Sharpening coffee grinder burrs!
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  1. #1
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    Question Sharpening coffee grinder burrs!

    Hi guys, I have about 12 blades that need to be re-sharpened and the company that was re-sharpening my blades stopped the program. I am starting to look at the option of buying a mill and doing it myself since a new set is 750$ each(was 350$ to resharpen). I asked a machinist friend to come and see if it would be a viable option but I was wondering how would you guys go about re-sharpening them?

    Any tricks or tips would be really appreciated!

    img-2994.jpg
    img-2995.jpg
    img-2998.jpg

    Thanks alot
    Alex

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    A mill is the wrong machine. You need some kind of tool and cutter grinder. I imagine cutter grinder shops exist that would be willing to bid this, especially in multiples.


    Sent from my iPhone using Tapatalk

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    I'll bet the Italians have a specially made machine to do the job....

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    Hard to say without actually having a part in my hands, but I do a lot of grinding. I would think with a surface grinder (6-12 or larger), a compound sine chuck, a small rotary table, and a shopmade fixture to hold the part to the rotary table, you could sharpen these. I think the $350 price is low, and why they discontinued that service. If the price to resharpen approaches the new part price, the part becomes disposable.

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    Quote Originally Posted by rklopp View Post
    A mill is the wrong machine. You need some kind of tool and cutter grinder. I imagine cutter grinder shops exist that would be willing to bid this, especially in multiples.


    Sent from my iPhone using Tapatalk
    Totally makes sense to use a ginder, im heading out to get a couple quotes!

    Thanks for the quick reply!!
    Alex

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    Wink

    Quote Originally Posted by digger doug View Post
    I'll bet the Italians have a specially made machine to do the job....
    Those are actually Swiss made hahaha its from Ditting!

    Quote Originally Posted by Barry Weeks View Post
    Hard to say without actually having a part in my hands, but I do a lot of grinding. I would think with a surface grinder (6-12 or larger), a compound sine chuck, a small rotary table, and a shopmade fixture to hold the part to the rotary table, you could sharpen these. I think the $350 price is low, and why they discontinued that service. If the price to resharpen approaches the new part price, the part becomes disposable.
    Ill take a look if i can find some used tools around! And yeah they discontinued resharpening those exactly because it was not profitable anymore!

    Thanks alot for the reply guys!!
    Alex

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    Looks to me like you'd need a VMC with a flaring cup grinding wheel in the spindle, and a 4th axis set on a sine table to get the required angle. CNC would be far easier to apply the complex motion required to get the wheel in and out of the cut safely. I think I'd go nuts trying to do that on some sort of manual grinder.

    That being said, I don't want to grind in my VMC

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    I can't see just how dull the edges are in your photos, but if they have a small edge radius, I would consider an acid dip. This is how files are sharpened. Probably a shallow amount of acid so only the working side of the disks are in the acid. And you will need some kind of supports, possibly glass beads or marbles.

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    Send them out for sure. A good friend of mine was the maintenance/espresso machine guy for a real high end coffee shop with 6-7 locations. He consulted me about the best way to get them resharpened, and after holding them in my hands I knew I couldn’t do it without tooling up. I gave him some numbers of tool and cutter grinder shops, and he called around and found some shops willing to bid. A very well equipped “old school” shop can do it, as would a shop with a cnc tool grinder; your best bet for a good price is to not be in a hurry, and send all of them at once.

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    Quote Originally Posted by EPAIII View Post
    I can't see just how dull the edges are in your photos, but if they have a small edge radius, I would consider an acid dip. This is how files are sharpened. Probably a shallow amount of acid so only the working side of the disks are in the acid. And you will need some kind of supports, possibly glass beads or marbles.
    I think the outside part is grinded flat! heres a close up picture maybe you can see better! Cant seem to get my phone to focus well lol!
    img-3002.jpg
    Thanks for the idea!!
    Alex

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    Quote Originally Posted by upthebikes View Post
    Send them out for sure. A good friend of mine was the maintenance/espresso machine guy for a real high end coffee shop with 6-7 locations. He consulted me about the best way to get them resharpened, and after holding them in my hands I knew I couldn’t do it without tooling up. I gave him some numbers of tool and cutter grinder shops, and he called around and found some shops willing to bid. A very well equipped “old school” shop can do it, as would a shop with a cnc tool grinder; your best bet for a good price is to not be in a hurry, and send all of them at once.
    I will call some shops around here and get some bids!

