Old 2x72 Belts - How Worn is TOO Worn?

[Cushing H.]

A few days ago I was profiling a series of blades, and like a good "frugal" belt user I used several previously used 60 grit ceramic belts to do that work (they had been used for beveling). the first belt did a good job, but it seemed to me that the steel continued to get hotter and hotter at a quicker rate (I did dip in water to keep temps down). Eventually I saw small areas where the steel was adopting oxide colors and getting REALLY hot .... so I swapped out that belt for a second "previously used" belt. The difference in heat generation was immediately clear (the second used belt did not heat the metal clearly as much). However, the first belt, though heating the metal, definitely continued to cut the metal.

So the question is - how worn is "too" worn before you just throw a belt out??? (with the understanding that they get cycled down to less heat-sensitive uses - like never use a significantly worn belt for final thinning of a bevel.

(as an aside, I am slowing getting more courage to run the grinder at faster and faster speeds. In this case I was running at 100 (meaning 100Hz???) - and oh man - can those belts really chew through steel!!!!! I would most definitely not want my fingers to contact say a 30 grit belt running at high speed!!!!!!)

 

[Stromberg Knives]

Yeah, I profile with 36 grit 3M 984f belts at around 6000 SFPM with a 3 HP grinder. It sounds and feels like the grinder is about to take off like a Hornet from an aircraft carrier.

I use protective goggles behind my 3M Versaflo PAPR full face shield. I've had belts break at full speed (one of my belt batches had defective belt splices) and slammed into my face shield, they sure can leave some hefty 'tire tracks' where they hit.

Regarding the overuse of old belts, I think you know when it's time to chuck them, it's more a question of actually doing it.

 

[weo]

Every professional knife maker I've heard respond to similar questions about belts have said:
"Use 'em like they're free."

If you haven't heard this before, I'm sure this won't be the first time.

 

[AVigil]

I gave up the mantra " use old belt for profiling".

I hate burning away the outline line in profiling. I use a new belt for profiling.

It is faster, easier to see the line and cooler.

 

[SBuzek]

If your profiling blades it doesn't matter if you get a color change, heck I've had them turn blue and brown, they will get fixed in heat treat.
After heat treat then watch the heat generated.

 

[Cushing H.]

Every professional knife maker I've heard respond to similar questions about belts have said:
"Use 'em like they're free."

If you haven't heard this before, I'm sure this won't be the first time.

Oh yeah - I have definitely heard this (sorry - I did mean to mention the phrase in my original post).

But it is basically the observation like SBuzek makes (that heating up an outline pre HT does not real harm) that sparked my question. As a hobbyist, I do not recoup the costs of belts by sales ... so it is always a temptation to "stretch" the things. maybe the answer is (at least for profiling) that you chuck them when either you are tired of dipping the blade to cool it off .... or it just is not cutting fast enough and you are getting impatient?????

Adam - I do get what you mean - the fact that the second belt ran so much cooler is really what made me think about asking the question.....

 

[Rhinoknives1]

I solved a lot of your issue by getting my patterns Water Jet cut. IMO , nothing more mind numbing than profile cutting & belt profiling a stack of the same blades.. When I’m doing a one of profile. If I don’t feel the worn belt is removing steel well. I put another less worn belt on..

 

[Cushing H.]

I solved a lot of your issue by getting my patterns Water Jet cut. IMO , nothing more mind numbing than profile cutting & belt profiling a stack of the same blades.. When I’m doing a one of profile. If I don’t feel the worn belt is removing steel well. I put another less worn belt on..

Lol. Yeah, definitely. Unfortunately most ofwhat i am currently doing is one or two of a kind ... otherwise i would most gladly hand the profiling off to JT. (He IS doing the HT. . )

 

[Fallbrook Forge]

If you’re using ceramics, they’ll continue to cut for a LONG time. But the won’t cut well. Once you notice they’re not cutting well, it’s probably time to retire that belt.

I like a fresh belt for profiling so I can really see my scribe lines and I don’t have to push into the grinder so much. The belts just eat.

Fresh belts do everything better

 

[navman]

I use old belts to set bevels for tapering tangs or grinding bevels, as well as for profiling and roughing handle material. I switch to new belts for actually going the taper or bevel.

When the heat build-up becomes too fast for my liking I toss the belt.

 

[Cushing H.]

I use old belts to set bevels for tapering tangs or grinding bevels, as well as for profiling and roughing handle material. I switch to new belts for actually going the taper or bevel.

