Non-conductive nomad 3 bed

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TLDR: I’m making a granite bed with threaded inserts so I can do conductive probing on my nomad 3. (Mostly to practice working granite but also because it’ll be mighty convenient…hopefully it gives some folks at C3D a chuckle :yum:)

I’ve had my nomad 3 long enough that it’s time to start making major modifications.

I spend more time than I care to admit just finding centers and such on metal stock. (I know we’ve all come together to find a decent 3D Touch probe option but it’s not as repeatable as I’d like and conductive probing is just much faster IMO)

Previous shenanigans:
In the very beginning I did things that would make TDA cringe…just put a thin shim of plastic on the shank of my tool for probing (between the collet and the tool, that can’t be good for collet life or precision!)

Then I wised up and used PEEK bolts for my work holding and non-conductive shims between the bed and stock. It works surprisingly well but again, just a hassle.

Current shenanigans:
Now that I’ve got some real metrology tools, it’s time to make a new bed for my little nomad.

Requirements:
Completely non-conductive without the need for coatings or shims.
Same threaded hole pattern as SMW table.
At least as rigid as SMW table.
Threads that can handle as much torque as aluminum 6061 without deformation or pullout.
The same size as the SMW table.

Extras credit:
A ~1 inch bore strategically placed to allow milling on the end of bar stock. (This has been discussed on the forum but to my knowledge, never done)

The Idea:
A granite bed with precisely located threaded inserts.
I’ve been practicing my granite work recently by bringing the tops and bottoms of small (extremely cheap) surface plates into parallel. Next up I’d like to practice hole making in granite. That brings us nicely to a threaded granite surface plate…I think.

Steps:

  1. Find a suitable piece of granite in thickness and cut to size
  2. Make that granite real flat
  3. Make that granite real parallel
  4. Create holes to anchor the plate to the nomad.
  5. Drill oversized bed of holes to allow for threaded inserts (anchored with appropriate adhesive/epoxy)
  6. Shim table since I won’t be able to surface it (had to do this with the SMW table as well, it’s not too bad really)

The threads are where we have a few options:
I could just plug these holes with slugs of 7075 or brass(it’s pretty), lap them to flatten the surface, then bore and tap with the nomad while the bed is in situ.
Or I could spend a bunch more money to get nice stainless steel inserts. Take the SMW bed, thread bolts though each hole, put the inserts on the bolts, and drop the entire bed of inserts into the granite base in one go. Essentially transferring the threaded hole locations (and precision) from the SMW table to the granite table.

I’m thinking oversized slugs that are bored and tapped will be the way forward unless I can find a cheap source for nice threaded inserts…blank slugs would give me a good opportunity to figure out thread milling I suppose.

Anyway, I’ll keep the topic updated as I progress. I know there are a few other projects I’ve left hanging but I plan on getting back to them shortly as well.

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First of all, awesome concept, Tyler :grinning:

There’s an older thread on CNCZone by a guy named mackeym who was building a lathe based on a granite surface plate. He did some experiments regarding pull-out of inserts that were epoxied into oversize holes in the plate and found out that externally threading the inserts helped.

This thread is a good read too.

I’d personally think about Helicoil inserts from McMaster-Carr because even the stainless ones are not expensive (versus solid-bodied externally-threaded inserts). Lube the bolts/studs with Vaseline or similar, thread on the inserts (you’d want to pre-break off the tangs unless you thought of a good reason for keeping them) and epoxy in as you propose. Just for workholding I wouldn’t think you need anything stouter.

I haven’t done any thinking at all about building a small lathe around a 6" x 18" x 2" granite surface plate using stuff I already have in storage, none at all… :wink:

And I’ll be interested in reading about your results here!

Randy

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For more traditional brass inserts, there are these available locally or from Amazon. If I were using them I’d file or cut lengthwise grooves across the external threads to increase the keying effect.

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Thanks for the great references, they are hidden gems for sure.
In exchange, here’s my go-to reference for granite/cnc building shenanigans: https://youtube.com/@piotrfoxwysocki?si=AWKCIhqspUJdutJ1
So many hours of great content and he’s done follow up lessons learned over the years.

