Slow Speed/High Torque Drill Press Mods for Drilling Large Holes

D.Crawford

D.Crawford

Joined
Jan 15, 2008
Messages
650
I'm in the process of building a hydraulic press and needed to drill some 1.250" holes in very thick stock. Neither of my two benchtop drills were up to the task. They were too fast & didn't have nearly enough torque. After reading several threads at some of the machinists forums I came up with the following to get the holes drilled... and the changes only took about 20 minutes.

This old Buffalo is the bigger, heavier of my two drill presses and also has a 1/2" chuck for large bits. I removed the old motor (1/3 hp I think) and the motor mounting plate.


I then bolted on a spare 1 hp motor (3 Phase) onto the mounting plate and re-installed it onto the drill press.
The pulley was drilled from 1/2" to 5/8" to fit the bigger motor shaft.


Lastly, I wired the new motor into my grinder's VFD. Now I have a variable speed drill press capable of drilling 1"+ holes in thick steel. A new belt insures that the extra power gets transferred to the work piece without slipping.


Hope this helps someone needing to drill larger diameter holes.
 
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Good point Count. That was my original plan because I wasn't sure the VFD would provide enough torque at slower speeds. I was fortunate that this worked out. The addition of a third pulley would let you run the motor at full speed & torque but have a slow enough spindle speed to do the job. Also a good option for someone who doesn't have a spare 3 phase motor.

Thanks
 
I'm planning to pick up a new 1.5hp motor this weekend and upgrading my HF Drill press. 3/4hp 3-pulley just isn't enough to drill 1" holes in 1/4" stainless. I've got a carbide hole saw, but it just bogs down too much. I'm hoping that upgrading to 1.5hp will be enough to make the difference.
 
cool!
where did you get that drill bit? when you get in those higher torque operation did you have trouble with the chuck slipping?

did you have trouble with the pulley not fitting on the new motor shaft?

Thanks for sharing.

Daniel Rohde
 
Daniel Rohde said:
cool!
where did you get that drill bit? when you get in those higher torque operation did you have trouble with the chuck slipping?
Click to expand...

Daniel, no problem with the bit slipping. The only trick was finding the proper feed rate to take a decent chip without gouging & hanging up on the work piece.
I got the bit in a trade, but they're available on Ebay.

Daniel Rohde said:
did you have trouble with the pulley not fitting on the new motor shaft?

Thanks for sharing.

Daniel Rohde
Click to expand...

Thanks for reminding me. Yes, I did have to drill the pulley out from 1/2" to 5/8".
 
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My solution was just to get myself a slow speed high torque drill press from 1890 =D This thing will punch 1 inch holes (without pilots) all day long even through hard steel if you use the right bit =)

You can find old camelback drills for cheap usually, because people think they're outdated... but they were designed for drilling through metal and whatnot.

DSCN3091.JPG
 
Justin.Mercier said:
My solution was just to get myself a slow speed high torque drill press from 1890 =D This thing will punch 1 inch holes (without pilots) all day long even through hard steel if you use the right bit =)

You can find old camelback drills for cheap usually, because people think they're outdated... but they were designed for drilling through metal and whatnot.

DSCN3091.JPG
Click to expand...

Great stuff Justin. I'll have to keep an eye open for one of those.
 
zaph1 said:
I'm planning to pick up a new 1.5hp motor this weekend and upgrading my HF Drill press. 3/4hp 3-pulley just isn't enough to drill 1" holes in 1/4" stainless. I've got a carbide hole saw, but it just bogs down too much. I'm hoping that upgrading to 1.5hp will be enough to make the difference.
Click to expand...

That will definitely get it done Zaph. I used a 56 frame motor and it was an easy swap out. Just make sure to pay attention to the motor shaft size in case you have to drill or replace your pulley.
 
Enquiring minds want to know what is the car in the photo!

Nice camelback.

I got one for free --- it had been in a garage fire. I haven't gotten round to fixing it yet. Even if it hadn't been burned, it needed some lovin'.
 
Justin.Mercier said:
My solution was just to get myself a slow speed high torque drill press from 1890 =D This thing will punch 1 inch holes (without pilots) all day long even through hard steel if you use the right bit =)

You can find old camelback drills for cheap usually, because people think they're outdated... but they were designed for drilling through metal and whatnot.

DSCN3091.JPG
Click to expand...

Justin, please forgive me my ignorance, but what is that lathe/steampunk looking bit in the fore-ground? Are there two drive belts on it? Sorry, I'm on my phone. :eek:
 
It's a Hunter Roadster, a Triumph TR6 based kit car from the 70s. It's waiting for a new transmission still so i been driving my TR7 rally car to shows in the mean time.

www.hathawayhunter.com

the lathe is just that, an 1891 prentice brothers lathe, which goes well beside my 1890 prentice brother's drill press.

The motor is underneath, running through a 1920's auto transmission for variable speed and reverse, to the top shaft which goes to the cone head. The belt in the front drives the horizontal feed

edit: added another photo

Here's another view of the drill press and lathe, you can see the motor and the auto transmission in this shot of the lathe.

DSCN3090.JPG
 
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Yaah, Justin, how about updating the thread on the car restoration?

I already checked, the motors at HF have the same shaft size as the drill press. I considered going with 220v, but decided I wanted to stick with 110v.
 
OK, here's the pudding. I installed a 1.5HP Marathon Electric motor, replacing the HF 3/4HP motor shown on the table. Everything was SUPER simple. Unbolt the old motor, use an allen wrench to remove the pulley and put it on the new one. Bolt on the new motor and connect 3 wires with blade connectors. Took about 15 minutes total, 10 minutes of which was trying to lift it off the table. This beast weighs about 90lbs. and is more akward than a dishwasher. At 13.6 amps it doesn't even need a dedicated outlet, but not much else can be running.

It now drills 1" holes with a carbide hole-saw much easier and quieter than the 3/4HP motor did. I can also crank up the speed from 220 to 350RPM and it doesn't slow it down.

drillpress.jpg
 
If somebody does a motor swap in the future,


remember you can swing the table around and crank it up to hold the motor in place as you bolt off and on.
 
@#$%^@#, yeah, that would have been a lot easier! I needed to take it down and clean underneath it, anyway. I also removed both belts and reconditioned them. I get a lot of dust from the forge bricks I drill that gets even inside the pulley compartment.
 
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