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[machinist] Reaming oversized? [many tips and references]
- From: Lawrence London <lfljvenaura@gmail.com>
- To: machinist@lists.ibiblio.org
- Subject: [machinist] Reaming oversized? [many tips and references]
- Date: Thu, 17 Dec 2015 19:16:20 -0500
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Thread: Reaming oversized?
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12-11-2015, 10:21 AM #1
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Reaming oversized?
I remember reading a method to purposely ream a hole larger than the nominal size of a reamer, but can't remember what it was. I'm talking on the order of less than a thousandth. Anyone know what that method would be? I'm looking to ream a hole about 5 tenths larger than my 0.124".
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12-11-2015, 10:32 AM #2
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There was something written in an old toolmaking book about using, I think Soda Water, which for some reason made the reamer cut oversize.
Seem to remember something about placing a bit of string in one of the flutes as another method. -
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12-11-2015, 10:36 AM #3
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My experience with reamers, if you want it to cut .0005 oversize, it will cut right to size. If you need it to cut to size it cuts .0005 oversize! Just change your mindset and think "I really need this reamer to cut perfectly to size!"
Originally Posted by Forestgnome
I remember reading a method to purposely ream a hole larger than the nominal size of a reamer, but can't remember what it was. I'm talking on the order of less than a thousandth. Anyone know what that method would be? I'm looking to ream a hole about 5 tenths larger than my 0.124".
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12-11-2015, 10:46 AM #4
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Depending on the material, I've taken an old carbide insert and dragged it down one flute.
I don't know if it throws up a burr or something, but I've had it work in the past. -
12-11-2015, 10:50 AM #5
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What I have found with reamers is this, ream with cutting oil for a larger hole, ream with coolant for a tighter hole, if you want it slightly extra large, ream with cutting oil and leave more stock to remove. Most people in my opinion leave way too much stock for removal. I have reamed zillions of ejector pins and for a hole around .250 I only leave about .002 stock per side to remove.
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12-11-2015, 10:53 AM #6
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I have found buying a quality carbide reamer and indicate it in saves a lot of $%##%&% .
And a few gray hairs along with the time saved screwing around. -
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12-11-2015, 11:05 AM #7
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I guess you could ream it with your .124 reamer and then buy a .1245 reamer to finish it. Originally Posted by Forestgnome
I remember reading a method to purposely ream a hole larger than the nominal size of a reamer, but can't remember what it was. I'm talking on the order of less than a thousandth. Anyone know what that method would be? I'm looking to ream a hole about 5 tenths larger than my 0.124".
Those other ideas might depend upon your work material as far as the final result. Most reamers are ground with only one flute geometry, probably for steel. But we know that different materials cut better with a certain tool geometry. Other variables are the original quality and the current condition of your reamer.
Larry -
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12-11-2015, 11:12 AM #8
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"TIPS OF THE TRADE" google in the search box
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12-11-2015, 03:46 PM #9
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IIRC, a few years ago someone posted about reaming the hole, then folding and placing a thin piece of shim stock on one flute to force the opposite flute to cut oversize. Haven't tried it myself and seems unlikely to work for only .0005" increase but might help a future searcher who needs a greater difference.
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12-11-2015, 04:36 PM #10
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What about heating the reamer to expand it before immediately reaming the hole after doing it cold to get near to the finished size?
Popular Science 1930 -
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12-11-2015, 05:01 PM #11
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I would "play" with your drill size on a piece of scrap. Leaving more or less stock will effect the reamed hole size....different materials....different results.
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12-11-2015, 06:09 PM #12
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A number of good ideas to try. Thanks. If it wasn't for the fact I'm only doing two holes I would buy the correct reamer.
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12-11-2015, 06:21 PM #13
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Depending on the depth you have to go you can always stone a .125 DR down. I do it to make 1/16 undersized for press fit holes all the time I'm sure the same would work. You'll just need to test it until it cuts just the way you want.
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12-11-2015, 07:57 PM #14
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Feeding a drill at reamer feedrate will often cut to the micrometer check plus .00005 to +.0002. Yes with a pre drill hole. Good to run a test part.
Split rod corcs cloth (sand paper) hone also works for two holes..
Lionelt's heat trick might be worth a try. but get it red and can loose the hardness. -
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12-11-2015, 08:16 PM #15
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Booze is right on it! Old world trick for Tool and Die Makers.
