Harbor Freight 1x30 Belt Sander

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Chum


Maybe I'm not perceiving this correctly, but I have yet to make the steel too hot to touch, even when it has been burned. I've only burned the edges.

I have been telling people this for years but they refuse to believe you can over heat an edge while touching the blade. It is one of those things which cause you to wonder how people can be so ignorant of science because this is so trivial to refute with a simple experiment.

Mike Stewart makes this argument all the time, he considers it so strong that it is a derp moment if you argue against it.

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Does dunking it in water before I grind helpful or not?

Yes, ice the water (with salt), get the entire blade down to zero. This won't help you not burn the blade, but it will allow you to grind the blade longer before you can't hold it.

To minimize the chance of burning make sure you keep your belts fresh, your passes fast, and your touch light. Dip in water before you even think you have to. As Cliff notes the extremely thin steel at the edge can heat up very rapidly without migrating back far enough for you to even feel it.

Use coolant, like water or simple green, to keep the blade from getting hot, not to cool it down after it gets hot.

Thanks guys. All these tips are helpful.

There is no question that I have burnt the edge of the blade and immeadiately grasped it between my fingers without it burning my fingers. If anything, I'm finding it difficult not to burn the steel. Probably because I am very impatient.


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member

Chum. Burning edges is probably the most common failure in people new to machine grinding because it's so easy to do without the right touch

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KnivesAndStuff (YoutTube)

Chum,

To be safer do one light pass and dunk the blade in water. Repeat. I do this on all HT blades if I do not run my cooling system. I takes longer, but, if you do a light pass and then water in conjunction with fresh belts it will make your chances of burning the blade much less.

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cKc
Chum. Burning edges is probably the most common failure in people new to machine grinding because it's so easy to do without the right touch

I'll develop said touch eventually

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mccullen
To be safer do one light pass and dunk the blade in water. Repeat. I do this on all HT blades if I do not run my cooling system. I takes longer, but, if you do a light pass and then water in conjunction with fresh belts it will make your chances of burning the blade much less.

Thanks Jeremy!





I decided to bust out about 20 different knives and just do a little grinding on each, in order. I was previously just working on 5 different knives, and I think having more knives to grind helps. I tend to get impatient and feel to the desire to grind something at all times. With 5 knives I was grinding them again too soon. With 20 I think they have enough time to air cool between grindings.

I also did a lot of holding on to the steel right after grinding to see if it would be too hot to the touch. I don't know if it was the thickness of the steel or not, but some steels "seemed" to get hotter than others if I did the grinding for the same amount of time and with similar pressure. My Delica G2 seemed to get much hotter than anything else I was working on.


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member

Chum just curious why are you grinding these knives? Re profile or sharpening?

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Mark a
Chum just curious why are you grinding these knives? Re profile or sharpening?

I eventually want to make my own knives, but I would also like to make the knives I own now better.

Reprofiling and sharpening.


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member

Chum, the next upgrade you should look at is the craftsman 2x42...I have it and have sharpened over 800 knives on it... Still going strong! I have a 2x72 but find myself using my 2x42 more, mostly because it is only 110v and offers quicker belt changes.

on a side note, I have heard that quenching your knife while sharpening in a bucket of cold ice water will actually cause of micro fracturing. I just use a spray bottle of water and give it a little squirt here and there. Don't know how much truth there is to this.

Here is an example from Roman Landes of a power sharpened edge, 220 grit Trizact :

[docs.google.com]

Note the 5 point HRC loss in hardness which doesn't even go all the way to the edge.

This process, while very common, is not as trivial as people make it to be and in general should be avoided unless you really don't care about the steel. If you do have to do it, don't water quench the blades, let them cool naturally and wet them after they have cooled.

[www.youtube.com]

OK, so I commented on this about the heat damage. But there's more to it than that. How are you able to say the edge doesn't feel sharp raking your finger from spine to edge like this? I sharpened this way for years. I really don't see how you go through all that and can't cut paper better than that. After seeing damage on several knives sharpened this way, I've abandoned it except as a shaping method for drastic lowering of edge angles.

The edge isn't apexed and he is jumping grits.

It is the same problem that people talk about on the Spyderco forum all the time : "I have ran through all four grits three times and the knife still won't cut paper - WTF?"

If it won't slice a piece of stiff paper then don't move from the coarse grit until it does because you have not even hit the actual edge yet.

This is what I get for searching youtube for knife stuff. Dfp (doublefacepalm) for I shoulda known better.

On a related topic, I had to resolve a problem with a beam/joist system today where the beam was made for a 2x10 floor but the floor was actually TJI engineered joists. In order to resolve it I had to change the mounting detail for the beam/joist, this involved drilling 20 holes in the 3/8" steel beam.

I picked up two drill bits :

-cobalt (which is just a high cobalt HSS, it isn't a cobalt bit)
-titanium (which is also not titanium, just titanium nitrided)

I said to the guys on site :

-use the cobalt one first (I was curious)
-use the slowest setting and least force which cuts the beam
-do NOT cool the bits, they are made to run hot

The cobalt one cuts the first hole no issues, cuts the second hole no issues. I turn away for a second to review some LVL installations and as I turn around the guy is sticking the HSS drill bit in a snow bank to cool it. When he tries to drill the next one nothing happens, the drill won't cut the steel at all.

