How does one measure reamers?

[Jim F]

First thing to learn, precision is not cheap.
Stop buying Chinesiaum junk.

 

[Dabbler]

@WobblyHand My most inexpensive reamer was around 100$ - made in USA, and still out of spec. That's why I 'fix em'

 

[gerritv]

No where was there a question or mention of the starting hole size. If there is not enough meat for the reamer to do some work on it won't ream to its nominal size. E.g.: https://www.hannibalcarbide.com/documents/pre-ream-drill-size-chart.pdf

Since chucking reamers cut at the tip, re-sizing per Dabbler's method is not too invasive. Between centres, same number of swipes on each flute.

 

[WobblyHand]

@WobblyHand My most inexpensive reamer was around 100$ - made in USA, and still out of spec. That's why I 'fix em'

It's good that you both know how and have the means to do so. Probably have a 100x more experience than I do, in this area as well.

Simply don't know how to do some of these things, as trivial as they seem to you. Just don't have the background yet. Some machining things are quite comfortable to me, as I have done them, screwed up a bit, learned and progressed. Others I simply have never seen such a machine or operation and have no idea what to do, or even how to even approach the problem. For example, I have practically zero experience grinding anything with precision, others complain about not getting optical grade surface finishes. Sharpening or grinding reamers is one of those things I have zero experience or even exposure. Until it was mentioned in this thread, I have never even thought about it. Just not in my life experience yet. If I had a half a dozen reamers that I didn't care about, and weren't too expensive, and an inkling of what to do, I'd even entertain trying it. I do like learning new things. But my financial reality for the next five months is I cannot afford to spend a lot of cash on ruining reamers. Perhaps if you knew of a video on this, I could watch it and get a better idea what to do. That would allay my probably irrational fears of throwing money down a toilet learning how to do this.

 

[WobblyHand]

No where was there a question or mention of the starting hole size. If there is not enough meat for the reamer to do some work on it won't ream to its nominal size. E.g.: https://www.hannibalcarbide.com/documents/pre-ream-drill-size-chart.pdf

Since chucking reamers cut at the tip, re-sizing per Dabbler's method is not too invasive. Between centres, same number of swipes on each flute.

I drilled with 7/32, then 15/64 (0.234375") , then attempted to ream to 0.2490" using WD40. Pin was 0.2495". Reamed hole was > 0.2503" since the reamer itself measured that big. Pin fell through the hole...

I don't understand the position of the stone relative to the reamer and spindle axis. How is the stone held in place so none of the edges are rounded over? I have never experienced this sort of operation. I do not understand the 3d geometry. If I could visualize it maybe I could do it...

 

[Dabbler]

You can use a tool and cuter grinder,to resize/sharpen a reamer, but that takes setup and skill, and of course the machine.

To do this manually, I chuck the reamer in a vise so it sticks out one side and align the cutting surface by hand. I use a firm even stroke along the grind line with a fine diamond hone. One or two strokes makes about a tenth. I don't get the Youtube uploading thing, or I could upload a vid, as I have 5 reamers to sharpen. When you sharpen them, they become undersized reamers (of course)

To remove about a thou is somewhere around 15 strokes per cutting surface, or about 4 minutes per reamer.

 

[Parlo]

I drilled with 7/32, then 15/64 (0.234375") , then attempted to ream to 0.2490" using WD40. Pin was 0.2495". Reamed hole was > 0.2503" since the reamer itself measured that big. Pin fell through the hole...

I don't understand the position of the stone relative to the reamer and spindle axis. How is the stone held in place so none of the edges are rounded over? I have never experienced this sort of operation. I do not understand the 3d geometry. If I could visualize it maybe I could do it...

A machine reamer cuts on the chamfer at the tip so don't worry about rounding the cutting edges over. It is the outside of the flutes that need reducing. Pop the reamer in a drill chuck - spin slowly in reverse - hold a flat oilstone vertically against the flutes to remove a few tenths. This will preserve the cutting edges.

 

[Dabbler]

Pop the reamer in a drill chuck - spin slowly in reverse - hold a flat oilstone vertically against the flutes to remove a few tenths. This will preserve the cutting edges.

try this. you have now dulled your reamer. Most people use dull reamers, so hey, why not? If you examine the result under a loupe or a toolmakers microscope, you will see a flat edge where your cutting edge should be coming to a point.

You absolutely *can* do this, as long as you sharpen it again by removing that flat by honing the relief angle.

 

[Parlo]

try this. you have now dulled your reamer. Most people use dull reamers, so hey, why not? If you examine the result under a loupe or a toolmakers microscope, you will see a flat edge where your cutting edge should be coming to a point.

You absolutely *can* do this, as long as you sharpen it again by removing that flat by honing the relief angle.

The reamers do not cut on the flutes. This process simply increases the land by a tenth or so.

 

[mattthemuppet2]

using reamers isn't a trivial undertaking. Seems like it should be, but it's hard to get right than would appear. First up I would drill with a good sharp C drill with plenty of WD40 or kerosene. Then countersink hole, which will be handy for getting the pins started anyway. Then ream with your undersize reamer and plenty of cutting fluid at 1/4-1/3 of the speed you used to drill the hole. Try and do it in one go if you can but keep an ear out for the motor slowing, as that will indicate that the flutes are packing with chips. Having a set of homemade go-no go gauges, or a set of small hole gauges, would be handy here for checking size.