Put the reamer shank in a vise. Take a HSS tool bit blank and drag the end edge of it at a approx. 30 deg angle along the flat flute putting most pressure
on the outside edge of the flute. Just one draw (pull). Turn your reamer slightly for the next flute to stick out parallel and drag again. Stop! Ream a hole and see what you get. You don't want to get to big. If you need more, drag the two flutes again and drag a third or fourth flute. A lot depends on the pressure you are using. Takes a little practice but it works! Not to be used for a great number of holes. Careful - it comes up fast.
Remember, you are doing the flat part of the flute, nothing on the outside. -
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12-11-2015, 10:08 PM #16
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If you want it to go just a little bit bigger, one way is to up the RPM and drop the feed rate, then feed at the same rate coming back out of the hole. That can buy you a couple of tenths. If you need more than that, dragging something hard down one flute is good for one oversize hole.
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12-12-2015, 12:04 AM #17
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For small parts, best method is to ream a thou or two under, and use the Sunnen to get correct size..
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12-12-2015, 12:13 AM #18
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Yikes! sounds like a good way to seize/gall the reamer in the workpiece.. Sounds like they were using the hot reamer to burnish the hole. Originally Posted by lionelt
What about heating the reamer to expand it before immediately reaming the hole after doing it cold to get near to the finished size?
Popular Science 1930 -
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12-12-2015, 09:40 AM #19
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Reamers have a circle land at OD so little can be done to make them cut larger. Also they are tapering back .0002 or so per inch so get smaller diameter each time they are shortened at each sharpening.
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12-12-2015, 03:28 PM #20
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Originally Posted by Davis In SC
Yikes! sounds like a good way to seize/gall the reamer in the workpiece.. Sounds like they were using the hot reamer to burnish the hole.
Just Googled and found the link to the article in Popular Science.
Popular Science - Google Books
Making reamers cut oversize, using taps for force fits, hints on center drills, improve surface blocks
Long link
https://books.google.co.uk/books?id=...ersize&f=false
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Thread: Reaming oversized?
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12-12-2015, 03:42 PM #21
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The article says about .001 perinch at boiling. So perhaps with out of the
freezer and a hot reamer you might get a larger hole..
So one might try dry ice to the part after at test part was tried for size.. -
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12-12-2015, 04:02 PM #22
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Chuck it up in an ER collet, works for me. Indicate it and tap it closer to center until you get the right sized hole. Speeds, feeds, and how much you are taking out of the hole all affects the size as well.
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12-12-2015, 05:57 PM #23
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You can heat beyond boiling by using oil instead of water. Need a thermometer, but you can get very controlled increases in size that way.
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12-14-2015, 04:36 PM #24
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If I want to squeeze a few tenths extra out of a reamer, I spin it faster than I normally would, and feed even harder than normal, and leave more material on the walls (about .006 a side, vs the normal .002 or .003). Has worked well for me in aluminum and stainless with HSS reamers. Though, I do have one burned up .250 reamer from when I got a little... uhh... enthusiastic. But an old German guy taught me this one, and it's done well for me.
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12-14-2015, 09:30 PM #25
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Tell the reamer "Ohh PLEASE cut to size, PLEASE!!!" and she'll cut oversize EVERY TIME. Originally Posted by michiganbuck
Reamers have a circle land at OD so little can be done to make them cut larger. Also they are tapering back .0002 or so per inch so get smaller diameter each time they are shortened at each sharpening.
Make her believe you need her to cut a bit oversize and somehow, someway she'll cut .002 under, even though she can't fit
in that hole afterwards, she'll do it just to spite you.
Already said, but you can get them to cut oversize by scraping/dragging the inside of the flutes with an insert or an endmill.
I've gotten them to tighten up a bit by spinning them backwards against a diamond file for a few seconds.
If it really matters, same as I do with a boring head. Test piece of a similar material. Drill the test piece and the
real piece. Then ream or bore the test piece, check it and then without removing the tool. Hit the real piece. -
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12-14-2015, 10:58 PM #26
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Drill sizes taper back on the way to the shank. Get out your mike and measure up the shank where the size is you want. Cut it off there. Do a very nice job of grinding the point.
Get another normal drill with a near size you want for the first cut. Then when entering the "finish" drill, slow the rpm so when you make contact you DON'T chatter. You should have steady command of moving into the hole. If things go smooth you should be ok.
