Beware cheap chucking reamers

[mmagliaro]

Some unsolicited advice about buying "precision" tools for cheap on eBay.

I have a 1.5mm chucking reamer that I have used to "precisely" ream out holes to 1.5mm.  I got it for less than 10 bucks off eBay.  That is about 1/3 to 1/2 what a reamer from the US or Germany would cost.  With the experiences I've had buying drill bits and other similar tools, you'd think I'd know better.

It worked fine for things like gears and axle bearings, because those run at low RPMs.

But in the course of fooling around with upgrading Rivarossi motors (my ongoing project of late), I found that my replacement armatures were a little tight in the RR bearings, so I reamed the bearings.  The armature seemed to fit beautifully after that, but made vibrations and noises, and oil would only temporarily quiet them.  Measuring that reamer, I found it to actually be .061".

Well, 1.5mm is .0591 and that's rounded to 4 places.   .002" error is okay for slow-rotating things like idler gears or wheels.  But in a spinning motor at 5,000 to 15,000 RPM, no way.  So I'll be paying the piper and getting some good reamers that are sized to 4 digits, as in .0585", .0590", and so on.

After that, I just spun the armature in the mill and ran some 2000 grit sandpaper on the shaft to take just a hair off it.  That made it fit nicely and run really quiet.

My guess is that the reamer is actually a 1/16" that is relabeled and sold as 1.5mm because they figured, "close enough".  Well... it ain't close enough.  Ya get what ya pay for.

[wvgca]

don't know if it matters, but 1/16 is actually 0.0625, 0.061 is close, and closer than 0.059

[peteski]

don't know if it matters, but 1/16 is actually 0.0625, 0.061 is close, and closer than 0.059

Difference between 0.0610" and 0.0625" is 0.0015".
Difference between 0.0610" and 0.0590" is 0.0020".

So the reamer is closer in size to 1/16 than to 1.5mm by 0.0005".  Your statement is not very clear to me, but I think you stated that the reamer is closer in size to 1.5mm than to 1/16".

[mmagliaro]

To clarify, first, yes, I know 1/16 is .0625"

My "guess" is that, at .061", it is probably a cheaply-made reamer that they are selling as 1/16" and
ALSO selling as a 1.5mm.   It's .0015 off from 1/16, and .0019 off from 1.5mm, so I don't know which was their intended
actual size.  It is unacceptable for either one.

[wvgca]

It's .0015 off from 1/16, and .0019 off from 1.5mm, so I don't know which was their intended
actual size.  It is unacceptable for either one.

quite true .. especially for your application ..

[woodone]

So how are we checking these? Petty hard to measure.
I would think you would have to bore & ream a hole and use a go-no-go gauge?

[mmagliaro]

So how are we checking these? Petty hard to measure.
I would think you would have to bore & ream a hole and use a go-no-go gauge?

Fair point.  All I'm doing is measuring the reamer itself with a caliper that is only good to .001" anyway, not a great way to do it.  But the caliper measures the reamer at .061", measures a 1/16" drill bit at .062", and measures several 1.5mm drill rods at .059", so it's a safe conclusion that the caliper is pretty good and the reamer is horribly oversized for a "1.5mm reamer".

[woodone]

Better go out and get a good 0.0001 C-clamp.

[mmagliaro]

Better go out and get a good 0.0001 C-clamp.

I don't know what this means.   A micrometer?  I have one of those too.  Some sort of dial indicator?

[Maletrain]

When I have measured the bit or reamer and then the holes that they make, there is a difference.  Holes are bigger.  And, yes, I also us the same micrometer to measure the tools as well as the plug gauges that I use to measure the holes. So, the difference is real.  Not an issue when drilling a 1/4" hole for a bolt, but can be a big difference for tiny bearings that need to fit tiny axles with specific clearance specs.

[woodone]

Max- —-C clamp, slang term for a micrometer.  I have seen people not knowing what a mike was used for, clamp together two parts.
Has for making holes, a reamer may make the hole larger that the size indicated on the reamer.
A lot depends on the material, speed & feed rate of the reamer.
A reverse twist reamer will give the best results.
It pushes the removed material out ahead of the reamer. A normal reset will force the material back and the removed  material will act like a grinding material, making the hole larger.

[Ed Kapuscinski]

Chinesium strikes again!