I’m thinking I’ll either go straight up utilitarian: off cut from my granite counter and stainless helicoils like you recommended.
Or it might be a fun opportunity to do something a little silly and source a trial/scrap piece of really nice looking blue or green granite (the rare, painfully expensive stuff) and brass inserts to make things really pop :slightly_smiling_face:

Unfortunately, I couldn’t find a slim enough piece of granite surface plate to start with which, that would have saved a good amount of time but I don’t want to lose the z height by using a 2” block.
(And I don’t want to deal with turning an inch of granite into dust.)
I’ll certainly keep the thread updated with choices and such I make along the way. (Things like which diamond drill and anchor adhesive, stuff like that)

So far it seems like one sintered diamond bit is all I’ll need to get through all of the holes. That would be convenient.

Sidenote, a little tag popped up saying it’s been 8 years since your last comment. Welcome back :slightly_smiling_face:

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Thank you for the welcome, Tyler! :smiley: It’s good to be back, and it’s been way too long that I’ve been out of circulation. I’m eager to get my 883 Classic out of storage from California.

Thank you for the Youtube link. I’ll check it out when I’m able (long story).

My own granite fabrication experience is minimal and long ago. I drilled a hole in a small surface plate to facilitate measuring pre-mounted tools for my (then) Tormach mill.

Years ago I had a granite topper cut for my wife’s Ikea rolling butcher block table. If you’re in an area that has In’n’Out Burgers, the drive-through window has a little shelf made of “blue pearl” granite. It’s beautiful stuff, supposedly found only in one mountain in Scandanavia somewhere (I don’t have access to Google currently so can’t look it up myself…) I found the Bay Area granite dealer that supplied at least the local In’n’Outs and had him cut a square. It is an inch or maybe a little less thick and maybe 18" square.

I don’t know if granite backsplash material is any thinner–when we had a house with granite countertops, the backsplashes were tile…

Randy

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That blue pearl granite is mighty pretty, along with the brass inserts might just be the way to go. Classy :ok_hand:

So tiles are obviously too thin which is unfortunate, lots of gorgeous 12x12 tiles for cheap.

Turns out back splashes or side splashes might work out though. They seem to be about 0.75” thick, just about perfect. Though it seems to be harder to find in say 8” lengths.

And finally, the surprising entry for getting small pieces of rare granite…cutting boards. I’ve never understood the whole granite cutting board market but I’m not mad it exists now :yum:

Yeah based on your experience with the core drill, just one nice drill should get the job done.

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Update, I’ve got a piece of 3/8” blue pearl granite on the way. Funny enough, the only place I could find is in California, rare indeed.
I don’t know how 3/8” is going to hold up but I figure it’s worth a shot. Worst case, it cracks when bolts at two extremes are tightened…and I don’t think that’s likely.
Plus reducing the mass of the bed can’t hurt :man_shrugging:

Also perma-coils are apparently very comparable to helicoils and much cheaper. Probably still go with the brass though :yum:

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Tyler, that is a great thought and thank you for putting it in my head. :slight_smile: For my theoretical granite surface plate-based lathe, I could tile a drilling guide using the Nomad (once it is back “home”), and use it to drill at least guide holes in the granite.

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The blue pearl slab arrived!
Photos do not do it justice. The mix of almost slate grey with flashes of silver and a gorgeous blue are just wild. Definitely one of the nicest looking types of granite I’ve ever seen.

IMG_7881
IMG_78813024×4032 2.71 MB

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IMG_78793024×4032 2.91 MB

I am still not sure on the method I’ll go with for threads but I’ve got a handful of single form threading endmills on the way. If I can get comfortable making m6 holes then I’ll likely go with brass slugs that are bored and milled once anchored.
This would give me much tighter clearances on my threads. Most of the inserts I’ve tried so far are just a little wiggly for my liking.

If I go this route I’ll also take the opportunity to design a top feature to facilitate flush plugs. Few things in life are more annoying than a bed of threads full of chips :angry: (and I’ll need them if I go with the tighter tolerances on the threads)

Hopefully I can start in on it this weekend :crossed_fingers:

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Single form threading tools and the nomad were made for each other. I’ve never made threads so perpendicular to the base :yum:

I used some super cheap ones from Amazon. I’ll write up a little post with the details once I get the fit of the threads juuuust right.

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