    Thanks alot for the suggestion!
    Alex

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    Question Example

    Here's an example of how one of my supplier is doing his sharpening. He can only sharpen one size of blades tho and i have 2 sizes. Is that a surface grinder? img_1339.jpg

    Alex

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    I just checked out the Ditting website, and it's interesting how they specifically demand that no "aftermarket" grinding disks be used, under loss of warranty. I'm not sure that would be legal in the USA. Also, they've stopped offering regrinding of their disks, seems they want replacement only.

    Grinding Discs

    Compared to the website pictures (granted, they're small), it looks like the OP's discs have been ground a number of times. I wonder what the practical limit is.

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    Quote Originally Posted by AlexyL View Post
    I think the outside part is grinded flat! heres a close up picture maybe you can see better! Cant seem to get my phone to focus well lol!
    img-3002.jpg
    Thanks for the idea!!
    Alex
    i think that is from metal on metal wear.

    the cutting edges appear to be significantly rounded as well which means a lot of metal will need to be removed. this will probably reduce the capacity of that disk, which may or may not be a good thing. the heat generated by the grinding process has a significant impact on the coffee flavor...

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    The grinder is a #2 Cincinnati T&C grinder.

    Tom

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    Here is how mahlkoening does theirs, on a tool and cutter grinder.


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    Quote Originally Posted by Milland View Post
    I just checked out the Ditting website, and it's interesting how they specifically demand that no "aftermarket" grinding disks be used, under loss of warranty. I'm not sure that would be legal in the USA. Also, they've stopped offering regrinding of their disks, seems they want replacement only.

    Grinding Discs

    Compared to the website pictures (granted, they're small), it looks like the OP's discs have been ground a number of times. I wonder what the practical limit is.
    Ive had em for more than 10 years. I dont think they are still under warranty lol! And yeah thats the reason im looking to maybe re-grind my own disks! When i used to send them for regrind they would send shims with it (im guessing for the amount they removed).

    Thanks!

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    Quote Originally Posted by johansen View Post
    i think that is from metal on metal wear.

    the cutting edges appear to be significantly rounded as well which means a lot of metal will need to be removed. this will probably reduce the capacity of that disk, which may or may not be a good thing. the heat generated by the grinding process has a significant impact on the coffee flavor...
    Yeah they are pretty worn out! that is jus one of the sets tho! if i can save a couple maybe itll be worth the investment!

    Thanks!

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    Quote Originally Posted by upthebikes View Post
    Here is how mahlkoening does theirs, on a tool and cutter grinder.

    Awsome!! Thanks for the picture!!

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    I'd assume these are center feed, and that the bigger gashes are spaces for the whole bean to get in between a pair of plates. Are they precisely shimmed so that the blades don't contact, or do you have a specified clearance for a particular grind coarseness?

    I can see after extensive or repeated resharpening, that you'd loose some capacity if the larger beans cannot fit into the big gashes, so you might have to regrind that part a little deeper if much material is removed.

    However, I still think a flaring cup CBN wheel could be configured to work on a VMC, but that's not a DIY project either. Sounds like you're only paying about $10 per blade, ($350/12)? That is so cheap you'd have to automate it. T&C grinding with a soft pink toolroom wheel would have you pulling your hair out, IMO. Nice to grind with, but the stone wears quickly. Round and round and round, you'd go, trying to keep the wheel flat so it doesn't turn over the edge. Or am I wrong? A super-abrasive like CBN would probably not wear significantly. I don't see any need for a razor sharp corner in the bottom of the flutes, so maintaining an acute corner on the wheel wouldn't be a big priority, perhaps.


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