Off Topic Arrrrggghhhhh. The Never Ending Parts-Needed Black Hole

Cushing H. said:
Ummm ... I’ve been cautioned on a number of fronts to NOT try to grind this ceramic ?
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I buy the 2x the length ones all the time and cut with a tile saw. Then I have two! I've got a little lip maybe 3/16" high, welded to my steel platen on the downhill side. I then float the glass on with JB Weld. Best of both worlds and the small lip does not affect mounting of the platen in the slightest. I don't have a tile saw either but the neighbor across the way does. I too have to use a torch to get the old glass off.
 
SBuzek said:
My shelf is held on by 2 1/8" brass pins peened in place, grind the glass to length.
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Yeah ... the preened pins is another option the ameribrade guy thought of. That might actually be the most straightforward way to accomplish this, BUT I would like it removable, because the shelf covers the screw that secures the platen to the brackets. Damn, now that I think of it, so will the glass. If the thing comes loose, there will be no way to to re tighten the bolt (can’t get a screwdriver into the head of the screw).

hmmm ... machining my own with small integral shelf is starting to look like a best option. (And let’s me use my full length of ceramic). Snow coming in at noon ... looks like I need to head out to my local hardware for some mild steel...
 
Cushing H. said:
That was actually my first thought, but the shelf came (pre drilled and tapped) with the glass, so I figured I would try to use. Famous last words...

I wonder if aluminum is safe enough to use as a platen?
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I don't see why it wouldn't be safe with the ceramic covering the aluminum. I have been thinking about ordering the Ameribrade combo platen with the 6" wheel and making a platen out of aluminum for it. I don't really see a good way to mount the glass to their standard platen and then attach it to the L-brackets, other than maybe welding the bolts on. It just seems easiest to machine a platen that has two tapped mounting holes, and you can add an integral shelf while you're at it.
 
Hubert S. said:
I don't see why it wouldn't be safe with the ceramic covering the aluminum. I have been thinking about ordering the Ameribrade combo platen with the 6" wheel and making a platen out of aluminum for it. I don't really see a good way to mount the glass to their standard platen and then attach it to the L-brackets, other than maybe welding the bolts on. It just seems easiest to machine a platen that has two tapped mounting holes, and you can add an integral shelf while you're at it.
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That’s the basic approach I am about to take. Just got back from Home Depot ... and they have 3/8” by 2” wide mild steel. Not as easily machined as aluminum ... but still should be doable if I take it slow. Will post photos...
 
This is a good place to remind folks to regularly search around ebay. I look for aluminum blocks, angle, and unusual shaped things. There are folks who will sell some drops and shorts for almost nothing just to get more than the scrap price. I buy them and set them in boxes and on carts of materials. Most cost about 1/10 of the price if I ordered it from a metal supplier. When a project like yours comes up I grab a piece of suitable size material and get right to work. For example, you can talke a piece of 3/8"x2" aluminum angle and make the whole platen from it. Rock solid and Easy-peasy!
 
Cushing H. said:
That’s the basic approach I am about to take. Just got back from Home Depot ... and they have 3/8” by 2” wide mild steel. Not as easily machined as aluminum ... but still should be doable if I take it slow. Will post photos...
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I'm looking forward to the pictures. Mild steel should not be a problem for the mini-mill.

It might be a good idea to use some thread locker for mounting the L-brackets. I have had good success with Vibratite VC3 for applications where I know I want to be able to undo it.
 
I drilled and tapped two 1/4" holes in my flat platen, screwed in two socket head screws, and ground them flush. I have (had...tossed it before putting all my gear in storage) a cheapo diamond wet tile saw that I used for cutting G10 and Carbon Fiber, worked great for cutting up a piece of pyroceram glass. I cleaned up the edges with a diamond needle file and JB welded it to the platen. (belt and suspenders).
 
Hubert S. said:
I'm looking forward to the pictures. Mild steel should not be a problem for the mini-mill.
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Well, yes and no. making progress, but just demo'd an end mill. Not sure if I started feeding too fast, or whether I should be using a fly cutter to mill down the large area the glass will go in to????????? I've never milled in my life - anyone have a suggestion, other than just buying new endmills (which I doubt is the answer....)
 
I just glued my glass on with jb weld. It's still there after grinding about 30 blades and I figure I will need a torch to heat it off one day when I change it.
 
