# How do reamers work



## SmoggyTurnip (Jun 23, 2008)

I have never used reamer.

I was looking at this reamer
http://grizzly.com/products/Chucking-Reamer-HSS-1-/G9457


and I became confused. It looks like the cutting edges are dead straight. So once the first part of the tool goes into the hole the diameter of the hole at the start is now cut to size so the rest of the reamer has nothing to do. It looks to me like the only part of the tool that would have any cutting to do is the tip. Is this correct?


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## Jadecy (Jun 23, 2008)

You drill to slightly smaller hole than a reamer and if it is a chucking reamer you put it in the chuck in place of a drill bit and run it through the hole with some lubricant just like you would a drill. This makes a very accurate and smooth hole. 
This is typically for small holes (ie. less than 3/4" usually less than 1/2"). 

There are all kinds of reamers. The most common I've seen are over/under chucking reamer sets. There are also taper reamers and adjustable reamers. If you lathe talestock is aligned and the drill chuck is good you will get a super nice finish on a very accurately sized hole. I use my over/under set quite a bit.

On larger hole you use a boring bar and a hone or lap to get close tolerences.

Hope that helps. 



.....missed part of the question

You are correct about the initial edge doing the cutting. Think of it as a straight flute drill bit but much more accurate. A helical drill bit does the initial cutting at the tip as well but the flutes continue on. Reamers do not self clean the debris so if it is a blind hole you'll need to back it out periodically and clean the hole.


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## Philjoe5 (Jun 23, 2008)

For some good info on reamers check out this site:

http://www.yankeereamer.com/Tech_Info/tech_info.html

Cheers,
Phil


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## Mcgyver (Jun 23, 2008)

Smoggy, you are correct, the cut on the ends. The rest of the flutes provide guidance and also permit many re-sharpenings....but taken care of a reamer will last a very long time with casual use. As with all cutting tools, my advice is that it is cheaper in the long run to buy quality. 

Like Jacey says, drill undersized, i go .005 - .020 depending in size then use the reamer in the drill press, lathe, mill etc for a quick way to get an accurate sized hole with good finish. The length of the shaft is such that and so that the reamer is somewhat flexible (this is done on purpose). It reamer will follow the hole and make up for minor errors if the chuck is a little off.


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## SmoggyTurnip (Jun 23, 2008)

If you wanted to make a .600 inch diameter cylinder for a stirling engine would you rather use a reamer or a boring bar or something else?


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## zeusrekning (Jun 23, 2008)

If you have a reamer the size needed I would ream then make piston to size. But it is not very often you have that "right" size reamer. And not so well to use on blind or capped cylinders b/c of the taper on the leading edge. 
Also, floating reamer holders are a god send. And if it is in your price range or if you stumble across one , a right hand cut left hand spiral carbide tipped reamer can leave a mirror finish in most anything if aligned properly or used in a floating head. 
Just my .02 
Tim


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## mklotz (Jun 23, 2008)

Mcgyver  said:
			
		

> Like Jacey says, drill undersized, i go .005 - .020 depending in size then use the reamer in the drill press, lathe, mill etc for a quick way to get an accurate sized hole with good finish. The length of the shaft is such that and so that the reamer is somewhat flexible (this is done on purpose). It reamer will follow the hole and make up for minor errors if the chuck is a little off.



And this is why, if you use a reamer with a short shaft, grasp only the tip of the shaft in the tailstock chuck. It allows it a bit of "wiggle room" so it can follow the hole. A floating reamer holder, as Tim suggests, is the real solution but few of us have one lying around or have the desire to add one more thing to the "to do" list. Actually, if you've just drilled and bored the hole and the setup hasn't been tampered with, I don't think a floating holder is required.

Holes made with drills are seldom round, straight or the right size. The accepted procedure is to drill to remove material, bore to make it round and then ream to bring it to size.

A 0.600" reamer will be pricey. Unless this an LTD Stirling, consider using a more readily available size like 0.625". Then the procedure would be drill 1/2", bore to ~0.6", and then ream.

Or simply bore it. Finish is more important than size in this application. Use the slowest power feed to bore AND to withdraw the boring tool from the hole with very fine final cuts using lots of lubricant.


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## zeusrekning (Jun 23, 2008)

Has anyone made a floating reamer head? Or know of any plans out there.
Tim


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## Bogstandard (Jun 23, 2008)

I would just like to add a little (in fact a lot), just to clarify things slightly.

Generally to us modellers there are basically two types of reamers, hand reamers and machine reamers, then subdivided into two for both types, fixed and adjustable.

Hand reamers are usually identified by having straight flutes, a square on the shaft end to be used with a tap wrench, and sometimes a centre drill in the square end to allow it to be set up on the lathe for HAND reaming, a hand reamer should NEVER be used as a machine reamer.

For general terms, a machine reamer can have either straight or spiral flutes, a morse taper fitting or a straight fitting that can be fitted into a chuck or collet.

