A2 vs D2 need advice for a special project

Matt Shade

Matt Shade

Joined
Nov 24, 1999
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I have to make a new set of cutters for a machine at work. Its an edgebander (commercial cabinet shop) and there is a shear in it to cut the edgebanding material loose from the roll as the board passes by. Its air operated and simply acts like a big set of scissors.
Sounds more complicated than it is, the parts are basically flat bars with a very abrupt single bevel flat grind on them. Two holes in each peice to bolt them on, the pivot and spacing and everything is already taken care of these are just replaceable cutters. The trouble is the machine was made in italy and OEM parts are outrageously priced and rarely in stock:jerkit:

So I've got the parts out and I'm going to make a pattern and order some steel, I just can't decide whether A2 or D2 would be better. I have access to a digitally controlled furnace, or I may send them out, so heat treating is not an issue on this.
The material being cut is mostly laminate (formica and stuff like that) so I want something very wear resistant (D2). The cutter also chops very fast, and chipping was occasionally an issue with the OEM parts, so I'm wondering if A2 might not be better.
Any thoughts? I know its kind of off the wall, and most of you have probably never even seen an edgebander but you know your steel and cutting tools :)

Any recommendations for a hardness to shoot for on either steel?
Thanks alot
 
I would say go with D2. Mainly because of the higher wear resistance.
Scott
 
butcher_block said:
have you thought about using cpm3v

sorry i have not worked with A2 or D2 so i guess im not much help
Click to expand...

Trouble with other alloys is getting them precision ground. I don't have a surface grinder, and the pivot and offset for the cutters is all fixed on the machine, no adjustments whatsoever. So I need to them to be flat, and the correct thickness or they don't shear properly. Otherwise, I might think about 3V cause then I could keep the left over stock for a knife :D


Scott
I'm leaning in that direction too. Do you think D2 will resist chipping good enough? The edge will probably be ground to about 320 grit so the blades have some bite as they come together. Its like a pair of scissors, I don't know if a polished edge will work very well.

Thanks guys
 
Keep the hardness at 60 rc and you should be fine. make sure you double temper. My blades are 60/61 and I've not had a complaint about chipping.
Scott
 
I've used A2 and D2 in tool and die. D2 really isn't that brittle. To me, the main advantage of A2 is ease of machining. I'd go with D2 based upon your description. I use the secondary hardening hump on a tool, but not a blade, I'm not sure which would be best for your shear, I'm leaning toward the second hump, which is about 875. It is very prone to decarburation which leads to a soft cutting edge if not well protected from the atmosphere. It also measurably benefits from a sub zero quench.
 
Thanks alot guys
I think I will go with D2, and I'll probably send it out for heat treat so that it can by cryo treated as well :cool:
 
:D :D I am a journeyman tool and die maker. Part of my trade is metalurgy and [/COLOR]planning to use the right metals for the right conditions. so this question is right up my alley! not to mention the tool you explained sounds just like one that I just built for a local office furniture supplier!
Generall rule of thumb is to use A2 when trimming or piercing and D2 when drawing, wiping, or bending (drawing=metal pullling around a complex form)
I see work on and or fix dies that have been in production for 30 years hitting hundreds of automotive parts a day that are .250 thick still using the same d2 forms and a2 punches.
A2 has less wearabillity then D2 has but the brittleness of D2 makest the sharp trim edges not hold up. I can go into more detail and get more scientific if you need me to but im making it easy. If you upper trim is rubbing past the part by any length (we call this land) you will want to polish this surface because it could possibly gual up. if you need more advice contact me
Th
 
D2 is often used for the knives that grind contaminated plastics for recycling, not A2. There can be rocks in the mix. They can chip out, but not as fast as lesser steels wear out. The grinders I'm thinking of ultimately moved up to using something like CPM 10V called (I think) A11.

I tend to think a better material for your application than A2 or D2 would be M2.

Let me retract something I said earlier about cold treating the D2. I believe (though I'm not sure) that multiple tempers to the highest hardening hump negates the need. The 500 degree temper for knife blades needs the cold treatment to complete the austenite conversion, but I think it all converts after a few trips to 875.
 
A2..............Trust me......I build theses thuings. You can nitride the front if you wanted to but not neccisary
 
Well you guys have me going in circles on this lol :D

On the one hand, I'd rather have them need sharpened once in awhile due to wear than have them chip out. On the other hand, they never cut anything harder than 3 millimeter edge banding which is pretty much like pvc, or laminate which is hard and somewhat abrasive but is very brittle and should break long before the cutters do.

I looked up some stuff on crucible's website and it lists industrial knives, slitters, and shear blades as typical applications for both A2 and D2. CPM 3v is the clear winner for toughness and abrasion resistance but I can't easily get it in the size I need.

I did a spark test on one of the peices and it shows very high carbon. Then I degreased it and applied some rust blueing compound, and compared it to how it reacted on an O1 blade and a D2 blade on some old beater knives I have so that everything I tested was a hardened peice. The shear blade stained less than the O1 blade, but much more than the D2, so I'd guess its somewhere in between on chrome content.
That leaves me guessing that it might be M2, which seems to fit the application. I can't get M2 in the size I need either, but D2 is very close in wear resistance and slightly better in toughness at RC 60. So I'm thinking I will go along with the majority here and use the D2.

