# Another DIY coffee grinder



## wito (May 10, 2016)

Ey folks, so after a really hard hangover







i got a really cool idea that i should make my own coffee grinder

So im dedicating this thread to my journey in building one

i made a really really rough sketch of my idea, so here it is









went with vertical flat burrs, but slowly i think this is the hardest way i could have chosen and it is kinda tough

kinda still not sure how the burr adjust will be, it it would be traditional and the burrs would be horizontal that would be kinda easy (maybe thats the reason all the manufacturers are going that way







)

if it will be over my current skill in doing stuff, maybe i go with conical burrs

dunno but at the moment i kinda like this, it needs a lot of tweaking and measuring and doing some things i have never done, but hey ending the last year i didnt know nothing about 3d printing and stuff and now i build my own printer and doing a second one, so a grinder should be fine?









anyway hope its ok to post these things here and would love some feedback from you guys if its possible or i just end up writing to my self for the next year or so


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## wito (May 10, 2016)

oh and here are some higher res pics


http://imgur.com/yJ1kf7u


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## dev (Jul 28, 2017)

Doesn't look half bad but you need a much bigger motor for light roasted beans.

There are too many conical start-up grinders and I personally think vertical large flat burrs is the way to go. There's a real gap in the enthusiast market for a sub 1000$ big, over 83mm, flat grinder.

Good luck.


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## les24preludes (Dec 30, 2017)

dev said:


> Doesn't look half bad but you need a much bigger motor for light roasted beans. There are too many conical start-up grinders and I personally think vertical large flat burrs is the way to go. There's a real gap in the enthusiast market for a sub 1000$ big, over 83mm, flat grinder.


Definitely agree with this - large motor and large flat burrs. The Monolith, with an excellent motor, pretty much does this already, and with 75mm burrs. You could go to 83mm with the burrs - plenty about in at least 5 different existing grinders. The Monolith has got most things right as far as I can see, and mounting the burrs at (not quite) 45 degrees seems a smart solution. It takes out the need for extra complexity with vertical burrs. It also has a neat detachable chute to minimise retention. Existing ways of tackling retention are brushing out and blowing out - both work and the combination works best. So those options are still on the table. The Monolith shows that you can reduce the size by not using a large aluminium housing which the motor doesn't require in itself. There's a lot of wasted space in designs like the Mazzers. The Monolith is a clever design in so many ways, and once you've seen the solutions it offers it's hard to think of better ways around it, though they must exist somewhere in the ether. A DIY version with a few mods could be built cheaper. It's just basic metalwork and engineering. Doesn't have to be metal either for some of the parts.


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## Nikko (Aug 20, 2014)

Why large motor? You do not need a lot of power to grind beans but the torque must be sufficient. You need to consider the speed at which the burrs will run and gearing. The way you have shown the gearing is from low to high. The other way will allow for a smaller motor.


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## ajohn (Sep 23, 2017)

Nikko said:


> Why large motor? You do not need a lot of power to grind beans but the torque must be sufficient. You need to consider the speed at which the burrs will run and gearing. The way you have shown the gearing is from low to high. The other way will allow for a smaller motor.


True but flat burrs need centrifugal force to make the beans hit the burrs. On 64mm burrs that appears to need the usual 1400rpm AC motor but I think that one make manages 1200rpm.via an asynchronous motor. Go to 80 odd mm and the same speed seems to be used except say Ceado that look to bring it down.







All ok but beans probably grind more quickly in the USA and anywhere else that uses 60Hz mains.

The grinding rate of the same size burrs varies. Some burrs are more aggressive than others. More power needed the higher the rate - Super Jolly and Mazzer Mini for instance, both 64mm. They all seem to vary in this area. Seems there is/was a standard - grinding rate spec'd at a grind that gave 25ml in 25 sec from a single, no mention of what bean.

Brushed and brushless motors can be very small at high power levels but only by running at high speeds - 10,000rpm *plus*. Angle grinders etc.

What power motor to use. They are usually sold with continuous output power rating and may have twice as much electrical power going in. Grinders aren't spec'd that way and some that use conical burrs look to use higher pole counts than the usual 2 or 4 to get the RPM down.







They still run faster in the USA.

Flat - conical. In principle conical can be run at any speed, flat needs it's centrifugal force. With a hopper on conical usually stores a lot more grinds under the burrs than flat. Weighing in, Niche for instance, most are flung out so retention can be very low and low speed should also mean less popcorning which can mess the grind up when this is done with flat. Comparing flat with a Sage grinder I have the impression conical has other advantages over flat for home use. Just an impression - at the moment anyway.