When the heat build-up becomes too fast for my liking I toss the belt.

yeah, that is kind of the conclusion i am coming to. Question: what do you mean by “set bevels for tapering tangs or grinding bevels”? Are you referring to hidden tang work?

 

[Bigfattyt]

I just got my first real grinder. A 2x72..... but no variable speed. 3000 rpm.

I re-ground an already heat treated knife to thin it out. I was amazed at how quickly the 36 grit ceramic moved things. The 120 grit ceramic still seemed to work without too much heating.

When I put a finer grit finish on the blade, I was surprised at how much more heat was generated with brand new, but higher grit belts.

I was dipping every single pass, even with the low grit ceramics to be sure not to overheat the edge.

 

[Horsewright]

I do it a little different. I do the vast majority of my profiling on a flat disc using 60 grit PSA ceramic discs. I only use belts for the inside curves and use a used 60 grit on a 3" wheel and used 36 on a 1" and a 3/4" wheels, again ceramics. I did 85 (AEB-L), Fri and Sun and used 5 discs. I use a disc until it doesn't cut well and then switch em. Used one belt, both used, for the inside curves. Got these done Fri afternoon:

And had about 30 odd more to finish on Sunday.

 

[navman]

yeah, that is kind of the conclusion i am coming to. Question: what do you mean by “set bevels for tapering tangs or grinding bevels”? Are you referring to hidden tang work?

I scribe lines on the back of the handle and on the edge of the blade and create 45 degree (steep) shallow grinds to index off of for progressive grinding bringing the angle down as I go. For instance, for a tapered tang, I scribe two lines ~.30 inches apart centered on the steel at the butt of the handle. I then grind a shallow bevel to those lines so I have a visual reference to keep the taper centered.

 

[Cushing H.]

I scribe lines on the back of the handle and on the edge of the blade and create 45 degree (steep) shallow grinds to index off of for progressive grinding bringing the angle down as I go. For instance, for a tapered tang, I scribe two lines ~.30 inches apart centered on the steel at the butt of the handle. I then grind a shallow bevel to those lines so I have a visual reference to keep the taper centered.

that is what I thought you likely meant. I do not do tapered tangs ... but I do scribe the center of the edge to use as a reference as I grind. I guess it is kind of instructive how much of a new belt comes off when I do that first 45 degree bevel......... thanks.

 

[Natlek]

Well , belts can be count as worm in two way .One way is with properly fractured grits and other way is with glaze-d grits ....When belt is glazed will create LOT of heat .Did you notice that worn but properly fractured belt /40 grit size for example / leave much more smooth finish then new one ? I addressed that to fracture of grits .....how they fracture down they are no more 40 grits ? So I profile my knives with worn belt on slow speed ,10 m/s ....works for me .From time to time / most time after grinding some mild steel/ i use diamond dresser with very light pressure , that works to .

 

[john april]

i use my belts in 3 stages. when new i use them for shaping handle material. as most of us know, its easy to get it too hot and it changes color or burns brown spots. i can shape the handle much faster with no worries. second stage is for bevels. third stage is for profiling. i usually have 2 or 3 belts in each grit hanging on a peg, in various stages of wear for different jobs. if i am doing my riccasso on the 2x72 @ 400 grit right before i start hand sanding, the last thing i want to use is a new belt. microscopically, the new belt has many high and low spots, and the high spots will leave deeper scratches than the rest of the belt, making more work for me. for that i would use a "medium used" belt.

 

[Kevin McGovern]

i use my belts in 3 stages. when new i use them for shaping handle material. as most of us know, its easy to get it too hot and it changes color or burns brown spots. i can shape the handle much faster with no worries. second stage is for bevels. third stage is for profiling. i usually have 2 or 3 belts in each grit hanging on a peg, in various stages of wear for different jobs. if i am doing my riccasso on the 2x72 @ 400 grit right before i start hand sanding, the last thing i want to use is a new belt. microscopically, the new belt has many high and low spots, and the high spots will leave deeper scratches than the rest of the belt, making more work for me. for that i would use a "medium used" belt.

so do you use ceramic belts for handle shaping so you can use a ceramic belt on bevels, or an AO belt? Or something else?

 

[DeadboxHero]

"Belt Mountain"

Pro tip. When the belt starts glazing and making more heat, use a sharp corner on a piece of scrap steel and jam into the running belt. Should break some sharp facets back on the abrasive grains and cut the bonding down. Gives you a little more life out of expensive ceramic belts before you toss them in the garbage.

Also use a cool mist set up.