How to Make a Clean Hole with 1 1/8" Dill Bit?

[EricH]

Originally Posted by DonRotolo

You cannot hand-hold a drill to make such a hole. This is dangerous. A drill press is the only safe way to make that hole with a drill bit. Your jagged hole is from the human inability to keep the drill perfectly centered on the pilot hole.

I'm going to disagree on that, Don. I'm willing to bet that with the right extra equipment, I could nail a 1.125" diameter hole with a hand drill, or two. I've done something similar before, though with a smaller hole. (I've hand-drilled one using a step drill, too. That was "fun".)

I'd be using some core drills, an egg cup or two, a drill block and clamps, and a bunch of bushings, ending with a reamer. For the larger holes, I'd use a much slower drill. It's definitely possible, but it'll take time. (I tried to hunt stuff like that up on McMaster yesterday, but no dice. Might have to try another source.)

[George C]

We've had great success this year starting with a centre drill, then 1/8 or so, then 1" (largest drill we have) then reaming to 1 1/8. As said previously, a 1 1/8 reamer has a very large shank and is very long. We cut it off just long enough so that when we chucked it up in a lathe with the teeth behind the chuck we didn't damage the teeth. We then turned the shank down to 1/2. We do as much of the reaming as possible in a vertical mill because it's more rigid, we can secure the work better and we can cut the rpm way down. Has worked really well.

[Andrew_V]

Perhaps hand reaming (with the proper undersized hole) would be applicable if powered isn't an option due to the large shank associated with large reamers. Basically tapping (so make sure its straight and because its reamer you don't need to back out to break chips )

(If you really have no other options adjustable hand reamers is an option albeit not the best option)

If you have a access to a mill a boring head and properly located hole would work too (but as the op stated just a drillpress)


Don't forget the lube

AndrewV

(edit quick google showed up a couple websites for a 1 1/8 reamer for around 50 - 70 dollars) (victornet, grizzly and amazon namely)

(heres a guide (reaming not included) http://www.micro-machine-shop.com/hole_drilling.htm)

[philso]

Originally Posted by AndreaV

The Machinist in me tells this is absolutely the right way, however I know the price of a reamer that big costs about as much as as most team's drill presses, and I've never seen a reamer larger than an inch with a 1/2" shank. Only the beastly industrial chucks go bigger than 1/2 shank"

Drills inherently do not drill precise holes. It is just not the nature of the tool, drills make 'close enough' holes. When using a drill for bearing holes you can expect a loose fit. When I use a drilled bearing hole I always use rivets or bolts hold it in place, as well as press it against a preferred side. some de-burring is to be expected.

Here are some tips for running monstrously large drills, but this applies to most machining operations. It amazes me how many "senior mentors" with years of experience in first/engineering/shop don't know these simple machine shop practices

-Predrill,centerdrill
This is more for location, I wouldn't predrill much more than 1/8 as doing so can lead to more vibrations later on. A drill is supposed to make a hole where there is no hole, if you prefer to step up the drills that is fine, but drill points actually do a pretty good job of starting the cut if used correctly.

-Use the right speed
Different diameter tools, and materials require different speeds(rpm). Basically small diameter tools go fast and larger diameter tools go slower. for your 1.125 HSS drill the right speed would be around 600rpm any faster and you are creating too much friction which creates excessive heat. Aluminum has a low melting point and likes to gall on hot tools that are not going the right speed. aluminum galling on tools has to be the leading cause of tool wear in first.

-Use coolant
Unless using carbide tooling, always use coolant. not only does it lower the temperature to prevent galling but it also adds lubrication for the chips to clear faster.

-Adjust feed/use peck drilling
I know plenty of people that punch their way through material with a spinning drill, instead of letting the drill actually cut as intended. If the above rules have been followed the drill should actually cut. there should be enough force to create a chip, but no more. If the material is getting stuck like you mentioned, there might be too much force applied for too long, and chips are not clearing as they should. Try peck drilling, this is when you drill for maybe a second or two, then back out allowing for the chips to clear, and re enter. rinse(with coolant) and repeat.