John

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## wito (May 10, 2016)

oh didnt expected to get some response, thank you guys

yeah i just put that motor there just for testing, cause i have a lot of them around me and its too soon to get some high quality highend motor

the sketched burrs are indeed 83mm, i used the measurements from mazzer for that, saw some 120mm SPP flat burrs, but couldnt find them cheaper, and 600+€ just for testing is ridiculous atm









hmm one of the knobs i used in the first pic was intended for RPM adjusting (the second as grind size) but if speed/velocity is my priority i maybe change that(kinda excited how the gears will work), but i will see that first as i build/print that machine first

and with the conical burrs, its maybe because they are childishly easy to build compared to the vertical burrs i intend use









the beta version will be in some very basich cheap wood and 3d printed parts and the plan is to go full metal (insert some metal song







)

hope i get to build it this month if the 3d modeling will go as fast as now, the only problem is still how to adjust the grind size, i have looked up some grinders on the web but im still not sure how they managed it

looking at the moment at the monolith grinder, looks very sexy, the 45° angle looks interesting, gonna study more on this one


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## dev (Jul 28, 2017)

You could look at Ek43 Turkish burrs as they are a bit cheaper than SPP.

The point of high rpm, high power and big burrs is that usually 20g of coffee spend a max of 2 inside the grinder so pop-corning or other issues become irrelevant.


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## Nikko (Aug 20, 2014)

ajohn said:


> True but flat burrs need centrifugal force to make the beans hit the burrs. On 64mm burrs that appears to need the usual 1400rpm AC motor but I think that one make manages 1200rpm.via an asynchronous motor. Go to 80 odd mm and the same speed seems to be used except say Ceado that look to bring it down.
> 
> 
> 
> ...


Not sure how much centrif force you need when the burrs are vertical. Seen some hand grinders with that configuration so probably not much. In my experience the mechanical power needed is less than 100W per g/sec


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## 4085 (Nov 23, 2012)

What flat grinders have vertical burrs please.....genuine question as I know of none. the Mythos and a couple of variants have the burrs at 45 degrees or so


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## ashcroc (Oct 28, 2016)

dfk41 said:


> What flat grinders have vertical burrs please.....genuine question as I know of none. the Mythos and a couple of variants have the burrs at 45 degrees or so


Isn't the EK43 & the vertical burr? Admittedly it also has an auger to help feed the beans.


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## 4085 (Nov 23, 2012)

ashcroc said:


> Isn't the EK43 & the vertical burr? Admittedly it also has an auger to help feed the beans.


Of course, you are right.....again though, I was not thinking of high end kit, and an auger or similar is needed (which is a good thing). never tried an EK yet, and do not want to as I have always disliked them and everyone knows I am a bigot....but since I do not like light coffee I am fine with that mantle...!


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## ashcroc (Oct 28, 2016)

dfk41 said:


> Of course, you are right.....again though, I was not thinking of high end kit, and an auger or similar is needed (which is a good thing). never tried an EK yet, and do not want to as I have always disliked them and everyone knows I am a bigot....but since I do not like light coffee I am fine with that mantle...!


There are the fuji grinders that are common in Japan & the kitchen aid artisan too. Can't think of anything lower that an EK that's good for spro though.


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## wito (May 10, 2016)

dfk41 said:


> What flat grinders have vertical burrs please.....genuine question as I know of none. the Mythos and a couple of variants have the burrs at 45 degrees or so


i know only of the mahlkonig ek43, but i saw some chinese clones of it on youtube as well



Nikko said:


> Not sure how much centrif force you need when the burrs are vertical. Seen some hand grinders with that configuration so probably not much. In my experience the mechanical power needed is less than 100W per g/sec


do you know the names of the hand grindres please? maybe that would help me in the design


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## wito (May 10, 2016)

dev said:


> You could look at Ek43 Turkish burrs as they are a bit cheaper than SPP.
> 
> The point of high rpm, high power and big burrs is that usually 20g of coffee spend a max of 2 inside the grinder so pop-corning or other issues become irrelevant.


hmm yeah getting SPP just for testing would be kinda fun and my wife would probably kill me instantly









but is it actually relevant to get bigger burrs than 83mm-ish for a home use/semipro grinder?

i know that with a 120mm the coffee would be grinded instantly but is it such a difference with a 9-20g-ish dose?


