# Renzetti-esque 123 blocks



## PeterT (Feb 11, 2020)

If you haven't seen Robin Renzetti's 123 block design, I attached oxtool video below. Totally cool. These are what 123 blocks SHOULD be. The problem with the Asian 123 'botched blocks' is the holes are either a thread pilot hole diameter or fully threaded & in a non-alternating sequence. Which basically makes them very difficult to attach together. Yo cant put the appropriate threaded bolt through the pilot hole to engage the threaded hole. You can put an under-size  threaded rod through, but now you have nut & rod protrusions that may limit clamping or datum surfaces. So these blocks are inexpensive I guess, somewhat attractive, a bit lighter weight, the holes are great for trapping swarf & oil, but otherwise rather useless over a solid block. They are fully hardened so no fun to ream out. And they continue to make them!

I tried playing around with a idea I had. The sketches better show the intent. Basically a through hole dowel pin, a threaded dowel pin & 8-32 cap screw. They can be one hole width apart regardless of stack-up orientation. Well, that was CAD world where everything looks wonderful. In reality its a bit fiddly to position them in the block holes & aligning the fastener holes. A skewer stick kinda solved that. But the bigger issue is the clamping doesn't feel very positive. I suspect this related to pin tangents on hole tangents makes for little contact area and a bit of position sliding until they are cinched secure. Back to the drawing board. Dragons Den will have to wait.


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## PeterT (Feb 11, 2020)

oops forgot the hardware


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## PeterT (Feb 11, 2020)

I found this picture somewhere in my travels. Looks like they machined a threaded insert that has kind of a low profile flat head that mates the hole chamfer, therefore no protrusion. This might solve one of my problems. But I think I'd have to have 3 different stud lengths available to allow different stack-up orientations.

I don't even really have a need for any of this. I just want to make 123 Lego's dammit!


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## John Conroy (Feb 12, 2020)

Yeah I am frustrated with my import blocks too. It would be so eady to fix the design but it's pretty much impossible to repair them since they are so bloody hard. Looks like a ton of work to make a set like Tom did. I wonder if his are hardened. It would be a good use for some of the material in the 6.75 inch or 4 inch 4140 logs I have. If you want to have a go at the project let me know and I'll cut off some slabs for you.


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## Tom Kitta (Feb 12, 2020)

Once Chinese start copying something it feels one needs power of few Gods to make them change something. No amount of pleading makes them fix it. Import companies don't care - they want to get it cheaper. And so cycle continues.


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## PeterT (Feb 12, 2020)

That's an interesting idea John (re the 4140). 123's are always fully hardened  ground, probably for commercial reasons that make sense. Both Robin & Tom used A-tool steel, outsourced the harening & did the finish grinding themselves. But one sees accurate tooling even for mill setup made from cast iron which are hand scraped for accuracy. They would be less hard as native CI & maybe cast is more long term stable, I dunno. The holes might present a challenge for scraping & I have no tools or experience there yet. But I know some guys with surface grinders! I will have to noodle upon this. If the functionality was more important than guaranteed 0.001" in all dimensions, it would the effort to try.

I thought I read somewhere somebody successfully drilled through the holes. They were apparently not as hard in the core, big surprise there. But it was a spendy CBN inserted drill or something like that. I bought one DCMT (lathe tool) CBN insert from Ali for a decent price but saving it for a specific application & who knows how good it is. Stefan did a video where he reground a disposed insert & it was pretty amazing what that thing was cutting through. Hard turning they call it.

Then I think, if you can buy a pair of offshore blocks for $20, maybe there is a way to send China the CAD file doing the holes the right way, order 25 group buy & be done with it? I've said this before, someone should submit a patent application showing all the details & I bet they would show up on Ebay next Tuesday LOL.


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## Tom Kitta (Feb 12, 2020)

Imagine ordering 100 sets... on alibaba. Waiting for it.... then finally it ships... then you see identical set on Aliexpress... with faster shipping... you order 1 and get it before the originals come. 

Well power of copying is strong with the Chinese - they say imitation is the best compliment. 

On the other hand whole machining world would thank us for fixing 1-2-3 blocks. 

Making your own is a ton of work - even if without holes if you have to keep dimensions close to 1" 2" and 3" - easier if the pair only needs to be matched.


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## Dabbler (Feb 12, 2020)

Even the hardened ones can be drilled with quality carbide drills.  If you are doing more than a couple of sets, it is easier to anneal the blocks and rework them.  Re-hardening isn't really required in a hobby shop. If you anneal them, there is no loss in dimension, but they may be a little less straight, depending on the alloy.  It would be worth a try!

 They can be easily re-hardened, and then reground for a loss of around .003 per dimension.  Undersized 123 blocks anyone?


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