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View Poll Results: My preference in a tapered reamer
Straight 1 50.00%
Fluted (spiral) 1 50.00%
Voters: 2. You may not vote on this poll

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  #1  
Old 09-06-2017, 10:28 AM
Sperry Sperry is offline
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Default Tapered Reamers: straight or fluted?

I've just ordered my first reamer, a 1:30 taper for violin pegs with straight cutting edges. A 1:20 taper I may want is out of stock straight but stock fluted. (Are all reamers tapered?)

Internet suggests fluted give cleaner cuts and are wanted if the hole is bushed.

Would a 1mm taper for 20mm length (1:20 taper) be the same as a 5˚ bridge pin hole reamer?

Comments wanted on reamers you use, please.
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  #2  
Old 09-06-2017, 11:53 AM
charles Tauber charles Tauber is offline
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A straight reamer has, by definition, no taper. It is used to "finish" straight, regular, cylindrical holes to a specific size and level of being cylindrical, usually where tight tolerances are required in size and shape. The hole is drilled under the intended final size and then a straight reamer is used to increase the hole size, ensure parallelism of the hole walls and ensure uniformity of diameter.

A tapered reamer, by definition, has a taper. It is used to create and/or finish holes that taper in diameter. Each reamer is manufactured to produce a specific range of diameters and angles.

The number of cutting edges can matter, depending upon the application. Woodworking applications often use a single flute (cutting edge) since it has less tendency than a multi-fluted reamer to produce out of round holes. The continuous metal bearing surface, broken only by the cutting edge, provides a greater reference surface than a multi-fluted reamer. Regardless, with practice, either can be used successfully.

Based on the wording of your poll, you seem to be asking about straight vs. spiral/helical flutes. If you ever intend to sharpen the reamer, don't buy a spiral/helical reamer. It is easy to sharpen a reamer with straight flutes, not so easy with helical flutes. For woodworking applications, straight flutes are generally used and produce good results.

Basic trigonometry gives tan(angle)=rise/run. The angle is then inverse tan(rise/run), which gives an angle of 87.14 degrees. The compliment is 2.86 degrees. Thus, your 1:20 reamer is 2.86 degrees.
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Old 09-06-2017, 11:56 AM
MC5C MC5C is offline
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All reamers have flutes - flutes are the cutting edge of the tool. Some have three, four, six flutes, some have straight flutes and some have curved or spiral flutes. In general, spiral flute reamers cut a cleaner, straighter hole, as the cutting surface is spread over more of the diameter of the hole it follows the hole better. I would usually prefer a spiral flute over a straight flute, particularly for hand work.

A 1:20 taper is also known as a 5% taper (1/20 is 5%) and is 2 degree, 52 minutes of angle. http://www.magafor.com/841/uk.htm

Brian
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Old 09-06-2017, 12:27 PM
Alan Carruth Alan Carruth is offline
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Not much to add, except that it's pretty easy to make a single fluted reamer: you just start with the diameter rod you want and file or grind away almost half of the diameter, so it ends up with a 'D' cross section. If you want a tapered reamer, taper the rod first. This will produce a nice round hole in wood, cuts when turned in either direction, and is easy to sharpen. If you're only doing a few holes you can use soft steel, or even aluminum in a pinch.
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Old 09-06-2017, 12:32 PM
Sperry Sperry is offline
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THANK YOU !!

I was mixing up my terms as well as other stuff. Confusing a 5% with 5˚ ...

A guitar luthier told me he uses a 3˚ and 5˚ for everything, usually the 3˚. Unless I'm mixing that up as well ...
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Old 09-06-2017, 12:37 PM
Sperry Sperry is offline
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Quote:
Originally Posted by MC5C View Post
A 1:20 taper is also known as a 5% taper (1/20 is 5%) and is 2 degree, 52 minutes of angle. http://www.magafor.com/841/uk.htm

Brian
Thanks for this link. Very interesting. The 1:30 reamer is 3.33˚ ...
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  #7  
Old 09-06-2017, 12:57 PM
Sperry Sperry is offline
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Quote:
Originally Posted by charles Tauber View Post
Woodworking applications often use a single flute (cutting edge) since it has less tendency than a multi-fluted reamer to produce out of round holes. The continuous metal bearing surface, broken only by the cutting edge, provides a greater reference surface than a multi-fluted reamer. Regardless, with practice, either can be used successfully.
Thanks for this detail. I tried to back out of my order but too late. The 1:30 model coming has three straight flutes.

When I tried cyphering it in my head, I imagined the opposite, a single cutting edge producing the out of round hole ... like so much else I try to figure out, it turned out backward.
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Old 09-06-2017, 05:32 PM
Truckjohn Truckjohn is offline
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TLDR: You are looking at the wrong types of reamer for musical instrument use. Buy the correct reamer through a luthier supply like Stew Mac or LMI..

----- onward and upward-------

You are mixing all sorts of terms and going all over creation but you don't realize it.

A 3 degree or 5 degree taper reamer refers to the actual angle of the taper per side.... A 3 degree taper is 3 degrees off 90 degrees on each side. Wood cutting degree taper reamers are commonly used to set various musical instrument pins.

A % or fractional taper refers to rise/run.... These are generally used by machinists on metal... 1/20 = 5% = 20 inches of length per 1" of size reduction.

Next is the type of reamer.... Chucking reamers are made to be used on a machine. Typically working in a mill or lathe. Hand reamers are made to be turned by hand. Spiral helix reamers are almost always made for machine use....

Most reamers for sale in machine tool catalogues are made for cutting metal.. They tend to cut very aggressively. Since they are made to be chucked into a very rigid and low runout machine - they tend to cut out of round in hand use.

Next... Wood reamers are set up differently than metal reamers. Often they are single flute reamers. These musical instrument reamers are made to cut very smooth holes into grainy wood without chattering or grabbing. Metal reamers make a royal mess in wood... They tend to dig in, wobble, and chatter badly...

Buy the right tool and your work will be clean and easy to control.
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