# How does one measure reamers?



## WobblyHand (Jun 15, 2022)

The reamer set I got yesterday don't seem to be on size.  I just tested them, but maybe I am measuring them wrong.  I was using my QuantuMike across the widest point (cutting edge) near the main cutting tip.  What is the right way to measure them?

The under sizes are supposed to be 0.001" under the "nominal" dimension.  One reamer measures 2.5 tenths under the spec.  (That's a pass to me.)  All others are at least 0.001" over the marking on the reamers.  Can't seem to win at this game, at least not playing the cheapskate card...

0.4990 measures 0.500x, 0.3740 measures  0.375x, 0.2490 measures 0.250x, etc.  

Are my expectations valid that if a reamer is marked 0.2490 that it ought to be within a 2-3 tenths of that? 5 tenths, worst case?  What the heck is the 4th digit for, if it isn't held?


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## woodchucker (Jun 15, 2022)

first, are these chucking reamers or hand reamers?
it matters because chucking reamers are straight, while hand reamers have a small amount of taper in the beginning to help get them aligned and cutting.

it seems yours regardless are over, and not measuring what they should.  across the highs they should be measuring marked size.


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## Winegrower (Jun 15, 2022)

Probably worth checking your mic calibration.


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## WobblyHand (Jun 15, 2022)

woodchucker said:


> first, are these chucking reamers or hand reamers?
> it matters because chucking reamers are straight, while hand reamers have a small amount of taper in the beginning to help get them aligned and cutting.
> 
> it seems yours regardless are over, and not measuring what they should.  across the highs they should be measuring marked size.


Chucking reamers.  Think these reamers are going back.


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## WobblyHand (Jun 15, 2022)

Winegrower said:


> Probably worth checking your mic calibration.


Probably, however, I measure the pins with that mic and they are 0.2495".  Also checked the QuantuMike against my cheapo vernier mike and it reads the same on the pin diameter to the tenth.  I'll see if I find the mic standard and check it.

The first bad reamer I got, I didn't measure it first, reamed the hole and my pin fell though the hole.  Measured the reamer afterwards and it was 0.2503" and the pin 0.2495", which make sense, considering the pin just slid right though the hole.


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## mmcmdl (Jun 15, 2022)

Drill and ream some test holes , then measure the holes . The reamer size is not what you're after , the hole size is .


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## MrWhoopee (Jun 15, 2022)

I'm with @mmcmdl, ream some test holes. The hard part is measuring them.


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## woodchucker (Jun 15, 2022)

mmcmdl said:


> Drill and ream some test holes , then measure the holes . The reamer size is not what you're after , the hole size is .


that's all well and good *IF he is on center*, if he is using a floating holder yea, but if he is off by 1 thou his cut will be 2 though bigger.
And it appears he already tested by drilling and reaming.
IF his reamer is bigger than stated by measuring, he is not going to get the 1 thou under.  If you were 2 thou under you might get a hole 1 thou under.. but a bigger reamer will never give you a smaller hole.

MY TWO CENTS and I'm sticking to it... btw, it's only worth about 0.10 cents today.


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## rabler (Jun 15, 2022)

It is interesting they are mostly measuring oversize.  I could believe cutting action would involve some elasticity, but I would guess that would depend a lot on material.   I seem to remember Stefan Gotteswinter on youtube commenting that different lubricant mattered too.  I can't remember which two lubricants he used, cutting oil and water soluble oil perhaps, but he claimed one definitely cut smaller than the other.


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## WobblyHand (Jun 15, 2022)

Of course my 1" standard is nowhere to be found.  But making relative measurements of my manual mic and the Mit fancy pants one shows they agree to the tenth, at 0.2495" and at 0.5001" using pins.  The 1/2" dowel pin is ground (sourced from McMaster) and I made a sharpie mark on it to measure the same way between the mics.  Used a mic stand even, to make the measurements.  Actually my vernier mic showed it was between 0.5001 and 0.5002.  My QuantuMike measured 0.500150".  So they both could be lying, but it seems they have already conferred with each other 

I figure the hole will NEVER be smaller than the largest cutting edge to cutting edge.  Can't figure out the voodoo it would take to be otherwise.  (Maybe with plastic that might happen, but not aluminum.)  As @woodchucker says, the hole could get bigger due to all kinds of reasons.  But if the tool itself starts out too big, it won't get smaller by reaming, at least that's what my logic is telling me.  


MrWhoopee said:


> I'm with @mmcmdl, ream some test holes. The hard part is measuring them.


I did ream using my first NFG reamer, the pin fell through, although the part I bought was claimed to be 0.2490".  The measured tip to tip on that reamer was 0.2503".  I got my money back on that reamer.

