Back Yard Mechanic needs to Drill 7/8" Hole

[BWBrown]

A trick (?) I do, is take a piece of 3/4" oak or other scrap of hardwood, using the hole saw first cut your hole in the wood. Then clamp the wood to the steel, using the wood as a guide (instead of the center pilot bit) has saved me many a broken or bent pilot bit. It also concentrates the cutting oil in the work area instead of throwing it all over the shop.

Maybe everyone else does this, but once I tried it, it has become standard practice for me wherever there is room for the clamps.
Bob

 

[Runner]

I usually use a step drill for stuff thicker than 1/4 inch or so. Not the most sophisticated, but gets the job done.

I drill a pilot hole first (on the drill press, if possible), then I use a regular hand drill for the step drill bit and flip the workpiece over when I'm halfway through to drill from the other side. This helps keep the hole from being tapered.

You can get big (up to 1 inch or so) step drill bits at Harbor Freight pretty cheap.

If the hole had to be super-perfect, I'd probably use one of the other methods.

 

[mustangsallysdad]

Hi All,

I am building a road grader. It is a low (as possible) budget project.
I am not a machinist but have a lot of patience.
I have almost finished cutting all the steel pieces and will need to drill four
7/8" and two 3/4" holes in 3/8" material for the lift arms and top link pins.
It looks like two drill bits from McMaster_Carr will run me about $100 . Or I could just get the 7/8" bit and use a bushing on the 3/4" top link pin.
QUESTION:
My drill press has a 1/2 hp 1750 rmp motor. I get a 5:2 speed reduction
using my slow speed pully for 700 rpm. Can I drill a 7/8" hole with this??
Or is there a better (cheaper) way ?

Thanks.

7/8" Hitachi S & D with a 1/2" shank at Lowe's is around $19. Low speed and cutting oil works great for me...be patient so as not to "work temper" the bit...I've been using the same one for a couple of years now.

 

[SkunkWerX]

Also, when using large bits, drill a pilot hole, or two.

For a 1" hole, in thicker steel, rather than bite it off all in one operation, I tend to drill a 1/4" pilot hole, then enlarge to 1/2", then up to 1".

In 3/8" thick steel shouldn't be too much trouble, but I'd still drill a pilot hole before moving up to the 7/8" solid bit.

Your drill press will handle it. take is easy, keep it cool, and don't use excessive down pressure. Let the bit do the cutting.

 

[tommu56]

I usually use a step drill for stuff thicker than 1/4 inch or so. Not the most sophisticated, but gets the job done.

I drill a pilot hole first (on the drill press, if possible), then I use a regular hand drill for the step drill bit and flip the workpiece over when I'm halfway through to drill from the other side. This helps keep the hole from being tapered.

You can get big (up to 1 inch or so) step drill bits at Harbor Freight pretty cheap.

If the hole had to be super-perfect, I'd probably use one of the other methods.

Most step drills are only designed for metal less than the dept of the steps.

Not that they wont work but when they first came out they were for sheet metal like electrical panels.

tom

 

[mustangsallysdad]

A trick (?) I do, is take a piece of 3/4" oak or other scrap of hardwood, using the hole saw first cut your hole in the wood. Then clamp the wood to the steel, using the wood as a guide (instead of the center pilot bit) has saved me many a broken or bent pilot bit. It also concentrates the cutting oil in the work area instead of throwing it all over the shop.

Maybe everyone else does this, but once I tried it, it has become standard practice for me wherever there is room for the clamps.
Bob

Great idea! Leaving a "well" for the cutting oil is good, useful info...I'll try it.

 

[tessiers]

I don't know why the winshield wash works but it does, My uncle told me about it and after trying it I have never used cutting oil since. It is cheap and it doesn't make nearly the mess as oil on parts that need to be painted later. I have a quart spray bottle that hangs right on the drill press. Works with twist bits as well.

I too have terrible luck with large bits. I work for a commercial fabrication and erection company and we use Hogan Drills (magnetic drill) and Milling bits, or an iron worker with punch. At home I use the hole saws or bring home a hogan.

What are the advantages of using windshield washer fluid as a lubricant? I've heard of using ATF, but this is the first time I remember anyone suggesting washer fluid.

I've not had good luck with large, cheapo drill bits. Seems like I ruin them pretty quickly.

 

[some zilch]

add another thumbs up for the HF big drill bits. i have been using mine for years, and they hold up extremely well for the price. definitly one of the better items at the store.

HF s&d bits=HF impact sockets

mine easily and repeatedly cut holes in 2" stock while building my wood splitter.

 

[Spudland_Dave]

or an iron worker with punch.

Thats what I was gonna reccomend..For less then the cost of the bits and in less time then it took me to type this reply you'd have all your holes punched....Just find a fab shop, prep everything by marking your holes, etc... and 98% of these shops will do this kind of work for beer money. They may not do it right on the spot, but if you can drop off the parts and pick them up later there should be no problem.

 

[jenkinsph]

When I built my 8' grader I had to drill 16 holes to mount the blades and also drill the mounting holes for the hitch. That is 16) 3/4-7/8 holes in 1/2" flatbar and 5/8" for the hitch, I used a pistol drill and holesaw bit to do this. Much easier than using a twistedshank bit IMHO. What saved me the most time was having a couple of small cnc bits to drill the pilot holes with 1/8" approximately. While I have a drill press the work was to large to hold in place to use it, I was very suprized how well the holesaw worked, took about 1.5 hours to do about 20 holes.