Reamer Question

[Ed Barker]

I ran into an issue tonight which I thought I'd seek some guidance on. After drilling a nice normal looking 1/4" hole in my blade I proceeded to ream it out to 5/16" for my pivot w/ a new reamer I just purchased from Enco. However, I was surprised that my hole ended up looking rather rough and non-uniform. Needless to say, I was pretty displeased with the results of that ream job and wish I could have gone back and just used a 5/16" drill. So my question is......what in the world did I do wrong? I sort of speculated that it may have been one of the following:

(1) My 1/4" pilot may have been much too small for the the 5/16" reamer? Maybe I should have used a pilot of 9/32" or 7.5mm?

(2) My reamer may have not been totally straight and true.....and it was approx. 8" long and may have accentuated any un-trueness (the imported reamer was made in Bosnia)?

I haven't had any issues to date with drilling nice uniform holes w/ normal imported machine drill bits on my drill press. Any recommendations from you all would sure be appreciated. Also, do any of you all cut your long reamers down to make them shorter such that they provide more working room in your press?

Thanks,
Ed Barker

[Ed Caffrey]

I've never tried to ream a 1/4" hole to a 5/16", but my instincts tell me that MAY be some of the problem. One thing that I have experienced is that if your using a 4-flute reamer, they have a tendency to not always produce a true hole if you have to take out more than a few thousandths with them, or the material your reaming is semi-hard. The issue you mentioned about the reamer possibly not being straight might also be a contributing factor. Just for the sake of being rigid I try to purchase the shortest reamers I can that will do the job. Sorry I can't pinpoint the probelm, but what I've written should help you figure it out.

[Ed Barker]

I just read a post by Geno in response to DoubleArrows "What Size" question:

http://knifenetwork.com/forum/showpo...84&postcount=5

Looks like Geno nailed the issue I created.....pilot hole was way undersized for the reamer!!

I'd still be curious to see if anyone shortens those long reamers. I sure could use the extra work space as I can't use my vice under my press when I have a 7-8" reamer in the chuck. Could I cut these reamers down on the bandsaw even though they are heat-treated?

Thanks
Eddy

[tmickley]

They won't cut in the band saw but you can use a dremmel cut off wheel to shorten them up. I've had to do that to a couple of mine.

[Osprey Guy]

I have very limited experience with reamers...

But WOW!!!....8" long?!?!?

In the past year I've purchased about a dozen or so carbide reamers.
I've gotten most of them from either MSC or Enco. Offhand, I'd say my largest is probably 1/4"...and I'm sure it's no longer than maybe 2 1/2" in length....tops!

It never occurred to me reamers came in such long lengths as 7" or 8"...

I would imagine that at 8", even the slightest amount of runnout would create havoc with that hole! (I had some minimal runnout problems, until I replaced the cheap Chinese chuck which came with my drill press, with a good German-made, keyless chuck by Rohm...It's been great ever since!).


Dennis Greenbaum

Yeah Baby!

[Ray Rogers]

In the world of general purpose machinists reamers are made long like that so that they can reach deep holes and so that they will flex. For folder making flexing is not an asset. I buy only HSS reamers and use a cut off tool to make them much shorter. With the short, stiff reamers I avoid the flex problem and often use them to cut a flat bottom in a shallow hole (after a little re-grinding of the reamer's end). Also, I think you have the correct answer about your reaming problem now - that was far too much metal removal for a reamed hole......

[Jeff Higgins]

I cut down all of my long reamers with an abrasive cut-off saw. All you really need is enough to chuck it up with. Also, Ed B: A good rule of thumb for reaming-to-size is to allow .005-.010 material to remove. Any more than that and the reamer won't do a decent job. Think of them as a wood plane - too much material in one pass will result in a poor finish, where as light shavings and you won't have to sand much? I dunno... maybe a bad analogy...

Ray: I'm like you. I usually only use HSS reamers and drills. When they go bad, they get the boot, and I buy in package quantity for further savings. A good heavy-duty HSS bit in skilled hands is better than a premium carbide in unskilled hands, agreed?

[Ed Barker]

Thanks for all your valuable input guys. I feel more confident that my next attempt at this will be more successful. Now....off to the Enco website to get some add'l drill bits that are just undersized a bit from my reamers!

Ed Barker

[Kevin Wilkins]

Originally Posted by Osprey Guy

I have very limited experience with reamers...

SNIP
until I replaced the cheap Chinese chuck which came with my drill press, with a good German-made, keyless chuck by Rohm...It's been great ever since!).

That's the ticket Dennis! Buy only German made tooling!!!! And to ease the pain of how expensive it is, drink German beer!!!

[Don Robinson]

You should never try to remove more than 1/64" from a drilled hole with a reamer. They are designed to remove only a few thousandths. Notice that the bottom of most reamers is flat. Also, removing too much metal will make the reamed hole oversize. The flutes on reamers are much shallower than on a drill.

For the sizes knifemakers use, you need to get yourself a set of number (or wire size) drill bits and select one that is about .010" smaller than the reamer.

[PeterAtwood]

However, my understanding is if you are drilling too close to the desired size of the finished hole then a reamer may not give you a perfectly round hole after all. Can any of you machinist experts confirm that? In other words, you WANT to take off more than a few thousandths or the hole may not end up round. Sounds like Don's recipe is the ideal amount.

[RJ Martin]

Reaming, like most other machining operations, can either yield great or poor results, depending on how it's done. First, .010 would be a good, maximum amount to ream, so, drilling your initial hole 1/64 undersized is fine, assuming you're using good drills in a rigid machine, and clamping your work so it can't move. You need a good hole if you want a good ream.
Second, reamers likes RIGID tooling like a mill or high quality drill press, and, they like to be turned slowly. Also, countersinking the hole is very important, as is the application of a good cutting oil.

Yes, cut down that shank!!!!!

[Jeff Higgins]

Originally Posted by RJ Martin

Also, countersinking the hole is very important, as is the application of a good cutting oil. Yes, cut down that shank!!!!!

Good thoughts on the rigidity aspect of reamers, RJ. I forgot all about mentioning to countersink the hole though. Lately, I've been getting reamers that have a slight taper to them on the bottom. Granted, these are in the larger sizes like 1/2" and above. I do think it helps quite a bit.

Another tidbit: It won't hurt your reamer much to slice off the bottom half of the fluted section when you feel that part is pretty dull. It also helps to make the reamer more ridgid, and any burrs left by the abrasive wheel can be smoothed off with a slipstone. I've also just chucked the reamer up in a cordless drill and made a chamfer on the end using the belt grinder.