Reamers How-To?

[macardoso]

Hi All,

Somehow after 5 years of working with reamers, I still am missing a lot of knowledge. I'm hoping that someone can share some tips with me!

1. My reamers tend to leave a bell mouthed hole when using them on the lathe. I hold them in a quality keyless chuck. I know my tailstock is slightly out of alignment but not by much. How close does the reamer need to be to true on center to cut correctly? My drill chuck has .003" TIR, is this even too much?
2. My reamers often squeal and leave faceted chatter marks when entering a hole right at the edge. How do I prevent this?
3. I was taught low speed and high feed for reamers. Can we be specific on SFM and feed per tooth?
4. Sometimes my reamers will bind in the hole as they get deeper. They're brand new and sharp, so I'm wondering if the grind geometry could be wrong?
5. Are reamers used only for hole size and not straightness? I am used to boring almost all my precision holes.
6. From another post of mine, it seems like the long shank of the tool is important to allow it to flex and center. Is this a requirement?
7. What percentage of the final hole diameter should the pre-drill be? Should the hole be bored before reaming?
8. Are my Shars import brand over-under reamers the source of my issues?

I don't trust reamers to make precision holes for me and I know that I should. Looking for help.

-Mike

 

[gerritv]

1. If you know your tailstock is out, then it would seem prudent to fix that if you are expecting precision reaming or even drilling?
4. Machine reamers only cut at the tip, if the hole size is too small then you might get binding (see #7 below), also need to clear chips frequently
5. Reamers can provide straight holes, sometimes you need to use a floating holder (Hemingway has a kit)
6. Short shanks will increase the likelihood of alignment issues (bent long ones as well of course )
7. This link provides a chart you can use as a guide. There are others that might differ a bit. https://www.hannibalcarbide.com/documents/pre-ream-drill-size-chart.pdf, drilling should be close enough.

A photo of your reamers would help, if you are using manual reamers in the lathe tailstock then from my early experience you will get some of the symptoms you describe, esp. chattering.

 

[macardoso]

1. If you know your tailstock is out, then it would seem prudent to fix that if you are expecting precision reaming or even drilling?

I'm usually the one ripping on people for posting obvious answers to their own questions! I know it needs to be done, just need to take the time!

4. Machine reamers only cut at the tip, if the hole size is too small then you might get binding (see #7 below), also need to clear chips frequently

Is it bad to remove the reamer halfway through the hole to clear chips?

5. Reamers can provide straight holes, sometimes you need to use a floating holder (Hemingway has a kit)

I'll look into that, Thanks!

6. Short shanks will increase the likelihood of alignment issues (bent long ones as well of course )

Gotcha.

7. This link provides a chart you can use as a guide. There are others that might differ a bit. https://www.hannibalcarbide.com/documents/pre-ream-drill-size-chart.pdf, drilling should be close enough.

That's exactly what I was hoping to find, thanks!

This is the set I picked up. Always been happy with Shars, so I'm not quick to jump on the import = garbage bandwagon.

0.124-0.501" Over & Under HSS Chucking Reamer Set

<!-- <ul><li>Plus .001" & Minus .001" in 1/8 - 1/2 by 16th</li></ul> -->

www.shars.com

 

[gerritv]

I learned to pay attention to the tailstock after breaking a few very small centre drills on my Taig. Messy to get those tips out of the work.

I keep the work spinning while withdrawing the reamer to clear chips. There is precious little space for chips on these straight reamers, the spiral ones do better but at higher cost of course. Don't forget to squirt lots of oil in the hole, clears chips and lubricates the next cut.

I have EU brand and Asian ones, no real difference for my hobby needs.

I would see if these other solutions work before spending on the floating reamer holder (assuming you even need it). That holder won't fix the other possible issues.

 

[macardoso]

Yikes, those floating reamer holders are $400 or more to buy new. I like the idea of kits, but my tooling I typically would prefer to buy complete and finished.

Also doesn't seem like there are a ton of options to buy reamer holders?

 

[mikey]

1. I assume you are providing a generous chamfer at the hole before reaming, right? Bell mouthing often occurs when the reamer does not make a clean entrance to the hole and it bounces/chatters or if the prereamer hole is too small or if your speed is too fast.

2. Correct size of the hole, generous chamfer will help. Speed also makes a difference; I try to ream somewhere near 100 rpm or so for reamers in the 1/4" range or bigger, slightly faster for smaller ones. If it chatters, try increasing feed.

