DoomChuck

[CedarSlayer]

Recently a discussion on changing grain orientation, viewtopic.php?f=9&t=5235&start=0, has a great deal of nice information. One of the things it showed was, Steffen's wonderful and yet frightening chuck for fine articulation of angle.



To give credit to where credit is due, apparently this was based on one by Bo, that was painted red, possibly to hide blood but more likely to reinforce the awareness of how deadly a design this can be.

Steffen requested that I share the results of my own work on this, so here is, DoomChuck, my version of this wonderful and deadly contraption.

Mine is probably all the more dangerous, because it is not as obviously dangerous. This is for use at low speeds and with great care. Due to projecting parts and potential for great imbalance.

I looked at as many images and videos of stummels being turned before finalizing my design. The DoomChuck has the convenience and limitation of being self centering, but combines the basic functionality and convenience of a stummel chuck and the bolt chuck.



Here is the chuck at it's widest open state. If I had made it a bit differently, the aluminum brackets could be reversed and add 4 inches to the possible chucking range. If I did this, I would probably need to use steel bolts instead of the plastic ones I am using. I have no plan to ever run a Doomchuck in the other configuration, as it would be at least as scary as the original, but it is a possibility.



This is mounted on one of the Penn State Industries Small Flat Jaw sets. http://www.pennstateind.com/store/CSC3000CTN.html



The bolts can reach the center if the jaw is closed to it's minimum gap.



Since I mangled down six plastic bolts, I can also use the full length ones or even use metal ones in case I need to.



The nuts are all up against the wood, and need to be secured back against the aluminum jaws before operation.



Since the whole thing can be spun around, reaching the nuts is not as hard a task as it could be.



By making this out of aluminum and plastic, I have managed to reduce the weight, expense and potential instability of the system without sacrificing strength or reasonable durability. If I need to use longer bolts to articulate the grip on an odd object or I need pointed ends to grip, I will have to use steel bolts. Plastic bolts will demonstrate instability if the length is too great.



Here it is with the nuts locking the bolts into position. Now it is ready to spin up, for the first time.



Here it is spinning away. Note that the lathe itself is reasonably well focused in this picture. This demonstrates that despite all the issues possible, in this case, the load is well balanced.

Later on, I will also make a gripper facing to line the jaws with for when I don't need the articulated screws. In this configuration it will be no more dangerous than a conventional stummel chuck. I will still call it 'DoomChuck!' because I never grew up, and think it sounds cool.

Bob

[smokindawg]

Quite the different setup........... But looks like it would work well and be very handy.

[CedarSlayer]

Well it is a simple enough solution, quite easily modified, and relatively inexpensive. All I need to do now is add the point pivot reference and normal jaw facing.

It is 2" deep, fine for most pipe work. Smaller projections are of course safer and more stable, but I can see where a 4" deep jaw might be handy. I will probably have to add a flange to reinforce this if I ever need to go that way.

Bob

[ToddJohnson]

Uuummm . . . is that 1/4" aluminum angle? If it is, I would suggest turning with a Kevlar vest and a full face-shield. It looks very nicely built, but I don't think I would trust its rigidity. Perhaps you could TIG a small aluminum triangle behind it to add some strength and keep it from bending, breaking, or turning loose of the stummel. Those would be my fears in no particular order.

TJ

[Sasquatch]

You can buy a stretchy collar, like a hair skrunchy, that fits over lathe chucks, and shows a rainbow as it's spinning - very nice safety feature.

I agree with Todd here - my experience with lathes and briar is that you gotta have the thing mounted ULTRA solid or it's gonna go across the room and break something. I would look at re-inforcing that puppy. It looks great though.

[caskwith]

That aluminium looks awfully thin and the plastic screws scare me!

Please just make sure you dont stand in line with it and wear a full face shield please.

[CedarSlayer]

The aluminum in use here, is Unanodized, Ultra-Corrosion-Resistant Architectural Aluminum (Alloy 6063) http://asm.matweb.com/search/SpecificMa ... m=MA6063T5 It is 3/16" thick 90 degree 2" x 2" angle.

