Back Yard Mechanic needs to Drill 7/8" Hole

[SPYDERLK]

Thanks for all the feed back. I never thought of a hole saw.
I was mostly concerned about the 700 rpm on my drill press.
It seems a little fast to me for a 1/2" hole so I was worried
about a 7/8" but I sounds like I should be OK.
If the hole isn't perfect nobody will notice - I cut all the steel
plate with a Sawzall. I clamped a couple of angles back to back
on either side of the cut line to use as a blade guide. Actually it came out
pretty good. Think I'll look for some cheap drill sets.
Thanks alot.

Im surprised no one addressed this speed issue. You are right. It is way too fast for those large bits. I really like the hole saw tricks mentioned to get a good hole. Thats definitely what Id do if constrained to the hi speed minimum you have on your press.
larry

 

[LetsRoll]

Try a machine shop.

Im surprised no one addressed this speed issue.
larry

SPYDERLK, Egon did by suggesting a machine shop (got to read between the lines ). 700 rpm's on his drill press will eat up his $100 drill bits really fast. No matter how good his skill is on sharpening his drill bits.

Thinking out loud here, I don't even think those drill bits will even cut those holes at 700 rpm's no matter what coolant he uses.

If it was me (in his shoes), I try a machine shop.:thumbsup:

 

[LetsRoll]

If a machine shop is out of the question, he can try changing his pulleys or even try a variable speed motor. The motor will need a variable speed dial as well. Probably all around cheaper to purchase another low rpm drill press.

Note: Variable speed motors (geared) are not cheap. The below links are just examples. The controller is not that expensive, but the gear motor is.

Gear Motor
0160-24A4BEPM-Z3

Controller
KBWM-120 | DC Drives NEMA 1 | Part No. 9380

 

[crbr]

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.

interesting

 

[Kernopelli]

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

I like this idea A LOT! I use bi-metal hole saws almost exclusively for larger holes and slow speeds with plenty of cutting fluid is the key to longevity...and making a mess.

I do find it interesting that you hint at having broken or bent pilot bits though. I have a pretty wide selection of hole saws as well as brands ranging from the inexpensive like Black and Decker to better brands like Greenlee, Milwaukee, etc. and the one thing that I have found to be consistent regardless of brand is the pilot bit. What I have found to be consistent about them is the high level of quality. I have only had to resharpen one pilot bit and never broken one. I have truly been amazed by there ability to stay sharp...even the "cheap" B&D bits I have (which BTW turned out to be pretty darn good). Short of some very expensive mill bits I lucked upon at an auction ( or I couldn't have afforded them) they are by far the most durable bits I have ever owned. I wish they came in a larger variety of sizes because more than once I have paid $20 for a bit that was decent but literally wasn't even close to as good as the cheapest pilot bit I have.

 

[captaincrab55]

Learn to sharpen your own bits on a bench grinder, its not hard.

Great advice.....:thumbsup:

 

[SPYDERLK]

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

I like this idea A LOT! I use bi-metal hole saws almost exclusively for larger holes and slow speeds with plenty of cutting fluid is the key to longevity...and making a mess.

I do find it interesting that you hint at having broken or bent pilot bits though. I have a pretty wide selection of hole saws as well as brands ranging from the inexpensive like Black and Decker to better brands like Greenlee, Milwaukee, etc. and the one thing that I have found to be consistent regardless of brand is the pilot bit. What I have found to be consistent about them is the high level of quality.

Me too! Regardless of the quality of the pilot bit they are not infinitely rigid and as the saw hole starts it can orbit the center. How do you avoid this? - or are you just saying they dont break? I have tried by pre drilling the center hole and then substituting a solid tool steel dowel rod for the pilot and still get a tapered hole because of an orbital start. How have you prevented this using pilot drills for entry guidance into steel??
larry

 

[Kernopelli]

Me too! Regardless of the quality of the pilot bit they are not infinitely rigid and as the saw hole starts it can orbit the center. How do you avoid this? - or are you just saying they dont break? I have tried by pre drilling the center hole and then substituting a solid tool steel dowel rod for the pilot and still get a tapered hole because of an orbital start. How have you prevented this using pilot drills for entry guidance into steel??
larry

Oh, I think you misunderstood my point, I am saying that I always use the pilot bit and have never broken one. I always make sure the set screw is tight and usually try not to extend the drill tip very far past the end of hole saw. Most of the pilot bit shanks have a flat spot near the end for the set screw but I rarly have a problem with keeping the bit tight if I push it farther up in the arbor past the flat and tighten it up. I will sometimes use a center punch to make sure I get the hole started exactly where I want it, especially if I am using the hole saw in a drill. 90+% of the time, I am using it in a drill press or mill though and the metal is clamped down so I don't worry much about the hole saw or the material moving around. This always gives me a good entry and 90 degree guide through the material. The thing about a hole saw is that it will never be a really precise boring device and if you are needing exactly round holes, there are better ( but much more expensive) ways of making them.

Because I try to keep the tip fairly close to the saw teeth and mostly use them in the manner that I do may have something to do with not breaking one? I would also think they are hard to break because they don't have a long flute or twist (or whatever you want to call it) on the shank where most drill bits break. The thing that I was really trying to impress was that I have found the pilot bits to hold up to repeated use like nothing else I have found for the money. They just flat stay sharp. I still use every pilot bit I ever bought but have worn out a number of hole saws. I don't know what makes them different or why they are different than "standard" drill bits but there is unquestionably a difference and it doesn't seem to matter what brand. I can tell you for fact that the pilot bits that Milwaukee, Dewalt, Lenox, Greenlee, Rigid and B&D are all much better than the "standard" drill bits ( I have a Lenox step bit) that they make. I have a dedicated tool box full of dull, broken or bits that have been resharpened 1-2 or more X's made by all of them and I have pilot bits made by all of them and have only resharpened 1 B&D bit 1 time and that was after using the snot out of it.

 

[BayouMan]

I just finished drilling 8 ea 1" diameter holes through 1/2" steel using a hole saw. This is for the boom pole build that I have posted in this forum. I drilled 1/4" pilot holes at each center punch mark. This allowed me to use the hole to center the pilot bit and not have to worry if the pilot bit was staying ahead of the hole saw. I used windshield washer fluid, while I drilled and it worked fantastically! I had read this somewhere else on this forum. I did break one pilot bit as I broke through and the circle plug dropped. The plug caught my vise and the tip of the pilot bit broke off. Not too bad considering I had to drill 8 holes.

M<ike

 

[BWBrown]

Daryl,
Saw your note ("I do find it interesting that you hint at having broken or bent pilot bits though.") You are right - the pilots are ususlly pretty high quality. But...

Whenever I have had to drill/hole saw a hole in metal using hand held drill - i.e. taillight holes in my flatbed - I have bent and broken many center drills. Doing it hand held, the pilot breaks through, and if you're not absolutely 100% perfectly square, the hole saw catches on one side and tries to go somewhere else.

Drill press limits the problem, but I still do the wood guide thing.
Bob