Thoughts/opinions on Blade finish prior to heat treating

[reefera4m]

I'm interested to know how fine a finish whould be best on blades prior to heat treating, i.e. hardening/quenching and tempering. My approach to date has been to polish the blade to 220/320 grit. My rational is that 1) it is easier to work the softer steel and 2) removing any deeper scratches/grind marks reduces the possibily of cracks or fractures along them.

I haven't seen any negative consequences from this finish but wonder if there could be.

[Alan L]

Depending on the blade I'll take it to either 220 or 400. If I go to a finer polish than 220 I use antiscale compound during the HT to prevent decarb.

I use the same rationale as you.

[NJStricker]

I generally go to 320 or 400 grit for my blades, which are high carbon (1080) quenched in peanut oil. You definitely want to get the deeper scratches out before HT, much harder to get them out afterward.

[Ray Rogers]

I agree with all of the above. That said, I tend to do all my grinding after the HT. That way, I avoid possible issues of stress risers, most warpage, decarb, etc. With practice and the right belts you can avoid the issues with the deep scratches but, even so, I would imagine that some of my finished blades may not be as perfect as some of yours although they are probably better than you might think .......

[DaveRuhlig]

I usually go to 220 - mainly because I start with 220 after HT to clean up the scale. It would make much sence for me to go to 400+ prior to HT if I'm just going to scratch it up w/220 after.

I should point out this is for my high carbon blades (10XX) - If I were doing stainless in an oven without scale it would be a different story.

-Dave

[DaveL]

I found that grinding after heat treat is a great way to go but when i do otherwise I go to 400.

[NJStricker]

Originally Posted by DaveRuhlig

I usually go to 220 - mainly because I start with 220 after HT to clean up the scale. It would make much sence for me to go to 400+ prior to HT if I'm just going to scratch it up w/220 after.

I should point out this is for my high carbon blades (10XX) - If I were doing stainless in an oven without scale it would be a different story.

-Dave

The one advantage I've seen with finishing to a higher grit is that you don't have quench scale sitting in the deeper scratches. Even with a vinegar soak, they are sometimes tough to get out.

[dbalfa]

I usually go down to 400 for tool steel or stainless. I will use a HT powder on the tool steels to avoid the decarb. However, 220 is not all that hard to clean up post HT with the right, sharp belts....

[ranger1]

400 grit for me.

[Arccher Moon]

What would be the best way with 5160? Looking for a working blade finish. Maybe down to a 400 grit for a final.

[reefera4m]

Arccher Moon,

400 grit is what I plan to finish my next knife of 5160 steel. I finished my last one with 800/1000 and while it gave an almost mirror finish it was more work than it needed to be and will probably require more maintenance. On the way to 800 grit I liked the look of the 400 grit finish the best.

The only plus that I have seen with the finer grits is that is it cleans up easier. That sounds like a contradiction with regards to my expectation of greater maintenance but its not. The maintenance require is associated with scratches - 800/1000 grit finishes show small scratches and they tend to stand out. On the other hand, high polished finishes don't trap water and/or other contaminants as much as coarser surfaces making them easier to clean and dry. Rust that forms seems to be much lighter and easier to remove and prevent. When I was wet sanding at 400 grit, rust formed almost immediately. When I moved to finer grits rust formation was less evident.

I suppose that an argument coud be made that a highly polished blade would be better for cutting and chopping due to its lower friction, but IMHO that would be a stretch.

[Ray Rogers]

Actually, you would probably find that a high polished blade can be a real problem if you're cutting something wet like meat or tomatoes. The wet material can really adhere to those polished surfaces ....