Tuftriding ?

Edited By WALLACE on 14/05/2014 12:46:48

We have a lot of bits done at work by Wallwork in Bolton. We use the Tufftride AB1 process, which come out a lovely black colour - rather like the firehole door and other bits on my Edward Thomas... It is possible to have silver-soldered assemblies done, but the process is rather close to the melting point of Easyflo 2; however I've had no problems other than having to paint the silver solder black to match the rest of it!

It adds little or no size to the part. You need to have bits you want as running surfaces smooth before processing, otherwise smoothing it off later is a) difficult and b) wears away the very thin surface hardening.

Much of our stuff is just plain mild steel - 220M07 (En1A) or 070M20 (En3B).

A very useful aspect of the process is its excellent corrosion resistance - better than zinc plating.

It's not terrible expensive, but it's usually done by weight with a minimum order charge, so if you're doing watch bits they'll work out expensive.

(edittid foar spelin)

Edited By Nigel Bennett on 14/05/2014 13:10:20

Not sure it would be applicable in our applications particularly steam may be high speed IC engines.

It is normally used on crankshafts that are subject to higher loads than would normally be seen e.g. high performance engines. It used to be more applicable but with modern engine design less so. In some cases where the RPM of the engine is increased significantly a change of material to a chrome-moly steel or EN40B is normally the route taken as it is better for nitro carburizing (Tuftriding is a trade mark for the process). The crank is either forged or machined from a solid billet both processes are expensive and you'll pay in excess of £1200.00 for a 4 cylinder crankshaft.

It is RPM that is the killer as the loads on the crank, rods and pistons become more significant the fast they travel.

Wallace,

Virtually any grade of steel will work, about the untimate is EN19 or EN21 which has a very tough core and take the process very well.

EN 21 is used for truck half shafts and EN19 is commonly used for spindles.

It's the last process in manufacture, everything needs doing first including grinding tapers and bearing surfaces.

The toolpost and quick change holders on my lathes have been tuftrided, it stops the day to day dings and the big TOS which is in use commercially and has been for about 15 years still looks like new.

If I make special taper tool holders like ER32 gear I have these tuftrided, again for a more durable surface.

It's not as good as thru hardening or case hardening but if it's like a tool holder the full heat treatment will cause distortion and then the added cost and time of having to sent it away for internal or external grinding makes it an expensive bit of tooling

According to the blurb the coating is only microns thick but if you do cock up and need to skim a surface it really takes some getting under even with decent tips and you get some spectacular fireworks off it.

As Nigel says cost could be a factor as the heat treat places charge a minimum labour charge and then by weight.

Our guys charge £34 minimum but the foreman keeps a book for me [ and other small users ] and tallies each job up and every so often I pay for what I have had done, this way I only get one minimum charge.

They used to have a bucket inside against the counter half full of salt water and a few 1/2" tuftrided rods sticking in it. At the water level it was just a flaoting crud and rust mass because of the crap in the air. If you pulled a rod out the top was clean and black, the bottom was slimy and at the transition point was a big crud washer which just wiped off leaving the whole rod clean and black.

The black surface is a matt black surface but if you then have the part hot blacked you get a real nice deep black shiny durable finish.

The camshaft on the Norton Commando (750 twin m/cycle, 1970s) was tuftrided to reduce wear, and it worked very well. I also understand that as the process introduces a compresive layer in the surface, it improves fatigue resistance (for the same reason that shot-peening does but without roughening the surface). This is a further benefit for crankshafts.

Cheers, Tim