Making reamer, no. of flutes?

[oldred]

I am going to make another chamber reamer (made a couple in the past that did "ok" but could have been better), my question is on the number of flutes used. On the other two I used four flutes because it was simpler that way but I have been told that an odd number works better, supposedly cutting smoother with less chance of chatter since the cutting edges won't be at 180 deg. directly opposite each other, is this in fact an important consideration? I have the equipment to do this with and some proper size O-1 bar and a print of the reamer I want but I need to make a decision on the number of flutes to cut, the print has the outside dimensions only with no mention of flutes.

Any other tips/suggestions for making reamers would be very much appreciated!

[Outpost75]

Odd number of flutes less prone to chatter. In factory production where a sequence of tools will be used common practice is to use 3-flutes for the core drill, 4 flutes for the rougher, 5 flutes for the finisher.

[DougGuy]

I like 5 flutes for throaters.

[Hinnerk]

I am going to make another chamber reamer (made a couple in the past that did "ok" but could have been better), my question is on the number of flutes used. On the other two I used four flutes because it was simpler that way but I have been told that an odd number works better, supposedly cutting smoother with less chance of chatter since the cutting edges won't be at 180 deg. directly opposite each other, is this in fact an important consideration? I have the equipment to do this with and some proper size O-1 bar and a print of the reamer I want but I need to make a decision on the number of flutes to cut, the print has the outside dimensions only with no mention of flutes.

Any other tips/suggestions for making reamers would be very much appreciated!

According to my Machinery's Handbook, 19th edition, "When fluting reamers, it is necessary to break up the flutes; that is, to space the cutting edges unevenly around the reamer. The difference in spacing should be very slight and need not exceed two degrees one way or the other".

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[john.k]

Howes gunsmithing books have the most detailed instructions for making reamers I have ever seen.....and are quite common and cheap on ebay....but you probably have them....(J.V.Howe...The Modern Gunsmith.....Funk and Wagnalls.)

[uscra112]

The more the merrier, but keep it an odd number.

[Moleman-]

Usually go with 6 and figure I'm not so precise that they don't vary a little from flute to flute when done. I use O1, and harden after fluting while spinning the reamer slowly in a drill press with a 18" extension on it to keep heat away from the drill press. Heat to cherry, hold a minute or so and then lift a gallon of oil up and let it spin until cool enough to hold.

[Cap'n Morgan]

Whether the number of flutes are even or uneven is not as important as having the flutes slightly unevenly spaced. That is, a four fluted reamer should not be divided into 4 x 90 degrees, but rather four different angles to prevent chatter. Nowadays end mill flutes are not only unevenly divided, but also has different helical angles (spirals) to prevent chatter build-up.

[Idz]

I never had chatter problems with reamers I made with 4x90 degree edges. But I would clamp the barrel in my lathe headstock and use a live center in the tailstock holding the reamer to ensure concentricity and then ream by hand while adjusting the tailstock to provide pressure. I was amazed at how well the reamer worked when held rigidly. Frequent removal and chip cleanout is necessary also.

[John Taylor]

There's always the "D" reamer with one cutting edge. No chance of chatter but much slower to use. Very easy to make.

[elk hunter]

There's always the "D" reamer with one cutting edge. No chance of chatter but much slower to use. Very easy to make.

X 2.

I've made and used fluted and D reamers, both work well and the D type is much easier to make. If you're only doing a one off chamber why go with a fluted type.