Machinist Clamp - DIY

The way I am doing it now.

And with the screws installed prior to surfacing.

Temporarily replace the screws with shorter ones?

You can make thumb screws from common pan heads by running a brass knurled nut or several hex nuts up against the head.

The fancier knobs I make for the sheet metal screws on my chimney that I remove to clean it are knurled 1/2" aluminum rod, counterbored for the head and covered with red heatshrink so I can find them if dropped in the snow.

--jsw

Actually that's one of the plans for the new clamps. Set them up using a common size screw like 1/4-28 so I can easily change screws for the appication. I have no issue with keeping a hex key handy for snugging them up. I buy 1/8, 5/32, and 3/16 short arm hex keys by the box so I can include them as needed with custom molds. At any given time there are a half dozen of them on the assembly bench.

The machinist clamps I have might work (well one would, the other is not long enough) for this particular mold, but they won't work for others that need a longer reach or that might have multiple slide bars. One of the things I wanted to do also was make the upper jaw with a half cylinder on the bottom of the top jaw so force could be more easily localized directly on the brass slide bar.

A basic clamp sketch.

At first glance, it would seem that a vise with soft jaws would be a better way to combine the slot and clamping (for sure, it gets rid of the upward protrusions). Before using loose bits and long clamps, could you just put some threaded inserts into the slotted Al plate, and use holddown clamps? A screw and a bit of U-section up close to the slot is easier on the holddown arm than the longnose clamp proposed.

Huh? Why or how would a soft jaw vise make any difference? Do you propose crushing the work piece? That would be counter productive, because then the brass bar would have to be driven out with a hammer, the slot recut, and the brass bar recut. Doesn't make any sense to me. Or are you proposing some form of clamp outside of the main work piece to hold the end of the brass bar. This isn't a good idea either as it does not hold the brass bar down into the slot where it needs to, and it could possibley cause (or allow) it to bow up and get overcut creating a destroyed workpiece. Also, if you didn't notice the main workpiece is in a high hold in the vise. It needs to be in that high hold in order to do everything in "one" setup on the machine

Not sure what protusion you are talking about. The handle for the slide bar can't easily or effectively be added on later. It has to be there. The curved corner edges of the brass bar need to stick out above the surface so it can be machined flat with the rest of the surface. Big voids from the curved edges would allow all the media to leak out of the mold cavity.

I really don't want to drive a screw into the surface of the mold for the U-section. Neither in the front where it may create hard spots for detail maching or in the back where I would have to machine it off or the customer will complain about the aesthetics. Now I am sure I could put stuff under the screw you propose and monkey around to prevent damage, but that's exactly the sort of extra work and time wasted I am trying to avoid. What I am doing now is working just fine already. I want to make clamps so I can do this sort of setup faster.

This is a one off work piece, but I routinely do work pieces of this type. Each one is different in the specifics. The brass slide bar may be at varying distances from the end of the main work piece and sometimes there are more than one of them. A long clamp will work because while the part is machined to be able to move in the slot it is a very close fit. There is friction. The long nose clamps have the advantage of working on multiple different setups easily and quickly, and they will not damage the work piece. It doesn't take a ton of force to hold it in place until the retaining screws are machined in. The retaining screws are just 10/32 in aluminum with a shim. They are also adequate to hold against all the rest of the machining forces to complete the part. I am sure the long nose clamps will generate as much holding force as that piece of half inch aluminum square bar under c-clamps at each end.

I just wanted to know if 1018 would be strong enough for my clamp (which will other wise work) or if I needed to go with a stronger or hardenable alloy. Do you know?

All the rest was background. I included the background because certain people in this group won't answer the question you ask without background.

So without further adieu... is 1018 strong enough to last for this application or should I chose a stronger alloy?

If the work piece is the brass, I was proposing a soft-jaw vise that put half the channel onto the fixed jaw, and half onto the moving jaw. It wouldn't cut the plate at the same time (is the plate also a workpiece?).

The long-jaw clamps might work with 1018 or not, but they aren't a great idea because the tightening screws, with such a mechanical disadvantage, have to take extra tension (and compression); friction in the tightening screws becomes a problem. I'm fond of buttress threads, which would help with that, but I don't know of any off-the-shelf support for making them.

I would try using cyanoacrylate glue to glue the brass bar into place. Then after milling heat to decompose the glue. Don't breathe the fumes though. Cyanoacrylate glues are great for this type of work. I sometimes glue parts to a faceplate in the lathe too. Your job looks, from the pictures, like it would work well being glued. Eric

If you haven't already looked you may wish to poke around StrongHand Tools website. I was thinking especially of their Adjustable Reach & Long Reach Multi-Purpose Pliers:

If nothing else looking around may give you some more ideas for making your own. They carry a lot of interesting and unique products...

They do have some cool tools. Thanks for the link. I see one I want. The three axis clamp for welding up machine bases would be really handy. If their locking pliers are decent quality they may be a substitute for Vise-Grip since IMO the VG quality isn't as good since they out sourced.

Its all one work piece that must be machined together. Even two of the three clamping screws are used as retaining screws once it is finished.

I could make a turning tool and/or a thread milling tool to cut them, but thats a bit of overkill.

I thought about glue, but I still need to mill the screw holes and slots first. Onece the screws are installed its not needed. The screws do the job. The screws are a part of the finished work assembly. They are milled in, the screws installed and the slide bar pushed up against the screws before doing the next step. The brass bar slides in the mold when finished and motion is arrested against the screws. If it was glued in the bar would be off slightly when pushed up against the screw heads later.

I never thought of CA glue for holding parts. I use Epoxy all the time. 5 minute with an hour of cure time under pressure usually works pretty good on aluminum. If cured for 24 hr sometimes its hard to peel off. I'll have to try the CA glue sometime.

Picked up on them from Jody, youtube welding videos. No experience with them but I haven't heard anyone badmouth the stuff...

Note the quick spinner for the adjustment on the locking wrenches. I haven't noticed that elsewhere.

They do. The fly in the ointment is that they sell through distributors (around here - welding suppliers) and those guys are very unlikely to have the full product line. PITA

I live by the second largest city in Michigan. I could probably find someone around town that has them but not at a price I would be willing to pay. For stuff like that I look on Amazon, eBay (buy it now)... you get the idea :)

Sometimes Home Depot can get stuff like that and will deliver to your local store for free. I think anything over $45 can even be shipped for free to your house. I've done that before on a couple odd items. Their pricing was very competitive at the time.

No good though if you want to handle or look it over first...

There was a fellow on Ebay selling an extended length replacement screw for locking VG brand clamping pliers a while back. I think his gimick was you could crank them down on stuff even if you couldn't get your hands in there. I don't remember exactly. Its been a while. It would have made a decent quick spinner too.