Recommendation? Making D2 flat and radius platen

[FredyCro]

So I ordered a piece of 5mm thick, 5 cm wide and 50 cm long D2 steel.

Plan is to make a flat and 36" radius platen from it.

1. Flat

This is pretty straight forward, radius the edges, drill and tap two holes, plate quench, flatten on a grinder/disc if necessary.

2. Radius

The steel might be on the thinner side to grind the radius in. If I would grind, I would drill the mounting holes, make a jig to mark the radius on both sides, grind to the lines, I guess grinder in horizontal position and platen fixed to a square block to keep everything square and even. If a 36 radius is too big for the steel, I could go for a larger radius (48" maybe). I could platen quench it (effectively one plate would take all the heat) or oil quench it (I have only canola oil)?

Second option (and this is where I need your input) is to bend the steel to the desired radius. The plan would be to cut a radius in a piece of hardwood, cover it with ss foil, heat the steel and then hammer in the radius gently with a wooden hammer or try to clamp the steel to the wood. Will this work or is it a dumb idea? Could I do this in one step, example being, heat the steel to austenitizing temp, bend it and just leave it to cool down to harden? Following this step I would make a 10mm aluminium backing that would take some of the heat from the platen and make the mounting to grinder easier. What are your thoughts?

I understand that higher temp (higher hardness) would be beneficial for a platen in terms of wear resistance?

As always, thanks for your input.

 

[Forrest Taylor]

Funny, I was thinking of a radiused platen recently.
Interested to see the responses.

 

[weo]

I'll be interested to see how hot forming works for you, if you go that route. I ground my 36" radius platen to shape.

 

[FredyCro]

I'll be interested to see how hot forming works for you, if you go that route. I ground my 36" radius platen to shape.

I got the idea from A Steeles YT vid. He hot bent a piece of mild steel.

Another idea just crossed my mind, what if built a small wood press (negative and positive of the radius) and just clamped the steel in place. I guess 5mm plate shouldn't be so hard to hot bend. I would add a bit of foil to the wood in hope that it wouldn't start burning straight away. Maybe hot bend it first at lower heat and then austenitize?

 

[FredyCro]

Also if I got it right 36" radius platen is 36" diameter, so the radius is actually 18"?

 

[Stacy E. Apelt - Bladesmith]

Yes, it is confusing.
The term "radius platen" is used to indicate the platen is curved. The proper term should be radiused platen, meaning evenly curved. (Technically, it should be called an arc platen.) However, in the knife and guitar industry, the term has been shortened to radius. The inch rating is the wheel size it imitates. So, a 36" radius(ed) platen imitates a 36" grinding wheel, which has an 18" radius.

 

[FredyCro]

Yes, it is confusing.
The term "radius platen" is used to indicate the platen is curved. The proper term should be radiused platen, meaning evenly curved. (Technically, it should be called an arc platen.) However, in the knife and guitar industry, the term has been shortened to radius. The inch rating is the wheel size it imitates. So, a 36" radius(ed) platen imitates a 36" grinding wheel, which has an 18" radius.

Thanks for clearing this up, any ideas on hot bending plans? Maybe grinding a short (4 inch) 36" platen and mounting to an aluminium backing would be easier?

 

[Natlek]

Second option (and this is where I need your input) is to bend the steel to the desired radius. The plan would be to cut a radius in a piece of hardwood, cover it with ss foil, heat the steel and then hammer in the radius gently with a wooden hammer or try to clamp the steel to the wood. Will this work or is it a dumb idea? Could I do this in one step, example being, heat the steel to austenitizing temp, bend it and just leave it to cool down to harden? Following this step I would make a 10mm aluminium backing that would take some of the heat from the platen and make the mounting to grinder easier. What are your thoughts?

I understand that higher temp (higher hardness) would be beneficial for a platen in terms of wear resistance?

As always, thanks for your input.

Instead of wood use thick mild steel which you will grind in desired radius .....you will make mess if you use hammer to bend D2 .Heat plate and then use strong clamps to fix it on mild steel .First clamp one side then other .................That should work to get even radius .........

 

[Scaniaman]

I have No experience here. But I think I would just grind the
radius platen from thicker hardened tool steel. Seems a lot easier?

