The Armour Archive

Thank you, Guys!

We got Will's ashes safely tucked away yesterday. I was pleased to see that the memorial badges went over well at the Service, even with the folks who knew him from other contexts.

It's time to try and move on now.

Mac

I have been buying abrasive supplies, and they have begun arriving on my front porch.

Here are four 9" grinding discs, of two different flavors,



...some 80grit 6" PSA discs,



...and a new diamond dresser.



The discs will mount on my horizontal spindle. There is a male 5/8"-11 thread to accept them.



With a disc in place, I thread a retaining screw into the female 5/16"-24 hole in the spindle....



.... and give it a little twist with a "stubby" wrench that hangs on the machine for the purpose.



The screw keeps the disc from unwinding and falling off the spindle as the machine slows down. That's usually not a problem, but if it does happen, it's a lot of trouble, so I'm pretty conscientious about making sure the screw is in place.

The first thing I need to do is get the grinding discs ready to use. There are two things that need attention. The obvious one is the shape of the "working edge" of the disc. We are going to need to dress that off nice and smooth, so it does not gouge the work. Unfortunately, there is a catch. These discs are never really spin true. By the time the manufacturers get the abrasive mounted on the ZDC hub, there is always some run-out. Here is what a new disc looks like in motion. That fuzzy black thing is the disc. The reason it's out of focus is because it is wobbling.



Now, you might say, "so long as the working edge of the disc is true, who cares what the back of the disc is doing!" Here's the problem with that. If we dress the face, but ignore the run-out, the disc will be end up out of balance because there will be a thick spot and a thin spot 180 apart. This will make the machine vibrate, and that will compromise the work. In addition, the working face will get out of true all the sooner if the disc is also out of balance. So, we have to start by getting the disc to run pretty true before dressing the face.

To do this, I mount up the tool rest so that I can use it to steady a welding chalk to mark the back of the spinning disc.



To make the correction, we must file away a bit of metal from the seating face of the hub, directly opposite the chalk mark. I have marked it wit a sharpy here for illustrative purposes only. I usually just lay the disc down in the same orientation, and remember that I must remove materiel from the opposite side.



Those circumferential marks tell us where the zinc hub is making contact with the steel face on the spindle. There will be one on the side with the chalk mark, and we leave that one alone. There will be one or two (sometimes more) on the opposite side from the chalk mark, and we must be sure to file them away.



By repeating the process a few times, the disc will come to run true enough that the chalk makes a mark most of the way around. It would be nice to continue until the mark want all the way, but diminishing returns makes it unnecessary as well as difficult.

After the run-out is minimized, the face is dressed with a diamond. Here is a pic of my new dresser compared with my old one. This work is pretty abusive to diamonds.



This edge is dressed and ready to use.



Mac

Hurrah!
You had told me you used standard grinding wheels and dressed them, but I must confess I was curious about the details of your process.
Your post and pictures are very timely.

I am always a bit reluctant to just take everything apart and get the process started. The cuisses looked nice in a more or less uniform blue/grey, and the flutes showed up well. Once the grinding starts the flutes will disappear in the grind lines and won't be visible again for days or weeks.



The first thing that has to happen is to grind away the hammer marks and "level" the surfaces, and the belt sander is well suited to that. I set it up with a fresh 80 grit aluminum/zirconium belt, and chose the flattest platen I thought would get into the curves. I plan to take three passes this way wherever that is possible.

My first pass on the cuisse backs is parallel to the upper hem.



Once I have ground away all the marks I can see, I am left with a couple places that are too deep the grind. These get plannished out, face down on a stake, and then ground.



The second pass is parallel to the bottom edge. I try to remove all of the previous scratches. Obviously, I can't get up close to the hem with this pass, but neither could the guys in the 15th C. The areas adjacent to hems always show more mistakes from the early grinding than other areas. That's just the nature of the thing.



The third pass splits the difference between the previous two. Again, I try to remove any scratch I can reach.



I'll give these another close looking at before I move on, but for now, they look OK.



These are all the places I can reach with the belt sander....



...so, it's time to switch to the grinding disc. The disc can get into the flutes in a way that a belt can not. Unfortunately, the contact patch is much smaller, so this process requires more skill and constant motion.



Here's what I had when I quit for the night. Tomorrow, I will do the big flutes on the cuisses, and then switch to a smaller disc to get the crotches of the flutes and the difficult stuff on the knee wings.



Mac

Is the mounted grinding disc of the same stuff as regular angle grinder grinding discs? If so, you must need a delicate touch not to thin the metal more than is necessary to remove the marks.

Wow, you need the firm hand of a neurosurgeon.. and its cool blood.

It's just a regular old angle grinder disc.... but when they are trued up so they don't wobble, and the face is dressed nicely, they cut much slower than they do right out of the box. I also have the machine running at its lowest speed. That's important. (I'll post the RPM number for that later today) The cutting noise is more of a "hiiissssssss" than a "brrrraaaaaatt"

Mac

Everything looks wonderful. Thanks for sharing the process with us. The badges turned out fantastic as well. Condolences on the loss of your good friend. It seems he lived a good life and enjoyed it to the fullest, doing the things he loved most.

