pic: Ultimate chain tool project



I decided to design these on a whim. I think we might use them as a training exercise for learning how to use our new Tormach CNC.

Defining features:
Alignment features to hold the chain in place
Buckets to catch the removed chain pin
A slot to insert a chain pin so this tool can be used to build chain
Case hardened all-thread mandrels

Feedback and suggestions would be appreciated.

Some things to consider:
Deep pockets with fairly small area need a lot of consideration paid to chip clearing.
Chain breakers put a substantial load on the threads. If using 6061, you may want to think about designing it for a Helicoil.
To run this on your Tormach, you will be using fairly small dia. end mills. To keep your chip load proper, this part will take a lot of time to process.

This is a really good training exercize. It will teach you a lot about setting up and milling small parts.

True. Should be a good test for rout planing and coolant systems.

Chain breakers put a substantial load on the threads. If using 6061, you may want to think about designing it for a Helicoil.

We’ve got some 7075 we’re planning to use but if it’s too tough to machine, helicoil is a good suggestion.

To run this on your Tormach, you will be using fairly small dia. end mills. To keep your chip load proper, this part will take a lot of time to process.

Very true.

This is a really good training exercize. It will teach you a lot about setting up and milling small parts.

That’s good I hope they learn a lot.

7075 machines like a dream. Honestly I would say it machines much better than 6061, pity that it’s so expensive.

+1, on both comments.

I would consider the next step up for re-usable fasteners - a keyed insert. The brand name I know is Keensert. These are much more robust inserts, but do require some specialty tooling. I would see if a local machine shop would lend the tooling to you. This was our standard insert for aluminum vibration tooling to allow easy install of control accelerometers. We found that using tanged or tangless helicoils over and over again was a bad idea and once we switched to Keenserts the problem went away.

-matto-

A couple of points:

  1. Why not machine it out of 1018 steel? Tormach can handle steel.
  2. Why do you want to push the pin out? I made one for my team and it’s set to push the pin out enough so you can break the chain while leaving the pin in. Then you have a pin ready to push right back in. This is much more secure than any connecting link you would use.
  3. I used an injector pin for the part that is actually pushing against the chain pin. These are very hard and won’t mushroom out, plus you can get them sized to fit thru the pin hole.
  4. Make sure you have enough leverage available on the handle to actually move the pin. We used a shcs so we can put a long allen wrench in it or even use a drill with a hex bit.

Some additional comments I didn’t see written:

I’d recommend you use fine thread rather than coarse thread. The screw will be easier to turn.

Are you machining the all thread down to the point? If I understood your description, it’s case hardened, but that won’t help you if you machine away the case. For our custom #35 chain tool (and the replacement we used for the #25 that broke) we used a hardened dowel pin inserted into the end of the screw.

I think the concern isn’t with the difficulty of cutting the material, but with the strength of the threads tapped into the block. If these strip, a helicoil is the logical next step.

I’m excited to see the development of not only an improved 25 chain break, but a 35 chain equivalent. Do you think instead of milling square protrusions, you could just press roll pins into the block to constrain the chain? This makes manufacturing much easier for you, and it avoids causing overconstraint by limiting the points of contact with the chain.

  1. Because we have some 7075 to use, and who else can say they have a custom chain tool cut from aerospace grade aluminum? :wink:
    2.Because, as stated in the description, this tool can be used to build chain (put the pin back in) if the pin is removed.
  2. Thanks for the suggestion, I might look into that, but we have the all-thread and hardening compound on hand, so we’ll probably start with that.
  3. Good point. The handle is home made, so we could easily put a longer peace of rod in.

The threads chosen were the finest threads of the correct size that we have a tap for.

Yes, I plan to machine the all-thread down to form the mandrel, but the case hardening will take place after that.

Both machining the block and the thread strength are a concern.

I think using roll pins is a great idea, but we don’t have the size we would need on hand, so the first one will probably be cut as shown.

The Dark Soul chain tools are made out of 7075. I have never seen the threads wear or strip out. I have seen the pushing pins fail, the screws get lost, and the groove where it pushes the pin through wear and deform. The dark soul tool does use dowel pins for the pusher screw and roll pins for the chain indexing.

