Ways to Clamp Shaft

[engrwpride]

I need a way to fix a 0.160" diameter shaft into a 1/8" x 1/2" x 1/2" hunk of aluminum. The shaft cannot be damaged with a set screw and I would rather not rely on the elastic deformation of the aluminum block with a slot for displacement of the aluminum material. The shaft needs to be easily removable and re-clamped. This is to hold a probe in a wind tunnel so the less intrusive the method of clamping is the better.

Do you all have any suggestions? I am at a loss for ideas.

Thank you!

 

[dvd]

http://www.mcmaster.com/#chucks/=fzccl0

 

[dvd]

http://www.mcmaster.com/#compression-fittings-for-carbon-steel-tubing/=fzcfol

http://www.mcmaster.com/#quick-disconnect-metal-compression-tube-fittings/=fzcgck

 

[engrwpride]

Possibly the worst thing about this is that the shaft diameter is 0.180 inches. Not a standard size being below the 1/4 inch threshold standard for shaft collars and stuff like that.

 

[GregLocock]

So what's wrong with a chuck? The reason you are getting little help is that it is such a banal problem that has already been solved a million times before, so unless you give us more constraints on the solution we just die of boredom.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[engrwpride]

A chuck would be too big. This needs to be the least intrusive on the airflow as possible. I am looking at 3/16" RC powerboat collets, where the threads for the collet nut would be threaded on a male end sticking out from the aluminum piece. The 0.18" shaft or rod goes through this middle piece. Dremel rotary tools use a 1/8 inch collet to hold the bit, and we use these collet nuts with the insert on our own threads for probes smaller in diameter.

 

[engrwpride]

The thin aluminum square piece will stand vertically upright with the shaft running through the middle. This shaft is actually a hollow sleeve that a cylindrical probe fits into. The aluminum rectangular part helps position the probe stem.

 

[engrwpride]

A bulkhead fitting would be perfect if it was easily and quickly removable, relatively tiny, and came in a 0.180 inch size.

 

[1gibson]

Can you access the end of the shaft? How about swaging?

 

[MiketheEngineer]

Could close the tolerances and use heat and cold to mate them.

 

[dvd]

The above statement about shaft collars makes it sound like they could be acceptable if found in the correct size range. Really not that difficult to fab your own shaft collars.

McMaster Carr sells a 5/32" dia shaft collar (

http://www.mcmaster.com/#shaft-collars/=fzlyx8)

which could be reamed and then chase the set screw threads with a tap. Use a nylon set screw (

http://www.mcmaster.com/#set-screws/=fzlzwx)

 

[engrwpride]

I appreciate all the feedback so far.

I thought about drilling a collar to the right bore diameter but then i run into the problem of how i would attach the collar to the square aluminum square piece. Welding is out of the question...maybe glue, but that is pretty tacky. Ideally, the aluminum square would have a hole for the collar to fit inside (with a set screw access hole) but it doesn't seem possible to press fit the collar.

I feel like there has got to be a better way, this seems like a common obstacle that i am not seeing a common solution to.

 

[dvd]

Sounds like you need to think about it and design something that works for your situation: it's either more difficult than you convey, or you're overthinking it.

 

[1gibson]

So, what was wrong with swaging? Design a close clearance fit between shaft and aluminum block, drill a hole in the middle of the shaft, and insert an interference fit tapered pin into the end of the shaft. This creates a (temporary) interference fit between shaft and block as the shaft expands from the pin being inserted. Remove pin to remove block. No permanent damage to shaft.

 

[dhengr]

One “better way” might be to describe your problem and what you are really trying to do in much better verbiage, and then include a couple sketches with loads, supports, piece sizes and dimensions, interconnections, etc. Remember, you can see it, we can’t from this distance; you’re working with it, but we have no idea how things fit together or what you are really trying to do or what the real constraints are. Your description leaves everyone guessing and you’re wonder why you aren’t getting any good ideas. There are plenty of smart people here, more than welling to help and give of their time, but not wanting to waste their time either. If you can’t describe your problem how can you expect any meaningful answers. Look at your OP and later posts; would you understand the problem from the terminology and info. given if you were not already involved in the development of the apparatus?

 

[MintJulep]

How about just a set screw with a Nylon tip?

 

[btrueblood]

Wind tunnel? I'd think it a good place for the application of cyanoacrylate or epoxy adhesives. Light, small, removable.

 

[dhengr]

The .125" x .5" x .5" aluminum pieces shouldn’t be a killer cost wise, nor should the .160" or .180" o.d. or i.d. tube. This really seems to be in a state of flux, or typo growth, but poorly described in any case, until late in the discussion. I’m assuming the probe goes inside the tube and is finally positioned length wise, and is the expensive part, again late to the discussion. Why don’t you just make parts for ten of these support devices; and then assuming the tube’s exact location, x and y, (I guess this would be longitudinally in the wind tunnel or vertically w.r.t. test item), on the .5 x .5 plate surface changes from run to run, but you say it’s in the middle (of what, middle of .125" or .5"?), drill accordingly; the length of extension just means a slightly longer or shorter tube. Then just epoxy your tube into the hole in the aluminum plate. Are you trying to position the probe tip at various distances from the test item, in the boundary layer? Won’t the probe cantilevered from your tube make one or two of those position steps? For the next step back just cut/grind .1" off your tube length, and repeat.

 

[GregLocock]

Loctite is often a good solution.

If you are wedded to a mechanical solution then you have plenty of space for a custom designed collet.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[hydtools]

Maybe something like the spilt flange mounting for a pitot tube pictured in this link:

http://www.alaron.ca/pdf/Dwyer 160 pitot.pdf

Ted