Thank you, Otto.

Mac

I got the big flutes on the cuisses ground out this morning. The disc was beginning to cut a bit too aggressively last night, so I began by re-dressing the working face. It was only a little "out", so it took but a minute to do. Over the course of these flutes, I re-dressed it another three times; once at the beginning of each "quarter".



I tried to get a pic that shows the faceted nature of the result, but somehow it just does not photograph well. When you see it with both eyes, and everything is free to move a bit, it is much more obvious.



The important thing is that the hammer marks are gone. The resulting facets are all smaller than hammer marks, and the next operation will blend them away... or at least that's the plan. Every process leaves its own marks and traces. In a well ordered protocol, those traces are effaced by the next step, and that step's traces by the one after that. The trick is always in coming up with a sequence that takes the least time to get from hammer marks to an acceptable finish. If that protocol uses cheap abrasives, so much the better; but on the whole, it's better to throw money at it than time.

Mac

That is awesome! Did you make your own belt sander? Those legs turned out lovely!

Cannot wait to see the harness completed. This will be truly awesome!

RPM

Mac,

It might be good to point out the PPE you are using and it's importance.
In at least one photo you don't seem to be wearing any, I am sure that was just to get the photo.

Tom B. wrote:Mac,

It might be good to point out the PPE you are using and it's importance.
In at least one photo you don't seem to be wearing any, I am sure that was just to get the photo.

It's true. I am not all kitted up in the first photo of the belt sander.

By the time I settle in, I am wearing gloves, ear plugs, and a dust respirator. Most of the dust gets picked up by the "sucklotron", but there is still plenty of stuff in the air that I don't want to breath.

If the work never got hot, I would not wear the gloves for grinding but it does, so I do.

I put in earplugs early and often. Anything that is loud enough that it makes you grit your teeth requires plugs. Likewise, for lower level noise that will go on for a long time. All in all, it's better to just put in the plugs when you hands are clean and not worry about what the noise level is. I started wearing ear protection pretty early on in my career, and my hearing is still pretty good for my age. I don't think this is just coincidence or good genes.

I confess to being a bit lax about eye protection. I rely a lot on my big old 1980s style glasses to keep stuff our of my eyes, and that mostly serves me OK. If I am doing something that will throw sparks toward me, I will put on a face shield. Likewise, if I think that there is a chance of the machine grabbing the work and chucking it. I am better about this since a few years ago, when my table saw shot a small chunk of 2/4 out and hit me square in the left eye. That little wake up call knocked the lens out of my glasses and blackened my eye. I do not believe in the Intervention of the Saints, but I swore that I would make up a pewter badge of St. Lucy... just in case... which I have done.

Mac

RandallMoffett wrote:That is awesome! Did you make your own belt sander? Those legs turned out lovely!

Cannot wait to see the harness completed. This will be truly awesome!

RPM

Thank you, Randall!

Yes, the belt sander is a home-built. It came out OK, but if I were to do it again, I would make it bigger. Something that took a 2X72 (vs. 1X42) belt would be more versatile and probably more economical as well.

Mac

Mac wrote:It's just a regular old angle grinder disc.... but when they are trued up so they don't wobble, and the face is dressed nicely, they cut much slower than they do right out of the box. I also have the machine running at its lowest speed. That's important. (I'll post the RPM number for that later today) The cutting noise is more of a "hiiissssssss" than a "brrrraaaaaatt"

Mac

I finally found the notebook entry about grinder speeds. It looks like my speeds are...

2450 RPM
1715 RPM
875 RPM
612 RPM

I am using the slowest speed with the grinding discs.

Mac

Mac, this was posted on another thread. Someone ripped off a pic of the armour you made for Toby. And is selling on ebay. http://www.ebay.com/itm/HEAVY-SPECIAL-G ... Sw14xWILUu You might want to raise some hell?

I wonder what the thing they are selling actually looks like.

Mac

It probably looks like hell. I know they couldn't achieve anywhere near the quality of your work.

We should collect the money and order one, just to see what they try to sell us.

Hmm, the listing was removed due to an "error".... more like a FRAUD!

I get solicitations form guys in India on a weekly basis and probably 50% of them include photos of other people's work.
Usually I recognize the work and call them on it, most of the time they don't respond.
Sometime they acknowledge that it is not their work be they claim to be able to make the same

I also send a note to the person whose photos they are using to make sure they know to keep an eye out.

Mac wrote:

Tom B. wrote:Mac,

It might be good to point out the PPE you are using and it's importance.
In at least one photo you don't seem to be wearing any, I am sure that was just to get the photo.

It's true. I am not all kitted up in the first photo of the belt sander.

By the time I settle in, I am wearing gloves, ear plugs, and a dust respirator. Most of the dust gets picked up by the "sucklotron", but there is still plenty of stuff in the air that I don't want to breath.

If the work never got hot, I would not wear the gloves for grinding but it does, so I do.

