Reaming oversized?

Forestgnome · Dec 11, 2015

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".

lionelt · Dec 11, 2015

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.

Mike1974 · Dec 11, 2015

Forestgnome said:
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".

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!"

Booze Daily · Dec 11, 2015

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.

5 axis Fidia guy · Dec 11, 2015

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.

cmccull166 · Dec 11, 2015

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.

L Vanice · Dec 11, 2015

Forestgnome said:
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".

I guess you could ream it with your .124 reamer and then buy a .1245 reamer to finish it.

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

onecut · Dec 11, 2015

"TIPS OF THE TRADE" google in the search box

jmcvo · Dec 11, 2015

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.

lionelt · Dec 11, 2015

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

toolsteel · Dec 11, 2015

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.

Forestgnome · Dec 11, 2015

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.

Whysosharp · Dec 11, 2015

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.

michiganbuck · Dec 11, 2015

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.

juergenwt · Dec 11, 2015

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.

charlie gary · Dec 11, 2015

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.

Davis In SC · Dec 11, 2015

For small parts, best method is to ream a thou or two under, and use the Sunnen to get correct size..

Davis In SC · Dec 11, 2015

lionelt said:
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

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.

michiganbuck · Dec 12, 2015

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.

lionelt · Dec 12, 2015

Davis In SC said:
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

Long link

https://books.google.co.uk/books?id...ge&q=popular science reaming oversize&f=false

Reaming oversized?

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