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

[Mendonsy]

The speed controller on a DC or VFD on a 3 phase motor are no good for this application. They don't have any toque at low speed.

They definitely do lose some power below about 15% of rated speed, but going one size bigger on the motor mostly solves that. My biggest concern was speed control and reversing so that I could use the drill press for tapping holes. The inverter drive works really well for that. The drive was about $150 and the motor was one that I had lying around.

 

[Raspy]

vidio,

The problem is that we want to ignore the proper speed, it's that these modern "Harbor Freight" style drill presses have very little power and it's hard to make the belts stop slipping. Lower speed means more torque. Larger pulleys don't slip the belt, etc.

I often find it hard to work within the limits of mine.

It's fun to see what others have done to compensate for these common problems.

 

[GLyford]

Low speed in a 5-speed drill press is somewhere around 760 rpm. About right for a 1/2" drill bit into mild steel.

Now add a little more carbon to that steel. Or try that in stainless. Or swap that 1/2" bit out for a 2" hole saw.

Pretty much every time I see one of these drill presses modified to go slower, it is one of these cheaper drill presses
with fewer and faster speeds.

It is a hack for people without enough machinery budget to try and stretch their machine capabilities enough to get
the job done. We know it's a hack. If we had a big machinery budget we'd be drilling on a bridgeport.

Sometimes a torched hole is good enough. This is on that spectrum of "get it done."

 

[KYErik]

It is a hack for people without enough machinery budget to try and stretch their machine capabilities enough to get
the job done. We know it's a hack. If we had a big machinery budget we'd be drilling on a bridgeport.

Sometimes a torched hole is good enough. This is on that spectrum of "get it done."

Well said. Everything I do is stretching the budget farther and farther and honestly sometimes I get a wild idea and enjoy the challenge of seeing if I can make it work.

Yesterday I was drilling some 3/4" holes and the belt was not slipping but the chuck is slipping/falling off of the spindle shaft (morse taper fit). Perhaps I have exceeded the torque for which this unit was designed

I did some googling and it looks like my options for keeping the chuck from slipping are:

1. Heat the chuck in an oven to 200 degrees or so and then tap it on with a rubber mallet and let it cool
2. Clean the mating surfaces and apply a little chalk
3. Clean the mating surfaces and apply loctite

 

[vidio1]

If a Morse taper is slipping after cleaning and reinserting often times it's a worn spot(s) or a mismatched angle of the mating surfaces. Imports sometimes have this problem.
Clean both mating surfaces well and completely cover them with Dykem or a dark colored marker. Lightly reassemble and then remove. This should wipe off the high spots and leave the low spots. This should give you an idea of where the problem areas are.
The proper repair for this is to lightly ream and then reinspect until you get around 75% or so contact. Go slow and recheck often. You can find Imported reamers for $20-$30 depending on taper size that will be fine for something like this.

 

[GLyford]

The class of machines involved here often don't even HAVE morse tapers, just a jacobs taper on the the end of the spindle.

 

[downsizingnow48]

I bought this 60 or 70 year old Duro for $40. Someone added an intermediate pulley sometime in the past. The slow speed is about 140 rpm. With a 1/3 hp motor and new belts, it will cut a 1" hole (with annular cutter) in mild steel. It struggles with 1.5" though.

 

[vidio1]

True. I hadn't considered the Jacobs taper slipping after I read Morse taper.

 

[KYErik]

My mistake on the taper type.

 

[GLyford]

That Duro looks like a better machine than most...a real spline, and not just a single sliding key to drive the spindle.