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## dev (Jul 28, 2017)

Santos 01BAR and the new Mazzer ZM have vertical burrs. Agree that these, like the EK43, are mostly grocery grinders but their uniform grinding pattern is quite a hit with high end espresso enthusiasts.

The whole point of a niche home grinder is single dosing which is tricky because there's no pressure pushing the beans inside the burrs. Pop-corning is the most common phenomenon which leads to the "dreaded" excessive fines. One way to fix this is using hybrid burrs, a la Versalab, with a conical set that crushes the bean into smaller particles while a flat set does the grinding, all at pretty low rpm.


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## ajohn (Sep 23, 2017)

Nikko said:


> Not sure how much centrif force you need when the burrs are vertical. Seen some hand grinders with that configuration so probably not much. In my experience the mechanical power needed is less than 100W per g/sec


if some one builds one from scratch that's the tough part to put a number on. All grinders seem to use an intermittent rating - 2 levels as well. Real commercial use and I suppose you might say not really then some consumer stuff with no rating given in most cases. RPM - most commercial end and close state that. There is also a video on youtube by one of the manufacturers that states a min rpm for flat - from memory a bit lower than what is usually used.








I have this large Parvalux motor kicking about that spent some time at an RAF base spinning a radar aerial about. 4000 rpm with a gearbox on the end. It's a brushed motor and those are probably the best type to get something with a grinder friendly shaped. Treadmills and other exercise machines usually use brushed - power usually overstated. No idea what rpm they give though. I have a Robur - they say 900w. There is no way the 750w motor on my lathe would fit in it. Probably weighs more than the entire grinder as well.

Interesting comments about popcorning when weighing in and ease of design. Personally I think Niche man very probably chose the sensible option. Problem from my point of view is needing to use 2 3/4 burrs as they are available and if conical is better in other respects - why I have a Robur at the moment - to see what it does weighing in.

John

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## les24preludes (Dec 30, 2017)

I think you can comfortably stop at 83mm burrs, since as you say they get very expensive above that. Plain 83mm burrs could probably be obtained for £25. You could go titanium later if you wanted. And as Dev says, you need to think about alignment as you get bigger. John sounds really helpful about motors - I'm presuming he's an engineer.

Vertical burrs: Santos 01 and 04, Fuji Royal, Fama (FCS106/230), Kitchenaid, EK43, older Minerva grinders

https://coffeeforums.co.uk/showthread.php?43495-Vertical-burr-grinders-e-g-EK43-Santos-01-Santos-04


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## MWJB (Feb 28, 2012)

dev said:


> Santos 01BAR and the new Mazzer ZM have vertical burrs. Agree that these, like the EK43, are mostly grocery grinders but their uniform grinding pattern is quite a hit with high end espresso enthusiasts.
> 
> The whole point of a niche home grinder is single dosing which is tricky because there's no pressure pushing the beans inside the burrs. Pop-corning is the most common phenomenon which leads to the "dreaded" excessive fines. One way to fix this is using hybrid burrs, a la Versalab, with a conical set that crushes the bean into smaller particles while a flat set does the grinding, all at pretty low rpm.


Excessive fines, is that even a thing?

Fines will be generated by the smallest gap, I don't know if there's any evidence that the Versalab produces an unusually low proportion of fines, likely needs less torque to spin the burrs though.

It's also worth being aware that the vertical flats mentioned all have an auger to feed the burrs.


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## Nikko (Aug 20, 2014)

dfk41 said:


> What flat grinders have vertical burrs please.....genuine question as I know of none. the Mythos and a couple of variants have the burrs at 45 degrees or so


No idea. it was quite old and the crank was driving the burr directly so rotating at hand speeds.


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## Nikko (Aug 20, 2014)

ajohn said:


> if some one builds one from scratch that's the tough part to put a number on. All grinders seem to use an intermittent rating - 2 levels as well. Real commercial use and I suppose you might say not really then some consumer stuff with no rating given in most cases. RPM - most commercial end and close state that.
> 
> -


The Wattage numbers on the grinders aimed at enthusiasts are often for intermittent operation so that the number can be bigger, as some push the myth that bigger is better. On "proper" motors the watts refer to the mechanical output but on the grinder motors I've come across it appears to be the max electrical input.


