My Drill Press Reduction: How to Bore the Big Ones

[-Brent-]

I came across the article a few years back and saved it upon finding it. At the time, I figured if I found a small DP I could do this conversion. Soon after, most of the parts presented themselves at an estate sale and then a garage sale.

In total, I've got about $60 (a little less) into the whole set-up. The DP came with a bunch of other stuff, which I fixed up and sold off netting me a profit. So, the press became "free" as did the mandrel and motor pulley.

The wood was left over from a shelving project leaving me needing to only acquire a pulley from Grainger and some belts from HF.

The big, lower pulley is a Congress 12 inch pulley. I had read about the Chicago pulleys being pretty low quality. After seeing one, I was convinced to spend a few bucks more. Granted, this isn't a fancy mod, quite the opposite, but that pulley was pretty scary and for $5 or $6 more dollars, it was worth upgrading.

The Accu-Link Adjustable V-Belts are from Harbor Freight and they're one of the best things HF carries. They're a "pass" for sure. I used a 20% coupon for each. They're pretty inexpensive compared to other options or even Accu-Links for sale elsewhere. The pulleys come in a 5-foot length, so I needed two to complete the job leaving a little left over.

Here's the article I referenced:

And, here's a vid of my first test:

Please know that this was just a test run. I still want to break it down and clean up the wood. Maybe hit it with some stain. As well, I need to get the belts' direction correct and finish fitting the pulley guard. I have another pulley that I am going to swap out on the top part of the mandrel. It matches the head pulley better... but really it's only a matter of OCD/symmetry for that change.

Anyway, that's it. I've never really seen anyone follow through on one of these reductions based on the article. I've only ever seen it mentioned. As for the speeds, I haven't figured them, yet. When I get some free time I'll crunch some numbers and post the results.

Thanks for looking.

 

[kbs2244]

I like it.

I put a treadmill motor on mine for low speed operation.
It works but the power drops off at low speeds.

That big pulley makes me think of a bicycle wheel.

 

[dogdog]

where do you guys find these parts ? except for that a-linked belt.

 

[-Brent-]

I found that mandrel at an estate sale. It was in a bin with pulleys and belts. The guy was a woodworker and fabbed up his own machines using pulleys.

You can find them new at industrial supply places like Grainger, Northern Tool, Amazon, etc. I've seen them at a place we have locally, when I was getting some other supplies for a different project I am working on.

As for pulleys, I bought the 12"er at Grainger. I paid for it online and went to the will-call at one of the local stores.

If you look at the article it'll have part numbers listed. You don't have to go by what's listed but it may be a good starting point.

 

[rsanter]

My only concern is that the belt has limited contact with the small pulley on the motor so that's where the slipping can/may/will happen.
You can add an idler pully on the outside of the belt to increase pully contact

Bob

 

[-Brent-]

My only concern is that the belt has limited contact with the small pulley on the motor so that's where the slipping can/may/will happen.

That's the one area where I messed around and paid some attention to the contact/wrap around on the drive pulley by varying the distance of the mandrel. At about 15 inches there's about a third of the pulley contacted. Which, from what I had read (quick search only) that 120* was okay for a drive pulley.

If it slips, and it may (like you say), I'll definitely address it.

One thing I didn't want to do was over-complicate anything. Anything that needs reworking will be part of the learning experience. And... good eyes! I appreciate the comments, for sure.

 

[-Brent-]

Here's one of the links I had used as a reference. Luckily, I emailed myself the link and still had it.

Glancing at it again, I fall within the 6:1 ratio, too. I don't take any of this as gospel, I just nerd out over things like this. It keeps me learning.

 

[nine4gmc]

Excellent, you should post some pics, great job!

 

[-Brent-]

Excellent, you should post some pics, great job!

Will do. Thanks!

 

[OccupantRJ]

where do you guys find these parts ? except for that a-linked belt.

McMaster Carr is a very good source for materials, and has excellent service. Just reading through their 3 inch thick catalog or their website is a learning experience itself.

 

[Kevin54]

Go to a place that repairs washing machines and dryers and ask them if you can have one of their trash units to strip out. I think some of the dryers have dual size pulies in the back. Not sure about the washing machines though.

 

[catalytic]

Cool project, but I have a different take on this that might be helpful if others are wondering how to drill big:

1. 350 RPM (a typical un-modified slowest small drill press speed) is just fine for a 1" HSS drill bit. Go with 135° if possible. Here's a very conservative chart for reference:

http://www.fnal.gov/pub/takefive/pdfs/Drill_Press_Speed_Chart.pdf

2. The limiting factor is often not the motor bogging down. Instead, you tend to see belt slippage and/or chuck slippage, especially since many littler drills don't have the nicest chucks or adjustable belt tension. Looking at the design in the article, it looks to me like everything bit the giant pulley is going to want to slip when that 1" drill pokes through. And if the belts don't slip, then the chuck might just eat itself by spinning on the stuck drill. (Not trying to criticize your project, just speaking from experience that it's something to look out for). To limit this, remember to use the chuck key to tighten ALL THREE chuck key holes (they all tighten all jaws, but each hole tightens the jaw closest to it more than the others).

3. A lot of drilling problems are due to bad technique. When I started machining someone told me to drill the entire hole without lifting the bit. For some applications this is a good idea (taking a continuous chip may leave a more accurately bored hole when it really matters). In general, though, it's really bad advice. What you actually want to do is "peck" firmly for a second or so, then lift and brush with coolant oil, then peck again...repeat. Doing this, you can use the recommended RPM's without getting your drill (i.e. drill bit) hot, which means that even big holes go a lot faster. It also prevents you from annealing and then taking the edge off your drills (bits) (ever get halfway through a hole and feel like things have slowed down alot?)

4. Work holding is key, and never more so than when using bigger tooling. The more time I spend machining, the more time I spend thinking about how to hold the work. Drills give radial (twisting) force and also lifting force, especially with big holes. This is dangerous, and any play in the work makes drilling way more inefficient. I have a few of these:

http://www.heinrichco.com/sdvise.htm

Other people like this one:
http://specialtytooling.eaglerockon...tchet-type-float-lock-vices-for-drill-presses

Whatever you use, just make sure you've clamped the hell out of it and thought about how you're going to stop it from spinning/lifting.

5. You may not want a drill bit at all. I assume you guys are using Silver Deming (reduced shank) 135° drills for big holes in smaller machines. Consider an annular cutter instead. You may find it's a lot more efficient, which your smaller machine will appreciate.

 

[JSharp]

very cool idea

 

[Speedfreakbbc]

Here is my slow drill press. It was my great grandpa's it even has an auto feed! It does have a little slop so I need to figure out how to cure that.

 

[-Brent-]

Excellent, you should post some pics, great job!

Here are some pics.

 

[-Brent-]

The pulley guard needed some modification. It now clears by about 1/4".

 

[y'sguy]

Here is my slow drill press. It was my great grandpa's it even has an auto feed! It does have a little slop so I need to figure out how to cure that.

Man that things cool. Show it some love!

 

[Nursepeter1973]

Cool project, but I have a different take on this that might be helpful if others are wondering how to drill big:

1. 350 RPM (a typical un-modified slowest small drill press speed) is just fine for a 1" HSS drill bit. Go with 135° if possible. Here's a very conservative chart for reference:

http://www.fnal.gov/pub/takefive/pdfs/Drill_Press_Speed_Chart.pdf

Great bit of information. Thankyou

 

[gazza]

I know its not a drill press but I saw this for sale a couple of years ago. Using a Honda engine/gearbox less the cylinder to gear down the speeds. Input chain onto one side of the crankshaft and output off the sprocket.