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Which Reamers To Buy?
- Thread starter Old Iron
- Start date
- Joined
- Jan 22, 2011
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- 8,031
99% of mine are LH spiral, RH cut chucking reamers, carbide tipped if the job justifies it.
- Joined
- Jan 22, 2011
- Messages
- 8,031
Straight fluted reamers can also give a polygonal shape to the hole. That's my primary reason for using them. LH spiral RH cut I get the best finish and chip control with.
I have a set of straight flute reamers because those are the only ones I've ever seen "on sale".
If you need to ream a cross hole I think the spiral flutes have the advantage there. Much less chance of snagging the edge of the cut-out and chattering. Or so I've read...
Oh yeah -- chucking only for machine use.
- Joined
- Jan 22, 2011
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I'll admit that the LH spiral RH cut are not as common, but I use them frequently for straight holes. Some of the best are made by the company Paddy referred to. Lavalee & Ide.
Here is one source:
http://www.discount-tools.com/lav-535l.cfm for standard sizes
http://www.discount-tools.com/lav-575l.cfm for dp sizes
I've generally had little trouble finding them as needed. But then, I have a local supplier who does much of the hunting for me. That helps. I don't do so well with adjustables. I have a couple, but they are straight flute, not my favorite. Bridge reamers are not what you want, unless you are fitting iron work in construction.
Here is one source:
http://www.discount-tools.com/lav-535l.cfm for standard sizes
http://www.discount-tools.com/lav-575l.cfm for dp sizes
I've generally had little trouble finding them as needed. But then, I have a local supplier who does much of the hunting for me. That helps. I don't do so well with adjustables. I have a couple, but they are straight flute, not my favorite. Bridge reamers are not what you want, unless you are fitting iron work in construction.
- Joined
- Jan 22, 2011
- Messages
- 8,031
Just thought of an old trick when Paddy mentioned Murphy's Corollary #7 about reamer cut size. It does seem like they won't cut the size you want especially at first. It should go without saying that fresh edges are not always reliable.
But anyway, if you get a reamer that seems to be getting dull, or just won't cut nominal size anymore, take a carbide insert and drag it along the inside of the edge of the flute, several times. Essentially, this just raises a small burr on the edge, but you can temporarily "upsize" the reamer for a few holes. Of course, the softer the material being worked, the longer it will last.
Making one cut a little smaller is easy, just spin it backwards against a stone, a little at a time.
But anyway, if you get a reamer that seems to be getting dull, or just won't cut nominal size anymore, take a carbide insert and drag it along the inside of the edge of the flute, several times. Essentially, this just raises a small burr on the edge, but you can temporarily "upsize" the reamer for a few holes. Of course, the softer the material being worked, the longer it will last.
Making one cut a little smaller is easy, just spin it backwards against a stone, a little at a time.
- Joined
- Jan 22, 2011
- Messages
- 8,031
One unconventional method of precision hole sizing is to ream within 0.001/0.002 under, and press or drive a precision ball bearing thru the hole. It has the advantage of compressing the material a bit as it passes thru, making it harder, and gives a very good finish (better contact for fit) if a bit of lube is used. A press is handy for this. This method used at times in sizing automotive valve guides. Just be wary on hard materials that thin parts are made of. Adjust undersize accordingly.
Thru holes only, of course.
Thru holes only, of course.
I've heard the trick about using the carbide bit before. But I have also always read that running a reamer backwards destroys it?
So what is up with that?
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- Jan 22, 2011
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Well, I can't say it is good for the reamer, because it obviously destroys some of the back relief, but I mentioned it as a desperate measure to get a reamer to cut smaller. In the case of a brand new reamer, sometimes a less than perfect grind can leave microscopic burrs on the edges, and a light hone can remove them and help get it on size. When I said stone it by spinning it in reverse, I meant very lightly, and not for long. It doesn't take much to reduce the size a few microns and lessen the tendency to over-cut. Also, sharp(new) reamers can tend to take a bit of twist, especially spiral reamers, and especially if too much material is left in the drilled hole. This "unwinding" can make them swell, so to speak, and cut larger than they measure. Drills and taps do the same thing, but is not usually as critical and is seldom noticed, or a problem.
On another tip, don't expect the reamer to cut dead on in a drilled hole in general, especially in the first few holes, or dead on location. Best to single point with a boring head, leave a consistent amount of material for each hole to be reamed. Generously apply cutting fluid.
I have fought with reamers on a 0.0003 total tolerance hole in Ampco 45 for hundreds of parts......learned a lot. Lots of press fits for dowels in die sets....I generally love reamers, for what they are good at.
On another tip, don't expect the reamer to cut dead on in a drilled hole in general, especially in the first few holes, or dead on location. Best to single point with a boring head, leave a consistent amount of material for each hole to be reamed. Generously apply cutting fluid.
I have fought with reamers on a 0.0003 total tolerance hole in Ampco 45 for hundreds of parts......learned a lot. Lots of press fits for dowels in die sets....I generally love reamers, for what they are good at.