I measured 0.250x on this latest reamer, (third one!) it was marked 0.2490".  (I can measure it again, but that's what stuck in my mind.)  Curiously, the one over size reamer I measured was as marked.  Don't remember which reamer it was, as I really wanted the set for making interference fits.

I'll measure the 0.251 and the 0.249 side to side.


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## WobblyHand (Jun 15, 2022)

Here's the measurements, I took of the 0.2490 and 0.2510 reamers, all 3 cutter positions (6 cutting edges).

Marking 0 deg 60 deg 120 deg
0.2490   0.24990  0.24990  0.25000  "under"
0.2510   0.25125  0.25105  0.25105  "over"

My conclusion is this undersized cutter is too large.  The oversized cutter is satisfactory.  These are measured back to back.  Micrometer zeroed at beginning of measurement.  Micrometer zero checked and was zero at end of measurement.  Zero measurement = 0.00000".  Mitutoyo QuantuMike.  Anvils were cleaned using sheet of paper between the jaws, prior to measurement.  Used a micrometer stand.

6 out of the seven _under_ cutters in the box measure 0.001" larger than stated.  The 7th one is on size or within tolerance.  

For reference, I have a 1/4" reamer from Alvord Polk Tool (APT).  Size on box: 0.2500".  After cleaning any residual oil on it, this is what I measured.

Marking  0 deg    60 deg   120 deg
0.2500   0.25015  0.25010  0.25005

Same micrometer, room, etc.  This tool cuts seemingly to size on my mill, although honestly, I haven't measured it.  I do know I have had zero problems with the USA reamers.  Everything fit as expected.  I found a couple of the APT reamers on fleabay, so I didn't get reamed. 

I know what the message is, buy good quality tools...  It's really easy to get tempted by these sets.

Seems that this set is going back...  Not going to put up with this sort of creative cheating.  The set is useless for my purposes.  Now at my fourth attempt at getting a real 0.2490 (or 0.2485) reamer...


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## Dabbler (Jun 15, 2022)

WobblyHand said:


> Seems that this set is going back...



If you have the luxury...   I've been known to make an undersized reamer (from an on-spec reamer) for a job at the end of day on a Friday that was needed for the  weekend.   I used a diamond hone a lightly touched all surfaces.  Made a nice press fit.


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## WobblyHand (Jun 15, 2022)

Already have the return shipping label.  This set is going back.  When 6 out of 7 "under" reamers are at least 0.001" oversized, you know there's a quality problem.  I tested the under reamers since I was burned twice already!  Now going for try #4 to get a correctly sized 0.2490" or 0.2485" reamer.  Curiously, the one over size reamer I spot checked was on size.  6 bad out of 14 isn't worth the money they were asking... 

I'm working with a forum member to pick up some US made reamers that should work out.  Won't have them instantly, but I feel better about it.  So my honey do project gets delayed.  Wish that weren't so, but that's what is happening.  The used reamer set will be less expensive than the "new" set.  Should I need to touch the used ones up, I won't hesitate to try that.  I don't have any guides though, so honing the edges would be tricky for me.  I know from experience that it's pretty easy to mess up an edge honing.  (I seem to do it a lot!)  Maybe I could make a fixture that would help.  Go on centers on a lathe and move the carriage back and forth?

Edit: Reject quality reamer set delivered to the post office.  Have receipt.  Touching up a one off, is one thing, reworking a large percentage of new set to get it in spec, is another.  This set was $100.  Sure it's cheap for real reamers, but it's pricey for the quality received.  If I were more experienced at this, and a bit more skilled, perhaps I'd just rework the set.  If the set was marked truthfully, it wouldn't irk me so.  But it was a counterfeit set, masquerading as something worthwhile, when it didn't meet it's own stated requirements.  Because it wasn't on spec, it was worth less.  But, it was sold as being on spec - because it didn't have ANY disclaimers.  I don't mind buying "crap" sometimes because I understand the use I have for it.   It took two replies to the vendor, because they didn't understand (or want to understand) why I was returning the set.  They finally seemed to understand the issue.  They will refund immediately upon receipt.