Regards,
Stanley Dornfeld -
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12-17-2015, 02:53 AM #27
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I've gotten them to tighten up a bit by spinning them backwards against a diamond file for a few seconds.Also they are tapering back .0002 or so per inch so get smaller diameter each time they are shortened at each sharpening.We've got a project to ream twelve holes in cast iron to .6296". I'm starting with a 16mm reamer, which is nominally .6299". Will be interesting to see where the diameters start and how much we have to manually modify the reamer to get there.Depending on the depth you have to go you can always stone a .125 DR down. I do it to make 1/16 undersized for press fit holes all the time I'm sure the same would work. You'll just need to test it until it cuts just the way you want.
jack vines -
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12-17-2015, 10:12 AM #28
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Never had success getting a reamer to cut over size. A dull reamer can cut over size from heat. The slotted rod and emery cloth works... with using a measure length of emery some control is made.
*Perhap a scrap reamer back spinning in the hole with compound would work.
A cut off .125 (or measured) drill might be the size you seek to use as a reamer or a good compound use tool..
To make reamer smaller:
Not uncommon for a reamer to cut .0001-.0002 over measure so to micrometer the reamer and end resharpen it to .62955 or .6296 would be a good start IMHO.
End sharpening back is much safer than back spin hone or OD grinding.
Stoning round back spin by hand can bevel the lead OD edge so not as good as end sharpen back the end cutting edge. Yes going to the back taper that is common in reamers and drills.
Stoning OD back is better done with reaming a hole in a soft steel or iron bar, put a side slice to that hole, then back spin with compound as you tighten the hole. that way the lead edge of the OD stays sharp. Used to do just that for taking .00002 or so, and even .001 or so. You can do this on a drill press. We had to make reamers that would cut dead on size..
Reaming a round slug (even on the drill press) also makes the special collect for holding a drill or reamer for re sharpening..slug in a tilted V block or clamped to an angle plate make the simple grinding fixture for re-sharpening (drill or reamer) end on the surface grinder.
For the reamer first spin the reamer round the amount of desired take off.. then tilt for side cutting edge and turn for clearance angle then use down feed to sharpen. Yes must use a small diameter wheel set above center (left or right of on the SG) to miss the following next tooth. For drill you just slash across point and then hand roll the secondary. Then thin the web. this makes a very close centered drill point. -
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12-17-2015, 10:17 AM #29
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A reamer only cuts on the face, not on the flank. Originally Posted by jmcvo
IIRC, a few years ago someone posted about reaming the hole, then folding and placing a thin piece of shim stock on one flute to force the opposite flute to cut oversize.
Putting a shim on the side will simply distort the hole, perhaps uniformly, perhaps not.
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12-17-2015, 10:45 AM #30
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Try leaving the least ammount of stock you can get away with in the hole prior to reaming--Think its leave less in for a bigger hole-leave more in if the hole is too big-could even try a different sleeve
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12-17-2015, 06:33 PM #31
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To hedge our bets, I bought a .629" reamer. We'll see how many, if any, tenths it cuts oversize. If it's close to .6296", we can finish with a hone. If it should cut undersize, we'll look into stoning down a 16mm.Not uncommon for a reamer to cut .0001-.0002 over measure so to micrometer the reamer and end resharpen it to .62955 or .6296 would be a good start IMHO.
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12-17-2015, 07:48 PM #32
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What is the hole dim. on the print? Is it 16H7? If that's what it is than all you need to do is buy a standard 16H7 reamer. Not knowing how to work in the metric system can cost you big time. For any metric size if specified correctly on a print there is a standard metric reamer that is made to give you max life within the required tolerance. No need to convert and than start stoning or honing. Converting is a can of worms as can be seen by your five decimal places. Time to get with the program.
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12-17-2015, 08:02 PM #33
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See my post #22 and than go out and buy DIN 1420 and also DIN/ISO 286 if you have more metric work in your shop. Originally Posted by PackardV8
We've got a project to ream twelve holes in cast iron to .6296". I'm starting with a 16mm reamer, which is nominally .6299". Will be interesting to see where the diameters start and how much we have to manually modify the reamer to get there.
jack vines
Default
What is the hole dim. on the print? Is it 16H7? If that's what it is than all you need to do is buy a standard 16H7 reamer. Not knowing how to work in the metric system can cost you big time. For any metric size if specified correctly on a print there is a standard metric reamer that is made to give you max life within the required tolerance. No need to convert and than start stoning or honing. Converting is a can of worms as can be seen by your five decimal places. Time to get with the program.
Converting and than buying "specials" will cost you big time. -
- [machinist] Reaming oversized? [many tips and references], Lawrence London, 12/17/2015
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