Another diamond lapper

[rabler]

Inspired by @Janderso, I’ve started my own diamond lapping machine. Thanks to him for the ideas and feedback.

I found a used geared motor, 3/8hp, 3ph, 170rpm on ebay. Also a Teco L510 VFD, 120v single phase input, for up to 1/2 hp. This is probably excessive frills, but I’ll get variable speed.

Ordered a 8” diameter disk of 6061, 1/2” sawcut, for the platten, and a 1/4” x 6” x 12” piece of stainless for the table from McMaster.

The motor has a 3/4” shaft. I had an odd piece of turned CRS that I turned into a hub.

Turning the aluminum platen was a bit of a challenge. I wanted the face true with shaft to minimize runout, but I couldn’t thiink of a way to turn the face and bore the hub for the motor shaft in the same setup.

I ended up mounting the hub on the platten first. 1/2” hole in the platten, press fit to the hub. Hub drilled and tapped for 1/4-20, so I can mount a simple center to true the lapping plates, or a washer to clamp the plates if desired although I expect magnets will suffice.

Turned the face of the platen with the hub clamped in a 4 jaw, and could turn enough of the rim and outside of the back face of the platen so it was true with the front face. Then I flipped the combination in the 4 jaw and indicated the cut part of the back face as well as the rim of the hub to within a 1/2 thou. Drilled and bored the hub to a close fit for the motor shaft.



Stll need to broach the hub for a key and drill and tap for a couple of set screws. Then cut recesses for the magnets.

Haven’t gotten past that in terms of finalized design, although pondering a few ideas.

 

[rabler]

Milled my piece of stainless flat this morning to make the table. One of the ideas that I'm inclined to pursue is to put the table on a pivot so it can be flipped up and back to make it easy to get to the platen to change disks/grits. Have some rough sketches but need to sit down and work out dimensions to see if it'll work. Thinking of using a spring pin on either side to secure it in position.

 

[Eddyde]

Looks like a fun project, please post more pictures!

 

[rabler]

A few more pictures...

I’m planning on mounting the vfd as shown, above the motor.

Had an issue with my face mill, top right side of table. It’s 316 stainless.










Haven’t decided whether this will be benchtop or on a stand like a grinder.

 

[rabler]

Saturday was mostly fab work, built the base. Square tube is 1 1/4”, base plate is 6” x 3/8” hot rolled. Overkill but it was something I had on hand. It adds a bit of weight to the base.
.
(edited comment: that backplate isn’t twisted, some sort of camera artifact)

The front of the base will eventually get a drip tray screwed to the bottom.


The vertical plate in back will hold the VFD. Holes still needed to mount that. Motor bolts to the bottom plate, which has already been drilled and tapped. Didn’t get pictures but four shallow blind holes (.625 dia x .210 deep) drilled in the platen for magnets.

Next need to machine arms for the table, and bend a shroud for the VFD.
Still need to broach the keyway in the platen hub too.

 

[FOMOGO]

Good example here by Steve Summers.This

was part two of the build. Nice work on yours Randal. Mike

 

[rabler]

Put in some ongoing work in the bathroom remodeling, then took a break to do a bit more in the shop on this project. Today’s accomplishments were to glue in the magnets, and make the shroud for over the vfd.


I wanted to round the top corners of the shroud, consistent with the round platen. I did a little math on using a piece of rod as a bending template. Backed that with some square stock just to make it clamp up right.


TIG welded that to the backplate.


Here’s a test fitup. VFD isn’t bolted in, so the yellow box is acting as a spacer.


My enclosure will get a front face, but I’ll leave the bottom and upper third of the back open for air circulation/cooling. The backplate, which the vfd heatsink/case will bolt to, is 1/4 thick so that will also help with cooling. Open bottom is probably not up to UL electrical compliance since someone could get their fingers under there and touch live contacts, but my shop, my tool.

 

[rabler]

Good example here by Steve Summers.This

was part two of the build. Nice work on yours Randal. Mike

Thanks Mike. It’s a fun project. Most folks think of it as a carbide grinder, but I’m primarily interested in honing HSS lathe toolbits. I have a hard time using a small hand hone as I tend to ever so slightly round edges which essentially makes a dull tool. This should be easier to get a clean angle.

 

[rabler]

Useful thing about this VFD is it will output 3phase at 220V using 120V single phase input. I believe this 1/2 hp version is the biggest model that Teco makes with 120V input.

 

[rabler]

Used the K&T 3K vertical to clean up a 20” piece of 3/8” x 6” hot rolled to start making the table mount.
400 rpm on a 6” face mill, 10 inserts, 8ipm, .030 DOC. Went through it easily.
Wouldn’t want this as my primary mill, but when it comes to a big job it really is a fun option.
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