How to drill and ream a large-ish hole with drill press.

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matthew-s
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How to drill and ream a large-ish hole with drill press.

Post by matthew-s » Sun Aug 05, 2018 10:01 am

Hello - working on my 3/4" Kozo A3, building to spec (brass, etc, etc).

Background
I'm trying to figure out the best approach for drilling the holes in the upper bolster for the tender truck pivot.
The spec for this hole is to ream it to 0.250". No further instruction is given.
The bolster is 19/32" thick. The hole needs to pass through it. The bolster is 5 3/16" long x 3/4" wide.

An earlier operation called for a similar hole to be done on the lathe, but on a much smaller, cylindrical part: Spot Drill, Drill with "D" Drill, then Ream to 0.250. This was an operation on the truck wheel bearings.

So, I started the hole with a spotting drill. I have an old Atlas drill press in very good condition. The table is as square to the spindle as I can make it.

Situation
I expect I'd be successful in drilling the "D"-sized hole in one shot. I am stumped on the reaming. The lowest spindle speed is quite fast, much faster than the reaming operation I did on the lathe.

I feel the position of this hole is not critical to 0.001". I expect it's more about getting it square, concentric, and with the right clearance for the post. Still, how do I do this?

I've already put enough time into these parts that I REALLY don't want to screw this up. A little extra time invested here to ensure success would be worth it.

Two Questions
1. Am I right in thinking I should go from the spot drill to the "D" drill? I feels like it would be the better approach over incrementally drilling larger holes.

2. How am I supposed to ream this? I have a sharp 0.250 chucking reamer. Here are the options I've worked out so far.
2.a Just run it through the drill press under power - it will be fine. Just do it quickly.
2.b Rig up a way to turn the drill press spindle by hand / manually, all while feeding the reamer!!?!?
2.c Chuck the reamer in my hand-drill. It is pretty high torque, and can turn at a crawl. The reamer will just follow the "D" hole.
2.d Figure out a way to put the reamer in a tap handle or similar, ream by hand, again counting on the "D" hole to guide the reamer. However the reamer shaft is polished. I'm not certain I could hold it well enough to hold up to the torque of the operation.
2.e (Oh, please no) Mount the bolster on the lathe's faceplate. Drill and ream on axis. I expect the alignment of this would be a real pain to do, especially twice, and may be no more accurate or successful than one of the above options.

Which of the above should I do? Did I miss a better way?

Thanks,

Matt

Bob D.
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Re: How to drill and ream a large-ish hole with drill press.

Post by Bob D. » Sun Aug 05, 2018 10:15 am

Not much problem with the hand drill. Only cutting a few thou. Can pass the reamer shank thru the D hole first than chuck it up. Use some oil. Pull the reamer back thru the hole under power and the shank keeps things aligned.
I don't think you'll have an issue with the drill press either. Let the vise float and run it thru. Can probably blip the power if you think it is really to fast.....

Bob
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Dave_C
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Re: How to drill and ream a large-ish hole with drill press.

Post by Dave_C » Sun Aug 05, 2018 10:20 am

Matt,

If you are going to use a chucking reamer it has to be started straight and on center with the hole you just drilled or it will be off center and off axis. I would not attempt to do this by hand or with a hand drill.

With the part on the drill press, after spotting the hole and drilling the hole, install your chucking reamer, take the belt off the motor and pulleys and turn the spindle by hand if you don't have a low enough speed to run the reamer slowly. Lube the hole and the reamer and just go slow and let the reamer do the work.

Of all the options you listed, this should give acceptable results.

Dave C.
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rkcarguy
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Re: How to drill and ream a large-ish hole with drill press.

Post by rkcarguy » Sun Aug 05, 2018 2:17 pm

What is your lowest spindle speed on the drill? That would be the deciding factor for me. I have 'blipped" the on switch on mine as well, when trying to get a lower speed. For me, this is when I've wanted to start a tap in a hole to assure that the threads are square to the piece I just drilled. Then I loosen the chuck, drop the table down, and finish tapping the hole by hand.
A "D" drill only leaves you .002" per side, this should be easy to accomplish if done quickly with a low enough speed.....maybe 125 rpm or less, or simply turn the spindle by hand and ease it through. Run too fast, and the reamer will vibrate and blow the hole out of size.

matthew-s
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Re: How to drill and ream a large-ish hole with drill press.

Post by matthew-s » Sun Aug 05, 2018 3:47 pm

I'm not sure how slow the drill press goes. I'm pretty sure it's faster than 125 RPM. I think I have the original manual downloaded from OWWM, but I have no way of knowing if the pulley's are original. I've given thought to putting a 3-phase and VFD on it, but decided if I started doing that kind of stuff, the A-3 would NEVER get done!!

Unfortunately, I toasted one of the parts already, and bent the "D" drill. All was going great - I was pecking away and the hole was drilling like butter. Then the drill broke through the bottom and jammed, grabbing the part & vise. Very ... exciting. :shock:

Yeah, I know you are supposed to clamp the vise, but I was not certain how to keep everything centered when doing so. I'm now of the mind that I need to just start the hole, and then clamp the vise down while the drill bit, locked down into the partial hole, holds the part in place. Then from there start drilling. Is that the correct order of operations?

What a painful lesson, expensive in time and money. Blah. I had to shut the lights and walk out of the shop.

rkcarguy - do you think I should use a smaller drill bit to leave more than 0.002 radius to ream?