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[HSC ///]

On the radius platen, what is the point and why? I get that it creates a hollow if you want that and simulates a large diameter wheel.

but why does anyone want this?
And to speculate, I doubt there are many actually using their radius platens.

I had one, never used it, sold it.
I think I would rather try a dished platen for convex grinding

 

[FredyCro]

On the radius platen, what is the point and why? I get that it creates a hollow if you want that and simulates a large diameter wheel.

but why does anyone want this?
And to speculate, I doubt there are many actually using their radius platens.

I had one, never used it, sold it.
I think I would rather try a dished platen for convex grinding

I would like to try it for s-grind, urasuki and full height hollow grinds also come to mind, but I am not sure how feasible these will be without water cooling the platen.
But the true reason is, because I can and I will have some steel left over from making the flat platen.

 

[Stacy E. Apelt - Bladesmith]

Here the basic method to make a radiused platen. Say you want an 18" radius (36" wheel):
Make a 36" and a 30" tool arm bars that fit the tool arm socket on your grinder from steel bars.
Drill a 1/2" hole at the center of the 36" bar, and a corresponding hole 2" from the end of the 30" bar..
Make a 2X8X1/4" flat plate. from mild steel. Get a piece of 1/2"X2"X8" D-2 for the radiused platen.
Drill and tap the two plates 1/4-20 so they bolt together the way the the platen will mount on your grinder.
Make the 36" bar a work arm from one by welding the 1/4" plate to the end in a "T". The extra bar past the hole is the handle end for grinding.
Using 1/4-20 bolts from the back side, attach the D-2 plate to the work arm.
If you are an engineering type person, bolt/mount/weld a weight of some sort on the handle end to counterbalance the platen grinding end to make the arm easier to swing up and down
Put the 30" bar in the tool arm and using a 1/2" bolt and washers/spacers, mount the work arm so it aligns with your flat platen.
Put a very coarse ceramic belt on the grinder, and move the tool arm in until the D-2 piece is flat against the belt. If needed, shorten the tool arm as necessary so the assembly will allow the D-2 to be slid up to the belt.

Now you are ready to make the platen.
Back the arm out until the D-2 does not contact the belt when the handle end is swung up and down.
Start the grinder and run on max speed. SLOWLY move the arm in until the D-2 just kisses the belt when swung up and down. Swing it a half dozen times and when it stops hitting the belt, advance the arm a tiny bit and repeat. You will do this by about .01" at a time until the entire surface is ground into the radius. Switch to a progression of finer belts and regrind the surface until it is at 220 to 400 grit.

When done, take off the D2 platen and set aside the 36" work arm for future platens. The other arm is good as a regular tool arm for jigs, wheels, platens, or work rests.
Mount the D-2 radiused platen on your grinder's flat platen and see how you do on urasuki.
A water chilled platen back is advised when using a radiused platen.

Note - By changing the work arm to 48" and drilling holes at 18 and 24", you can use the arm to make platens simulating either a 36" or a 48" wheel.
.

 

[Scaniaman]

Claryx has a great looking water cooled one. I'd just pick that one up and call it a day. At 200 euros plus tax, I don't see a cheaper way around that one..

 

[Natlek]

Well Stacy , that would work for sure ................but to much complicated my friend ...
Draw a line of 36 or whatever radius you want on D2 plate , fix plate in jig and grind it in two minutes ...............

 

[FredyCro]

Here the basic method to make a radiused platen. Say you want an 18" radius (36" wheel):
Make a 36" and a 30" tool arm bars that fit the tool arm socket on your grinder from steel bars.
Drill a 1/2" hole at the center of the 36" bar, and a corresponding hole 2" from the end of the 30" bar..
Make a 2X8X1/4" flat plate. from mild steel. Get a piece of 1/2"X2"X8" D-2 for the radiused platen.
Drill and tap the two plates 1/4-20 so they bolt together the way the the platen will mount on your grinder.
Make the 36" bar a work arm from one by welding the 1/4" plate to the end in a "T". The extra bar past the hole is the handle end for grinding.
Using 1/4-20 bolts from the back side, attach the D-2 plate to the work arm.
If you are an engineering type person, bolt/mount/weld a weight of some sort on the handle end to counterbalance the platen grinding end to make the arm easier to swing up and down
Put the 30" bar in the tool arm and using a 1/2" bolt and washers/spacers, mount the work arm so it aligns with your flat platen.
Put a very coarse ceramic belt on the grinder, and move the tool arm in until the D-2 piece is flat against the belt. If needed, shorten the tool arm as necessary so the assembly will allow the D-2 to be slid up to the belt.

