In article ,
"Dave Baker" wrote:

[...]

In short, the less stock you remove with a reamer the better IMO. Also the
slower the speed the better within limits. In rigid high speed production
setups it is often suggested to run at half the drilling speed but I always
find a much slower speed does the job best for the home machinist. Maybe 80
rpm for a 1/2" reamer and 150 for an 8mm one. Much less chance of chatter or
taper developing and less heat build up in the job.

Well, then. Mystery solved! To get down to specifics, I dug up my
notes. I needed to ream a hole .625", or 5/8. So, following the
instructor's instructions I wound up with a 19/32 drill, which the
project cabinet just so happened to have a plethora of in various stages
of devastation. IIRC, I wound up running the reamer around 700-800 RPM,
where the proper speed (according to the teacher) was closer to 600.
I'm guesstimating the "good speed" would have been more around a tenth
of that.
Attempt #2 (which I think I'll be doing next Monday) will get a much
gentler treatment.
What would you say about feed rate? When he demonstrated he pushed
the reamer through a 2 1/4" deep hole in about two seconds' time. I
assume a much slower RPM would mean an equally slower feed?

While I'm here, we had to lay out the part prior to machining it.
What, exactly, is the point of that? Is it really just so you can
double-check yourself and make sure you don't do anything stupid, or am
I missing something obvious? We didn't have to center-punch the part
before drilling, we simply used a center-drill first, so I don't see
much benefit to this. Then again, maybe we're supposed to do this just
for the sake of it because later class (which I'm not taking) will do it
"for real" and they're just giving up practice.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
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