I also thought Bob D's idea of drawing the reamer up backwards through the hole to be interesting - I can see how that might keep everything a bit more square.

rkcarguy
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Re: How to drill and ream a large-ish hole with drill press.

Post by rkcarguy » Sun Aug 05, 2018 5:02 pm

Sorry that happened, I've experienced that many times and it's no fun. Eventually you get a super-sensitive feel for when the bit starts to break through though. Easing up on the feed and taking light pecks will usually prevent that. I know on grabby materials, I've set the quill stop just shy of breaking though, then twist it down with one hand while I peck drill with the other so the bit can't take a big bite and get stuck when it does pop through.
I like taking a light cut with the reamer, as long as the hole cleans up completely all is well.
As far as reaming from the bottom, I'd be concerned it could pull a part up and out of the vice if it's a cast part that's hard to secure solidly.

John Hasler
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Re: How to drill and ream a large-ish hole with drill press.

Post by John Hasler » Sun Aug 05, 2018 6:37 pm

matthew-s writes: Yeah, I know you are supposed to clamp the vise, but I was not certain how to keep everything centered when doing so. I'm now of the mind that I need to just start the hole, and then clamp the vise down while the drill bit, locked down into the partial hole, holds the part in place. Then from there start drilling. Is that the correct order of operations?

Clamp the part down from the beginning. If you don't have an x-y table tap the part into exact position under the spot drill with a hammer before tightening down hard. Spot drill, drill, and ream in one setup. You can reduce the grabbing on breakthrough problem and improve the quality of the exit hole by drilling into a piece of sacrificial aluminum. If you are worried about power reaming (note that the reamer won't self-feed as a drill bit might) rotate the chuck with a strap wrench or pipe wrench.

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Re: How to drill and ream a large-ish hole with drill press.

Post by JoeKahan » Sun Aug 05, 2018 9:10 pm

Matt,
Not sure it will help you or not, but I once wanted to turn my drill press very slowly. I took the drive belt off and ran the spindle with a socket on the end of my VSR cordless drill. Worked great for what I wanted to do.
Joe
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Glenn Brooks
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Re: How to drill and ream a large-ish hole with drill press.

Post by Glenn Brooks » Sun Aug 05, 2018 10:04 pm

I’ve had good success starting the hole to initially locate it properly, then using the drill mounted in the spindle, push down on the work to clamp the vise in position. When doing this particular operation, I usually always center punch the location first, to get it located accuractly and started.

Now, being a bit of a heretic, I would like to suggest that alternatively, perhaps you really don’t need to ream this hole in the bolster at all. Just drill it with a .250 drill. These things take a lot beating and tend to wear themselvs into a position they like over time. So it’s possible you won’t really see a performance Improvement that would warrant the extra time and care it would need to ream super nice sides inside the hole. I assume you will drop a roll pin, or bolt through the hole? And if this is the king pin that holds the truck to the bolster then, maybe the only critical operation might be to center punch it properly..something to think about,perhaps. :)

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NP317
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Re: How to drill and ream a large-ish hole with drill press.

Post by NP317 » Mon Aug 06, 2018 12:45 am

Question: What material were you drilling?
If it was a brass alloy, you should dull the two cutting edges on the drill to prevent that grabbing, especially at the bottom of the hole!
Kozo H. describes how to do the drill modification in his books.
And always have the part securely clamped.

And I also vote for hand-turning the drill chuck to ream the hole, by whatever means is comfortable for you.
Lastly, you want the reaming process to be vary shallow. WITH lots of lubricant. Leaving more than 0.002" cut depth could be too much for the reamer.
~RN

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Greg_Lewis
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Re: How to drill and ream a large-ish hole with drill press.

Post by Greg_Lewis » Mon Aug 06, 2018 12:27 pm

As Glenn wrote above, if this is a kingpin hole in the bolster, it probably doesn't need the accuracy of a reamed hole.

As to locating in the drill press, I prefer not to use a center punched hole but to scribe the location and then use a pin like the one in the photo below. The end of the pin is ground to a point which I center on the scribed lines using a magnifying hood. I can get extremely close with this; anything that needs to be dead on is done in the mill.
IMG_7551.JPG
Then I use a center drill in the holder shown to start the hole. If you use a nice sharp center drill and just barely touch it to the bluing on your mark-out, you'll see if you got it on the lines or not.
IMG_7552.JPG
As to reamers, I'm not comfortable with the idea of pulling a reamer backwards through the hole. Chucking reamers are made to cut on the end, and the inside or back end of the flutes is not ground for cutting. Hand reamers, however, are made slightly barrel shaped so the lead end is a tiny bit small and the full diameter is reached about half way up. If you check the hand reamer in the photo below, you'll see a center hole in the handle end, which you can center up with a locating pin in the drill chuck and ream the hole with that. You will, however, need plenty of clearance below the part for the lead end of the reamer.

FullSizeRender1.jpg
For drilling in soft materials, I start with a much smaller drill diameter, say 1/8 inch or so, and work up to the final size in small increments. Stoning off the cutting edge of the bit is also a good option but that creates a bit you'd either have to resharpen or save just for the soft material.

Oh, and always, always, use whatever it takes to hold any part regardless of size down tight on the drill press table. And never trust the vise to do the job alone. Be sure the vise is also bolted down. Some day I'll tell y'all how I know this.
Greg Lewis, Prop.
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Re: How to drill and ream a large-ish hole with drill press.

Post by Harold_V » Mon Aug 06, 2018 4:12 pm

Good post, Greg.

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