Hand reamers have a longer tapered lead in, normally roughly the length of the diameter of the reamer, but in certain cases can be up to a third of the length of the reamer. So because of this, a hand reamer has to be able to penetrate right thru the job so that the parallel areas of the reamer has gone all the way thru the hole. So usually it is no use trying to finish to size a blind hole with a hand reamer, all you end up with is a tapered hole.

Machine reamers usually have a parallel cutting flute, with a very small taper lead in that does most of the cutting. You can get some with no lead in, that look like an end mill cutter, and these are to allow you to cut a very square square edge to the bottom of a blind hole.

One point to notice when using hand reamers, they are usually only for removing 1 or 2 thou of material. Machine reamers can take out a little more. I won't tell you how much I take out as it could be misleading as I tend to use industrial solid tungsten ones for my mainly metric work, but there are charts that give recommended removal rates, but as a general rule around 5 thou should be OK. Material choice is also another governing factor in the amount of material you can remove, stainless will be a lot less than brass.

A point about reamer removal from a hole, whether it be hand or machine. A reamer is never removed straight out from a piece of material, in the case of hand, the reamer is kept rotating in the same direction of cut until it is safely out of the hole, machine reamers are the same, do not turn the machine off with a reamer still down in the hole, extract it first, then turn the machine off.

Feeds for reamers. A hand reamer will feed by the amount of pressure you put on it, just take it smooth and steady with plenty of lubricant, again taking note that if you extract the reamer to clean out swarf, keep it turning in the cutting direction.
A general feed rate for a standard machine reamer is approximately 2 to 3 times the feed rate as you would use with a twist drill. Clean out the swarf regularly and plenty of lube.

How long will reamers last? I have seen jobs on mnemonic steels where the reamer is thrown away after one cut. There is no hard and fast rule, but if you abuse one, don't expect it to give good service. If it binds and polishes in the hole, time for it to be buried. Because we don't use them a lot, you can expect a good few years out of a set, but do remember, they do go blunt after a fair amount of use.

In the UK I buy my sets from Tracy Tools. They are not usually in the catalogue, so if you give them a call they can usually make a set up for you. From there you won't get a matching set, as they make them up out of brand new industrial cutters, they don't look pretty in a stand, but they will last a lot longer than normal hobby sets. The last set of 1MT machine reamers, from 1/8" to 1/2" in 64ths cost me around £60 to £70. A very worthwhile investment (about £2 to £3 each).

Just a note, if you are using a machine reamer, try to keep the portion that you want to be straight, parallel and smooth outside of the chuck jaws. Make the part too long if necessary. Too much jaw pressure can cause you to end up with a triangular hole.

Just a quickie on adjustable reamers, even thought they are a great idea, unless you know exactly how to use and set them up, you may as well try using a lollipop stick to get to the size you want. Also, the standard ones are hand reamers, NOT for machine use. You can get machine adjustables, but it is not worth going down that route.

This long prose is only touching the surface of reaming, but hopefully it has let you know the basics. I am sure that people can add a lot to this, purely thru personal experience.

John

I forgot to add, if you see reamers piled together in a box at a boot or garage sale, unless they are in boxes, or still have their protective coating, forget it. They can be used for their tool steel content to make scrapers or something similar, but not as reamers. They are just not worth resharpening.


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## bretk (Jun 23, 2008)

John,

 A great Primer, as usual, on reaming holes. (I could, but won't, go there :big Thanks! I love this site, Never fail to learn something new. ;D

-Bret


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## Bogstandard (Jun 24, 2008)

To get back to my ramblings from yesterday, I have rooted high and low and come up with examples of what I was on about.


This pic shows a standard hand reamer with its tell tale square drive for use with a tap wrench. In the end of the square drive section is a centre drilling, to allow it to be supported centrally when used in a lathe or mill.








This one shows the three basic types of machine reamer, from left to right. A normal solid tungsten straight shank machine reamer, in the middle is a 1MT shanked HSS machine reamer and one the right is a tungsten tipped chucking reamer with no lead in taper, for getting square corners in the bottom of blind holes. Very little metal should be removed when using this last type, maybe 1 or 2 thou only, and is usually following a previously reamed hole.







This is how your reamers should be stored when not in use. If you haven't got the original protective materials, they should be mounted in a rack of some sort, to stop the sharp edges being damaged. If you throw them in a box together with no protection, you may as well make it the scrap bin, as they will soon dull to unusable.







This is what they will soon end up like if you don't look after them. These weren't mine, they were in the bottom of a box of tooling I bought.
The bottom one is an adjustable chucking reamer, if you look closely at the end you can just see an adjusting screw for opening up the flutes.

The top one should be in a rogues gallery for murdered tooling. This is supposed to be an adjustable hand reamer, but as you can see, one of the cutting blades is missing and it has been highly abused. 
I personally don't like adjustable reamers, as unless they are kept in perfect tip top condition and spotlessly clean, good results are difficult to achieve. But I do suppose they fill a niche where non standard sizes can be cut at reasonable costs.







This is my set of morse taper reamers, one machine and two hand ones. The amount that they are used, doesn't justify buying a matching set, just ones I could get hold of at a reasonable price, at the time I needed them.







There are many other types of weird and wonderful reamers, but for what we do, these standard types are just fine.

John


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