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  • Use of reamers

    Can you please help a first time user of a reamer? I suspect that I should ream at quite a slow speed, correct? How much lub should I use, and what is best method to keep the reamer from damage, and to keep it sharp as long as possible? Please email me [email protected]. Best, Jack

  • #2
    What type of reamer are you talking, Jack? A straight reamer, or something tapered like a chamber reamer or taper pin or Morse reamer?
    I always ran me reamers too slow, until the last year or so. (I gunschmidt) I went up from around 80rpm to 140rpm, and I'm getting better results. The guys on the board will probably tell you to look it up, speeds and feeds etc. They are right, of course, but all I want is a fast answer! "Who's got time for a 4 minute baked potato? Slow microwaves..." to quote Homer Simpson...
    The reason I asked straight or tapered hole is the way they cut. Straight reamers cut on the leade, and that's all. Tapered will cut along their entire length. But now that I think about it, I don't know why I asked in the first place. In either case, it's important to back out and clear the swarf out of the flutes before it starts packing up. That will cause your hole to go off line and/or enlarge. When you clean the reamer, you have to get all the chips off it, making sure there are no strays on the cutting surface. Again, it could cause your hole to stray. I keep a couple brushes handy and a squirt bottle of lube to flush it off. And a pan to catch the drips. Gets pretty sloppy! So I make a half dozen passes, cleaning the reamer each time, advancing .050" tops, then stop and mop everything down. THis is chamber reaming without a roughing reamer, so you're taking quite a bit of metal out with just a reamer.
    If you're just taking a few thou' out with a straight reamer, you can go quite a long way before flutes need degunked. The key is to not let the flutes get packed solid with chips! Shoot, just read your post again. e-mail me directly he says! ooops too poor to pay attention I guess.

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    • #3
      First time user: Never turn the reamer backwards. Keep turning it in the cutting direction as you go in and out. This is to prevent damage to cutting edge.

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      • #4
        A few rules of thumb for reaming. Have to say it - speeds and feeds, but mostly speed. You figure the RPM's for your drill for the material. Ream speed is 1/2 to 2/3 the drill speed.

        Feed rate is about double as well.

        Here are some tricks when reaming.

        1. Pilot drill should leave 3% for a final ream operation. For example - Reaming .375 for finish, drill hole .011 undersize. Realizing there are no common letter, fractional drills to hit this, go next smaller, remembering drills have a tendency to cut oversize a bit.

        2. Countersink the top of the hole when possinle with a .015 break edge minimum above finish size (example - a .375 ream, .405 diameter countersink). Not necesarily needed, but starts the tool off better, and from my experience, helps finish through the entire hole, and helps lead the ream.

        3. Ream through, let the tool do the cutting. It will almost self determine feed rate.

        4. Use plenty of fluid start to finish - flood it, be liberal.

        5. Stop the ream rotation when you break through the bottom of the hole, or get to depth. Pull ream out when stopped. Prevents Oversizing and spirals in the hole.

        The three percent rule is another one from my tool box notes and formulas from old machinists, and I have seen this in only one book. There are some rule of thumb standards in many books, but the three percent works best in all situations.

        CCBW, MAH

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        • #5
          You could use also metric drills that may be closer - but I did not want to bring that up.

          If your hole has a slot you must use a spiral flute reamer - these are more money but are more useful than straight flutes. When you are done wipe it with a clean cloth and return it to its storage container (it prevents dings to the edge).

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