Harbor Freight drill press mod- lowered rpms to 200 to improve results drilling metal

[KYErik]

I bought a cheap harbor freight style drill quite a few years ago (Cummins brand) but found the speed to be too fast and the motor too weak to effectively drill thick steel so it sat around for quite a few years. The motor is only 2.4 amps (probably around 1/4 hp or less) and the lowest possible rpm combination of the belt on the step pulleys was 780 rpm.

First I removed the step pulley that was attached to the spindle. It had a 7/8" bore. I found a 16.5 inch diameter steel pulley on on old piece of farm equipment, removed it from its hub and carefully welded it to a 3 inch steel pulley with a 7/8 inch bore. It took awhile to get the large pulley perfectly centered on the small pulley so that it would spin true. I also flipped the step pulley on the electric motor so that the 1.5 inch step was on top.

I bought a 50 inch 3/8" wide belt for about $14.

Now the drill press has plenty of torque and cuts thick metal very nicely with nice long stringy metal "chips". I drilled a couple of half inch diameter holes in 1" steel (1/4" pilot hole, then finished with a 1/2" bit) and it did great.

 

[Big Barn]

While you may have achieved the desired lowered RPM's, I think your big/small pulley ratio is too great. You may lack adequate belt contact on the drive (small) pulley.

This is usually why a jackshaft system is utilized.

Terry

 

[KYErik]

While you may have achieved the desired lowered RPM's, I think your big/small pulley ratio is too great. You may lack adequate belt contact on the drive (small) pulley.

This is usually why a jackshaft system is utilized.

Terry

Good point- but no belt slippage so far drilling those 1/2" holes. I will be drilling some 7/8" holes within the next two weeks and I will report the results here.

 

[fidowanttobe]

!! I did the same thing! :thumbsup:
14" pulley tho. What could the high speed pulley settings possibly be used for?? Glass? Made an old Chinese drill press that was completely useless and bound for the scrap functional afterwards.
Have you engineered a guard for it? I am still in the planning stage on that as the handle is uncomfortably close to the big pulley now.

 

[TCJatko]

!! I did the same thing! :thumbsup:
14" pulley tho. What could the high speed pulley settings possibly be used for?? Glass? Made an old Chinese drill press that was completely useless and bound for the scrap functional afterwards.
Have you engineered a guard for it? I am still in the planning stage on that as the handle is uncomfortably close to the big pulley now.

Nicely done. Good idea to make a guard. Things could get uncomfortable if you lean too close to the pulley.

 

[vidio1]

The original rpm's are correct for using a 1/2" bit in mild steel or softer material. Faster speeds are needed for smaller diameter drill bits or softer material. This assumes a sharp, properly ground bit and correct chip load. Do yourself a favor and find an online speed/feed chart or calculator. Most are free. FYI those long stringy chips aren't ideal, they're a hazard. Lift up on the handle every few seconds and it will break the chip.

 

[Sawyer Rob]

This is one of the better ways to do it,

SR

 

[flyerdan]

That Jet must only be turning about 35 rpm, but at 750 ft. pounds of torque.

 

[Big Barn]

Haha, SR. Looks like I have the same drill press. I added another jackshaft and fabbed up a new belt belt guard though.





Terry

 

[KYErik]

Nicely done. Good idea to make a guard. Things could get uncomfortable if you lean too close to the pulley.

Good point- though I have the drill press up on a tall pedestal so that the big pulley is at eyebrow level (and I am 6'3). No worries on getting my hair caught- to say I have a receding hairline would be a compliment

My knuckles do come close to hitting the large pulley- there is probably only about 1/2" of clearance between the end of the handles and the pulley. Thankfully the pulley is spinning toward me directly above the feed handle. Probably the only way to get enough clearance for a guard would be to chop a little off of each of the 3 handles.