I'm probably overthinking this and either alloy would work fine, especially when you consider that the original cutters are poorly designed and I can improve their geometry pretty easily. And for the price of the OEM cutters, I can make multiple sets and still be cheaper :eek: Probably going to place the order tomorrow morning, so I'll check back here one more time though to see if anyone else has any input.

Thanks for the advice everybody
 
just to make it harder for you
all you ahve to do is call crucible and ask them to PG a bar for you there prudy good about that
 
Matt,
I bought a Brandt KDF-660 C last year and we have had to replace the guillotine on it as we'll. I got a local machine shop to make a new one out of D2. D2 is high wear, works great and is common. The factory ones even on the German machines are made out of swiss cheese;)
When you need new top and bttm trim knives call one of your saw and router suppliers. I deal with http://gladu.com/english/ http://gladu.com/english/ tools and they custom make me everything from carbide to diamond tooling for my CNC router. They will copy your knives for half the cost of OEM and they will be higher quality. Get them to template a brand new one not an old one so the tolerances are exact.

Cheers
Kelly
 
Thanks alot Kelly, great to hear from someone who has done this before :cool:
I'll go ahead and order the D2. Going to make the parts myself this time, because a design change is in order. I don't remember the brand of the machine off the top of my head, but its not that well laid out and the chopper never really worked right. The bottom cutter is stationary and the angle the upper blade comes down at prevents it from getting a full overlap. Tends to only cut 2/3 of the way through the banding which then has to stretch and break. On PVC you can get away with that, but on laminate it always leaves a chip on the corner of your panel. I figured this was just due to wear, but my boss says this has been a problem from day one, so buying OEM parts to use or copy probably won't help much :grumpy:

Thanks again everyone for the input,maybe one of these I can get back to talking about knives :D
 
Either A2 or D2 may be suitable, they are kissin' cousins of grades, hence the mixed recommendations. D2 leans toward better wear, A2 leans toward better toughness (more forgiving), but both are in similar ballparks. However, because you report you have previously seen chipping on current blades, I would suggest using the A2 for its greater margin of safety against chipping. In a working environment, the safety benefit of a tougher material might offer a compelling reason to choose it, at the expense of possible gradual wear, which might be easily accomodated by occasional resharpening.

The suggestion of CPM 3V does cover both properties pretty well. DId you say it was not available in the size you want? Is it an unusual size or something?

Do you have any A2 or D2 around your shop? You say you spark tested the piece. If you have a known piece you can put side by side & test at teh same time, you might be able to see if it is one or the other. Because you have already seen chipping in teh existing blade, and because you are not sure what it is made of, I suggest you be as conservative as you realistically can be, to guard against inadvertently getting something more brittle than what is already there, since you know you have seen brittleness problems with it.
 
Thanks for the advice. I already ordered a bar of D2 this morning though, so I guess I'll find out one way or another now :D

One thing that I think will help alot is making blades that overlap properly, and knowing that that is what was causing all the problems before. The air pressure to the cutter is variable, and I think they were running it much too high sometimes in an effort to get it to cut better. So if its not being hammered on so hard, I doubt chipping will be much of a problem.

The trouble with getting steel the correct size in other alloys is that the upper cutter mics out to .380 inches thick, and I need to be very close to that in order for the shear to work right without a lot of work. By ordering precision ground 3/8" oversized D2, the stock should be .385"-.390" thick, leaving just a little bit of room to clean up the face after heat treat. Thats close enough that if I need to tighten it up any I can stone the mount for the lower cutter, or tighten up the pivot between them. I know I could have custom ordered something in another alloy, but its alot easier to just go with something thats already available.
 
Shear blades require clearance which is dependent on the material being cut .You'll have to work that out- too little or too much and the material will not be cut cleanly.
 
the "gap is called break. 6%-10% of stock thickness is nominall. 6% gives a slightly better shear edge but requires more tonage. 10% does just the opposite but both will work just fine.
 
Fortunately the shearing in this operation is just to release the roll of edgebanding from the panel as it passes by. It is not a finish cut, there are trim saws that take care of that.
The edgebander is a linear machine with a bunch of individual components in a straight line, with a conveyor to carry the panel past each one.The panel goes in the front of the machine and a roller applies hot glue to the edge of it. Then another roller presses the laminating material to the edge and rolls it into place as it passes by. The shear cuts the excess laminating material close to the panel so that it can be drawn back and stuck to the next panel coming through while the first peice continues along to all the trimming operatings. This elminates wasting large lengths of laminating material between panels.
Its not an ideal set up, but seems to be how its done on all or most machines of this type. You can't really follow any sort of rule for setting the gap or break because the machine cuts a variety of material from half millimeter thick PVC edgebanding to 3 millimeter thick PVC edgebanding, as well as veneer and laminate, and there is no adjustment on the shear. I'm just hoping to duplicate most of the original dimensions while making blades that close all the way :)

I really appreciate all the respsonses to this thread. There's a lot to learn from here, and it always amazes me how you can ask an off the wall question like this here and not only get responses from knifemakers, but also get to talk to die makers, cabinet builders, and metalurgists :D
 
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