We had to replace a Dark Soul when a student somehow cross threaded it and then started wrenching down hard on it after it started to get stuck. We had a long conversation about when to ask for help.

We tried a variety of repairs, but ultimately had to buy a new one. If you can make your own new tool when something like this happens because you own a CNC, material may not be a concern. Dark Souls were on a 2 week back order at the time so we were in a bit of a panic.

-matto-

I believe they meant sizing the pocket such that you can only press the pin out enough to have a little bit left over. That way, you never push the pin out all the way and subsequently be unable to push it back in, which is the most common failure that people seem to have with these.
Also, for rebuilding, I know that the Dark Soul tool has a very wide mandrel for pushing the pins back in. Have you thought about incorporating that rather than relying on the same pin to reassemble?

I don’t know if you already got this or not, but this tool is hopefully designed such that it can press a pin back into place after it has been entirely removed.
Are you suggesting that it would be better to design for pushing a pin in that has only been partially removed? Maybe that would be easier.

Also, for rebuilding, I know that the Dark Soul tool has a very wide mandrel for pushing the pins back in. Have you thought about incorporating that rather than relying on the same pin to reassemble?

Yes, I have thought about this. Testing should show if it is helpful or not.

Yup, the DarkSoul tool is sized such that there is a pocket that generates a hard stop when the pin is hanging in just the outer link. This frees the chain to separate, and the pin stays stuck in the outer link.

It can be a little tricky otherwise to align the pin back into the hole for the outer link such that when you apply force it goes in, versus binding up slightly crooked. Leaving the pin in the link makes this a non-issue.

Understand how that process works. I have done it before (although not with a dark soul tool). I just thought that designing a tool that could reassemble a pin after it was entirely removed would be an improvement.

The idea of the current design is that it would have a channel for the old pin to be loaded into, such that the pin would automatically be aligned by the tool.

Are you saying that this design would not work as intended, or would not be an improvement? I guess I’m not sure why people think pressing the pin part way out is a better solution, when it requires a certain width of chain, and that the pin does not accidentally fall out.

It is a lot harder to get the pin started and properly aligned, without deforming the pin / hole / chain link, if it is fully removed from the chain. It doesn’t really require “a certain width of chain” any more than a size specific chain breaker already does (like these, which require 25 or 35 chain). The pin doesn’t fall out that easily but you do have to be a little careful.

Not saying this wouldn’t work, though. Maybe you can machine a matching block that slips into the pocket with the relief / hardstop set for the right distance to allow this? That way you have a tool that can do both partial and full removal.

Are you saying that this design would not work as intended, or would not be an improvement? I guess I’m not sure why people think pressing the pin part way out is a better solution, when it requires a certain width of chain, and that the pin does not accidentally fall out.

It was less a comment on your design and more a comment on my experience with the DarkSoul tool. The pin is a press fit in the outerlink, so if it is still fully in the outer link, it is not going to fall out very easily while you are handling it.

As it is a press fit, even under perfect alignment, it is having to generate some force before it slips back into the hole. That force can force things out of alignment if everything is not perfectly restrained. Perfect restraint can lead to some tolerance stack-up issues in an actual part/tool. It is my opinion that leaving the pin in the outer link is the simpler solution, but I’m also interested to see you try it your way and validate/invalidate our observations.

I did mean to do it that way (partially remove a pin so it stays attached to a plate) but…
Is the pin supposed to go where the mandrel is after it’s been fully pushed out in order to push it in? That makes this a lot easier. As in, push the pin up the hole the mandrel pokes out of, put the chain pieces to be attached on the guides, then press back in?

I’ve actually never been able to get the Dark Sould hardstop to act like one. I always have to get it most of the way, pull the chain out, try and tug the chain apart, and remove a pin a bit at a time to get it perfect. What #25 chain are you using / where are you getting it?

The hard stop is made of aluminum and the mandrel is made of steel, so the mandrel+thread is strong enough to punch a hole in the hardstop. At least, that’s the reason why many of our dark soul chain tools’ hardstops don’t work like they’re supposed to. If you’re careful with the new and shiny dark soul chain tools the hardstop should still work as intended.