michiganbuck
Diamond
- Joined
- Jun 28, 2012
- Location
- Mt Clemens, Michigan 48035
looks like the radius could be larger, or the angle adjusted down a little to make a smooth wider scalp.
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That's the thing, I didn't have a chance to sharpen the blades I just gave the ones I got a visual inspection. They looked clean and grabbed the back of my nail, but they are likely dull. I have a dedicated carbide grinder (#400 wheel on it) and parts for a low speed lap that I haven't put together yet, but I don't want to grind inside the house and I've got a ton of blades that I want to sharpen, so setting everything up is a project in itself. I just wanted to make sure the Junker repairs looked viable and was hoping I could get some experience, but sharpening practice is the next thing on my list.How do you sharpen the blade? It looks as if it is scratching more than scraping.
The radius was very close to 90mm which I know is a bit aggressive for roughing, but I was dealing with a very small surface that was already quite flat. The Biax had a very small angular range where it felt it was cutting effectively and creating chip dust. If I had too much angle of attack it would chatter and bounce (not sure if I should have tried to muscle it, but I assumed that was not the right move) and trying to shallow it out to get a wider cut, it would lose bite and just skate (I'm guessing that's a sign of a dull blade.) I tried using the other edge of that blade with similar results, then switched to the factory Biax spring steel blade (60mm) that came with the other tool. It was also likely dull although I noted it had other nice characteristics. To the eye, even with a loop, the blade edges are shiny and well defined, no obvious chips, but I'm assuming at this point that an untrained visual assessment doesn't cut it when it comes to blade condition.looks like the radius could be larger, or the angle adjusted down a little to make a smooth wider scalp.
You need to sort out the sharpening to do any serious scraping. I made my rig out of a tiny cheap grinder plus a cast iron disk and a wooden rest. Works well enough for my needs. An inexpensive 400 grit diamond lapping disk from China will also work well, mounted on the same kind of small hobby grinder motor.
A photo is here: https://www.practicalmachinist.com/forum/threads/studer-rhu-450-from-the-1960s.343863/post-3108490
I also made a radius jig: https://www.practicalmachinist.com/...450-from-the-1960s.343863/page-4#post-3111305
QT Ops website. Two rotating abrasive wheels are required, a resin-bonded diamond wheel (perhaps a d150 100mm cup wheel), the other a cast iron or ceramic disk loaded with a fine (3 micron seems to work) diamond lapping paste.I have a simple website with info about getting started openscraping.com, the site needs a bit more work but it will give you an idea about preparing blades etc and the other equipment needed.
As for the router project that is a different thread altogether, for a router using aluminum extrusions there is no need to scrape that plate (and doing so would be profoundly difficult without a large reference surface plate and a crane)
Luke
I DON'T grind the bevel right to the centre
On the Baldor 500, you can adjust the inboard/outboard position of the tilting tables considerably. You might take a peek at the underside of the table on your grinder to see if that's possible on your machine. It's pretty common to have to move the tables outward when you increase the tilt angle.A real lapping plate wouldn't fit the way I'm attaching it as there's only a few millimeters gap between the wheel and the tilting tool rest.
Unfortunately not. Although the table is easy to remove, it is designed around a specific wheel size. The thick pins it rides on are fastened in v-ways ground in the support collar. The choice of pivot point means it can move through its entire range with little change in the gap, which is nice, but there is just enough room for the thin electroplated laps.On the Baldor 500, you can adjust the inboard/outboard position of the tilting tables considerably. You might take a peek at the underside of the table on your grinder to see if that's possible on your machine. It's pretty common to have to move the tables outward when you increase the tilt angle.
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