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## ajohn (Sep 23, 2017)

Excessive fines does seem to be an aspect to "worry" about and popcorning on flats does seem to cause that especially weighing in. There has bean posts on it. One mentioned dividing a larger dose into the grinder and comparing shot tastes. The other aspect is people who use a tube hopper or otherwise and add a weight.

When I read dividing a dose my immediate reaction was hang on that could go wrong so when I converted the mini for weighing in I added a weight to keep the beans down for as long as possible. I haven't really tried using it without the weight as grinds can finish up several feet away from the grinder and I have no lid. Grinds also coat the inside of the lens hood. These are all pretty coarse grinds, way coarser than the real ones that come out. A few times the weight hasn't work as well as it should and when that happens there is a definite change in taste and a lot more than I would expect from any change in the shot size that comes out - if that changes significantly at all.

Once the weight can't press down on the beans due to the ledge the grind rate drops way down as the beans are popcorning more so I am still probably getting a proportion of grinds that aren't as they should be.

John

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## MWJB (Feb 28, 2012)

ajohn said:


> Excessive fines does seem to be an aspect to "worry" about and popcorning on flats does seem to cause that especially weighing in. There has bean posts on it. One mentioned dividing a larger dose into the grinder and comparing shot tastes. The other aspect is people who use a tube hopper or otherwise and add a weight.
> 
> When I read dividing a dose my immediate reaction was hang on that could go wrong so when I converted the mini for weighing in I added a weight to keep the beans down for as long as possible. I haven't really tried using it without the weight as grinds can finish up several feet away from the grinder and I have no lid. Grinds also coat the inside of the lens hood. These are all pretty coarse grinds, way coarser than the real ones that come out. A few times the weight hasn't work as well as it should and when that happens there is a definite change in taste and a lot more than I would expect from any change in the shot size that comes out - if that changes significantly at all.
> 
> ...


How does popcorning cause more fines? How have you measured this?

Popcorning is generally thought to cause the last beans in the dose to be ground coarser, thus pulling up the average for the dose, coarser. Feeding the beans makes the whole dose coarser, unless you set the burr gap finer to compensate. It is not yet known what the physical difference is between the profile of a whole single dose ground at a coarser setting, compared to a finer set, bean by bean dose.

The grinds should be able to make a nice cup, if they do that, they are 'as they should be'.


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## wito (May 10, 2016)

at the moment popcorning is not my biggest fear

im more afraid of getting way too much electrostatic and not be able to minimize/maximize(dunno which term is correct







) coffee retention and have huge coffee clumps

i have kinda an ide how to avoid popcorning and also figured out a way how to adjust grind settings, maybe i get to it tomorrow but im shooting a wedding this weekend so maybe ill get to it next week or maybe the next one if my new espresso machine comes in









but love you guys i have never expected to get such a response and so much information on one place







)


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## ajohn (Sep 23, 2017)

MWJB said:


> How does popcorning cause more fines? How have you measured this?
> 
> Popcorning is generally thought to cause the last beans in the dose to be ground coarser, thus pulling up the average for the dose, coarser. Feeding the beans makes the whole dose coarser, unless you set the burr gap finer to compensate. It is not yet known what the physical difference is between the profile of a whole single dose ground at a coarser setting, compared to a finer set, bean by bean dose.
> 
> The grinds should be able to make a nice cup, if they do that, they are 'as they should be'.


As some one mentioned recently if some one has been weighing beans in and switches to a hopper the grind will need setting coarser as the grinds have to push the stuff in the grind chamber out. A lot less pushing is needed when weighing beans in so the setting needs to be finer.

Fines. No I haven't measured them and wont be. Fines might be the wrong word. Doesn't matter to me. All that matters is taste and as mentioned that changes when the weight doesn't function correctly so I have joined the popcorning matters brigade.

John

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## ashcroc (Oct 28, 2016)

ajohn said:


> As some one mentioned recently if some one has been weighing beans in and switches to a hopper the grind will need setting coarser as the grinds have to push the stuff in the grind chamber out. A lot less pushing is needed when weighing beans in so the setting needs to be finer.
> 
> Fines. No I haven't measured them and wont be. Fines might be the wrong word. Doesn't matter to me. All that matters is taste and as mentioned that changes when the weight doesn't function correctly so I have joined the popcorning matters brigade.
> 
> ...


So you're using fines to describe a courser grind? I'm lost by your contradictions.


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## ajohn (Sep 23, 2017)

ashcroc said:


> So you're using fines to describe a courser grind? I'm lost by your contradictions.


