There were three questions on reaming in my shop class mid-term exam, and I got all of them wrong, so I need to learn more about the correct values for this operation.

The first question was, "The feed rate for reaming a hole in a drill press should be ___ that of cutting. I didn't read it carefully and thought it was speed, so I chose 1/2. The other choices were 2 times, 4 times, and 1/8. I think the correct answer is 2 times.

The second question was, "The stock allowance for reaming a 0.375" diameter hole is:" I thought the answer was 1/64", which is the next smaller fractional drill size, but the choices were: 0.003", 0.060", 0.012", and 0.032". Since the decimal equivalent of 1/64" is 0.016, none of the answers were correct, so I chose the next larger fractional equivalent of 1/32" or 0.032", which is correct for a 1/2" hole. The instructor put an "X" next to 0.060", which I know is wrong, and when I questioned it, he said it should be 0.012", which is a 0.365" drill. The closest drill is a "U", which is 0.368".

The third question was, "The stock allowance for a hand reamer with a 0.500" diameter is:" The choices were 0.015", 0.009", 0.004", and 0.032". I chose 0.032" which is correct for machine reaming, but the correct answer was marked as 0.009", although the nearest drill size is 31/64" or 0.4844" with a 0.016" allowance. I don't recall hand reaming discussed in class, although it may have been on the day I was late.

I'm not protesting these, as I think some of them come directly from the NIMS certification test, and the instructor has said that the test is not well designed and some answers are questionable, but the idea is to be able to pass the test.

I found the following information on reaming, although mostly on machine reaming:

http://www.gammons.com/useofreamers.html

This mentions hand reaming and recommends 0.002 to 0.004 allowance:

http://www.ctemag.com/aa_pages/2010/100604_Reaming.html

I have a set of reamers in commonly used sizes from 1/8" to 1/2" but they are labeled RCST or maybe RC5T which is probably for an RC5 running/sliding fit. I used the 1/4" reamer for a part I made, and a 0.250" shaft fit smoothly, but I wanted a press fit. So I used a chisel to make a rough "knurled" section where I wanted it to grip, and that worked well.

In another case, I found that I could get a decent press fit by first drilling 1/64" undersize and then following with the exact drill size to shave off a few thousandths, and that seemed to work quite well. This was using drills from my $69 HF 115 piece HSS TiN coated set, which seems to be quite good, but I got them long ago and quality may vary.

The first question was, "The feed rate for reaming a hole in a drill press should be ___ that of cutting. I didn't read it carefully and thought it was speed, so I chose 1/2. The other choices were 2 times, 4 times, and 1/8. I think the correct answer is 2 times.

The second question was, "The stock allowance for reaming a 0.375" diameter hole is:" I thought the answer was 1/64", which is the next smaller fractional drill size, but the choices were: 0.003", 0.060", 0.012", and 0.032". Since the decimal equivalent of 1/64" is 0.016, none of the answers were correct, so I chose the next larger fractional equivalent of 1/32" or 0.032", which is correct for a 1/2" hole. The instructor put an "X" next to 0.060", which I know is wrong, and when I questioned it, he said it should be 0.012", which is a 0.365" drill. The closest drill is a "U", which is 0.368".

The third question was, "The stock allowance for a hand reamer with a 0.500" diameter is:" The choices were 0.015", 0.009", 0.004", and 0.032". I chose 0.032" which is correct for machine reaming, but the correct answer was marked as 0.009", although the nearest drill size is 31/64" or 0.4844" with a 0.016" allowance. I don't recall hand reaming discussed in class, although it may have been on the day I was late.

I'm not protesting these, as I think some of them come directly from the NIMS certification test, and the instructor has said that the test is not well designed and some answers are questionable, but the idea is to be able to pass the test.

I found the following information on reaming, although mostly on machine reaming:

http://www.gammons.com/useofreamers.html

This mentions hand reaming and recommends 0.002 to 0.004 allowance:

http://www.ctemag.com/aa_pages/2010/100604_Reaming.html

I have a set of reamers in commonly used sizes from 1/8" to 1/2" but they are labeled RCST or maybe RC5T which is probably for an RC5 running/sliding fit. I used the 1/4" reamer for a part I made, and a 0.250" shaft fit smoothly, but I wanted a press fit. So I used a chisel to make a rough "knurled" section where I wanted it to grip, and that worked well.

In another case, I found that I could get a decent press fit by first drilling 1/64" undersize and then following with the exact drill size to shave off a few thousandths, and that seemed to work quite well. This was using drills from my $69 HF 115 piece HSS TiN coated set, which seems to be quite good, but I got them long ago and quality may vary.

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