Makeshift Lathe Advice

[Alex Melton]

Hello,

Currently, I am making my knives using a 4x36" belt sander. Although it works for many applications, I want something more. I can't really make the convex or concave bevels I want by using it, so I've set out to try and fabricate my own 2x72" belt grinder. The first step I am taking in the fabrication process is making aluminum wheels for the belt to run on. I cast the aluminum into old green bean cans. After taking apart the cans and getting the aluminum block out, the next step is to machine the aluminum into a perfect cylinder, make sure the sides are flat and can hold the bearings, and then round off the sides to allow proper tracking. One problem, though. I don't have a lathe to do this on. I've seen YouTube videos showing how to turn your drill press into a makeshift lathe, so that's what I was planning to do. The thing that troubles me is this:

What tool should I use to machine the aluminum on my makeshift lathe? Should I use a cold chisel, or is aluminum soft enough that a woodworking chisel could work?

[C Craft]

Alex one thing those Utube videos won't tell you is that a drill press does not have the bearing design for lateral work. The bearings are designed to bear pressure straight down. Once you use one as a lathe that side pressure will destroy the bearings in short time!!!

If you got to go with a lathe start watching estate sales, craigslist and do your research on the lathe that you are going to buy!!!

[Alex Melton]

Oh, alright, thanks. I definitely don't want to break my drill press. I really don't have the money to buy any sort of lathe right now, but I'll try and find a different solution.

[James Higson]

It will take ages but you could drill a hole in the middle and put a bolt through, then attach that to your hand drill. Then spin the block of aluminium on the hand drill against your sander.... should get it relatively evenly round??

Edited July 12, 2017 by James Higson

[Alan Longmire]

To answer your original question about what tool to use should you rig a lathe out of something, no, neither woodworking chisels nor cold chisels will do the job, and to try might kill you.  Do a little research on metal lathe tooling.  You'll see it is very short, very stout, and meant to be firmly clamped in a rigid holder.  While it is possible to turn metals freehand, it requires tools more like scrapers than chisels, and very long handles to clamp said tool under your arm so as not to get beaten to death with the tool.

If you were to chuck up an aluminum puck in a drill press, spin it up, and try to shave off a bit with a wood chisel, best case scenario is you can find the chisel again, you aren't bleeding too much, and the quill still fits in the drill press.  Same with a cold chisel, except you probably wouldn't bleed as much since they aren't as sharp.

What you might be able to do is attach the puck to the shaft of an electric motor and, using wood blocks as height gauges, VERY carefully take light strokes with files.  This is still dangerous as hell, but the biggest risk here is to your fingers.  The possibility of having a chisel shot through your chest is much lower.

[Aiden CC]

As others have said, a drill press lathe would not work and would likely harm you and the machine. IMO, it would likely be better to just purchase the wheels you need. However, if you are dead set on making the wheels, here is one way you could consider:

You'll need a compas and calipers for this. Frist, establish flat and parallel sides. I do this for pieces of stacked handles and have a method I like. First, grind one side flat. Then, using sand paper on a flat surface (I use a block of granite, some people use glass plates, etc) lap the piece until the side is flat. This will be your reference. Then, grind the opposite side until it looks parallel, then check with calipers. Adjust until you've ground it to where the thickness is the same around all the edges (if you check four spots with intersections forming perpendicular lines you know it is incredibly close). Then, lap the side you just ground until it's flat. Check for parallel, adjust as needed. It's a bit tedious, but you can get good results. 

Next, choose a center point and mark it with a punch. Use your compas to scribe out a circle (you can color the surface with a sharpie and then scratch into that) and save the compas size so all of your wheels are the same. Set the table on your sander to 90 degrees and grind down close to the line. Now you can go down to the line with files and finally sand paper with a hard backing. When you're done, you'll have a circle with parallel sides which will be very close to round and will have a mark at the center for drilling. 

I'm sure there are other ways (spinning the piece in a hand drill against your sander could be with looking into), but if I had to do it, this is likely how I would go about it. Or you could buy pre-fabricated wheels. 

[Brian Dougherty]

13 minutes ago, Aiden CC said:

...Or you could buy pre-fabricated wheels. 

I'm not a fan of plastic wheels, but for the money, these would probably get you up and going for good while:

http://www.ebay.com/itm/Belt-Grinder-2x72-wheel-set-knife-grinders-/262109013596?hash=item3d06ea265c

[Alan Longmire]

I forget who it was, but somebody around here used skateboard wheels and bearings on their grinder.  You can also use laminated hardwood for larger wheels as long as you don't go too fast.  I'd think laminated hardwood drive wheel, skateboard tracking and idlers, steel platen.  I don't think anyone has come up with a good way to make contact wheels at home, unfortunately.

I also apologize if I came off too harsh in my first post, but the thought of you sticking a wood chisel into whirling aluminum scared me into making sure you realized just how bad an idea that was!

[Zeb Camper]

So, I'm no machinist, nor do I do any casting, but I do know some history on the subject. In an older time, people would make wooden prototypes for sprockets, cogs, and such. Then they would make castings of those. I'm guessing they used the same techniques in the making of the wooden paradyme peices mentioned by Aiden CC. Sand casting probably wasn't used because they were attempting to mass produce, but perhaps could get you closer to your desired shape (I would make it oversized, then machine it to your exact specifications). Somethin to think about. 

[Zeb Camper]

Oh, and I just thought of this I guess because I think too much. If you made a wooden prototype, you could also use water displacement to judge the volume of the part you want to make, and the amount of aluminum you need to melt. I also know steel will not stick to aluminum. if you chose to sandcast I wonder if you could (after you buried your wooden prototype into the sand) run a smooth steel rod through it's eye and into the sand. Carfully remove the prototype and then cast it.