I have a 4’6” x 8’ x 1” table top with 9/16” laser cut holes in it (160 holes - 6” OC). I would like to enlarge them to 5/8” or 3/4” but I am unsure of the best method to keep the hole in the same location without it walking. Car reamer? Viking Hole Hog? I have a mag drill. Any suggestions would be great! Thanks
A reamer would be your best bet. But you need to be hole needs to be within 2% of the hole you are trying to ream.
5/8" = .625 Closest drill would be 39/64" = .609 or 15.5mm = .610"
625-609 = .016
2% x .625 = .0125
So you would be trying to take to much material with the reamer.
They do make a bridge reamer and a 5/8" bridge reamer is tapered and starts at 7/16" So this might work. Mabey someone else or @jason can chime in as I have never used one.
You aslo have the same problem trying to go with a 3/4" hole
here is a link to a Bridge Reamer, you would want to make sure its not to long for your mag drill.
Let us know what you ened up doing so others can learn from you
Good Luck
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Your best option is to redrill the holes with a annular cutter and drill template. It will definitely be faster than the reamer option. Since your table is 1” thick it’s going to be slow drilling with the spiral reamer. Also without the drill guide the chances of it wondering off to the side is very likely. The spiral reamers have a lot of surface area and work better with thinner material. You’ll probably need a bushing or step pin with the drill template if you want to keep your current hole center.
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I agree with Jason mostly. I would add consider going for a carbide tip cuttered as they are better suited to deal with the HAZ that the laser would leave if it is a problem. Truthfully though if you have a 3 jaw drill chuck for the magdrill I would probably myself at least try centering the unit using a 9/16 bit then change to the 5/8 or probably even 3/4 depending on how brave I was and running a twist drill. I it is sharpened coencentircly pretty good chance of it staying alignined and really 1" isn’t stupid thick just thicker thank anything thinner 
use plenty o collant and see how she does. if you can slow your drill down at all this helps especially with the twist drill’s which are readily avalible at most hardware stores even in po-dunk colorado in larger sizes
But he has 160 holes to enlarge… I think Jason’s comments are spot on.
–Larry
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A piloted counterbore would be one way. But 6" OC is on the large size for a fixture table.
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Thank you for the suggestion! I am using it mainly as a work bench/welding table but I wanted a few holes in it for clamps and pins. It was going to cost double to do 4” OC and no idea what it would have cost to do 2” OC. Thanks again
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This is…a bit pessimistic. The 2% is one general guideline, but as reamer sizes go up, so does the permissible allowance. The designers of a 5/8" chucking reamer expect you to drill a 39/64" pilot hole (0.609" pilot for 0.625" final size). That should be fine.
Also, 2% of 0.625" is 0.012(5)“, not 0.007”.
(What would the alternative be? I suppose you could drill .609" with your 39/64" and then get a custom 0.617" reamer and follow that with a 0.625" reamer…but nobody does that! Or they would come in sets! Well, not without CNC interpolation.)
I find it a little weird that Machinery’s Handbook doesn’t seem to discuss this. Maybe I’m not looking in the right place though.
I disagree with re-drilling the holes. You’re going to tear through twist bits. Unless you use a spade bit, if that’s an option in that size and fits the mag drill.
A bridge reamer would work, though you might need more than one with enlarging laser cut holes. The hardened edge will be your problem.
Buy a cheap mist coolant setup and spray your bits while reaming. I would start with 5/8, see how it goes, then step up to 3/4 if you want the larger size. Check out McMaster Carr for bridge reamer options. 160 holes is not that bad.
Hey @JohnHawkinson
You are correct I am not sure how I got that but thank you for correcting me. I will go back and edit my post so its correct.
I guess you can tell im not a machinist and not very good in math.
Thanks for the follow up!
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I haven’t seen it listed yet. But there are drill bits called core-drill bits that are a cross between, what I would consider to be, a reamer and a drill bit. They are piloted in whatever size is necessary, and I’ve seen them jump anywhere from a .250" to well over .500", going into aluminum an inch+ thick, with accuracy to the thousandth.
I’d be curious to see how they’d fair with upsizing holes in thick steel.
Out of all the different bits I’ve used, core drills have been the most reliable, consistent, and easy to use when upsizing holes of all sizes. I wish they were more common outside the aviation industries.
Here’s an example of one I have commonly used
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Hey, I hate to be ridiculously practical here, but is all the time and effort worth it, with still no guarantee that you will be happy with the end result. I’d bid this out to a machine shop with a CNC mill or other cutting set up.
Ok, I withdraw my suggestion as reworking an existing matrix is probably nothing a machine shop equipped to do it would bother to take in, and if they did probably price prohibitive.
I have a shop made table with 5/8" holes on 3" centers. It is 4’ x 8’. It has 512 holes that i drilled with a mag drill and annular cutters. All you need to do is take your drill with a 5/8 annular cutter, line it up so it precisely lines up with your hole, lock the mag drill down. Then without moving the drill, change to the size cutter you wish to enlarge. Cutting fluid is your friend here.
