Grinder Station, Part III

[francist]

In Parts I and II we looked at the two tool rests or heads specifically, but in order for this all to come together in a seamless operation I had to make a few adjustments to the grinder unit itself.

It started out as one of those dual-purpose things from KMS Tools — 8” grey wheel on one end and 2” x 42” belt on the other. The grey wheel I used for years with just the standard rest, but the belt I never cottoned on to. It was loud, vibrated like crazy, and was just a generally unappealing accessory to what should be a straightforward tool. So I got rid of it.

The trouble is, without the belt part there was no real provision for mounting anything else except a very shallow step on the shaft. To boot, the cup wheels I had my heart set on have a 1” arbor hole which was way bigger than the 5/8” grinder shaft. Guess I need to make some wheel hubs...

A few more AutoCAD layers later I had designs for new wheel hubs complete with an integral balancing disc mounted on the back. In theory, using a heavy material (leaded brass is heavier than steel, believe it or not) in an eccentric shape should allow rotation of the disc to correct for out-of-balance wheels. This would probably require semi-circular slot milling (buy rotary table) and a means of checking the balance to begin with (build wheel balancing rig using salvaged roller blade bearings and scrap aluminum extrusion). Along the way I stopped for tea with a wonderful girl named “Alice”....

Here’s a wheel hub with balancer ring mounted in a (yes, salvaged) ice skate sharpening ruby wheel. I haven’t actually used this wheel yet but I like the narrow width for grinding the “scoop” on some shaper cutters. The balancing stand is surprisingly sensitive given that the bearings aren’t any great shakes.

The same hub style is used on the Type-11 cup wheel. I need a bit more of a weight differential on the disc as it doesn’t quite get me to full balance, but I think I’ll just solder a second layer of brass onto the fat side and that may do it. The screws provide a mechanical belt-and-suspenders to the solder joint anyway. Oh, and I had to make a sheet metal guard for cup wheel too seeing as how the one for the belt was no longer with us.

So you see, a few minutes of thinking and a couple hours of effort can get you a really nice setup...

Thanks for coming along for the ride.

-frank

 

[YYCHM]

How do you set up the correct angles to sharpen an endmill?

 

[francist]

Mostly I just eyeball to the existing angles, and if it’s too far off I’ll just correct until it looks about right. I haven’t done that many yet for it to become a problem although I could see for a specific grind one might want to make a sample to reference off of. I find that’s often easier than trying to set an angle using something like a protractor, especially for small cutters.

 

[YYCHM]

Mostly I just eyeball to the existing angles, and if it’s too far off I’ll just correct until it looks about right. I haven’t done that many yet for it to become a problem although I could see for a specific grind one might want to make a sample to reference off of. I find that’s often easier than trying to set an angle using something like a protractor, especially for small cutters.

This little jig works well http://homews.co.uk/page121.html and provides some guidance for setting the correct angles.

Your turn buckle approach is pretty cool.

 

[RobinHood]

I love that wheel balancer. Looks like I’ll be modifying mine with rollers. Seems a better design than rolling on precision ground rails as the arbour can “slide“ along the rails as opposed to purely roll as it would with your roller design.

 

[francist]

Thanks, I dig it too but that’s just because it has flashy red bearing seals

Yeah I thought about the ground rail design as well but couldn’t see myself trying to level the thing every time I wanted to check a wheel. Not like I do this every day or anything, but I didn’t want to add yet another level of preparation to what seemed to me a simple concept. I’m really pleased with how well it works — at least for the speeds a bench grinder spins up to. A proper surface grinding machine might demand more precision, I don’t know. I’m waiting for David_R8 to get his fired up so we can try....

-frank

 

[PeterT]

This isn't the picture I was looking for but is kind of a frame / dual bearing concept commonly very seen in RC helicopters & similar applications. I made one for myself but gave it away. Its relatively easy to adapt it to other balancing needs. Best to sandwich 2 plates of stock & cut/drill all the features so the frames are as identical as possible. Some people use bearing races by themselves, others use larger discs on pinion axles. Then just some standoffs to separate the plates. I guess you could even do the tripod leveling thing.