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sha_ba_do_bang
03-27-2006, 05:56 PM
What is the difference between a reamer and a drill bit, i've seen a reamer and it obviously looks different than a drill bit, but how and why do you use them over drill bits?

Thanks

Paul Monds
03-27-2006, 06:11 PM
Drills are used to do just what the name implies. The tolerance on hole size is reasonably close to the size of the drill but can be affected by material, feed rate, accuracy of the grind etc.
Reamersare used to finish drilled holes to accurate sizes and provide a superior finish inside the hole.
Holes to be reamed are usually drilled 1/64" undersize and then reamed at relatively slow spindle speed with lubricant.
Reamers come in different types ie. hand powered, machine powered, adjustable size, or tapered for taper pins or tie rod ends etc.
Paul

Ron Naida
03-27-2006, 06:13 PM
Drills don't give you a round hole especially if you have re sharpened inaccurately. Better to drill undersize by .001 or so then ream to clean up to size. You can still get bell mouth or sloppy holes if not careful reaming.

Boring is better yet depending on what equipment you have. My opinion only.

Ron Naida

sha_ba_do_bang
03-27-2006, 06:51 PM
I need to drill (or ream) holes in my aluminum fuel rail for fuel injectors, what should i do? Also, what is boring?

Is 650rpm to fast for reaming? thats the lowest my drill press goes.

Does reaming leave the bottom of the hole flat if you dont drill all the way thru? Like it would leave a nice step for somthing?

Randall
03-27-2006, 06:53 PM
Ron did you mean to use .001? Thats not enought to ream, bout half a thou per side some people cant pick up and bore a hole with only .001 left (I get pissed if someone only leaves me with .001 and I have to finish the part lol).About .010 is the min for reaming and a 1/64th under is better.

Randall

Randall
03-27-2006, 07:02 PM
Branden, 650 RPM is too fast for what you are doing. I think you want a hole that is suitable for an o-ring is this right? If so you want a good finish to the hole. As for as the bottom you can flatten the bottom of a drilled hole with a reamer (espeacielly in ALum) but it will most likely "walk" some and change the hole size. It might be best if you find someone with a milling machine and knock this job out with a touch of help. With the mill this should not be a big deal.

Just my thoughts

Randall

ralph
03-27-2006, 07:27 PM
I need to drill (or ream) holes in my aluminum fuel rail for fuel injectors, what should i do? Also, what is boring?

Is 650rpm to fast for reaming? thats the lowest my drill press goes.

Does reaming leave the bottom of the hole flat if you dont drill all the way thru? Like it would leave a nice step for somthing?

Reamers are tapered to progressively cut to the proper size, kind of like the taper on a tap, but less severe. If I remember correctly, machine reamers are meant to cut at 1/4 the cutting speed of a drill. Drilling speed can be roughly determed as follows: 4 times the cutting speed of the metal divided by the diameter. Cutting speed is a combination of the cutter material and the metal and can be found in in the Machinery's Handbook or various online sources.
That said, reaming wont do the job for you unless the remer can get at least half way into the hole.

A drill won't give you a properly sized or round hole.

I'm thinking a mill of the proper diameter will be the best tool for this job. Unless your holes are already the right depth, get a center cutting mill. If the hole size is special, a cutter grinding service should be able to size one for you inexpensively. I've got one locally that shapened some mills for me about 6 months ago for $7 each. You can chuck an end mill in your drill press and down feed it, but don't try to mill with it.

Randall
03-27-2006, 07:58 PM
Ralph I believe that you are decribing a hand reamer which is tapered. A machine or "chucking" reamer is one diameter after the small chamfer, just went and measured a few of them to refresh my memory. You can use a machine reamer in a blind hole I have done it a lot. Depending on the size of the reamer I run them from slow to slower. A 3/4 reamer at about 40 to 60 rpms with cutting oil and removing only about .005 to .007 inch material per side.

Randall

Ron Naida
03-28-2006, 04:21 AM
Randall, you are correct .001 or so is too little to leave.

Ron Naida

ralph
03-28-2006, 07:05 AM
Ralph I believe that you are decribing a hand reamer which is tapered. A machine or "chucking" reamer is one diameter after the small chamfer, just went and measured a few of them to refresh my memory. You can use a machine reamer in a blind hole I have done it a lot. Depending on the size of the reamer I run them from slow to slower. A 3/4 reamer at about 40 to 60 rpms with cutting oil and removing only about .005 to .007 inch material per side.

Randall

Never knew that. Thanks Randall. :mrgreen:

strtrcer222
04-05-2006, 08:12 AM
When i worked at a machine shop I ran all reamers at 120 rpms and could ream a hole to within .0005 of an inch.

Randall
04-05-2006, 08:37 AM
Just a couple of questions about just running the reamer at 120 rpm. What size 1/8th or 1 inch? What material Aluminum or heat treated 4140? Do you run all you drills at the same speed? I will agree there are some time that 120 rpm (or higher) is acceptable but determining the proper speed and feed is worth the effort for max tool life.


Randall

rsanter
04-05-2006, 09:58 AM
ideally to do this you need to be using a milling machine.
if you are going to do this on the drill press you have this is how I would go about it.
1 drill hole undersize by about 1/8
2 use an undersize endmill (try a metric one or one that has been resharpened) to clean the hole to round and have a nice square bottom
3 ream hole to final size by chucking ream and turning by hand only

remember to make this work you will need to set the part where you need it and clamp it in. drill the hole, swap to the end mill and then swap to the ream without moving the part. this is how a multi setp operation is done in a mill

bob

strtrcer222
04-07-2006, 08:40 PM
Running a reamer at 120 rpm's is good for any reamer up to about half inch. Any bigger and you want to start reducing the speed. It all depends on your setup. I ran all my reamers at this speed and they lasted me for the 4 years I worked there. Just make sure you keep it well lubricated.

joatmon
04-08-2006, 06:15 PM
According to Cleveland Twist's booklet "Care and Use of Reamers" reamers are to be run at 2/3 drill speed. So determine speed of given diameter drill based on SF of work material and drill material and 66% of that will be reamer speed. Typically a 1/4" HSS reamer is comfortable at 900RPM in L/C CRS with lots of oil flood.
However, running slower with HSS tends not to be particularily harsh. HSS is pretty forgiving of slower than ideal speed, but totally unforgiving of overspeed. Err to the slow side and it will not get hurt, but feed must be reduced accordingly lest gobs of oversized holes be the result from over feeding.