paul
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Posts: 8
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Post by paul on Sept 26, 2008 18:44:20 GMT
While the lathe is bust....get out the old file! Not very exciting but at least it's an interesting shape that might be as difficult to machine as to make by hand (although probably quicker!). It's a yoke to control a spool type valve. I filed to shape then silver soldered in the bush. For some reason that eludes me my reamed holes are always a gnats doofer too big...I think I need drills nearer in size to the finished hole. (Taking it slow, one pass as recommended).  |
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Post by jgb7573 on Sept 29, 2008 8:34:08 GMT
Nice looking piece of work Paul. How big is that?
By the way, how are you deciding that the reamed hole is too big? I don't have a solution, but am curious.
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paul
Member
Posts: 8
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Post by paul on Sept 29, 2008 11:49:43 GMT
The holes are 4mm & 3mm... I'm sticking a piece of 4mm silver steel through & feeling a bit of wobble but maybe the bar isn't that accurately made?
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Post by jgb7573 on Sept 29, 2008 13:27:44 GMT
Silver steel is ground true, so it should be good. For diameters less than 25mm, the tolerance is +0, -0.015mm. So it CAN be slightly under nominal, but not much!
In a link like yours, I think I'd expect a bit of wobble, but not a lot. I shouldn't have thought you'd have a problem with it though.
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paul
Member
Posts: 8
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Post by paul on Sept 29, 2008 15:15:44 GMT
No, I don't think it'll be a problem John, it's just flipping annoying!
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Post by spurley on Sept 29, 2008 19:02:03 GMT
Do you have a micrometer, a set of 'number drills' and 'feel'? If so try the shanks of each drill in turn in the hole to see which is the best fit then have a quick measure to see what size hole you have. As an aside you could measure the SS with the mic to check it's accuracy too?
One possibility for this phenomena is 'run out' in whatever machinery you are using for the reaming operation. For example if the chuck in your drill press is runing a bit 'off' this could oversize holes. Otherwise, I think I read somewhere that machine reamers can cut slightly over size. Maybe have a careful measure with your mic on the subject reamers to see if they're the culprits!
Cheers
Brian
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paul
Member
Posts: 8
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Post by paul on Sept 30, 2008 7:42:42 GMT
Thanks Brian. I should have the full set of numbers drills by next week  I did the reaming on the lathe after turning but my lathe has thrown a wobbler or two in the tailstock alignment so maybe thats the trouble? |
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I did the reaming on the lathe after turning but my lathe has thrown a wobbler or two in the tailstock alignment so maybe thats the trouble?