Why I hate mirror polishing...

[Matthew Gregory]

So because I'm a super genius, I figure I'll make a 4 inch blade out of 1095 that I've done before flatground, except this time I'm going to hollow grind it and polish it to mirror finish...
Brought the blade to 400 grit with the grinder (numerous wonderful little flat spots from trying to keep the tip hollow ground but swept upward), hand sand to 400. Back to 120, because now I can see all the little scratches I missed. Up to 400. Back to 120. Up to 400. Back to 120.

Up to 400. Back to 120.
Up to 400. Back to 120.
Up to 400. Back to 120.

...so either I suck (which is most likely the case), or most people avoid polishing like this for a REALLY good reason.

 

[hammerface]

LOL... I'll have to keep that in mind if I ever attempt mirror polishing. I'm guessing that's why many don't do it. Plus after finally getting it to a mirror finish - any little scratch would show up...

 

[fitzo]

Try this for the "next round"...coat your blade with magic marker. It'll stick down in the deep scratches. When you finish the "cleanup" grit, look carefully with magnifiers for any residual lines of color. Got that trick from Goddard's book. It works.

All I can offer is that you ain't the Lone Ranger. I'm headed into the shop to return to 220 grit after a 1500 grit hand finish.

You've got the right idea though. There's a big difference between a real mirror polish and mirror-polished scratches.

 

[miden]

MrPurple, have you registered at the jackass thread yet, it seems you qualify like so many other of us.

I do it the long way round, it is really painstaking but I am sure others do it like this too unless they are maybe real boffins. I have not made many knives but all so far have been 6" or longer. All have been hollow ground.

I only grind up to 220 grit, get it pretty close and then I hand rub with 220 grit on a piece of wood that I made to the same radius as the contact wheel.
Obviously you go opposite direction to the grind. (I mean 90 degrees)
My piece of wood is 1.5" wide. I still have difficulty grinding a 6" blade perfectly evenly so the hand rubbing at this early stage is to get the blade even and the wide block helps otherwise, if the wood it too narrow, the en-even contours just follow the narrow block and you do not get them out.
Also, if the blade is un-even then you will also battle to get it even as you go through the finer grits.
When I am happy with the 220 grit hand rubbing, I move to the next grit of belt on the grinder and if there is still en-eveness I go back to the block. It is not a fast job but then I am not making these things en mass for my bread and butter. I have time and until my skills have improved I will have to do this if I want a half decent blade.
I know your main question was about the scratches but believe me, this way helps for that too.
I am sure there are other easier ways and I would love to hear them too.
Hope this helps.

Mike

For Heavens sake do not try to buff the little scratches out, you will kill all definition on the blade.

 

[Matthew Gregory]

MrPurple, have you registered at the jackass thread yet, it seems you qualify like so many other of us.

Please refer to post #23 in the above-mentioned thread.

I could have been first, with MY qualifications!

The idea of a 'sanding stick' is fantastic! That would have helped a ton. I also like the idea of stopping at 220 and hand sanding with the same grit, then moving up in grit back on the grinder. Going to try that next time around...

If I may ask, what do you boys use for belts? So far I've been experimenting with all different kinds, but my skills are only just developing into something discernible, and I'm very hesitant to answer to 'knifemaker' when people use the term towards me!

 

[butcher_block]

i have belts up to 800 grit
not sure why i got them i have found out that its better most the time to go to 400 then start hand sanding sometimes i go to 600 or a cork belt but thats bout it
also trizact sp belts are nice
my .02 might not buy much tho as im just a freshmen here
butch

 

[miden]

MrPurple, Happy to see you were not offended by the jackass remark, seems you know how it was intended.:thumbup:
Up to 220 grit I use Norton ceramic, a really good belt that is used by a lot of guys, it is good, does the job and lasts well. You can get belts for half the price but they last less than half as long and...it is a tool and if a tool does not do the job it turns into torment.
For the finer grits I go with 3m trizack and they are good too. No doubt there are different opinions, lets see what happens and we can all learn from the experience of guys who have been at it for longer.
I generally only grind up to 600 grit and then hand rub to 800 and then if I want shiny, I just use polishing cream with a rag, I do not like buffers but that is just a personal thing and I definitely agree with the saying "to each his own". Everything I say is just my opinion and I am a proud part of the jackass community too.