-Clean/sharpen the cutting edge
There's a high chance the cutting edge has already been galled, so clear it of any aluminum before attempting to cut again, use pliers not your fingernails please! Only attempt sharpening the tool if you have somebody on board who actually knows how to do so. Beware! a lot of people think they know, but actually make it much much worse.

-Good work holding.
If the part is not held securely on a vise it will wobble around, making the already oversize drill hole even bigger. Should also help with vibrations. Also safety! can't stress the work holding enough!

Drilling a 1.125 hole into 1/8 aluminum plate will never be perfect, but hopefully those suggestions help.

As mentioned above, never do this in a hand drill, and if a mill is available that will provide a much better work holding than a drilling press.

The other night, I made a pair of bearing holders for our collector rollers doing what Andrea described (except I used new drill bits and no coolant) and the bearings were a perfect slip fit. I did the work on a no-name floor standing drill press much like the ones you can buy at HF and no fancy or expensive equipment. The following expands on what Adrea suggested. It isn't the only way to do it but I think it illustrates how to apply the principles she outlines. The only suggestions I would add to Andreas list would be to use templates where appropriate and to take the time to do the job well enough that someone else does not have to spend more time afterward to make corrections and adjustments so that what you made will actually be useable.

I clamped a stack of 5 blank 1/8" aluminum plates and the template in a drill press vise to drill all 19 pilot holes (some were for mounting to the collector arm, some were for mounting the spacer made from 2 " x 1"tube). Fortunately, the plates were cut out by the sheet metal shop at work and they matched each other very closely. I also used 2 C-clamps to clamp the stack of plates down in the vise and to the drill press table.

I used the template to drill the 3/16" holes to clear the 10-32 mounting screws with all 5 plates in a stack. The template was removed. I then drilled the one bearing hole to 1" with the 5 plates still in a stack. I set the belts on the drill press to give the slowest speed possible to avoid any chatter once I went past 1/4". The height of the drill press table was set so that the shortest and longest bits would all work.

To go from 1" to 1 1/8", I clamped one plate in the vice, centered the workpiece using the 1" step on the step drill, clamped the workpiece down in the vice and to the table with a C-clamp and added a second C-clap to help steady the vise. The resulting hole was just under the size needed to insert the bearing.

I deburred the 1 1/8" hole and carefully adjusted the hole size by "scraped" the inside of the hole to get a slip fit on the bearing. The scraping was probably the most tricky part of the operation needing 3-4 iterations to get the right fit. It was done with a Spyderco folding pocket knife with a 2 1/2" stainless spear-point blade that was sharp and stiff. I have used for many things for over the last 15 years. I would not use a snap-off utility knife nor would I use a box cutter since those blades are not stiff enough for me to do this successfully.

I used a second template (made from the first) to drill the spacer made from a 3" long section of 1" x 2" rectangular aluminum tubing. I clamped the spacer in the drill press vise. and clamped the vise to the table with two C-clamps. I ensured that the spacer was seated on the flat section of the vise so that the hole would be as close to perpendicular as possible. The 19 holes were drilled to 11/64 since the mounting screws were 10-32 thread-forming types. All holes were drilled through both side of the tubing. As I moved the vice around the table, I kept the workpiece pointed in the same direction. The table and vice are not perfectly perpendicular to the drill bit. Drilling each hole with the workpiece held in the same orientation means that the hole in the back side of the tube (1" away) would be offset by the same amount. I then drilled the bearing hole out to 1/4". I then used my Blue Mol 1 1/8" hole saw to drill through each side. I know that my hole saw "wobbles" and give a slightly larger hole than the nominal size. This was so that the hole would clear the bearing.

The end result was that hole pattern on any mounting plate (9 mounting holes, 1 bearing hole) would match up with hole pattern on either side of any spacer. The parts were all interchangeable. When assembling the plates onto the two sides of the spacer, all 18 screws went in straight and bearings also went into the mounting plates without interference from the spacers, indicating that the clearance holes were sufficiently concentric with the tap or and slip fit holes. In all, this work took about 5 hours though I actually made four sets of spacers. I still have to make a second set of mounting plates for our other robot.


PS: Andrea, I just looked up the team you mentor. If we had not moved away from TO, my son would likely be on our team. We were living in a house just south of Yorkdale Mall. Congratulations to your team for making it to the finals of GTRE and winning "Highest Rookie Seed".

