Floppy End For Acme Shaft

Chewy

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I need to put a floppy end on a 1/2-10 Acme shaft. Think of the pad on a C clamp. But, it needs to pull back under light pressure. I'm making a wood clamping device for the drill press. A fixed 3" x 4" x 5/8" aluminum block with 2 guide rods sticking out. A similar block slides along the guide rods to clap a piece of wood in between. When you loosen the clamp it pulls the block back away from the wood.
A store bought version uses a rounded bolt head that fits into a keyhole. They used a tee slot cutter on the slot and the bolt just slides up in the groove. They used plastic and it ain't worth a damn. I have already re-milled it twice. That is one option. The other is to use s depressed center washer and secure it to the shaft with a C clip. Then attach two strips too the block to sandwich the washer in. The third way is to run the shaft through the block and secure it with a C clip.
The reason for the slop/flop is to handle the square blocks not being so square. Clamping force is about "snug", un-clamping is what is needed to slide the block back on the guides. any other solutions come to mind?

When I do this on "real" work jigs, I sandwich a piece of metal between thrust washers. Then I am only limited to the shear force on an Acme rod or my welding. On this job I'm trying for the KISS principle. I'm leaning toward idea 3. The Acme rod is aound 3/8" when turned down for the handle or C clip. Comments anybody?

Thanks Charles
 
Somewhere around here I have a pair of old Wilton quick release bench clamps which feature a half-nut for quick release from the work. They may be similar (but probably not...) to your idea. I'll try to find the model number and post.
 
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Choiliefan, your post about the toggle clamps didn't show up on board. I think the end would fall off on the retract stroke. I have C clamps missing toggle pads here that have never retracted under load. Been playing with CAD and I think I will go with direct through the block. Make 2 press fit washers to fit turned down shaft. Put a clip in groove to retain. That means I have to make a cutting tool about .05 wide to cut groove. Could get interesting.
 
Without pictures it’s really hard to grok what you want. But my limited take is maybe it’s just out of the wrong plastic. UHMW or Delrin is some crazy stout stuff and it might be the original was like out of PET or something less durable. Maybe just remake the one piece of plastic instead of the whole clamp?
 
This a commercial $40 vise that in my opinion is worth $5. Next vise up is $55. It has metal jaws. Both have to be held with your hand or clamped to drill press table. There are vises from other vendors. I am making a base that bolts to the table and the vise will slide in it. It has runners on it that take a sliding plate. Picture a machinist vise that stays in Y axis but can slide about an inch in X axis.
Bonus! You can slide the vise right out and use the base for quick drilling of a piece of wood and than slide the vise right back in and start using it without setup. After 2 years of using it I have a list of improvements that I want to add in.
Here is a link to vise being replaced. It does work, but the wiggle/wobble will give you motion sickness.:rolleyes:


This link shows the jaw and screw setup similar to what I'm doing. The screw is hard fixed to the sliding jaw and I want give in it.


Buying everything new from Stock Car Steel and Ebay, I will have about $35 in it and my time. It will be able to handle larger pieces and quicker.
Think of the difference between a HF vise and a Kurt. Stopping my wife from b****ing about drilling,,,,,PRICELESS!! :)
 
Thanks for the links. That’s somewhat different than the picture in my head of a c-clamp pad. I’m not exactly clear why you need the wobble when the jaws are going to be on guide rods. Wouldn’t the guide rods defeat the wobbly?

I’ve reread your OP and i could maybe be off base but does the plastic moving jaw stick, and the bolt head and then pull out of the t slot? Maybe it just needs a full t nut to even the pressure on the soft plastic so it won’t pull out? Still sounds like the wrong plastic to me, but it sounds like your on to your own fix so onward and upward.
 
The plastic jaws are wore out from gripping the wood. There is not much thickness to recut the vee groove. Also at some point she overheated a piece of wood and actually melted some of the plastic which further reduced the grip. I didn't ask!! I want the wobble to handle the wood not being cut real square. She has had to sand some blanks by eye to get them to stand straighter for drilling. Think of fixed and movable jaws on a machinist vise. I will make the holes in the sliding jaw a little oversized for give. There is a limit to how out of square it will stand.

Her orignal request was to remake the plastic jaw out of metal. When I looked into it, I decided to make a whole new setup that would solve several problems. The bolt does not pull out of the Tee slot. It does pull the blocks back to open up. I don't think crimped on pads will stay there for long, so I am thinking about the shaft going through the hole and being retained by a washer and clip.

FYI. There is a brass tube that glues into the blank. You then turn between centers. You want the hole to be as round and straight as possible. The current vise has allowed the bit to wander and ruin some blanks. Not a problem with local wood. Look at the bucks for some exotics and you want to minimize mistakes. Also I should be able to clamp up to 3" square and drill centers in Salt & Pepper shakers.

Look at the bright side! A $150 dollar Craftsman lathe on Craigslist 2 years ago turned into:
A bigger band saw.
A planer.
A sharpening system.
A 12 X 20 Jet wood lathe.
A 20" bed extension for said lathe.
A 3/4HP 3ph motor and VFD for the Craftsman and now to be used with future end of bed turning.
A second smaller drill press just for her.
A custom made lathe & drill press bench lowered just for her.
A very happy wife!!!
 
If I could just figure out why SHE needs a surface grinder!!
 
Just the fact she melted the plastic or wore it out seems to me it’s totally the wrong plastic. UHMW or Delrin is hard to get it to melt under friction. Working with both has totally changed my opinion of so called plastics. Both are easy to machine and if you make them thicker so you can remachine them as needed. Both plastics are VERY robust. I’m sure if that’s what was on there originally you’d not be having this problem. You can get big chunks of either of eBay for cheap.
 
I actually have some in stock big enough to make the jaws. That is why I took it apart to get the measurements. Decided it was just to crappy a design to warrant me making a better replacement jaw.
 
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