tool with two discs. The published split is the wheel. Stihl UK specifies the TS 410 at 300 mm (12 inch) and the TS 420 at 350 mm (14 inch). The inch name is the same choice, not a third diameter.

Builders Equipment puts the difference in one line: the pair differ by wheel size, and the TS 420 wheel is 350 mm by 20 mm. That 20 mm is the bore. CMT's TS 420 page agrees on the bore and adds a maximum cutting depth of 125 mm. Seddon lists the same 125 mm depth, plus 3.9 m/s² and 98 dB(A). Those vibration and noise figures are dealer data for that model, not an exposure time.

A guard is built around one rated diameter. Stihl UK states each diameter on its own page, and none of these pages shows a shared guard. The 20 mm bore and the 125 mm depth are dealer figures for the TS 420. In a hire shop, read the diameter on that model and write it on the blade case before the saw goes back in the van.

When 300 mm is enough

The Stihl TS 410 blade size is 300 mm. Keep that saw when the cuts you already finish use a 12 inch wheel and the spare blades in the box are 300 mm. Paving units, blocks and shallower masonry are the jobs where this diameter is enough, because the disc you own reaches the cut.

These sources do not publish a cutting depth for the TS 410. You cannot scale the TS 420's 125 mm down because the blade is 50 mm smaller. Depth depends on the guard and the flanges, not on a fraction of the diameter. If a drawing demands a stated depth, look that depth up on the TS 410's own data. Until then, 300 mm tells you the wheel and nothing about millimetres of cut.

Buying the TS 410 so you can fit a 350 mm blade later is the expensive error. These pages do not show the wheel and the guard as interchangeable. A 350 mm disc in the same cupboard is not a spare. Hire the 350 mm saw when the 12 inch wheel runs out of reach.

When you need 350 mm

Step up to the TS 420 when the cut needs the 350 mm wheel. Stihl UK specifies that diameter for this model. CMT and Seddon both publish a maximum cutting depth of 125 mm, so a drawing that asks for that depth is a reason to shortlist this saw and then confirm the figure. Kerbs are the usual trigger.

Measure the section you cut most weeks. If it sits inside the 125 mm published for the TS 420, the larger saw matches the drawing. If the section is deeper than 125 mm, that published maximum is not enough, and the method needs another look.

The Stihl TS 420 blade size to order is 350 mm with a 20 mm bore, the size Builders Equipment and CMT both attach to this machine. A disc marked only as 14 inch still has to match that diameter and that bore. Seddon's 3.9 m/s² and 98 dB(A) are machine data for the TS 420 alone. They show the models are documented separately, and they do not say how long you may run the saw.

The 125 mm figure belongs to the TS 420. It is not a rule for every 350 mm cut-off saw. A Husqvarna 14 inch saw is absent from these sources, so leave 20 mm, 125 mm, 3.9 m/s² and 98 dB(A) on the Stihl machine and read that maker's UK page. If you already own the TS 420, buy a 350 mm blade the guard is meant to cover.

What you buy for the larger saw

Once the machine is the 350 mm class, order a 350 mm diamond blade and leave 300 mm discs out of the basket. Check diameter, then bore, then the material named on the listing. Dealer pages put the TS 420 bore at 20 mm. This article does not treat an unnamed reducing ring as a standard part of the saw. If the listing omits the bore, do not guess it from the diameter.

Sort concrete, kerbs and masonry on the 350 mm diamond blade comparison, then confirm the centre before you pay. Read the saw fit guide before you assume every 350 mm disc shares a 20 mm hole. The buying guide covers what to check on the blade itself. Those pages are about the larger wheel. This hub has no 300 mm blade comparison, so the 350 mm table cannot be reused for the TS 410.

The dealer pages used here quote neither a blade price nor a machine price. In that comparison the top pick is the PRODIAMANT 350 mm, 20 mm bore, ASIN B0171VPD7A, at about £54.78. It names concrete, reinforced concrete, granite, kerbs, brick and masonry, wet or dry, and states EN 13236. The 4.3 stars are from 1,078 amazon.co.uk ratings shared with the 25.4 mm variant. Asphalt is not named. One UK review needed a washer that was not in the box, so check the flanges. If both saws stay on the fleet, mark the 350 mm crate with the 20 mm bore.

Keep each blade on its own saw

A 350 mm blade is 50 mm larger in diameter than a 300 mm blade. On the TS 410 that larger disc sits outside the wheel Stihl specifies, and the guard on the 300 mm saw is the wrong cover for it. Leave the guard on. A washer, a spacer or a longer bolt does not make an oversized disc into the rated wheel. The wheel and the guard are a pair.

A 300 mm blade on the TS 420 fails the other way. The smaller disc may pass into the larger guard and still be outside the flanges and the published 350 mm specification. If Stihl's page for that model says 350 mm, the replacement is a 350 mm blade. Fitting the smaller disc is not the rating.

Half of the 50 mm diameter step is 25 mm, and that 25 mm is not a cutting-depth gain. The only depth number here is 125 mm on the TS 420. Measure the material, then use the depth published for the saw in front of you.

Stop when the guard will not close, when the bore needs an undocumented adaptor, or when the blade label shows a diameter the saw page does not list. If the guard, the diameter and the model do not already match, a competent person should take the cut. Match 300 mm to the TS 410 and 350 mm to the TS 420 before the engine starts.