Machining/Mechanical question...

Will Carter

Will Carter

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Joined
Mar 23, 2005
Location
Burlington
Machining/Mechanical question...
I'll try and explain it without a picture...cause right now I've got no software to draw a picture on...no not even Micro-paint...

We've got a 1.5" round hole in a piece of 2" thick steel. We really need this hole to be .75" to insert the same size bolt and be able to connect another part with some hefty torque...say 175lb-ft .

So we need a 'reducer' of sorts. However, welding in a 'reducer bung' is not an option. Can't weld to the 2" piece cause we're gonna need to be able to swap back and forth from the 1.5" hole to the .75" 'adapter'.

The .75" bore in our bung also needs to be centered in the 1.5" original hole.

I'm thinking I'll start with a piece of 2" round, leave a .375" lip and turn the remaining length down to 1.498" to fit inside my hole. Drill in a .75" hole and we have a centered bung. Now just make one for the other side and we're set....but here's my question...(that took long enough, right?)

Do I need to make these two adapters touch in the middle or can I just make them a shorter size with a gap in between when they're torqued (remember, 175ftlb)?

If they need to touch in the middle, how much distance should I leave to make that 175lbft transfer from clamping the two adapters together to actually holding the adapters onto the original piece of 2" plate? I'm thinking this is going to be a .003"-ish number, right?

The 'part' is actually a suspension flex joint that will be mounted to this 2" plate in single shear...so it will see those sort of forces if you can imagine...

I hope that was clear enough...
 
I'd love to help but you lost me at "helo," hey just kidding. Anybody can figure this out and provide a picture I'd like to see what he's trying to discribe. Seems like something I'd try and make complicated like a football bat at a soccer game. Seriously somebody draw this so I can figure this out.:beer:
 
I drew (past tence of draw?) a picture and snapped a pic of it with my phone but it's taking forever to get to the email account...in a bit...
 
while your waiting I think "I have drawn" might work Drew is my name he-he!:bounce2: I want to see this picture, it's got me curious!
 
OK, I think I see what you're trying to do, I don't think you want the 2 adapters to touch in the middle at all, leave 1" or whatever. If I understand it correctly, the lip is just a big "washer", the 1.498" bore locates the adapter in the 2" thick piece. The clamp load is going thru the shoulder of the lip into to 2" thick piece, you're critcal section is the height lip, so leave some beef there.

That's if I'm reading it correctly :huggy:
 
I'm guessing this "jig thing-a-ma-bob" is going to be used to mock up the location of multiple link mounts......If so the space your refering to is for weld distortion.....a little tolerence for removing the said welded pieces maybe......or the "dummy mock up spacer"......................I don't understand the large torque # for something your going to remove a few times.
 
Im thinking the "flex joint" will mount between 2 of these 2" plates, almost like shackles?
 
RenegadeT said:
OK, I think I see what you're trying to do, I don't think you want the 2 adapters to touch in the middle at all, leave 1" or whatever. If I understand it correctly, the lip is just a big "washer", the 1.498" bore locates the adapter in the 2" thick piece. The clamp load is going thru the shoulder of the lip into to 2" thick piece, you're critcal section is the height lip, so leave some beef there.
That's if I'm reading it correctly :huggy:
Click to expand...

I pretty well read it this way, too, and agree with RenegadeT. Leave a gap, you are just making self-centering washers. Like he said, beef on the "washer" (exterior) portion is what you need...maybe start with something bigger dia. than 2" (that only leaves you 1/4" of contact around the 1.5" hole).
 
heres a quick pic of what i think hes talkin about
pic.JPG

X3 on what said above.... also if you could camfer the 1.5" hole a lil and radius the shoulder the same on the backside, it would help with stress concentration....
 
If you dont let the 2 parts touch then that shoulder on the spacer needs to be as large as possible. The thickness of the shoulder on the spacer should be as thick as possible as well. All of the torque from the bolt will be transferred to the shoulder if the 2 spacers do not touch.

IMO, I'd leave a small gap, maybe .010" between the parts. During hot/cold days, the material will swell and shrink enough to bridge this gap along with the torque of the bolt. The torque of the bolt will apply force to the spacer and then the spacer to the 2" block and nothing will move.

If you let the 2 spacers touch, regardless of how much you torque the .75" bolt the spacers will spin inside the 2" block (assuming the tolerances allow it). I'm not sure what you are using it for, but this should be considered before you decide on a design
 
as long as the 'top/head' of the spacer has full coverage (4) I would think you would be fine with a gap in the 2 halves If not you will easily bend the top off. (with that much clamping force)

brb with my mad paintshop skillz...


thing1.jpg
 
If you want the 2" piece to be part of the "flex" and move or rotate....let it touch.
But, If you want this piece stationary leave a gap big enuff that 175 lbs. of torque won't bring them together. ( which really isn't likely consider the 2" piece ain't gonna squish much!)


Matt
 
What's the single shear part of all this and why does it need to be assembled and taken apart? Unless you just like the idea of a bushing; maybe for a grease fitting), why not just drill a 3/4 hole to start with? Still confused. All of the responses make sense from each point of view. I don't see the big picture yet. Are the spacers a way of using some stock laying around with the wrong size hole in it?
 
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