I walk over, tell them to change the bits and to NOT cool the titanium one because if they do the titanium will react with the water and form titanium hydroxide which while you can't smell it is known to cause temporary erectile dysfunction and can last about a week, though it has no long term effects. The rest of the 18 holes are drilled without issue.

As I walk off I hear one of the guys say to the guy who drilled the holes "You better not have cooled that $%*& titanium bit!"



Edited 1 time(s). Last edit at 02/04/2014 06:48PM by CliffStamp.

I'm glad I'm not the only one that does stuff like that.

That's awesome.

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Always in search of a good choppa'

Lol that's just funny!!

I was trying to drill out some 3/8" holes on the liners of my gayle bradley and just can't... It tore my cobalt bits up, and snapped the edges off of a carbide bit I bought (which are expensive). I was trying to keep it cool by spraying oil on it, but it isn't working... What a pain! Maybe I should just go slower with the cobalt bits and not try to cool them (I was using windex for these).

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razoredgeknives
Lol that's just funny!!

I was trying to drill out some 3/8" holes on the liners of my gayle bradley and just can't... It tore my cobalt bits up, and snapped the edges off of a carbide bit I bought (which are expensive). I was trying to keep it cool by spraying oil on it, but it isn't working... What a pain! Maybe I should just go slower with the cobalt bits and not try to cool them (I was using windex for these).

You can get a stepped drill that is meant for thin material like that. It is hard to enlarge a hole in thin stock without one.

Anyone know how to slow one down? We had some cold snaps down to -20 below, and the electric motor was turning real slow on my HF grinder. I liked the degree of control it gave me, and far less worry about heat build up.

I once had my skill saw so cold it would not turn.

You could get a fan controller wire it into the plug and set your speed like that.

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chad234
Anyone know how to slow one down?

No, but good question.


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member

Fixed speed drives are in general not meant to be varied though you can force it by simply using a dimmer though the motor will not like it at all. If you want a variable speed grinder you need a variable drive.

If you are looking to control the rate of material removal then it is easily done through grit/belt manipulation, applied force and techniques such as layered grinding.

variable frequency drive but not worth it on a 40$ sander unless you have such equipment at hand and I think you still lose torque

swap motor for dc

You can rip the thing apart and set it up with pulleys but, not really worth it

Rip apart and chuck the driveshaft in a high torque drill?

Handheld belt sanders can be slower and I sometimes put them in my vise

if you want slow, just get a 4x36 wood sander.

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KnivesAndStuff (YoutTube)

the 4x36 grinders at home depot aren't bad for what they are, and you can get belts for them at jantz all the way down to 600 grit, and they have a disc grinder on the side also.

I started making knives as a kid with a 3x21" belt sander clamped upside down in a vise with the trigger locked down, so you can find just about anything that will work.

but it is pretty easy to build a 2x72 grinder if you have some basic tools. pick up wayne goddards $50 knife shop to help you get started. grinders are pretty simple machines. I have 2 that I built that I use everyday. one is a single speed and the other is a varabile with step pulleys, both are set up to run either wet or dry, and I doubt that I have more than $200 into each of them. just keep an eye out at the salvage yard for parts and materials. I am actually thinking about building another one that will run very slow just for sharpening and final sanding on handles with a very small platen, and a very large slack belt area.

how deep will using one of these sanders ruin the temper on my knife? will it completely change the level and quality of the heat treat? i only ask because after seeing the prices on these, i've decided i want one as it will save a lot of time.

"knives save lives" on youtube
all i want for christmas is more arm hair -DK-

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DK
will it completely change the level and quality of the heat treat?

If you run them dry (no coolant) and you hit the edge, yes they will. How much damage is going to depend on hot you let the edge get and you have no control over it aside from knowing if you damaged it severely when you see scaling.

it will ruin the temper throughout the whole blade? or will i be able to sharpen through it? "If you run them dry (no coolant) and you hit the edge, yes they will" when you say that, do you mean the combination of the two? or that i can run it dry as long as i don't hit the edge? will i be able to use coolant on a cheapo $80 belt sander from ebay? or will it ruin the sander?

"knives save lives" on youtube
all i want for christmas is more arm hair -DK-

I can kind of answer your questions.

Running it dry with damage the edge even with light passes, and no scaling. Even dipping it in water didn't help much for me. But the damage didn't last that long, and after 2-3 sharpening the edge stopped burring (edge retention seems to be lower though, could be the thinner edge).

Its less damaging to the steel if it isn't touching the edge, since there is more metal to absorb the heat (the edge is very small and has very small amounts of metal so its easy to damage). So you can be less worried about steel damage if you are working on the flats.

I don't know if its bad for cheap belt grinders to run them wet, but I run my wet now. I just let a hose trickle on it. Time will tell if that damages it, but it seems fine.