Cobalt or titanium spot weld bit: the steel sentence

Two packets can look like the same upgrade. One flute is gold. The other is bright, and the bullet says high-speed steel with 5% cobalt. A cobalt or titanium spot weld bit choice is that difference in words. Colour is a finish. Five percent is a sentence you can point at. If the percent is missing, it stays missing.

The Products Compared editorial team compared the twelve amazon.co.uk listings in this set on 15 October 2026, plus Sealey's own page for the AK4734, Castle Brooke's size notes, a Laser Tools article, and owner threads on The Mini Forum. There is no lab cut and no mill certificate. A qualifying purchase can earn a commission at no extra cost to you. The rows, including the prices below, sit on the spot weld drill comparison.

In short

A cobalt or titanium spot weld bit is two claims. Five percent cobalt, written in the listing, is the steel. A gold or titanium colour is a coating. Sealey, Bohaner, and Gasea print 5%. VBVOO says cobalt content and gives no percent. Gainsten, Heyung, JETHMA, and the Gosknor five-piece set do not say 5%. A three-times-longer bullet is a claim, not a test.

The sentence you need to see

High-speed steel is the family name on most of these packets. The sentence that changes the buy is HSS with 5% cobalt. Sealey writes that for the AK4734: 8 mm, 80 mm overall, for galvanised and high-stress steels. Castle Brooke, a UK trade page, marks 6 mm and 8 mm spot-weld bits as 5% cobalt, spur point, bright finish. Laser Tools describe an 8 mm bit as HSS cobalt 5% beside a separate crown cutter.

Bohaner copies the percent: 5% cobalt, a 6 mm bit at 66 mm overall and an 8 mm bit at 79 mm overall. Those lengths line up with the Castle Brooke pair. That parallel is on the page. It does not prove they are the same tool. Gasea also says HSS with 5% cobalt for a 6 mm and an 8 mm bit, and the title spells cobalt as Cobale. The spelling is a listing fault. The percent is still written. Cobalt, cobalt content, and 5% cobalt are three different levels of claim.

The sentence is the alloy the seller has put in writing. It is not a weld count, and it does not approve boron or press-hardened steel. Sealey's high-stress line stays on galvanised and high-stress panel wording. Mig Tig Arc's note on that style of 8 mm bit is mild steel, not boron. Size and the cobalt line together are on the spot weld drill buying guide.

What a gold colour is

A gold flute is a surface. The usual name is titanium, titanium nitride, or titanium-plated. Gainsten says high-speed carbon steel with a titanium nitride finish, in 6.5 mm, 8 mm, and 10 mm, listed at about £7.48 with 4.1 from eight reviews. The same bullets say the bits last three times longer than uncoated ordinary bits. That multiple is advertising. There is no timed test here, and it is not a result against a cobalt bit.

Heyung is five 8 mm bits at about £10.99: high-speed steel with a titanium-plated finish, and no cobalt. The star line is 3.4 from three reviews, and the only UK-headed text says the bits do not cut. Gosknor's five-piece set, about £12.99, claims HSS and a titanium coating on five 8 mm bits, with 3.9 from 26 reviews. One UK review says a bit was still sharp after 40 welds. Another says it will not drill 1 mm steel. Neither review is a hardness test of the plating.

On The Mini Forum, restorers say not to buy the cheap gold ones. That is owner opinion about colour sold as a grade, and it matches these bullets: a gold picture, carbon steel or a plate, and no 5%. JETHMA's five 8 mm bits are uncoated HSS, about £11.49, 4.2 from six reviews, and one UK reviewer used about one bit every 10 welds. Uncoated is a finish statement, not a cobalt percent.

Listings in this set, side by side

Three listings print 5%. Sealey's AK4734 is one 8 mm bit at about £7.99, 4.6 from 192 reviews. The maker page states HSS with 5% cobalt and makes no gold-coat claim. The maker's list was £11.94, which is not the amazon.co.uk shelf. UK reviews split between a long restoration on one bit and a chip, a blunt edge, or a snap after about three welds. Gasea's 6 mm and 8 mm pair is about £7.79, 4.4 from 57 reviews, lengths not stated. Two UK notes say about three uses on a classic Mini sill, and one bit blunt before a weld was drilled.

Bohaner is about £12.99, 4.5 from 60 reviews, 6 mm by 66 mm and 8 mm by 79 mm. One UK review estimated 80 to 90 spots still cutting. Another says the metal is soft and this is no HSS. No certificate picks a winner. VBVOO, about £7.59, says HSS with cobalt content and a titanium coating, in 6.5 mm, 8 mm, and 10 mm, 46 mm overall, 4.5 from two reviews and no review text. It gives no percent. The set-name field describes a different 8-piece hex set, so use the title.

The BGS 1632, about £16.92, calls its 8 by 80 mm drill cobalt HSS and does not print 5%. That word belongs to the solid drill, not a gold flute. Gainsten, Heyung, JETHMA, and Gosknor's five 8 mm bits do not say 5%. Topcloud, about £12.96, says only high quality. If you want the percent, the shortlist is Sealey, Bohaner, and Gasea. Which fits one 8 mm job is on the best spot weld drill bit page.

A coat and cobalt can both be written

A coating and an alloy are different layers, so a listing can claim both. VBVOO writes cobalt content, a titanium coating, and a self-centring tip. The flute can look gold and the shank can still be a cobalt HSS, and you still would not know the percent. Cobalt content might be a trace or a deliberate 5%. Filling in 5% from another brand puts that figure in your head, not on the packet.

A 5% cobalt bit can be bright. Sealey's AK4734 page and Castle Brooke's bits are described in steel words, not as a gold product. Bright does not prove the percent, and gold does not disprove it. Gasea's misspelling does not remove the 5% in the bullets. Heyung's titanium plate does not become cobalt because the pack holds five bits.

You cannot test the coat and the alloy with a magnet or a thumbnail, and this comparison did not. An edge that died on weld two can mean a thin coat, a soft core, heat, or a cutter that skated. The blunt spot weld bit notes keep those causes apart. A review that says this is no HSS belongs to Bohaner, the listing that made that HSS sentence.

What you still cannot claim

A 5% line is not a life guarantee. Averaging a restoration, a snap after about three welds in 1.5 mm mild steel, and an 80-to-90-spot note into one duty cycle would invent a number nobody published. Gasea at about £7.79 and Bohaner at about £12.99 both print 5%, and the written records still split.

Gainsten's three-times-longer line is about uncoated ordinary bits. One UK review reports a blunt edge after two welds, one of eight ratings. That does not prove the multiple false in a lab, and it does not make the coat into cobalt. US copy that pits a coating against a cobalt bit is a different advert. Leave it off this page.

An Amazon surface field that says Boron on the AK4734 clashes with the bullets. Sealey's boron wording sits on the carbide AK4740, listed at £47.94 on the maker's page, outside these twelve. A high-stress bullet on a 5% HSS bit stays inside the steels that bullet names. If the vehicle information says press-hardened or ultra-high-strength steel, hand that flange to a method written for it. For ordinary mild-steel spots, buy the listing whose material line you can quote, then match the diameter to the weld you can see.