I put in earplugs early and often. Anything that is loud enough that it makes you grit your teeth requires plugs. Likewise, for lower level noise that will go on for a long time. All in all, it's better to just put in the plugs when you hands are clean and not worry about what the noise level is. I started wearing ear protection pretty early on in my career, and my hearing is still pretty good for my age. I don't think this is just coincidence or good genes.

I confess to being a bit lax about eye protection. I rely a lot on my big old 1980s style glasses to keep stuff our of my eyes, and that mostly serves me OK. If I am doing something that will throw sparks toward me, I will put on a face shield. Likewise, if I think that there is a chance of the machine grabbing the work and chucking it. I am better about this since a few years ago, when my table saw shot a small chunk of 2/4 out and hit me square in the left eye. That little wake up call knocked the lens out of my glasses and blackened my eye. I do not believe in the Intervention of the Saints, but I swore that I would make up a pewter badge of St. Lucy... just in case... which I have done.

Mac

I though this was your Face/head PPE

Some say he eats Formax sandwiches with mustard and onion. All we know is that he is called The Stig.

Mac

I have been doing some abrasive process tests this afternoon on a reject vambrace front from the pile of shame.

There are two things I want to show you. The first it the effect of heat treatment on the degree of luster in the finish. The hinge rivet hole had to be moved on this plate, and I had welded up the old hole. That area has been above the austinitization temperature and has air quenched. The structure is probably perlitic, rather than martinsitic, since I had no trouble punching the new hole, but it it certainly harder than the surrounding area. You can see in the outside pic how much brighter the finish is. Harder steel takes a brighter finish.



The other thing I want to say is about finishing processes in general. Many folks will tell you that the key to getting a good finish is in not skipping over any of the grits. They would have you go dutifully from one to the next... 80gr-120gr-180gr-220gr-280gr-320gr-400gr-600gr, and then on to a series of polishing compounds.

I have to disagree. The vambrace plate above has had the following treatment.....
--three passes at different angles of an 80gr belt, backed with a firm platen to remove the hammer marks and level the surface
--one pass of an 80gr belt, backed with padded platen to remove the facets from the firm platen passes
--one pass under a slack 80gr belt to blend the surface a bit more
--two passes at different angles with 320gr

The 320 is in the form of 1" aluminum oxide strip on the cylindrical face of a 12" MDF wheel. There is a layer of felt between the MDF and the sanding strip. I'll show pics of the wheel later.

I am not sure where I will go from here, but I certainly will not introduce any steps between 80 and 320.

Mac

I am never careful enough to go through all of the grits. Just not worth the time, energy or thought.
I haven't tried skipping from 80 to 320, but I skip various steps. I think it tends to be 120, 220, then I mess around. I never like the transition from 220, but I also don't like how little life I get out of 320 grit stuff. I am probably running things to fast.

Thanks for the "stuff is harder air cooled" - that looks like a piece of (originally) dead annealed 1050 which was worked but not heated except where you welded it. I have found that heating for hot work (also pretty hot when I do it, but not welding heat) and "air cooling" causes the material to be a lot harder. Still workable, but it has a certain amount of "fight back" unlike the annealed stuff that is mushy in the way mild is mushy.

Wade

This is the wheel I used on the vambrace plate earlier.



The ends of the abrasive are tucked into this slot, and secured by twisting a piece of lens -shaped tubing in the hole at the end of the slot.



I got the idea from seeing drums like this one.



The abrasive came on a big roll.



I have not replaced the abrasive on this wheel in a number of years, and the truth to tell, I can't remember exactly how I have it stuck in place so it does not wonder off the edge. I think I used some tacky adhesive, but I can't recall what it was.

Mac

That MDF wheel is a slick idea! Did you build it? I may have to steal that design. I've been using greaseless compound on a wheel, but it's finicky and hard to 'charge' up on my underpowered wheel.

Jeremy,

I did make that disc, although I used a friend's lathe; mine is not big enough.

I have other discs of that size that I charge with greaseless compound. Mostly, they have leather or felt rims, either glued right onto the wood, or with a layer of foam in between.

Mac

OK... So this is not the least bit funny. It's been over five years since I put that abrasive strip on that wheel, and I have no solid memory what I used as an adhesive. I have a sort of recollection of having had a sort of PVA-like glue in a squeeze bottle that I bought for sticking down discs. I'm pretty sure that went bad with age, and I tossed it out. Now, I can't find any place that carries a similar product.

My temptation is to use a spray adhesive on the periphery of the wheel, but that is going to be messy.

Does anybody have a clever idea?

Mac

The stickiest PVA glue I know of is that 'tacky' stuff in a brown bottle you find at fabric stores...

That'd be Aileen's Tacky Glue that you're thinking of Jeremy. It does work well - I use it for hobbies. It will dissolve in water, so cleans up fairly easily but is far stronger than Elmer's.

Galileo- Yep! That's the stuff. I use it all the time...

This stuff might do the trick

E6000
http://eclecticproducts.com/products/e6000.html

Tom B. wrote:This stuff might do the trick

E6000
http://eclecticproducts.com/products/e6000.html

I like that stuff. Not quite as permanent as a two-part epoxy, but close.

Two sided tape.