Reamer reaming oversized

On Thu, 2 Apr 2009 04:10:47 -0500, paulwilliams wrote:


Drill 'em deeper, leave the ball in.
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sur> ely a precision ground shaft should be the exact size, ie., 5mm?
Depends on what tollerance they shaft has been ground to, this is signified by a lower case "h" followed by a number, Silver steel for example is usually ground to h6 this would give a location/clearance fit with your H7 reamer. For the fit you want then the shaft needs to be k6 or n6 which are light interfearance fits.
Jason
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Hi Paul,
please forgive my ignorance of probably accepted machining principles. my friend is the machinist, but I am looking for ideas etc that will lighten his load It seems I am trying to do a Similar thing to yourself but at lower Speeds 10,000 to 20,000 rpm with 10 cm diameter x 1.2cm discs initially made from nylon ( to check feasibility) then machined aluminium. I am still at the ideas phase. though will prob start work In next week or so.looking to push fit discs to a couple of old graupner turbo 820s with max rpm 24000.or poss use a prop adapter.
I am very interested in how your project turned out,
how you balanced your discs/was this necessary? (i assume so with 50k rpm) what's the diameter of your discs
I am especially interested in how you fixed the discs to the shaft/geometry of your discs/were they solid discs etc
you mention socket cap screws are these better than grub screws
or any experience that you have had with your project
this is what I am trying to build ( initially 2 Contra rotating discs)
http://www.youtube.com/watch?v=3Z1yjSqU67s

many thanks
AndyL
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Andy-lok Wrote: > Hi Paul,

> my friend

I followed the advice given in this thread: ream at low rpm, feed in the reamer and when it bottoms out, switch off the machine and then withdraw the reamer. This now gives perfectly acceptable results on most motors, except for those with shafts which are very undersized - many thanks everyone!
I also found that a new, sharp reamer seems to ream a smaller hole than an older, not-so-sharp reamer. You can order any size reamer you want, I found this very useful site:
http://www.sussextools.co.uk/show_product.php?pinf=1-100-1-1-3 -----
I'm turning small diameter couplings (< 12.7mm) at high rpm - your discs would need to be very well balanced. We balance small model propellers using a magnetic balancer, this is simply a length of 1/8" or 3/16" ground steel rod with precision ground points on each end suspended between two magnets. The heavy blade falls to the bottom and material is removed from this blade until each blade is as near as dammit equal in weight - crude, but effective. You could do something similar to balance your discs, or you might need to look at dynamic balancing, similar to how a car wheel and tyre is balanced.
Socket set screws are just grub screws that you tighten with a hex driver instead of a screwdriver - same thing, different driver.
Paul
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