I know I ask a question about every month hope you don't mind.
Problem: I'm building a small backhoe and I need to drill a bunch of
1" holes in 1/4" wall SQ tubing and 1/2" thick plate steel. I'm unable to bring the parts to my mill in my shed due to size. I've been drilling using 1/2" gear reduction drills and reduced shank drill bits
1" diameter. I'm burning up my drills, getting hand cramps and making shoddy holes. I bought a drill guide but it doesn't fit my drill. I've sharpened my bits (I have 5 bits that I'm rotating) and I'm using ATF and kerosene as my cutting fluid.
Question: Any ideas how I might make drilling these holes easier and or better in quality? The most important thing is getting holes thru my 3"x 1/4" thick tubing aligned. I also need another new 1/2" drill because I burned up the armature so bad that I can't dress it up.
Someone posted a while ago about a hand-crank drill that had a clamping arrangement and a fine-thread feed screw (googlepause...) hmmm, no hits for "hand drill screw feed". Maybe it was in one of Lautard's books. Anyway, it was reported to be very good at drilling big holes in hard-to-drill materials. If you don't have too many holes left and you were going to buy another drill anyway, maybe that'd do and you'd have a tool that might very
?t=73529&highlight=&sid=bd25b514ecbf76a81a8fd04a4473bf49 Unka' George [George McDuffee] ============ Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.
Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.
A tool rental place should be able to set you up with a magnetic base drill. It looks like a small drill press with an electromagnet in place of the stand arrangement. The bits look like hole saws. The one I used was made by Milwaulkee. Maybe called a "rotobroach"?
It's very difficult to put enough pressure on a hand held drill to keep
1/2" and larger bits cutting properly. And when you do get the pressure, you need a very low speed drill to have sufficient torque to pull the drill. If you aren't getting nice curls of swarf, you don't have enough pressure or sharp enough drill.
I have an old Metal cased Black and Decker 1/2 drill. Sp> I know I ask a question about every month hope you don't mind. >
I used an old all-metal Portalign clamped to the work to drill structural steel for a home made front end loader. The pilot hole is
1/8", then 1/2", then 3/4, 7/8, etc. Brushing a little pipe threading oil on the bit helps a lot. Once the subassemblies became large and heavy I hung them from the rafters for precise drilling on the milling machine.
***************************************** In the Trades we call that an Old Man. I made one years ago out of pipe. Two sections of pipe and a coupler. Weld a hook on one end of the pipe. Make a sleeve that will slide over the pipe. Weld a metal saddle to the sleeve.The saddle is made to fit over the handle of the drill that you use. This allows you to plum the drill using the saddle,which is welded to the sleeve. The sleeve will be able to slide along the pipe. Using a small chain attached one end to the hook and dead head the other end around a solid anchor point. I made each pipe sections 24 inches longs. This allows it to fit in one of tool boxes. You can make them any length that works for your needs.This old man will give you all the down pressure that you need to drill holes in difficult areas and helps with the drilling of multiple holes. I hope that this will help. Millwright Ron
The biggest help will be drilling a pilot hole that is about the size of the web of the 1 inch drill. You could make a jig to assure that the holes are aligned. Something that would clamp on the 3 inch tubing with 1/8 or 3/16 holes to guide the pilot drill so the pilot holes can be drilled from opposite sides of the 3 inch tubing. Once the pilot holes are aligned, remove the jig. You should have no problem drilling from both sides and still being aligned.
If you can support the drilling machine on axis, hole saws can work very well. I use them to drill holes up to 1 1/2" Dia. and up to 1 1/2" deep in mild steel. You really need pretty low speeds, like 150 rpm or so for a 1 1/2" saw, but I use lots of pipe threading oil and get by at 345 rpms. At 1", 400 rpms should be okay. I can get about 2 dozen 1 1/2" deep holes or 1 3/8" diameter, for example. This is using a Starret metal cutting hole saw. I bet I could double the saw life if I could go slower. Do a lot of "pecking" to clear chips. In deeper holes, drill a small hole just to the inside of the periphery of where the large hole will go This will help, but not eliminate the need to retract (peck) the drill to clear chips. For example, I drill a 5/16" "clearing" hole for this purpose when I drill more than about 1/2" deep holes. Last note: In my own experience, these hole saws drill a little oversize, like 15 thou for a 1 3/8" saw. Holes are relatively clean, but not perfect.
You've had some good advise on machinery to use, you need to get some decent cutting fluid. You aren't trying to lubricate the thing, you're trying to cut it. Get some high-sulfur cutting oil, the black, stinky stuff they use on large pipe threading. Yeah, it's obnoxious, but it works a whole lot better than home-made mixes. Kerosene is good for aluminum, not steel. ATF belongs in a car.
You might want to look at a portable line boring machine. They cost the earth considering what they are made of, and that makes me think about making one, but I have not yet. Someone here or on a tractor forum mentioned getting one from army surplus or the like for a more reasonable price. With that you could drill undersized and then bore out to the size of hole you actually want. I don't recall if we've been through this part in a past post, but I strongly advise making your holes suited to a bushing suited to your pins, rather than suiting your holes to your pins (I have an old backhoe, which was not properly greased by a prior owner, and had various other forms of abuse - but I didn't know much about what to look for when I bought it, and the price was "right").
If the holes are made to the pins, or the bushes are allowed to wear past the bush and into the bush-hole, refurbishment goes from: "pull the pins, yank the bushings, put in new bushings and pins, good as new"
to: pull the pins, yank the remains of the bushings (if any), line-bore the bushing-holes oversize, or weld to build them up and them bore back to original size, put in new bushings and pins"
...a difference of some hours or days and a good many cuss-words.
You might also want to get more creative with either bringing the parts to the mill, or the mill to the parts. In a past discussion related to this sort of thing, someone mentioned building a portable boring setup "on the machine" using the head of a mill, and some sort of creative temporary attachment (bolt-holes or tack welds). If you have a small milling machine or mill-drill that permits mounting the head or column in such a manner that the base is out of the way, you might be able to bring that to the backhoe and get the job done. Some of the little China mills are not far off the price of a good 1/2 drill, though I don't know how well suited they would be to that adaptation.
I'm thinking about buying a 3/4" heavy duty gear reduction drill and mounting it to a one of those add on mill tables and use the cross feed on the mill table to push the drill thru the cut. I'd have to modify the mill table to make the feed screw heavy duty.
I'm also calling around trying to rent one of those magnetic base drill presses.
Were it me I'd use an annular cutter and a rented mag base drill. Done a hunderd times. Some have a spring loaded center so you center punch where you want the hole and drill it. No pilot holes and all that crap.
I once saw a large drill with a jackscrew on the back. The workers spot welded a U-shaped frame to a heavy steel plate to be drilled. The drill was placed under the frame and the jackscrew backed out against the frame to put pressure on the drill. You could do something similar with a jackscrew on the frame to press on the back of the drill. Maybe clamp the frame to your work piece.
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