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reaming of square tube
2

reaming of square tube

reaming of square tube

(OP)
Hi All,

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

RE: reaming of square tube

I don't know what 75 x 5 shs is, but if you want to take material off the inside of a closed object (especially one with straight walls), broaching would be a good suggestion.

RE: reaming of square tube

(OP)
Sorry I should have been more specific. 75 x 75 x 5 (mm) square steel tube approximately 1300mm long with one closed end

RE: reaming of square tube

To gain 1 mm in 75, assuming the material is steel, you could expand the end.

For which purpose, you could make up some sort of square wedge expander.

Or just fill the portion you want to expand with water, and freeze the assembly.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: reaming of square tube

(OP)
Thanks mike, however I need to remove approximately 1mm in total from the I.D to allow a 65 x 65 steel tube to slide inside the whole way.

RE: reaming of square tube

Fill it with acid.

RE: reaming of square tube

With the new information, I am inclined to agree with MintJulep.

RE: reaming of square tube

Can you not reduce the 65 x 65 tube?

Or as Mike first suggested, expand the end of the 75 x 75 tube, and then machine the outer surface back to size.

RE: reaming of square tube

Perhaps a robot to polish the inside?  

Heating the tube a section at a time?

Taking the 1 mm from the outside of the inner tube?

Patricia Lougheed

******

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RE: reaming of square tube

Buy telescoping tubing that is made to fit one inside the other.

It would be easier to make the outside of the male tube smaller than the inside of the female tube bigger.

RE: reaming of square tube

Oh! I just realised you want the whole 1300mm expanded ... and you have one end closed. That definitely complicates things.

So, 1st choice > reduce the 65 x 65 tube.

2nd > Fabricate a new tube using suitably sized plates or channels.

3rd > Cut the 75 x 75 tube in half (length wise), mill the insides to suit, weld the two halves together.

RE: reaming of square tube

2
So is this a one-off or production qty?  There is no practical way to expand or broach the ID of a closed end square tube.  Buy telescoping tube, as another poster suggested. Uni-Strut and others sell it.  If you are dealing with large qty, just have a mill make what you need.

RE: reaming of square tube

GT067

chem milling of the inside seems to be the best idea
there is vendors who specialize in this work.
do not try this your self since working with acid take special safety handling procedures & equipment.


next time it is possible to make the exact square tubing
by using sheet metal formed & welded, welds planished & draw formed (draw bar) to the exact size needed then the end cap welded by a tubing mfg.

MfgEngGear

RE: reaming of square tube

(OP)
Thanks so far for all the help. 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. Fabricating a smaller tube(63x63) to slide inside is the easiest way to go, however the customer needs the unit to conform to the exact standards as their existing units. I am extremely interested in the process of chemical milling so if anyone has any experience or advice in regards to the type of acid and time frame etc. it would really help.
Cheers

RE: reaming of square tube

Rotsa ruck!  Structural tube just isn't made for telescoping.  There are a few specialty manufacturers out there that do this.  If you need to do this on a production basis, find one.

RE: reaming of square tube

Chemical milling is probably unlikely to work on a closed-end pipe.  You need to have a constant chemical environment to get uniform milling.

Some sort of electrolytic approach might be possible, i.e., a 1.3-m long electrode that can do one side at a time with electrolyte flowing in the small gap between the electrode and the tube.  But that seems absurdly difficult to me; the cost of doing something like would be high.

I fail to see why you can mill the OD of the insert.  That would be a 10x easier task.

TTFN

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RE: reaming of square tube

EDM?

RE: reaming of square tube

I'll bet EDM could make a nice tube.  You probably would need to start with a thicker wall, though.

RE: reaming of square tube

You might do it with a sinker type EDM pumping the slurry out of the tube, but you are going to need a bunch of electrodes.
B.E.

RE: reaming of square tube

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

RE: reaming of square tube

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


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RE: reaming of square tube

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: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: reaming of square tube

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.         

RE: reaming of square tube

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.  

RE: reaming of square tube

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.

RE: reaming of square tube

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

thats why I recomended remove & replace.

RE: reaming of square tube

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

Quote (GTO67):

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.

RE: reaming of square tube

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.  

RE: reaming of square tube

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.

 

RE: reaming of square tube

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.

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