Need Advice For Using a Chucking Reamer

Lucky for us, we can often ream a hole and then make the part to fit the way we need it to. There are advantages to being a hobby guy who is making one off parts. :)

On the other hand, it is good to know how your drill and reamer choices can be done on a more informed basis. I often use the Yankee guide I'm attaching below; hope it helps.
 

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OK, here's what I'm making. I bought a boring bar holder off ebay to use with 1/2" boring bars, and need to make a reducing
sleeve for it. So, I need a 1/2" hole to match the boring bar diameter. I thought I'd use a reamer since it would be more accurate
than drilling, and I happen to already own a reamer. Boring would be fine, but I'd have to bore 3 inches deep,
which seems a stretch for a boring bar that fits down a 1/2" hole. mikey, when you say a plus size hole, how much are we talking?
Since the holder "pinches" the sleeve down, I would think I've got some leeway here.
 
Why not just use a tool holder with a V cut in the bottom? Usually marked 250-102 on the cheap imported AXA holders.
 
Oh, okay. A sleeve needs a clean finish and should ideally be bored to the pre-reamer size to ensure the hole is straight before you ream it. However, I understand that boring a 3" long hole is difficult if you lack the proper bar (5/16" or 3/8" carbide bar). When I made my boring bar sleeves, I drilled and reamed it and it works just fine. And you're right; you do not need a super-precise fit because you're going to slit the side of the sleeve anyway.

Assuming you are using mild steel, then the correct pre-reamer drill would be about 31/64". The way I did mine (I've only done 4 of these sleeves but I've reamed many holes and the principles in the Yankee paper work well) was to spot drill, then pilot with a drill that spans the web of a 29/64" drill. Then I drilled with a 29/64" drill to bulk out the hole, then drilled with the 31/64" drill. This gives me a pretty clean and straight hole. Then I used a 1/2" reamer.

I have found that sulfur-based cutting oil works well. Reamers cannot take a lot of material off so the way we use them matters. What works best for me is to chamfer the entrance hole, then coat the reamer and the hole with cutting oil. I set speed at about 100 - 200 rpm and make a single pass manually so I can feel a slight resistance to feed all the way down the hole (teeth are cutting continuously) until the reamer tip emerges on the other side. I shut the machine off and withdraw the reamer. I have tried many ways to ream - low speed, high speed, withdraw under power, etc. I have found that my reamers cut more accurately, produce a better finish and stay sharp longer by doing it as above, or at least this works best for me.

I think you're doing it right. A finely reamed finish in the holder reduces chatter in the bore so reaming the sleeve is the way to go if you cannot bore it.

I also suggest that you make two lengthwise cuts on your sleeve; one through cut and one expansion slot opposite the slit like in the pic below. This allows the sleeve to clamp easily without cracking the sleeve.

sleeves.jpg
 
Why not just use a tool holder with a V cut in the bottom? Usually marked 250-102 on the cheap imported AXA holders.


That's what I've been using, but the boring bar holder should be more rigid and that frees up another tool holder for normal lathe tools.
I got the boring bar holder cheap since it was missing the sleeve that normally comes with it.
 
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Thanks for the detail Mike. The only 3/8 boring bar I own isn't carbide, so I'll drill it per your suggestion. My usual cutting
fluid is Rapid Tap. Not sure if it has sulfur or not, but I usually get good results with it and I can slop it on. My biggest concern is that
my tailstock won't make the full pass. I was thinking I could back up the reamer a small amount, stop the machine, reset the tailstock,
start it up and finish the pass, but I don't know if that would grab when I start it up. Or, I could finish the last 1/2" or so manually
with a tap handle to keep that from happening. What do you think?
 
You'll do fine with Rapid Tap. Just be generous with it.

I would do as you suggest - stop the machine at the limit of your tailstock ram and back the reamer out of the hole. Retract the ram, clear the reamer and hole of chips, re-lube, advance the reamer into the hole and back up so the tip is just clear of the contact point. Lock the tailstock down, restart the machine and then finish up. The reamer cuts only at the tip and creates it's own chamfer; it will self-center when you resume and it won't grab. The flutes will also help center the reamer in the hole so you should be fine.

Just for future reference, if you have a QCTP then you can buy or make a tool holder with a drill chuck attached. It takes more to set up and get it on center but you can then use the saddle to give you all the travel you need when using this tool.

You got this, brother - go for it!
 
I'm planning slitting the sleeve. Thanks for bringing it up though.
 
My biggest concern is that my tailstock won't make the full pass.
I don't know if this idea would work on your lathe. It's a modification I made to my Grizzly 9x20 for deep drilling. The pin on the underside of the door hinge screwed to the tailstock can be hooked into the T-slot of the carriage. I can then use the carriage to drive the tailstock back and forth. Disadvantage: The tailstock lock has to be released, or at least loosened, so centering accuracy might suffer. But then, a chucking reamer shouldn't be rigidly positioned anyway ... should be allowed to find its own center.

HPIM2578.JPGHPIM2579.JPGHPIM2581.JPG
 
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