Reamed hole not round?
Reamed hole not round?
(OP)
Hi All,
I have 17mm dowel with a H7/g6 fit. However the parts do not want to play ball, I can't even get the dowel started.
The manufacturing engineers of the supplier tell me the hole is drilled and reamed with a 17H7 reamer and checked with a bore gauge.
The dowel is ground to g6.
So any ideas whats happening? My suspicion is the hole is not correct, the dowel seems about right when checked with a mic. I don't have access to anything to check the bore really.
Is it possible the hole is out-of-round or thee is some other kind of form error? No geometric controls exist on the drawing other than the H7 size requirement.
Any pointers?
Thanks.
I have 17mm dowel with a H7/g6 fit. However the parts do not want to play ball, I can't even get the dowel started.
The manufacturing engineers of the supplier tell me the hole is drilled and reamed with a 17H7 reamer and checked with a bore gauge.
The dowel is ground to g6.
So any ideas whats happening? My suspicion is the hole is not correct, the dowel seems about right when checked with a mic. I don't have access to anything to check the bore really.
Is it possible the hole is out-of-round or thee is some other kind of form error? No geometric controls exist on the drawing other than the H7 size requirement.
Any pointers?
Thanks.





RE: Reamed hole not round?
RE: Reamed hole not round?
No lead in chamfer i'm afraid. No obvious defects that I can see.
I suppose I could ask them to check roundness of the hole?
RE: Reamed hole not round?
B.E.
You are judged not by what you know, but by what you can do.
RE: Reamed hole not round?
Look at Cerrosafe to duplicate the geometry of the hole. "Cerrosafe shrinks during the first 30 minutes of cooling and then at the end of an hour, is EXACTLY chamber size." http://www.brownells.com/gunsmith-tools-supplies/b...
Until you know what is wrong you won't know what to do to fix it.
RE: Reamed hole not round?
RE: Reamed hole not round?
Thanks for the replies.
Could be some thermal issues, but we'd be talking only small variations in room temps as far as I can see. I wouldn't expect that to be enough to significantly effects fits - happy to be told otherwise though.
RE: Reamed hole not round?
RE: Reamed hole not round?
RE: Reamed hole not round?
RE: Reamed hole not round?
Aidan McAllister
Metallurgical Engineer
RE: Reamed hole not round?
I did consider that but for a H7/g6 (clearance fit) I shouldn't have to go to such lengths!
I'll take another look at trying to offer the dowel up to the hole in a more accurate fashion.
Sorry I wasn't being clear with my terminology, there is a lead in chamfer on the dowel, nothing on the hole.