Gee what a wonderful contribution to the thread. 2nd hand sniping too.

John

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## les24preludes (Dec 30, 2017)

wito said:


> at the moment popcorning is not my biggest fear
> 
> im more afraid of getting way too much electrostatic and not be able to minimize/maximize(dunno which term is correct
> 
> ...


I've had a Mini, Super Jolly and now Major. The clumping went down with the burr size. I get almost no clumping with the 83mm burrs - nothing that bothers me at all. I don't know if there are any other variables between these grinders but it's looking to me as if you should not have problems with 83mm burrs. I don't seem to have any issue with electrostatic either. I haven't looked into why. I have a DIY aluminium funnel on the Major which is earthed to the body and I give it a sharp tap at the end of every grind with the long handled brush I use to sweep out grinds from the burr chamber and chute. I grind into a container and the grinds all come out. I also blow grinds out with a lens hood. There are easy ways of dealing with retention between blowing and brushing. You just need a short chute which is completely accessible with a square tipped brush the width of the chute. I bought mine in Leyland SDM. It's 32cm long and 18mm wide and has quite stiff bristles. Perfect. It looks a bit like this and seems to be called a Fitch Brush

https://www.homebase.co.uk/monarch-lining-fitch-brush-18mm_p395230


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## ashcroc (Oct 28, 2016)

ajohn said:


> Gee what a wonderful contribution to the thread. 2nd hand sniping too.
> 
> John
> 
> -


You what?


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## Batian (Oct 23, 2017)

I bought these to do the same job, and many others.

I whittled the handle down to suit.

https://www.wilko.com/en-uk/wilko-lets-create-artists-brushes-assorted-styles-12pk/p/0339086

Also available:

https://www.wilko.com/en-uk/wilko-lets-create-artists-brushes-assorted-styles-25pk/p/0339087


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## MWJB (Feb 28, 2012)

ajohn said:


> As some one mentioned recently if some one has been weighing beans in and switches to a hopper the grind will need setting coarser as the grinds have to push the stuff in the grind chamber out. A lot less pushing is needed when weighing beans in so the setting needs to be finer.
> 
> Fines. No I haven't measured them and wont be. Fines might be the wrong word. Doesn't matter to me. All that matters is taste and as mentioned that changes when the weight doesn't function correctly so I have joined the popcorning matters brigade.
> 
> ...


Popcorning makes a difference, but it makes a consistent difference. In that respect, if your other prep is good, it doesn't matter unless aiming for the finest possible grind.


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## MWJB (Feb 28, 2012)

ajohn said:


> Gee what a wonderful contribution to the thread. 2nd hand sniping too.
> 
> John
> 
> -


I think we can do without ad hominem comments.


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## wito (May 10, 2016)

Finally had some time after a hectic weekend and a sick eye :/

removed that random funnel model i found on the internets and made my own, added something like anti-popcorning bridge, im gonna test it on my mazzer super jolly after i print it tomorrow, kinda excited how it will perform

got rid of the small knobs and added a huge one for grind calibration with a thrust bearing(hope thats the correct term) an engineer friend of mine will come for a visit to my place







and help me with the part how to set the grind and the settings will not change









maybe we gear that thing somehow and go back to the smaller knobs

also added some bearings for the gearing to make it more stable and smoother, hope so









































aaaand a link to imgur:


http://imgur.com/4jT3ml7


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## wito (May 10, 2016)

holy F...

popcorning is real

im on the 11th version of that funnel and jesus, the differences in grinding are huuuge

not really sure how to explain it but in the version 2 i had to grind extremely fine on my super jolly and later on its a little bit better

on 2 versions the beans stopped mid grind to "flow"(dunno what the englis term for that is) to the burrs and that was a tremendous difference to the final coffee

im gonna look more in to it this week

and hell 3d printing is the future of prototyping


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## ajohn (Sep 23, 2017)

@wito What 3d printer did you buy? Might interest others. A few anyway.

John

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## wito (May 10, 2016)

oh im using a heavily modified anet a8 and almost finished with a hypercube evolution


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## ajohn (Sep 23, 2017)

wito said:


> oh im using a heavily modified anet a8 and almost finished with a hypercube evolution










You've managed to get me interested in buying one - again. I'm surprised by the price drops since last time I looked. I was and still am inclined to look at the models formed into a sort of cube via a metal frame. It makes more mechanical sense to me. People who get to grips with sorting out all of them and learning to use them do some amazing work on them even on low cost machines.

John

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