reaming of square tube 2

[GTO67]

Hi All,

I need to ream / hone or grind about a mm from the inside of a 75 x 5 shs. All ideas appreciated

 

[Tmoose]

There is only one to modify?

I think the clearance to allow assembly may need to > 1 mm.
If the fabrication and assembly included welding, the outer tube is probably less straight than it was, and some grades are allow to be bowed more than a mm in a 3 foot length

http://www.prolamsausa.com/pdf/co_brochures/Mechanical_ASTM.pdf

In air or hydraulic cylnders To overcome bent components or distortion At some point sliding is best accomplished by a snug fitting piston of limited length at the end of the slider, and a snug fitting section at the start of the cylnder.

http://claymore.engineer.gvsu.edu/~jackh/books/plcs/html/plcs-93.gif

I think an iron butterfly with carbide wings, or wings made from sections of mill bastard files could be attached to a ramrod, and stroked several thousand times by the design engineer while he is watching TV at home, in a process similar to the one shown here.

http://www.ehow.com/video_5112994_clean-muzzleloader.html

 

[GregLocock]

I like that idea.

If the actual problem is that disassembly is unthinkable, then designing a custom process is the Holmesian solution.

Shapers have always been the bastard children of the machining world, but they have a time and a place. The advantage is that the way they control the dimensions is the same as the required function.






Cheers

Greg Locock


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

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[KENAT]

So reducing the wall thickness of the 75mm tube is OK, but reducing the wall thickness of the 65mm tube is not?

Tmoose idea sounds appealing given your situation.

You'll want a vacuum with a long hose too to make sure and suck the swarf out of the bottom.

Posting guidelines faq731-376

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

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[racookpe1978]

So this customer demands that the "new" sliding assembly (of 75 mm outside and 65 mm inside tube) must be equal to the previous assemblies?

Why?

Is there any practical reason for this demand? Concur with previous: remove the outside of the inside tube steel. (A shaper cannot maintain that good an accuracy down the inside of a 1300 mm tube.)

Acid etching an "equal" amount from all sides of the outer tube seems very risky - One section will always go deeper than the "average" - and to slide, "all sections" must become deeper than the minimum. So many parts will be too deep.

 

[unclesyd]

The largest shaper I've seen had a stroke of 12" so it would take a pretty elaborate extension setup to be able to machine the entire length of the tube.

If the tube was off and open ended there are several ways to enlarge the ID, like hydroform, expand on a draw bench, or machine on an old fashioned planner mill.

Sunnen has a square bore honing system, but the stroke is limited to 16".

I don't believe that acid etching to reduce the wall would work without a large circulation setup to mitigate some of the problems mentioned above. When I use to reduce car body thickness we had a vat with 2000 gals of acid and it was very tricky. We lost about 25% of the bodies we tried to thin down.

ECM would also take a very elaborate setup and one heck of power supply.

 

[mfgenggear]

Seems like the best bet would be to remove & replace the part.& eat the cost of re-assembly.

it's not pratical to rework/repair the square tube assembled.

I like the Idea of expanding too.

 

[CorBlimeyLimey]

Maybe some kind of Abrasive Blasting technique?

http://www.google.ca/#hl=en&safe=of...aqi=g10&aql=&oq=&gs_rfai=&fp=17446b09f625c317

 

[mfgenggear]

problem lies we no nothing about this assembly.
having foreign particles contaminate every thing is not good

thats why I recomended remove & replace.

 

[CorBlimeyLimey]

mfgenggear ... That, apparently, isn't an option;

The problem is that the tube in question has already been fabricated in place and the unit has been powder coated and fully assembled. The cost of dissassembling and reassembly far out weighs the cost of the basic structure so it needs to be repaired in place.

That's why alternatives are being suggested.

As you state, we know very little to nothing about this mechanism, so contamination may or may not be a problem. Either way, contamination could possibly be minimised (or totally mitigated) with judicious placement of coverings and deflectors.

 

[unclesyd]

Removing 1 mm of metal by blasting is chore. I don't believe that abrasive blasting is the way to go as it doesn't remove much metal per sweep.
I looked Abrasive Flow Machining (AFM) but it is too much metal to remove.
I also looked at electrolytic grinding and again the ammount of metal that needs to be removed precludes a simple setup.

I would like to ask the OP if the problem of removing metal from the inner tube is strength consideration or keep everything the same type problem. If it's a strength problem the inside tub could be reinforced. If it's the other there is a problem.

 

[mfgenggear]

LIMEY

sorry about that.
What I was trying to say like uncle said any type of machining or chemical would be not practical.
even if blasting was sucessfull it would distort the part.

to even get close it will probably need to be power sanded
and hope for the best.
1 mm material is a lot of material.

 

[ornerynorsk]

Sometimes you just have to bite the bullet and do what's needed. Maybe you replace the structure with a new one, chalk it up to education. Do what's right. Mistakes are not often remedied by putting another mistake on top of it.