Hardinge CHNC chip shield pics/info?

Would you be interested in a copy of the maintenace manual and the parts list manual? Will have these pics and A LOT more.

email me (remove the .NOT)

Karl

Ralph,

While you can actually weld PC, it isn't very pretty or clear. There are cements available for PC but again it will not make the crack disappear. Acrylic solvent will work if the edges of the cracks are touching. Just use scotch tape across the crack to hold the edges together. Rub the tape down tight so the cement doesn't get under it. Dip an artists brush into the solvent and then touch it to the crack. Capillary action will suck the solvent in. Let it dry for a least an hour. If the cracks are wider, 3M makes a thick structural adhesive for PC, but you need the static mixing gun to use use it. If it's just one or two cracks, cementing will give you some additional usage. If what you have is actually crazing ( many small cracks ) you should really replace the guard.

I took a quick look and didn't see anyone offering replacement curved guards. If you need I could give you a quote on forming one for you. I would need a sketch.

Will

Will,

1) Is there a shelf life for the material his shield is made from? a.) What is the cause for the crack/s?

2) Does having a crack and/or cementing a crack defeat the "Safety" features of a shield?

Tom

Tom,

His shield is probably polycarbonate because of the materials inherent resistance to breakage and higher operating temp.

I was told that the major cause of interior ( not exposed to UV ) PC cracking is environmental pollution. Could be the coolant. An interesting observation about double wall skylights. The inside dome exposed to the living space usually crazes before the outside dome. Talk about indoor air pollution!

Anything that compromises the original shield integrity would lessen the "safety" feature. If the PC has cracked for any reason, it can't be as good as it once was. ( Hmmm..sounds like a C & W song)

As they say about helmets, if it has protected your head once... retire it.

Will

Will,

I had the bright idea of making a replacement lathe door window from scratch resistant PC. (McMaster-Carr) Within a few days It was cracked at some of the drilled hole locations. Within a few more months all the hole locations have massive cracks now.

What happened? Did my water based synthetic coolant attack the cut hole edges? or is scratch resistant PC more susceptable to stress concentrations at holes, etc???

I drilled the holes dry with a hand drill thinking it would last forever. Now I wish I had programmed it instead.

Greetings Clay, If PC stands for polycarbonate then I think you didn't get what you ordered. Polycarbonate should not crack from holes drilled through it and susequent exposure to oil or water soluble coolant, synthetic or otherwise. However, plexiglass will. If plexiglass is exposed to virtually any type of oil it will start to crack. Polished plexiglass takes a long time to start cracking. But if it is scratched, stressed, or has any microcracks that are exposed to oil it will crack. A drilled hole exposed to oil will crack fast. A hole drilled and tapped with water soluble oil will crack severly overnight. ERS

Does the drill make a difference? Will a brad point do it?

I remember drill> >

For drilling plastics and brass a slightly modified drill tip is required. Grind a small flat on the flute side of the cutting edge with a whetstone. The entire edge of the lips are treated this way. This gives you zero rake. In other words it will now scrape. Always ease the drill thru as it starts to break thru (by feel). No splits or cracks, ever. RichD

On plastics, you must drill and oversize hole to allow for expansion and contraction. The way I did it was to drill an oversized hole big enough to put a piece of rubber tubing inside the hole that the bolt will go through. Plastics move a lot with temperature changes and if you don't allow for the movement the window is garanteed to crack. The other thing is not to tighten up the screws too much and use a flexable caulk that will not get hard so it will move with the temperature changes.

John

I learned all about tight fits in fragile materials after the 94 LA earthquake. Our wall mounted toilet tank fell off, and luckily survived. It's lag type mounting bolts had rusted completely through.

There was another set of mounting holes in the tank back, and yours truly utilized them to remount... with new 'snugish' fitting lag bolts,

3/8" IIRC.

Several years later, I noticed a hair line crack propagating up the front of the tank. Investigating, I found the crack originating from one of the newly rusting bolts swelling in it's hole. The crack had started going vertically straight down, spread across the bottom of the tank, and was creeping up the front... and had yet to leak a drop.

The tank separated vertically into two pieces as I was removing it to replace the toilet.

Erik

My memory isn't like it used to be but I'm pretty sure that polycarbonate can crack around holes and that some oils do help this happen. Randy

That may be so but I've never seen it. And I've machined lots of polycarbonate. It's softer and less stiff than plexiglass. My first experience machining the stuff led me to do some research on polycarbonate. Turns out one use for it is "bullet proof glass". So myself and a co-worker decided to test it. From about 10 feet 1/8" thick polycarbonate would stop a .22 long rifle. No cracks. The plastic melted and deformed and sometimes captured the bullet. Three pieces 1/8" thick laminated using a special CA glue and primer from Loctite would stop a .30-.30 or .308 (I don't remember which and don't know which is more powerful). The bullet would not be captured but would instead melt an oblong crater in the plastic and leave at what appeared to be a pretty shallow angle. ERS

Most of it is epoxy coated now, you'll see it is green instead of brown.

Gary H. Lucas

It's well known that PC motorcycle helmets should not be painted. The solvents in many paints can weaken the PC. There are some types of paint that are safe, but I have long forgotten what they are.

Steve R.