Reasons for heat treating before/after grinding main bevels

[David Mary]

The softer the steel, the more gummy and grabby it is on belts, hence the more likely to pull out of the groove when grinding. Hardened steel "skates" so you don't have that problem. I grind everything post HT because it works with my process of getting blanks waterjet or plasma cut, and heat treated before I have them in hand.

 

[Alex Topfer]

There's probably also a question on stock removal vs forging
I forge in bevels, so there isn't much to grind and I want to keep mass to limit decarb during heat treating. If i were doing stock removal I might grind more pre-HT, as it's easier.

As others have said it also depends on blade thickness and type of steel used

 

[navman]

AEBL post Ht is an absolute dream to grind.

 

[Vardavak]

Spoken from somebody who makes only a dozen or so knives per year - it depends on the thickness of the blade. Anything <.125" I'll for sure grind post HT, thicker than 1/8" it's sorta your choice even with AEB-L which is known for being "warpy". I ground dry belt for several years. As navman says you dip in water each pass and keep the blade moving across the belt - don't linger at one spot. Not too much of a problem keeping blade from turning color.

Lately I've started using a mister system to put a water mist on the blade while grinding - that works really good. Allows a bit faster bevel grinding without overheating. I'll still dip in water after several passes because a blade can still get that nasty blue color, especially the tip. With the footswitch I added to mister I really wish I'd had the mister setup years ago. If you've already got an air compressor a nice mister system can be setup around $50 including the footswitch. The footswitch allows the mist only as the blade is in contact with belt so no so much wasted water and not near so messy.

I don't think the type of steel matters when grinding post-HT - heat is created when grinding and if any portion of the blade turns brown (light brown around 400°F) while grinding the HT is affected. If you see a dark blue, HT is ruined as dark blue is over 500°F. The problem of overheating isn't much of a problem until the bevel starts getting down to the thin edge. A thin edge can overheat so easy. The trick is to grind light pressure, move quickly across a "sharp" belt, and dip in water every pass.

navman, good time, but a few drops of what? {g}

Stacy, you got your post in as I was hitting "post". Good idea on using a high temperature temper steel. If it's tempered at 1,000°F not much danger of overheating while grinding bevels.

Do you have a link for a good system with a foot pedal?

 

[David Mary]

AEBL post Ht is an absolute dream to grind.

I have this dream as well

 

[Stacy E. Apelt - Bladesmith]

Do you have a link for a good system with a foot pedal?

It can be one of two ways:
1) Use an electric foot pedal to open and close a solenoid valve in the air line.
2) Use an electric foot pedal to open and close a solenoid valve in the water line.
However, using one foot pedal to control both solenoid valves would be the best way. This is what dentists have on some of their equipment.

I have a bunch of 1/4" water/air rated solenoid valves that would be easy to add to the lines. One more project to build.

A cheap HF foot pedal will do the job. You have two choices ... a step-and-hold pedal that keeps the attached machine running as long as you press the pedal, or a step-on/step-off pedal that starts and stops the machine by foot. Both have their uses and are good to have both in the shop. For example: A drill press or angle grinder is best with a step and hold pedal. You want those machines to stop as soon as you lift your foot. A grinder is best with a step-on/step-off pedal. You will need the freedom to move a bit while grinding as well as solid footing.

 

[Ken H>]

Do you have a link for a good system with a foot pedal?

B08MF2F8GF is the foot pedal and B071DXGGP4 is the mister - just do a search on Amazon for those items. The mister is around $19 shipped and the foot pedal is about $17 shipped. You will need a bit of tubing and fittings, something like this B0BTJVBMQ8 for another $17 or so, depending on how far away your air compressor is. It doesn't take a large compressor at all since you're only using air when foot pedal is pressed. I sit a gallon of water on back of grinder which lasts a good while, more than 1 blade for sure.

 

[redsquid2]

I recently noticed a dark spot near the edge while grinding some AEB-L, but then I kept grinding and ground away the dark spot. Will the temper still be okay? If anybody knows thank you.

 

[navman]

Dark spot as in dark Blue/purple? If so, it is highly likely the temper in that area is ruined.

 

[redsquid2]

Dark spot as in dark Blue/purple? If so, it is highly likely the temper in that area is ruined.

Yeah I don't remember the exact color but probably dark purple. The spot was about 1/4" across.
I can do some testing and see how the edge holds up. Thank you for your reply.

 

[Fiddleback]

I grind every bevel and also taper tangs before HT. Never understood messing with grinding hardened steel more than is necessary. Warpage is something I no longer worry about since I discovered straightening hammers.

 

[Scaniaman]

If you grind bevels and tangs before HT, you quench in oil yes?

 

[Stacy E. Apelt - Bladesmith]

I do both.
On thin blades... usually .060" ... I profile, harden, and grind post HT. I use a water mist to keep the blade cool.

Thicker stock, and of course hamon blades, get completely shaped then hardened. I still use the mist post HT for clean-up and final details.

 

[Fiddleback]

If you grind bevels and tangs before HT, you quench in oil yes?

That is completely dependent on the steel. Even the term 'oil' is too vague. I use fast quench oil for fast quench steels like W2 and slow quench oil on steel like 01 or 1084 (most steels I use are slow quench). Stainlesses and A2 get plate quenched. The quenching medium has nothing to do with whether or not the bevels are pre ground.

 

[Scaniaman]

I was thinking the steels that can be quenched both with plates or in oil.
Like if the bevels are ground they get no contact with the plates and hence a less optimal cooling rate? I don't know, just a thought.

 

[navman]

Peters' air quenches the steels I use (plate/forced air), and I routinely taper tangs pre-HT.

 

[Linus Knives]

I've done all my main bevel grinding Pre HT. I don't usually have problems with warpage because of doing stainless and plate quenching. And I have a carbide straightening hammer!
Linus

 

[Stacy E. Apelt - Bladesmith]

I was thinking the steels that can be quenched both with plates or in oil. Like if the bevels are ground they get no contact with the plates and hence a less optimal cooling rate? I don't know, just a thought.

Heat conduction in steel is pretty high. If you clamp a blade with bevels in plates, it will suck away the heat from the contacting surfaces fast. As the surfaces contacting the plates lose heat, it draws the heat from the bevels and edge areas that are not in contact by conduction. This may be somewhat slower than if all was in contact, as in a profiled only blade, but it is more than fast enough for any air cooling blade steel. The prime advantage, besides speeding up cooling time, is that quench plates prevent or lessen warp. The edge in most air cooling steels is not susceptible to bacon edge, so not contacting the plates isn't a worry. Very minor warp on a distal tapered blade may happen. but it would be limited to 1/2 of the blade thickness. I find that warp is virtually a non-existent concern with plate quenches.

The above is somewhat simplified, as most blades placed in quench plates are in a foil packet, adding another layer of surface for the heat to pass through. It doesn't make any difference in the result as long as the blade is thicker than the folded edges of the packet..