I would not trust this structure in a production environment or at high speeds with a very unbalanced load, but it is well within spec for clamping a small block of wood. As you suspect, Sasquatch, It does need some reinforcement for rigidity however. Since rivets are much stronger than welds on aluminum and much more resistant to fatigue, I will use rivets for construction of the supporting structure. I will be making that modification fairly soon. I suspect that over time, without a brace, the angle would wear and catastrophic failure would result. So far, the DoomChuck is exceeding expectations. As with any new gizmo I make, and I habitually make new gizmos, it will be closely inspected each time I use it, and I am fairly religious about avoiding being in possible throw path of any massive spinning tool.

The nylon bolts are performing exceedingly well. http://www.mcmaster.com/#94320a648/=8x1zqg I expected that they would, since I have used them for jigging much more demanding applications than this. Truthfully any chuck with bolts in it puts a certain amount of fear into me. I am not entirely comfortable with rivets either, but having used rivets on aluminum quite a bit, I have learned that rivets, properly installed, are one of the lowest failure joining methods that you can come up with.



Here is the DoomChuck with the pivot point drilling guide and jaw facings. This is a much safer configuration of the DoomChuck but it still needs a brace for rigidity. I do not plan to turn on the lathe with the pivot point guide attached. I will use it to position blocks in the chuck, and then remove it before turning the lathe on.

The pivot point concept was borrowed from Seth Thile's wonderful if difficult to load web page, http://www.sethilepipes.com/index.php?o ... &Itemid=68

Seth apparently learned it from J. T. Cooke. In any case, as long as the tailstock on the lathe is well aligned, this will allow for easily lining up the draft hole and the chamber.

Bob

[CedarSlayer]

As an update, without the bolts, the soft jaw configuration needs the two sides being gripped to be quite parallel in order to grip well. So it works fine for turning some of the nicely flat mesquite I am using, but most of the briar chunks that I have will not grip securely as the two major sides are not very close to parallel with each other. Since I only plan to rarely use the DoomChuck with the bolts, this is going to require a remake.

Actually I am not that sad really, I like making tool, this still works for the odd shape as intended, and it was not expensive to make.

Bob

[SWM]

Bob!

This looks very good! Though there are some - well let's call them "thoughts" rather than "objections", that have been already been adressed in this thread:

The construction as a whole looks a bit on the "delicate" side to me (which would probably scare me more than the martial appearance of the original ). Since I have no experience with plastic bolts I will just believe what you said about stability etc.. Personally I would make this from 100% steel - I really like the design (and I love the name) and would not worry so much about the weight since it is for work at low speeds. Then I would go for a wide chucking range and long bolts to really use the advantage this gives in altering stummel orientation.

Don't hesitate to use the doom chuck with the bolts. I drill all my stummels this way (actually I don't have any other - though I tried a two jaw pipe chuck at Bertram Safferlings workshop). After you have some routine it is a quite fast and easy way to get the job done. And it works every time...

Once again: Real nice job!

Best,

Steffen

[FredS]

. . . this is going to require a remake.

This is not uncommon. It's not a bad thing either. Use what you learned on the first one. Apply that, plus what you found to be weakness' to the second one. Unless someone hands you a set of plans and instructions, you're bound to be unhappy with the first of anything you make. Live and learn.

[CedarSlayer]

After loosing faith in DoomChuck, I am now planning a complete overhaul. DoomChuck 2 the revenge of DoomChuck, will be much tougher.

DoomChuck basically works, but I would not trust it. It does not pass the rubber mallet test.

After seeing it's capabilities for all sorts of things, and the potential speed of work, I rather like the concept however. I have decided that making a production grade version will be worth making. I want to make a version that I would trust at speed.

Enco has a great deal on some high tensile strength cast iron angle irons with side webbing that looks like it might do for the basic framework. http://www.use-enco.com/CGI/INSRIT?PART ... A=418-4510 At under $10 for the pair, these may be ideal.

Cast Iron is common enough in chucks, but I don't have perfect faith in cast iron at velocity. I suppose I would have faith in vascomax, but cast iron is a lot more fun to machine, much cheaper and a lot easier to obtain.

In any case I will keep you posted.

Bob

[KurtHuhn]

Hmmm. The problem with cast iron is that it's very brittle. In thick cross sections it's fine for stationary jigs, but I wouldn't trust it in motion. I don't think I've ever seen cast iron chuck jaws or bodies. The potential for injury is so high. All of my chucks have steel jaws and bodies, and the only cast pieces on my tools seem to be the beds and main housings where sectional thickness is so great that failure is an exceedingly remote possibility.

