How does one measure reamers?

mattthemuppet2 said:
using reamers isn't a trivial undertaking. Seems like it should be, but it's hard to get right than would appear. First up I would drill with a good sharp C drill with plenty of WD40 or kerosene. Then countersink hole, which will be handy for getting the pins started anyway. Then ream with your undersize reamer and plenty of cutting fluid at 1/4-1/3 of the speed you used to drill the hole. Try and do it in one go if you can but keep an ear out for the motor slowing, as that will indicate that the flutes are packing with chips. Having a set of homemade go-no go gauges, or a set of small hole gauges, would be handy here for checking size.
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Is a c drill a reference to a centre drill?
There are reams of information everywhere confirming the advantages of a correct angle spot drill to a centre drill. In fact; there is a global industry making spot drills precisely for this purpose.
Centre drills are for centres!!
For standard sizes - use a spot drill of the finished diameter to produce a precisely positioned counterbore as a spot for the drill and a precise guide for the reamer.
 
Easy there, letter C drill, 0.242". I've had a letter D drill (not a D bit!) cut oversize before, so I do one below to make sure I have material left for the reamer to cut.
 
Or...

Drill with C drill.

Take pins done to 1 thou larger and be done.

Sent from my SM-G781V using Tapatalk
 
tq60 said:
Or...

Drill with C drill.

Take pins done to 1 thou larger and be done.

Sent from my SM-G781V using Tapatalk
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If I can't find an on size reamer that's what I'll do.

Didn't want to make 10 more pins, but that's a good way out of this situation. I do have a APT 0.2500" reamer, so I could turn down 5/16" stock and get it done. Thanks for the ideas.
 
mmcmdl said:
If they are oversize by a few tenths , throw them in a lathe , spin them backwards and hit them with a stone , lap or hone . Easy to knock a tenth or two off .
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Really? This works?
Doesn’t ruin the reamer?
 
mmcmdl said:
Yes , it works .
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But as I said above, it leaves a flat on the relief side of the cutting edge, allowing the reamer to skate or polish the hole. this is bad. You have to then take a hone or T&C grinder and grind that flat off. In soft steels this is is less important, but to do anything with tool steel it is essential. In very soft stuff like brass the flat polishes the hole but doesn't ream it. This leads to inconsistent results and galling.

been there tried it. got \corrected by a very experienced tool and die maker. He had reamed tens of thousands of holes in his career, and it turned out he was right.
 
Dabbler said:
But as I said above, it leaves a flat on the relief side of the cutting edge, allowing the reamer to skate or polish the hole. this is bad. You have to then take a hone or T&C grinder and grind that flat off. In soft steels this is is less important, but to do anything with tool steel it is essential. In very soft stuff like brass the flat polishes the hole but doesn't ream it. This leads to inconsistent results and galling.

been there tried it. got \corrected by a very experienced tool and die maker. He had reamed tens of thousands of holes in his career, and it turned out he was right.
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Reamers do not cut on the flutes, there are no cutting edges apart from the 45 degree chamfer at the tip. The flutes are there to guide the reamer straight and to clear the chips. Are you referring to hand reamers?
 
OP. Got my money back on the over under (but really nominal) reamer set.

Ordered and finally received a used L&I 533.2485 reamer. It actually measures very close to 0.2485". (Within tenths) And guess what it reams a hole that is smaller than my 0.2495" pin. A 3 ton press, presses the pin I made in place, like I meant it. When I get some more reamers (some time soon I hope) maybe I can look into touching one up. In the meantime, I will be able to finish this super important honey do project - fixing our kitchen corner cabinet!
 
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