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Oh snap!

Draker

Well Known Member
Rest In Peace, my 0.311" reamer!

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That got my heart going when this thing loudly snapped in half. This unfortunate tool met its end while reaming the -7A gear mount holes for the main gear legs. Thanks to great luck, it did not damage the workpiece while breaking. I've learned here that when a tool breaks it's usually not a bad tool but bad technique. Anyone have any tips for properly and safely using these very large reamers? I would like to not repeat this one.
 
My 2 cents worth

Don?t push too hard, or you could bend the tool & then it?ll snap. Ensure you?re dead in line with the hole (or in this case it would?ve been holes?), bit of lube on the reamer. Apply even pressure, and let the reamer do the cutting
 
To emphasize a point in the first reply, I always get better results using cutting fluid and using minimal pressure. You usually can get a sense of when the tool may be binding - when this happens, back off a bit and check alignment.
 
They don't work for everybody. I broke 2 before taking the gear to have the tapers wire EDM'ed.

*Edit* Ignore the above please. I thought it was a taper reamer being discussed. Obviously not fully awake at the moment.
 
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Ryan,

You shouldn?t be removing too much material with the reamer. Just take it slow. I would use lower rpm too.

Ray
 
I don't know if this is right or wrong, or applicable or not, but IIRC a few folks a while back advocated for pulling the reamer through the hole, rather than pushing.

More experienced folks may want to weigh in here...
 
The gear legs are heat treated as are the bolt holes at the top of the gear legs and therefore almost as hard as a reamer or drill. I similarly broke a twist drill while enlarging the hole at the top of the gear leg. The suggestion of "pulling" the reamer through the hole will allow the reamer to be aligned with the hole better than "pushing". Cutting oil will help. Using a very slow speed will help.
 
"Pull" rather than push sounds interesting but how would that work when the tool will not yet pass through the holes? For example, prior to reaming, I believe the -7A gear weldments come from Vans drilled to 9/32".
 
When reaming a close tolerance hole a drill bushing should be used for all stages. Step reaming is also a good idea especially with hardened steel.
 
"Pull" rather than push sounds interesting but how would that work when the tool will not yet pass through the holes? For example, prior to reaming, I believe the -7A gear weldments come from Vans drilled to 9/32".

Reamer shanks are smaller than the flutes. Put it through backwards, connect to drill. One would have to inspect the reamer to be sure the flutes have appropriately sharpened/formed features on the shaft end. Some sort of bushing on the non-flute end would be necessary to get the initial alignment coaxial.
 
A couple things..

Welcome to reamer 101! At my day job, we run reamers well over 2" diameter all day long. Reamers are very brittle due to hardness,and will not handle even the slightest of side loading well. The only part of the reamer that "cuts" is the beveled edge on the front of the reamer, and typically, it will be custom ordered with a short pilot section that is cut down to the starting hole size.The flutes merely keep the reamer going straight through the hole. If you are using a "straight" (unpiloted) reamer that is .311, you will rely solely on a steady hand to keep it straight through the hole, and it should be run slowly with moderate pressure and well lubricated. "Pulling" a reamer can only be done with one made to do so, typically called a shell reamer that is slid over a boring bar and run with specialized device you wouldn't need for an RV project. When I run a reamer through an object, I will often pull it out using only hand rotation of the drill motor to remove it, thus preventing any additional material damage from the back edge of the flutes. Good luck!
 
Thanks for all the tips. It sounds like it would be always preferable to use a drill press to work the reamer when possible, rather than a hand drill, in order to prevent the possibility of side load and hand wobblyness. Live and learn.
 
The reamer should only be removing that last little bit to bring it to size. Don't try to remove 1/16" with it. 10 thou maybe? Alignment is also critical. Not easy to do.

In shop class back in university a guy was hauling on a 5/8" reamer in a huge radial drill. The flutes were packed full. It sounded like a 357 magnum when it went. Scared the **** out of 20 people in the shop.
 
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