Now you are ready to make the platen.
Back the arm out until the D-2 does not contact the belt when the handle end is swung up and down.
Start the grinder and run on max speed. SLOWLY move the arm in until the D-2 just kisses the belt when swung up and down. Swing it a half dozen times and when it stops hitting the belt, advance the arm a tiny bit and repeat. You will do this by about .01" at a time until the entire surface is ground into the radius. Switch to a progression of finer belts and regrind the surface until it is at 220 to 400 grit.

When done, take off the D2 platen and set aside the 36" work arm for future platens. The other arm is good as a regular tool arm for jigs, wheels, platens, or work rests.
Mount the D-2 radiused platen on your grinder's flat platen and see how you do on urasuki.
A water chilled platen back is advised when using a radiused platen.

Note - By changing the work arm to 48" and drilling holes at 18 and 24", you can use the arm to make platens simulating either a 36" or a 48" wheel.
.

Thanks for the write up. That sounds like a neat and very precise way to do it.

Claryx has a great looking water cooled one. I'd just pick that one up and call it a day. At 200 euros plus tax, I don't see a cheaper way around that one..

Cheaper yes, better no. If I end up using it a lot, I would probably invest in a water cooled one. I just want to try this on the cheap and decide if there is a benefit for me there and if it is something I like or not.

Well Stacy , that would work for sure ................but to much complicated my friend ...
Draw a line of 36 or whatever radius you want on D2 plate , fix plate in jig and grind it in two minutes ...............

My steel is on the thin side for doing it like this, but this is is the simplest method i guess, and while not as precise as Staceys method, I think it will be enough for me to try it out and see what is what.
10-15cm long 5mm thick d2 backed with 10mm alu to take some of the heat.
If I am courageous I will try to bend D2 and grind alu as a backing.

 

[Natlek]

My steel is on the thin side for doing it like this, but this is is the simplest method i guess, and while not as precise as Staceys method, I think it will be enough for me to try it out and see what is what.
10-15cm long 5mm thick d2 backed with 10mm alu to take some of the heat.
If I am courageous I will try to bend D2 and grind alu as a backing.

You complicated simple thing..........from that thickness you can get around 5 inch long plate with 45 cm. radius ......and that is more then enough for two inch blade .But why you need this s-grind , urasuki is behind me ................That is big radius and wont help with food release at all.Only will make better cutter ........
Take me half minute to draw that radius ...................and maybe another half to grind if i want to do that .Go in shop and do that my friend , and from rest make some nice hunting knife .....D2 is good steel

 

[Keith Nix]

I sure wish I could do everything in two minutes. It takes me four to six. Makes me sad

 

[FredyCro]

If this is still of interest to someone, I finished the project yesterday while the oven was heating up for the knives. Flat platen was straight forward.
Radius platen is about 64 cm (32 cm), I drew the radius and roughly cut it out on the bandsaw out of piece of 2x4, cold bent the steel with pliers in the vice and kept checking the radius, I got it quite good in the middle but not perfect towards the edges which shouldn't matter much. Drilled and tapped the holes and canola oil quenched at 1070°C with about 30 min in the oven. Then while the steel was still hot I went straight to my wood jig and clamped as good as I could and dunked it in the bucket of water. The 65 HRC files isn't biting in either platen. I will take down the high spots (if there are any) in the horizontal set up on the grinder. The flat platen has nice radiuses for the plunges and is perfectly flat.

 

[Natlek]

I will take down the high spots (if there are any) in the horizontal set up on the grinder.

I wonder what will happen if you mount radius plate on grinder and you put belts upside down ? I mean with grits from platen side and run grinder ?

 

[FredyCro]

I wonder what will happen if you mount radius plate on grinder and you put belts upside down ? I mean with grits from platen side and run grinder ?

That was another idea, maybe with a heavy grit belt it would work. But really I don't want to put deep scratches in and I think that I don't have any twist in the platen, so that it should be a 5 min job on a worn 120 grit.