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## Parlo (Jun 15, 2022)

Some reamers around this size have 5 or 7 flutes so an appropriate vee micrometer is required to measure them.
What tolerance are they made to? Most standard reamers are made to produce either H5 or H7 holes which are both minus to plus. Maybe they are H8 or above, it may be worth checking the suppliers quoted specs. A H8 @ 1/4" diameter is +0.0008" / -0.00.
If you want to reduce the sizes, try running the reamer slowly in reverse and hold a flat oilstone against the flutes. Try to taper it by a few tenths over the first inch then the size can be adjusted bigger by reaming deeper.
For a tight 0.250" use a hand reamer which already has a taper and control the fit by the depth ( maybe from both sides ).
With any new reamer I always cut a few test holes first, just to burnish in the cutting edges.
It's not good, but at least you can make them smaller. Making them cut larger is more of a pain by scraping the inside of the flutes with a piece of carbide to raise a burr.
I find coolant makes the reamers cut tighter than with cutting compounds.
Spiral flute reamers are known to cut larger than straight flutes.
When chasing tenths, the whole setup needs to be considered for the tooling to perform to spec.
My tip is to use a spotting drill with the diameter ground slightly undersize at the front and use it to produce a short counterbore to start the reamer. Here is a demo video that you may find interesting.


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## WobblyHand (Jun 15, 2022)

Parlo said:


> Some reamers around this size have 5 or 7 flutes so an appropriate vee micrometer is required to measure them.
> What tolerance are they made to? Most standard reamers are made to produce either H5 or H7 holes which are both minus to plus. Maybe they are H8 or above, it may be worth checking the suppliers quoted specs. A H8 @ 1/4" diameter is +0.0008" / -0.00.
> If you want to reduce the sizes, try running the reamer slowly in reverse and hold a flat oilstone against the flutes. Try to taper it by a few tenths over the first inch then the size can be adjusted bigger by reaming deeper.
> For a tight 0.250" use a hand reamer which already has a taper and control the fit by the depth ( maybe from both sides ).
> ...


These were 6 flute straight reamers, so they are relatively easy to measure.  Thank goodness!  Actually it wasn't all that easy to get the high points, but kind of figured it out.

At the moment, I have no fixtures that are rigid or sturdy enough to try what you are mentioning.  Still a rank beginner at all this.  If I get some junk reamers maybe I can practice on them, could be a good learning experience.  

That being said, when using first rate reamers I didn't seem to have much of a problem.  I've reamed out tool holder sleeves in steel without issue. Got fits that were expected.  However, now I am going for interference fits and getting close to the right numbers is important.  Being 0.001" over means there's no interference fit anymore.  I am using the reamers to achieve interference fits.

Ill take a look at the video.  What do you use for coolant?  The last aluminum I reamed was with WD40.  The pin fell through.  That's not what I was trying for - but that reamer measured large, 0.2503 at the tips, although marked as 0.2490", and the pin is 0.2495".  Might be I need to adjust my technique... Make bigger pins to overcome the bad reamers.


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## mmcmdl (Jun 15, 2022)

If they are oversize by a few tenths , throw them in a lathe , spin them backwards and hit them with a stone , lap or hone . Easy to knock a tenth or two off .


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## Jim F (Jun 15, 2022)

At work we measure them with calipers.......


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## mmcmdl (Jun 15, 2022)

You can close up oversize holes easily for interference fits if necessary .


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## Jim F (Jun 15, 2022)

mmcmdl said:


> You can close up oversize holes easily for interference fits if necessary .


You should see the die we got in today..............


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## WobblyHand (Jun 15, 2022)

mmcmdl said:


> If they are oversize by a few tenths , throw them in a lathe , spin them backwards and hit them with a stone , lap or hone . Easy to knock a tenth or two off .


The reamers I sent back were over sized by over 0.001".  A tenth or two, I wouldn't care about.  

I have a lot of respect for you and others that have machined for a career.  What's really easy for you is traumatizing (not truly, but you get my drift) for someone who hasn't done it before and has no hands on guidance.  Once you've done it, or experienced it, I'd bet it would be much easier the next time.  I don't even know how to hold the stone right to accomplish the above, it's outside of my experience.  Nor do I even have a reamer to practice on.  I know I'd ruin the heads the first go around.  With guidance, maybe I could be passable after a couple handfuls of reamers.  By myself and the (alive) spiders in the basement, it would take me a whole bucket of reamers to get respectable results.  And I still wouldn't know what size hole they made...

Because my shop is limited and just starting, buckets of essentially free and low risk material aren't around to experiment with, which in a sense adds to the stress of getting it right.  Maybe those buckets weren't initially free, but they have been fully amortized, so they are effectively free now.  I have some stock like that, excess from a project.  

Not trying to make excuses, but we are in different realms of experience and access.  You know the business of machining and machines, and me, well, _I don't even know jack yet_.  I'm trying, but I'm at least 50 years behind you in machining knowledge.  I don't even expect to know a 1/10 of what you and others know, but maybe I could make a couple of passable objects in the remaining time I am granted on earth.  I've learned a lot from you and others on this forum, and for that I am grateful, but I have a long way to go.  

