Chucking Reamers

jocat54

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I have never used a reamer but think I would like to have some on hand at times, so my question is what sizes ---it looks like most that I see are over or under sizes--I think I would want like .125, .250, .3125,.375, ect. Why all the over and under sizes? Sources?
 
Reamers are typically chosen to produce a fairly precisely sized hole with a good finish. They can be oversized to provide a slip fit or undersized to provide a press fit of a pin of known diameter, like dowel pins. I, for one, don't often use dowel pins; I make what I need to the size I need. I usually use on-size reamers and cut the stock to the fit I want. But I'm a hobby guy and don't have to make a part to someone else's specs.

Reamers are available in almost any size and they can be custom-made to the size you want. Sets can be very expensive if you buy a name brand like Alvord Polk or L&I or Chicago-Latrobe, etc. You can find sets on ebay for not bad prices. Amazon also has a good selection and sometimes has them on sale for stupid low prices.

Straight flute, RH spiral, LH spiral - take your pick. Reamers are a huge discussion.

I have fractional sets, metric sets and some over & under sizes, too, but to be very honest, I usually bore the hole I need. That way, I have a straight hole with a fine finish in the size I need.
 
I have a small collection, mostly Ebay finds. 5/16", 3/8", 1/2", maybe couple more. Straight flute. No overs or unders. I like the USA ones best.
Mark
 
I have all of the above types of reamers,
the under and over sizes are made for clearance
obviously you can't put a .375" part in a .375" bore and have rotation of the mating parts
but if you reamed the bore to .376" or .377" you would have a running fit
if you wanted to put a bushing in a bore and wanted a press fit, by the same example
a .375 OD bushing may get a hole reamed to .3745" or .374" for a press fit.
 
I have a small collection of reamers that I've bought over the years, sizes that I needed only, no sets.
All of them are Alvord Polk, C-L, Yankee plus a Cleveland expanding reamer set that I don't use much.

The AP reamers, IMHO, are the best. Amazon has AP reamers for great prices. I buy them one at a time since the selection is enormous.
I would only buy new reamers. A dull reamer is not easy to sharpen by hand, and you really need a sharp reamer to cut on size,
or as close as a reamer can cut. Stock removal for the metal you're cutting is also key. Leaving too much or too little can dull a reamer
or ruin your work.

A-P and Yankee have charts on their respective websites. I personally like the Cobalt straight flute chucking reamers.
Spiral flutes work best on cross holes but can be used on straight holes.

I also use end mills to ream some holes or to start holes for reaming.,
when size spec permits. Getting the right pre-ream hole is very important, but like Mikey and others have written, boring is the way to go to get
a good final hole size if it's critical. I bought one import reamer once and never again. They go dull quickly. Ebay is hit and miss. Too many odd sizes.
And don't forget to buy the correct, corresponding pre-ream drill or end mill for the metal you intend to cut.
 
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In my business, I had standard size chucking reamers (which generally cut slightly oversize) and an over/under set; if dowel pins are used relatively often, they are just the thing. I also had hand reamers, both solid and expanding, the best type for limited expansion and nicest finish are the spiral type, solid adjustable type made by Millersburg and others.
It is possible to grind machine reamers undersize if a special size is necessary; they are simply ground undersize cylindrically; they can be backed off at an angle to lessen friction, but will function without backoff. Machine reamers are sharpened by ONLY sharpening the chamfer at the end.
 
John, I have found chucking reamers on e bay in lots that were pretty cheap, (40 reamers for $50) Sizes from .0625 to 5/8. I have ordered some that I needed and paid full price when I could not find them otherwise. I like exact size, not overs or unders. If I need an over for a slip or sliding fit then I use an old machinist trick I read about, lay a small piece of brass shim stock, usually .001 to .002 thick over two of the flutes and run the reamer through the hole again, then check the fit. Doesn't hurt the reamer and you don't have to have a garage full of reamers in stock.
 
I buy carbide reamers, just the sizes I need for the project on hand.
 
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