Mike

 

[Bowiemaker]

I mirrow polish most of my blades and sometimes it can be a problem getting all the scratches out.I rough grind with a 60gr belt and heat treat at 150gr. after heat treat I go over everything again with 150gr then 320gr then400gr and then buff.But I must make sure all scratches from the preceding grits are gone (easyer said than done)You may be making too big a jump from 120 to 400.Try a 180 or 320 in between if you have it. Somthing else I'll do once in a while is take a worn out 400gr and put a little white compound on it and go over the hollow grind before buffing,sometimes it helps...............John

 

[David Schott]

I do mostly hand work after inital grinding post-ht. Ive found the higher the grit, the more time I spend fixing grinding skitters than finishing the knife. Plus, I look at it like a mini workout.....haha

I have had a great grinding night so far tonight...just finished grinding 2 neckers, a little utility,and a nice 9" damascus blade from 1/4" stock....ill be posting separatly about the norton blaze belts ive been using. The 60 grit is almost TOO sharp for 1/8" stock. I swear on one of the lil neckers I put the primary bevel on in one pass, haha!

 

[TexasNativeDRJH]

Try this for the "next round"...coat your blade with magic marker. It'll stick down in the deep scratches. When you finish the "cleanup" grit, look carefully with magnifiers for any residual lines of color. Got that trick from Goddard's book. It works.

All I can offer is that you ain't the Lone Ranger. I'm headed into the shop to return to 220 grit after a 1500 grit hand finish.

You've got the right idea though. There's a big difference between a real mirror polish and mirror-polished scratches.

That magic marker tip is a very good one to use. That same technique is used in automobile body shops for spraying catalyzed primer. A "guide coat" as they call it is spraying a misty contrasting pigment to the primer topcoat, (eg: black over grey) to determine when to quit wetsanding the orange peel texture on the surface before painting. It prevents breaking though to bare metal or the galvanized/aluminized coating. Sounds like Goddard knows his stuff.

 

[David Schott]

Grits can be deceiving, too....when you think youre done with a grit, sand some more...

Also, try alternating directions until 600grit. I do mine in diagonals, pposite directions. It makes the prevous grit's scratches in a different direction...much easier to see.

going to a true 400 is the hard part. after 400, 600-1200 go pretty fast.

Another thing is to try a light etch. At lower grits, a quick dip in FECL will make those deeper scratches stand out a bit more.

 

[John Andrews]

Yep, that Goddard fella does know his stuff! I do a lot of mirror polish blades. The most aggravating part of having a finished knife is those little scratches the mirror polished blades seem to attract just before you box up the knife to send. I have decided that the easiest quick fix for those are a touch of diamond compound and quick rub, and then ship before the scratch elf strikes again.

 

[Raymond Richard]

Finger prints look there best on a mirror finish. When I first started doing shows I'd always have something to keep me busy. Never could figure out why most fellows look at a knife with there fingers first.

 

[Matthew Gregory]

You may be making too big a jump from 120 to 400.Try a 180 or 320 in between if you have it.

Sorry if I mislead everyone... I went back to 120, then 220, then to 400 grit - just figured I'd skip a grit to save typing!

Thanks to everyone for the tips and techniques! I think I'll try the wood block shaped to the radius of the hollow grind, and definitely try the magic marker trick as well.

So far, I've been using 50 grit Norton Hoggers for shaping, then to 220 grit Norax, then a quick sweep with a Scotchbrite Medium belt (maroon), then on to 400 grit 3m cheepies. I've underwhelmed with the 400 grit cheepies, and I'm not sure if the Scotchbrites are helping or hurting. I just ordered some new belts from Pop's (REALLY nice guy, btw), so I'll report on them when I get 'em.
I really dig the Norton ceramics, but they're awfully pricey... and I think I'd like to do more business with Pop's, so I'll be trying some more (better) 3M belts.

 

[fitzo]

I would seriously stay away from any scotchbrite belts in a mirror polish sequence. That's just my opinion.

 

[miden]

MrPurple, just so you know, the wood blocks are not my invention, I saw that on the internet years ago on Bob Engnaths site.
Some guys use a remodeled hockey puck too. They all work. Choose your own poison. What they all have in common is the need for elbow grease and patience. Good music and no short term plans for the day are advisable.

Mike

 

[John Andrews]

I would seriously stay away from any scotchbrite belts in a mirror polish sequence. That's just my opinion.

I agree with this! I have suffered some deep scratches using Scotchbrite while working down to mirror polish.

 

[Michael J. Spangler]

all i do is take the blade as far as i can on the wheel or platen then i start hand sanding from there
i usedto go from 220 up but i realized on a satin or a mirror finish it doesn't matter if i use the wheel up to 120 or up to 600 it always turns out the same
other than the fact that i use much less elbow grease when i do all the work on the wheel. for an 800 grit hand rubbed satin it takes literally les than 10 minutes to do a small knife post KMG work

 

[miden]

"Small" being what Michael?

Can you get it perfectly even on the grinder? I am not there yet, hence the need for elbow grease.:grumpy:

Mike

 

[Michael J. Spangler]

yeah for a small blade (under 5") i can get it scary close. i can do larger blades but for the sake of the argument we'll stick with that. its easier to take it high as you can and spend more time working on your grinds, because someday someone going to order a machine satin blade, and if ya havent practiced machine satins can be quite tough!
good luck with it