Hoping to learn a little bit more every day.  This is why I hang out on this forum.

I never knew how darn frustrating reamers could be, until I wanted to make a press fit...  So much to learn...


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## Jim F (Jun 15, 2022)

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


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## Dabbler (Jun 15, 2022)

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


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## ub27Rocks (Jun 15, 2022)

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.


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## WobblyHand (Jun 15, 2022)

Dabbler said:


> @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.


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## WobblyHand (Jun 15, 2022)

ub27Rocks said:


> 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...


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## Dabbler (Jun 15, 2022)

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.


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## Parlo (Jun 16, 2022)

WobblyHand said:


> 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.


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## Dabbler (Jun 16, 2022)

Parlo said:


> 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.


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## Parlo (Jun 16, 2022)

Dabbler said:


> 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.


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## mattthemuppet2 (Jun 16, 2022)

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.


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## Parlo (Jun 16, 2022)

mattthemuppet2 said:


> 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.


Is a c drill a reference to a centre drill?
There are reams of information everywhere confirming the advantages of a correct angle spot drill to a centre drill. In fact; there is a global industry making spot drills precisely for this purpose.
Centre drills are for centres!!
For standard sizes - use a spot drill of the finished diameter to produce a precisely positioned counterbore as a spot for the drill and a precise guide for the reamer.


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## mattthemuppet2 (Jun 16, 2022)

Easy there, letter C drill, 0.242". I've had a letter D drill (not a D bit!) cut oversize before, so I do one below to make sure I have material left for the reamer to cut.


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## Parlo (Jun 17, 2022)

mattthemuppet2 said:


> Easy there, letter C drill, 0.242". I've had a letter D drill (not a D bit!) cut oversize before, so I do one below to make sure I have material left for the reamer to cut.


I C what you mean.


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## tq60 (Jun 17, 2022)

Or...

Drill with C drill.

Take pins done to 1 thou larger and be done.

Sent from my SM-G781V using Tapatalk


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## WobblyHand (Jun 17, 2022)

tq60 said:


> Or...
> 
> Drill with C drill.
> 
> ...


If I can't find an on size reamer that's what I'll do.

Didn't want to make 10 more pins, but that's a good way out of this situation.  I do have a APT 0.2500" reamer, so I could turn down 5/16" stock and get it done.  Thanks for the ideas.


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## Janderso (Jun 17, 2022)

mmcmdl said:


> If they are oversize by a few tenths , throw them in a lathe , spin them backwards and hit them with a stone , lap or hone . Easy to knock a tenth or two off .


Really? This works?
Doesn’t ruin the reamer?


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## mmcmdl (Jun 17, 2022)

Yes , it works . 



Janderso said:


> Really? This works?
> Doesn’t ruin the reamer?


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## Dabbler (Jun 17, 2022)

mmcmdl said:


> Yes , it works .


But as I said above, it leaves a flat on the relief side of the cutting edge, allowing the reamer to skate or polish the hole.   this is bad.  You have to then take a hone or T&C grinder and grind that flat off.  In soft steels this is is less important, but to do anything with tool steel it is essential.  In very soft stuff like brass the flat polishes the hole but doesn't ream it.  This leads to inconsistent results and galling.

been there tried it.  got \corrected by a very experienced tool and die maker.  He had reamed tens of thousands of holes in his career, and it turned out he was right.


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## Parlo (Jun 17, 2022)

Dabbler said:


> But as I said above, it leaves a flat on the relief side of the cutting edge, allowing the reamer to skate or polish the hole.   this is bad.  You have to then take a hone or T&C grinder and grind that flat off.  In soft steels this is is less important, but to do anything with tool steel it is essential.  In very soft stuff like brass the flat polishes the hole but doesn't ream it.  This leads to inconsistent results and galling.
> 
> been there tried it.  got \corrected by a very experienced tool and die maker.  He had reamed tens of thousands of holes in his career, and it turned out he was right.


Reamers do not cut on the flutes, there are no cutting edges apart from the 45 degree chamfer at the tip. The flutes are there to guide the reamer straight and to clear the chips. Are you referring to hand reamers?


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## WobblyHand (Jun 21, 2022)

OP.  Got my money back on the over under (but really nominal) reamer set.  

Ordered and finally received a used L&I 533.2485 reamer.  It actually measures very close to 0.2485".  (Within tenths)  And guess what it reams a hole that is smaller than my 0.2495" pin.  A 3 ton press, presses the pin I made in place, like I meant it.  When I get some more reamers (some time soon I hope) maybe I can look into touching one up.  In the meantime, I will be able to finish this super important honey do project - fixing our kitchen corner cabinet!


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