[roystur44]

Use a drill press with a c'bore tool like this one

http://www.mscdirect.com/product/006...&026=-99&025=c

drill a .250 pilot hole and use the pilot hole to guide this tool.

[catacon]

We have had great luck with carbide hole saws like this one. They get expensive in larger sizes, but they cut extremely nice holes.
http://www.grainger.com/product/IDEA...511?s_pp=false

[Greg Needel]

I have had good luck with step drills and we use them quite often, specifically when just cleaning up holes cut on our cnc plasma.

A few years I found this http://www.mcmaster.com/#4080a26/=r1d6zv It works well if you are trying to drill a hole from nothing, I do recommend using a drill press for this, as it can still walk out like a regular hole saw, but the finish is much better.

[AndreaV]

That counter bore(basically a giant end mill) and carbide hole saw are beautiful!

I love machining! Just when you think you know what you're talking about there's a cool new toy or way to do the same job easier!

[pmangels17]

Whatever option you choose, if it is not carbide, make sure you use oil! Also, we bought a cheap mega-box of chip brushes at harbor freight. We use them to brush away chips whenever we are cutting anything. It helps the drill cut more efficiently and prevents chips from getting in the way of the oil (sometimes it helps if there is oil on the brush). Also, please be really careful to secure your work onto the machine otherwise it will wobble.

[DonRotolo]

Originally Posted by EricH

I'm going to disagree on that, Don. I'm willing to bet that with the right extra equipment, I could nail a 1.125" diameter hole with a hand drill, or two. I've done something similar before, though with a smaller hole. (I've hand-drilled one using a step drill, too. That was "fun".)

I'd be using some core drills, an egg cup or two, a drill block and clamps, and a bunch of bushings, ending with a reamer. For the larger holes, I'd use a much slower drill. It's definitely possible, but it'll take time. (I tried to hunt stuff like that up on McMaster yesterday, but no dice. Might have to try another source.)

Eric, I have no doubt you could DO it. My point was that it's not SAFE to use a hand-held drill for such a large hole using the OP's twist drill setup. Core drills react differently to snags than twist drills.

That also doesn't mean I have never done it. But I know the dangers and addressed them. Case in point: I still have all my limbs, and in proper working order.

[colin340]

To help a junk drill press make better big holes fill the column with concrete. http://www.teeterconsulting.com/mach...g_Machine.html

BUY A MILL WHEN YOU CAN!! 3-4 bottle and can drives = a old knee mill
https://washingtondc.craigslist.org/...359358574.html

[JamesCH95]

I would vote step drill, and then maybe reaming to the final size.

I've always had good results using step drills, in a hand-drill or otherwise.

[dradel]

You can also look into annular cutters. I'm not sure what type of equipment you have available but thought I would mention it.

[amullen]

for drilling any holes start with a center drill to make a pocket for the drill point to follow. After that for anything large you need to incrementally increase or "step up" your drill sixes. Make a through hold with a 1/4 and go from there. For Al i would say you are safe increasing by 1/4 for each step. (So 1/4 to 1/2 to 3/4... ) to your end size. If it is something harder like steel then increase from 1/4 in 1/8 steps. If the hole needs to hold a tighter tolerance it may be worth your money to undersize the hole and purchase a reamer of the proper size, ream it to an interference fit, and then press the bearings into place. All of this can be done in the cheapest of drill presses as long as you're careful. Make sure your cutting speeds match that of your material, use good HSS bits, and use lube. For lube, i prefer either safetap or mobil thread cutting oil for general purpose use. Although for a tight tolerance and very good finish machining Al i personally use JP 54 jet fuel. Disel will also work in a pinch but it will leave a bit of a residue that will need scrubbed off with either alcohol or acetone. Do not use fuel oils on steel though, if you get overzealous and spark off the drill you will have a very very bad day. Hope this helps!

[themccannman]

This is totally doable by hand (assuming you don't have a mill or drill press which would be the better option). Use a stepper bit, or you can just step up your bit size incrementally, start with a center punch, then center drill it, then 1/8", then go up by 1/4" each bit if you want your hole to be as precise as possible. I would highly recommend getting a stepper bit though, they're nice to have and always give you really clean holes.