Enlarging A Reamed Hole

FREDROSSE

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When building a steam boiler, I had the tubesheets made, which use 1.250 diameter boiler tubes. The tubesheets came in with the reamed holes exactly 1.250, and I had trouble inserting the boiler tubes, the holes needed to be enlarged by a few thousandths. My only reamer was 1.250 also, so I put some 0.005 brass shim stock covering only about 1/2 the diameter of the reamer, and ran the reamer thru the 1.250 holes. Fortunately this worked very well, I was able to enlarge all 96 holes quickly, and then proceed with building the boiler.

Has anyone else made a reamer to cut a slightly larger hole with this method?

TubesheetStamping.JPG
 

ARKnack

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I would have thought that the shim stock would have been eaten up when reaming. Good solution.
 

brino

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My only reamer was 1.250 also, so I put some 0.005 brass shim stock covering only about 1/2 the diameter of the reamer, and ran the reamer thru the 1.250 holes.
Hey FREDROSSE,

Neat on-the-fly technique; I am glad it worked out for you.:encourage:

To be considered as a go-to technique, could you comment on two points:
What hole size did you end up with? (did it expand by 5 thou?, likely the reamer cut into the shims too...)
Did they remain round?
-brino
 

EmilioG

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Cool. Glad it works. May come in handy in a pinch.
What RPM? Drill press or mill or?
I imagine that the reamer pushed against the shim while cutting, so it must have been slow yes?
How was the shim placed? above the cutting end? below?
 

Ed ke6bnl

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do you need to put the tubes int he header and expand them to fit and seal, I have seen that in large boilers at work.
 
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f350ca

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I've done the same thing a few times, works like a charm.

Greg
 

Line_Bore

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I've used that trick on smaller holes if I didn't have access to (or time to make) a barrel lap. A cigarette rolling paper works well.

Sent from my LG-H345 using Tapatalk
 

Vintagengineer

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This is an old toolmakers trick, very well known in the UK. You can also grind a drill to cut oversize.
 

Toolmaker51

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Shimming a reamer is not unheard of. Brass and soft steel work best, and don't really show mark from reamer. The flutes of a reamer don't so much cut along the length, only the first small portion. Their action is more burnishing of tool marks. They taper away [less] from the tip.
Normally the shim is cut resembling a iso-triangle. The point, inserted between a pair of flutes holds it in place, the shape allows a gradual increase of diameter without collapsing shim or jamming in hole. Get results by steady feed rate, as the uncovered corner edges produce something like boring.
 
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