Personally, to make a chuck like this, I'd look at steel angle or U-channel. A36 hot rolled won't be as rigid as cast iron, but it will be more than sufficient in decently large cross section for these purposes, and it won't shatter if treated wrong or fatigued at speed due to an imbalanced load. Speedymetals.com should have something in the right size for you.

[CedarSlayer]

Thanks, Kurt, I too have reservations about cast iron. It is fairly common however in a lot of chucks, adapters and face plates. Back plates are almost always made of cast iron. One if cast irons nice qualities is that it will dampen vibrations. It is not as resonate as a lot of other materials.

The thought however of cast iron fracturing and being thrown with a stummel across the room or worse does however make me nervous about it. I don't like the idea of DoomChuck 2 being in 3d. Things coming at my face from a lathe does not sound like a good idea. Aluminum at least tends to deform before it fractures. Cast iron does not give as much warning. A36 will probably do fine, do you think 1/4" will be heavy enough on a 2" x 3" angle to avoid needing a brace? I don't mind welding in a brace, but having it open would make it a lot easier to adjust.

Bob

[ToddJohnson]

I suppose I would have faith in vascomax

Me too. I can't remember if that's the one that keeps my blood pressure low or helps me pee though.

TJ

[CedarSlayer]

Massive doses of fresh garlic would probably help more with both of those issues.

Vascomax is the steel I would use if money was no object. It's expensive and it chews up ceramic grinding belts faster than ceramic grinding belts chew it up. Kind of like a high tech spring steel. Stainless and tough.

Bob

[KurtHuhn]

Thanks, Kurt, I too have reservations about cast iron. It is fairly common however in a lot of chucks, adapters and face plates. Back plates are almost always made of cast iron. One if cast irons nice qualities is that it will dampen vibrations. It is not as resonate as a lot of other materials.

You made go read about iron.

I did not know that there were different grades of "cast iron", including something called "semi-steel" which it turns out is just a marketing term (seen it when I buy chucks). I always thought there was cast (high carbon, brittle) and wrought (low carbon, ductile), and that was the end. It makes sense though. Steel is the same way - change the alloy and the properties of the material are completely different.

Now I know why my old anvils "ring" when struck, and that piece of crap I picked up at a garage sale "thumps" when struck.

[KurtHuhn]

Vascomax is the steel I would use if money was no object. It's expensive and it chews up ceramic grinding belts faster than ceramic grinding belts chew it up. Kind of like a high tech spring steel. Stainless and tough.

Jeez, really? The only time I've heard of anyone using Vascomax was for knives. What would the benefits of using it in a tool or jig instead of 1075 or 1050 (assuming you needed it hardened and spring tempered)?

[CedarSlayer]

I got to play with a little bit of vascomax. I made a spear plane and an oyster knife out of it. The stuff really impressed me. I am not impressed with the edge it holds, but if you are going to extremes, vascomax is definitely the far end. For an oyster knife, it is probably the best possible material. I just think it would be fun to have a stainless steel chuck.

As far as a lathe implement, it is considered a top end choice for high performance rotors, so it would be about as overkill as you could get. On the more reasonable side, I suppose 5160 would be my first choice. Durable and unlikely to work harden. I suspect that a chuck made out of that would still be overkill. I doubt my lathe will outlast any of the chucks I have.

I have an ASO myself. (anvil shaped object) I still use it, but I also have a railroad tie, and it is a much better anvil. The day I put a few decent faces on it and a nice square hole in it, I will probably stop using the HF 'anvil.'

From what I have read, Simi-steel is a pig iron with some scrap steel melted into it.
Bob

[KurtHuhn]

From what I have read, Simi-steel is a pig iron with some scrap steel melted into it.

That's what I read as well - basically diluting the carbon content by adding mild steel. It also seems to reduce the brittleness quite a bit.

[FredS]

I have an ASO myself. (anvil shaped object) I still use it, but I also have a railroad tie, and it is a much better anvil. The day I put a few decent faces on it and a nice square hole in it, I will probably stop using the HF 'anvil.'

Every metal shop should have a hunk of railroad track on a stump. There is no end to it's uses. My Dad made some little 4" long "anvils" from some narrow gauge track he picked up in the mountains 30 years ago. When I was a teenager, I re-arched the leaf springs for a '41 Willys (Jeep) with a sledge hammer and a RR track anvil.