How does one measure reamers?

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...
 
WobblyHand said:
Seems that this set is going back...
Click to expand...

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.
 
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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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.
 
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 ).
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.
Click to expand...
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.
 
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 .
 
You can close up oversize holes easily for interference fits if necessary .
 
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 .
Click to expand...
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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