first flat grinds

[Matt Bufford]

I did my first flat grinds today, one with the jig and one free-hand. Also got my feet wet with a little file work!
I sent the first one off to HT this morning, but still have a bit of work to do on the drop point.








I'm excited to see how they come out after HT

[Ray Rogers]

They look good. It might be just the pictures but they look more convex than flat. If that is the case then you can flatten them more after the HT is done. Most first timers tend to get convex on their first few flat grinds .

The file work looks very good. Now you need to put the details in it - you have the vine, now add the thorns ....

[Matt Bufford]

Originally Posted by Ray Rogers

They look good. It might be just the pictures but they look more convex than flat. If that is the case then you can flatten them more after the HT is done. Most first timers tend to get convex on their first few flat grinds ...

they look mostly flat to me. But I would imagine any convex on the could be attributed to the cheap graphite platen face on my griz - it notched pretty quickly in a few spots where I did some plunge cuts, so I wouldn't be suprised if it has developed a concave spot where I do my bevels.

[kcorn]

I used to have the same problem with graphite tape on my platen. The best thing I ever did was buy a piece of ceramic glass and mount that on my platen. It is unbelievable what a difference it will make in your grinds. You can find the plates for sale here:

http://www.hightemptools.com/ceramicplatenliners.html

Just make sure and use pins below the platen to make a shelf for it to rest on in case the adhesive fails. There are some good threads on here that explain how to safely mount one. I used pins for the glass to rest on and red high temp rtv adhesive to adhere it to my metal platen.

Give it a try. It is well worth it!

[Matt Bufford]

Wow, those are way cheaper than I thought they would be. Which size would you recommend using on the griz? Is there any benefit of going shorter or longer?

Why the red rtv? I would think a high temp epoxy would be choice


Thanks

[Ray Rogers]

Use the length that matches the flat part of your platen. These are, after all, a kind of glass - you don't want any unsupported areas because they won't flex very much before they break.

You use tape because epoxy is much. much more difficult to remove if you ever have to replace the glass. I've been using pyroceram for many years and had to replace one that I hit with something heavy and cracked it, can't hardly wear them out though. And, be double darned sure you install pins or a shelf of some kind under it to support the glass so that it cannot slide down because the tape cannot prevent the glass from sliding. Even epoxy should not be relied on to keep the glass from sliding, a lot depends on the epoxy used and how well you prepped the materials. So, don't play Russian roulette with a potential glass grenade - attach a metal shelf/foot/support/pins/something to the metal platen to prevent the glass from sliding ...

[jdale]

I just looked at the platen FAQ on the high temp tools site and part of this statement struck me as odd:

"The lifetime you will experience with your ceramic platen liner is dependent on several factors, such as the frequency with which you grind, whether or not you use your platen to profile on (not a good idea), etc."

I am refering to the part about using your platen to profile being a bad idea, it this the case? I am not able to think about other place (on my sander) that would work to do a profile.

[Matt Bufford]

I've been profiling on my wheel after cutting the basic shape with the band saw.

[Ray Rogers]

Again, that comes back to how much you actually use it. What they mean is, the thin side of the metal that you are profiling can wear a groove in the glass. This would happen because when you profile you use the tool rest and the tool rest usually sits in the same place every time which is where the groove could form. A lot will depend on how close your blade out line is at the time you start to grind the profile - the closer it is, the less grinding. My tool rest is adjustable so I change the height now and then. I saw my profiles very close before I grind and I do as much profiling as possible on my contact wheel and small wheel (basically everything but the edge can be done this way). And, when I flat grind I'm usually higher up on the platen than where the profiling was done so if there is a groove it's not in my way. Taken altogether, these methods have allowed me to use the same glass for at least 12 years.

Wearing a groove in the glass is another possible reason why you might have to change the glass eventually, so that's another vote for the tape instead of epoxy ....