Hand reamers: what tolerance?

oregonclockmaker · Aug 22, 2007

So I've got a part that needs a finished hole of .125" to fit over a stud that is slightly (.1245) smaller, and still rotate freely. Having never power reamed anything that small, I decided to order a spiral flute hand reamer.

Since I only need to do one of these, I opted for the "import" reamer from MSC. I got it, reamed the hole, and....it doesn't fit.

Checking with the gage pins, a .124 just barely slides into the hole; the .125 doesn't. It would appear that the reamer is slightly undersized.

So, is the problem a) I'm expecting too much accuracy from a hand reamer, and +/- .001 is within their normal limits; b) I should have gotten a straight flute reamer, or c) I shouldn't have been a cheap so-and-so by choosing the "Made in Bosnia" import over the undoubtedly better USA brand?

The answer will determine whether I send the reamer back for credit.

-=[ Grant ]=-

toolmakerjim · Aug 22, 2007

i dont use hand reamers for power reaming.

sent it back and get a .2500" quality reamer and problem solved.

or.

get an adjustable hand reamer and you can tweak it to the size you want...jim

Rudd · Aug 22, 2007

Grant, do a search here, or more likely in the old general forum. You can up the size of the reamer a tiny bit by dragging a piece of something up the gullets, like the back end of a drill bit.
Looks like from MH 12 Table 2 p. 1120 you're looking for a clearance of .0004 to .0014 for a 1/4" hole, that's as small as they list.
Tolerances for said reamer are +.0001 to +.0004, so, yeah, you should have gotten more than you asked for in clearance, up to .0009. Glad it's you and not me dealing with tiny little things like that.

oregonclockmaker · Aug 22, 2007

Thanks for the replies.

Just a note to toolmakerjim - this is a 1/8" (.125") hole, not a 1/4" hole! There are - near as I can tell - no adjustable reamers in this size. Wish there were, that would solve my problem. Also, this was not for power reaming; sorry I didn't make that more clear.

Rudd - yeah, I checked MH and found the same thing. I'm wondering what the tolerance for a reamer half that size would actually be?

Oh well - from both of you I get the impression that the problem is a cheap reamer. Back it goes - next time I buy 'Murrican! (It really is made in Bosnia!)

-=[ Grant ]=-

rockfish · Aug 22, 2007

On common sizes such as 1/8", I try to keep a selection of .124, .125 and .126 reamers on hand just in case I need to send another reamer in the hole. Sneak up on it and you'll get just the size you're looking for.

toolmakerjim · Aug 22, 2007

my mistake get a .125 machine reamer

check metric sizes and maybe you can get a .1252" or so...jim DAMN I HATE IT WHEN I MAKE A MISTAKE

Joe D Grinder · Aug 23, 2007

I'm prone to lap holes that small..Joe

Davis In SC · Aug 23, 2007

DAMN I HATE IT WHEN I MAKE A MISTAKE

Ah, those mistakes are not bad, no harm done. The ones I hate are in metal, such as drilling a hole too big..

C.M. · May 19, 2018

Joe D Grinder said:
I'm prone to lap holes that small..Joe

Old post i know but am in a similar circumstance. Can I get directions and guidance for lapping holes to within +/- 0.0001 inches ? I'm dealing with the brass cylinder of a trumpet that is about 0.665 diameter by 4 inches....through hole.

Milland · May 19, 2018

C.M. said:
Old post i know but am in a similar circumstance. Can I get directions and guidance for lapping holes to within +/- 0.0001 inches ? I'm dealing with the brass cylinder of a trumpet that is about 0.665 diameter by 4 inches....through hole.

With a brass instrument I'd probably not lap it, as lapping typically uses a softer tool than the workpiece to prevent compound embedding the wrong way. For your application, and presuming there's only a tiny bit of metal coming off to get the right fit, I'd try a fine grit sandpaper taped and spiral wound around a wooden dowel.

Carefully run this improvised flap wheel inside the bore, taking only a little material at a time until you understand how aggressive the process is, and cleaning/test fitting frequently. Perhaps use kerosene or similar for lubrication of the cut and for cleaning. Use a short axial length of paper to ensure you can focus on one section at a time, so you don't over cut one area while finishing another.

I know we have a few instrument makers who read this forum, perhaps a pro will chime in.

JRIowa · May 19, 2018

You would be much better off by starting a new thread than to hijack an 11 year old one.
JR

eKretz · May 20, 2018

Definitely better to start a new thread, but I'd probably use Timesaver's "non-embedding" lapping compound for that. The yellow can is specifically made for softer metals and according to the maker can even be used for Babbitt.

Wild West · May 20, 2018

First off, don't buy from MSC. They're the most expensive place to buy cutting tools; even more than McMaster.

TDegenhart · May 20, 2018

Wild West said:
First off, don't buy from MSC. They're the most expensive place to buy cutting tools; even more than McMaster.

McMaster isn't that bad, only problem is they don't tell you the brand. Can usually call and find out the brand. They are high quality tools though.

Tom

DMF_TomB · May 21, 2018

oregonclockmaker said:
So I've got a part that needs a finished hole of .125" to fit over a stud that is slightly (.1245) smaller, and still rotate freely. Having never power reamed anything that small, I decided to order a spiral flute hand reamer.

Since I only need to do one of these, I opted for the "import" reamer from MSC. I got it, reamed the hole, and....it doesn't fit.

Checking with the gage pins, a .124 just barely slides into the hole; the .125 doesn't. It would appear that the reamer is slightly undersized.

So, is the problem a) I'm expecting too much accuracy from a hand reamer, and +/- .001 is within their normal limits; b) I should have gotten a straight flute reamer, or c) I shouldn't have been a cheap so-and-so by choosing the "Made in Bosnia" import over the undoubtedly better USA brand?

The answer will determine whether I send the reamer back for credit.

-=[ Grant ]=-

.
most keep selection of sizes -.001, -.0005, +.0005, +.0010 etc. material if got hardness variations can cause less than perfect holes. if you return reamer many places will not sell you stuff. or they will charge you 200% more and require minimum $200 order or charge $200 to fill out the paper work in addition to what ever you buy. really if somebody tried to return a reamer they used i can understand them refusing to sell you anything more.

eKretz · May 21, 2018

DMF_TomB said:
.
most keep selection of sizes -.001, -.0005, +.0005, +.0010 etc. material if got hardness variations can cause less than perfect holes. if you return reamer many places will not sell you stuff. or they will charge you 200% more and require minimum $200 order or charge $200 to fill out the paper work in addition to what ever you buy. really if somebody tried to return a reamer they used i can understand them refusing to sell you anything more.

You're answering a guy who posted in 2007.

C.M. · Jun 1, 2018

eKretz said:
You're answering a guy who posted in 2007.

And others may have the same issues. I don't think it's all that important when the original post is made, rather that it gets an answer for future searches.

Search

Largest Manufacturing Technology Community on the Web

Search

Hand reamers: what tolerance?

oregonclockmaker

Aluminum

toolmakerjim

Titanium

Rudd

Stainless

oregonclockmaker

Aluminum

rockfish

Titanium

toolmakerjim

Titanium

Joe D Grinder

Titanium

Davis In SC

Diamond

C.M.

Guest

Milland

Diamond

JRIowa

Diamond

eKretz

Diamond; Mod Squad

Wild West

Hot Rolled

TDegenhart

Diamond

DMF_TomB

Diamond

eKretz

Diamond; Mod Squad

C.M.

Guest

Similar threads