Cushing H. said:
Well, yes and no. making progress, but just demo'd an end mill. Not sure if I started feeding too fast, or whether I should be using a fly cutter to mill down the large area the glass will go in to????????? I've never milled in my life - anyone have a suggestion, other than just buying new endmills (which I doubt is the answer....)
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I'm not a machinist either, but had some training a long, long time ago and remember just enough to be dangerous... I have an indexable face mill that has worked well for me. The only insert I've ever broken was machining a piece of railroad track too aggressively. I don't see why an end mill would not work for what you are doing. There are tables and apps for feeds and speeds, but I am not sure how applicable all that is to a manually controlled mini-mill. For an end mill, my approach has been to use the same rpm I would for a drill bit of the same diameter and then increase the depth-of-cut until the mill no longer sounds happy, and then back off just a bit.
 
I'm just playing..... that is why I bought extra end mills :) I suspect I just got too aggressive with the depth of cut. with only a 1/2" diameter end mill it is going to take a LOT of passes to work that face down. Looking at fly cutters on amazon right now.... little machine shop has a nice one .... but I would have to wait for shipping. one advantage of a fly cutter (other than the increased diameter) is that it is relatively easy to sharpen the bit....
 
Oh yeah ..... I just found little machine shops speed and feed calculator .... and I was definitely overloading the end mill (too deep, too fast a feed). Oh well .... that is how you learn.....
 
Those little diamond wheels for a Dremel work pretty well for cutting ceramic glass. Menards sells the Tool Shop branded wheels pretty cheap, IIRC.

As for an aluminum platen, I've used steel and aluminum for my platens, and either works about as well as the other. Aluminum is easier to machine, though the steel is nice if you use a magnetic angle finder to set your platen angle. You could always attach some steel plate to the back of the aluminum.
 
It actually just occurred to me that instead of machining down that large flat & removing 1/8” of steel with the endmill... I can go to the grinder and hog out most of it, then go to the mill to clean it up. Much faster...
 
ok .... pictures. first, I had gone to home depot and bought a 3" piece of 3/8" x 2" mild steel (shown next to the original platen for comparison):
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cut the mild steel to a length of 9""
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then went to the mill, squared up the ends, then milled to depth (leaving 1/4" material below it) a single channel on the left side, 1/2" in width, leaving a 1/4" shelf on the left side. THAT left something like 8" of steel 2" wide to then get down from 3/8" thick to 2/8" thick. clearly tried to hurry it (too high RPM, too fast a feed rate, and too deep a depth of cut). Ended up with only about 1/4 of the material removed, an awful surface finish, and one totally dead 1/2" endmill.

so .... today I took the thing to the grinder. very much like grinding a bevel: scribe marks on either side of the flat to indicate the 1/4" target thickness. That went fast :). Took it down to within about 0.02-0.03 of the target thickness over the entire 8" length, then went back to the mill. the picture below is after a number of passes .... now at 0.01" above the target depth of the slot on the left. you can see from the difference between the milling marks and the vertical grinding marks how the milling is taking out the unevenness of the grind. at 0.005" depth of cut per pass, this should take maybe two more passes and then a final shallow pass to get everything uniform up the shelf on the left and do a final cut on the shelf itself
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I should have thought about using the grinder in the first place......
 
Yeah, you should have taken it to a 36 grit belt and then just cleaned it up with the mill. It doesn't even need to be all that neat since it will be coated in JB weld.
 
Stacy E. Apelt - Bladesmith said:
Yeah, you should have taken it to a 36 grit belt and then just cleaned it up with the mill. It doesn't even need to be all that neat since it will be coated in JB weld.
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NOW you tell me! :)

Looks like I am down to two more passes - which will need to wait until tomorrow. Still .... I just dulled another endmill. I dont know ... maybe this steel from HD is harder than one would expect? I'll be kind of pissed if I snap a tap when it comes time to complete those threaded holes.....
 
I have used a Koolmist system when milling steel on my mini mill and that seemed to help. You shouldn't have any trouble tapping the holes if you use the mill to get the tap started. With steel, you probably want to turn the tap by hand and just use the mill to keep the tap aligned with the hole.
 
That is a lot of work.
For my first platen I bought a piece of surface ground D2 and had it heat treated.
 
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