3. See #2.

4. It may be that the hole is not straight or is not sized correctly. I have never had a reamer bind but I am also careful in my predrilling selection and procedure. If you are step drilling, try spotting and then go directly to a one size smaller drill than your prereamer drill to drill the hole. Avoid pilot drills other than this pre-prereamer drill; small pilot drills can bend and drift. Then use the prereamer drill, then use the reamer. The rationale is that a reamer cannot negotiate turns in the bore so the hole needs to be fairly accurate.

5. A reamer can actually straighten a hole but not if it is off by more than maybe 0.005". If it has to be straight and precise, bore it.

6. Chucking reamers are long to enable their use in drill chucks and tailstock chucks. This allows them to self-center in the chamfer.

7. The prereamer hole depends on the material. The harder the material, the less the reamer can take off and there isn't a percentage that suits all, at least not according to Alvord Polk who make some of the finest reamers in the US. Yankee Reamer has a very good guide that I am attaching that will give you the details.

8. Having no idea of the quality of Shar's reamers, I don't know. I prefer to use reamers from known good suppliers. I use mostly Alvord Polk, PTD. Others like L&I, Yankee and Cleveland make good ones.

Reamers are good for speed. Once you nail down the drill sizes you need and have a reamer size that produces the hole you want then a reamer can produce nicely finished holes of close to the right size repeatedly. BUT if you want a hole that is straight, finely finished and of a precise size then boring it is the best way to do that. Although I have multiple sets of quality reamers, I usually bore my holes - faster for me.

Not to be contrary but a reamer, like most metal cutting tools, is designed to cut only on the way in. If the hole is properly sized then chips are usually not an issue because you have a lot of flute space to collect them. I suggest you ream with a steady feed all the way to the bottom (without actually hitting the bottom of a bore) then shut the machine off before withdrawing the reamer. Your reamers will last a lot longer this way.

Reamers also require generous amounts of cutting fluid. This helps the size and finish.

 

[macardoso]

1. I assume you are providing a generous chamfer at the hole before reaming, right? Bell mouthing often occurs when the reamer does not make a clean entrance to the hole and it bounces/chatters or if the prereamer hole is too small or if your speed is too fast.

I was not, but I will be from now on!

2. Correct size of the hole, generous chamfer will help. Speed also makes a difference; I try to ream somewhere near 100 rpm or so for reamers in the 1/4" range or bigger, slightly faster for smaller ones. If it chatters, try increasing feed.

Sounds good

5. A reamer can actually straighten a hole but not if it is off by more than maybe 0.005". If it has to be straight and precise, bore it.

My drills do tend to cut pretty straight. Would you still try to bore holes say down to 1/4"? I may need to get some small carbide boring bars as I cannot reliably hit close diameters this small.

6. Chucking reamers are long to enable their use in drill chucks and tailstock chucks. This allows them to self-center in the chamfer.

Got it

7. The prereamer hole depends on the material. The harder the material, the less the reamer can take off and there isn't a percentage that suits all, at least not according to Alvord Polk who make some of the finest reamers in the US. Yankee Reamer has a very good guide that I am attaching that will give you the details.

Thanks for the attachment, that is a great resource

Not to be contrary but a reamer, like most metal cutting tools, is designed to cut only on the way in. If the hole is properly sized then chips are usually not an issue because you have a lot of flute space to collect them. I suggest you ream with a steady feed all the way to the bottom (without actually hitting the bottom of a bore) then shut the machine off before withdrawing the reamer. Your reamers will last a lot longer this way.

Probably also avoid scratches from the cutting edge scraping back through the bore.

Reamers also require generous amounts of cutting fluid. This helps the size and finish.

I was at least doing that one thing.



Trying to align my tailstock. What does one do (short of scraping) when the tailstock is higher than the headstock?

 

[eeler1]

Digging deep into buried memory banks, but as a general rule of thumb, isn't the hole supposed to be within 0.015" of final size before you use the reamer? And less is better?

Agree with what they all said, alignment, straightness of hole, etc. And don't run reamer in reverse.

 

[mikey]

I have some tiny boring bars from Micro 100 so I can bore pretty small. I have several sets of reamers so I can also ream pretty small. However, if the hole must be precisely sized and must be straight then I bore it. It is rare that this is the case but I would rather bore it if the hole size is critical.

Drills produce trilobular holes that are sorta straight. If the hole is a through hole to pass a bolt then drills are fine but if they are used for something like a press fit then a reamer is better. If you have a precision fit for a bearing or something then boring it is better. Depends on the situation.

 

[macardoso]

Thanks for all the advice. I'm working (failing) at aligning my tailstock, so when I get that done I will try out all of the tips posted above.