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MachinistBlog.com

Plans, projects and how-to's for home machinists

Installing a Drill Press Chuck

Properly installing a drill chuck on your drill press requires you to pay attention to a few simple details.  Done well, your chuck will be accurate and will stay put until you remove it.

Drill presses and many other machine tools use Morse tapers to enable the user to attach a wide variety of attachments to the machine via an arbor having a Morse taper to fit the machine and an opposing taper to fit the accessory to be attached. For a drill chuck this opposing taper is typically a Jacobs taper.  An accurate arbor is very important so buy one you can trust; Albrecht and Jacobs make good ones.

Fitting a male arbor taper into a matching female taper produces interference-fit joints that are very tight and accurate.  Once their contact surfaces are brought into intimate contact they will lock as long as their surfaces are burr-free and clean.  Since these tapers are ground to a high degree of precision they are also self-aligning.  When installed correctly the arbor will go in straight and stay there unless someone beats them out of alignment with multiple blows from a hammer during or after installation.

To install an arbor:

1.  Wipe the arbor and socket with a clean rag.  Don’t bother with solvents for now – we don’t want a lock yet.

2.  Inspect the socket and arbor and completely remove any burrs found with a diamond coated tool or fine file.  An Eze-Lap diamond hook sharpener works really well for removing burrs from a chuck taper.  Note that even new chucks and arbors can have burrs so don’t assume its okay because it is new.

If you gently spin the arbor in the socket any burrs will usually produce a bright line that is clearly seen.  If the bright line is on the arbor then the burr is on the chuck taper, and vice-versa.  Work on that burr until it is gone.

Smoothing a burr so the defect lies beneath the surface of the taper will not prevent a good fit as long the rest of the taper is untouched.

3.  Once all the burrs are gone use OOO steel wool or a Scotchbrite pad and lightly go over the taper and arbor to remove any invisible dirt or superficial oxidation; do this even with new arbors and chucks.

4.  Now use lacquer thinner or acetone on a lint-free rag (clean old T-shirts work) and clean the socket and male arbor surfaces; after this do not touch these surfaces with your hands.  Rubbing alcohol contains oil and won’t work well on tapers.

5.  Retract the jaws of the chuck into the body and place the nose of the chuck on a solid, clean, flat surface like an anvil or smooth level concrete, not your wooden work bench.  A sheet of paper laid down first will prevent marring the nose of the chuck.

6.  Slide the male arbor end into the chuck’s socket with a gentle twisting motion and it will self-align.  You can cock an arbor when pushing it straight in – trust me.

7.  Position a piece of wood over the end of the arbor and use a steel hammer to deliver a single firm tap straight down onto the end of the arbor.  You do not need to hit it with an overhand, powerful blow – just a firm tap, please.  With the chuck sitting on an unyielding surface this simple tap is all that is necessary to seat the arbor.  Try to resist hitting it more than once. If the arbor and socket were clean and burr-free that arbor will stay in there until you take it out, and it will run true.

To install the chuck into the drill press you must do the same prep work as above.  Move the table out of the way so you can work.  Slide the chuck (jaws still retracted) and arbor into the socket with a gentle twist and, protecting the nose of the chuck with a piece of wood, deliver a single firm tap to the nose of the chuck.

Your chuck is now installed and should stay there until you need to remove it.  When you do need to remove it, it will come out easily.

Now let’s go make some chips!

Mikey
September 2010

How to Grind and Use the ‘Contrary Finishing Tool’

This excellent article was written by Bob Bickerton, a new contributor to Machinistblog.com. It was originally published to the files section of the Yahoo 7x12minilathe discussion group.

The slowest feed rate on the Mini-lathe is about .004 in/revolution. This is fine for many applications but when you want a nice, smooth turned finish the slowest rate isn’t slow enough. You can set the knife tool to ‘rub’ and that helps sometimes. And, there have been modifications published that allow the slow feed to be reduced, but all require building something for the lathe. Here’s another option that only requires one to grind a HSS tool blank to a different shape. It’s a “Contrary Ground Finishing Tool” described by Frank Burns on page 58 of the Jul-Aug. 1997 issue of Home Shop Machinist magazine. Here’s how I do it.

I turn the OD of the work piece with the usual ‘knife tool’ until it’s about 10 thousandths oversize. Then I mount my ‘finishing tool’ and adjust the cross feed to just skim the surface (about a thou or so). Note the cross slide in feed dial reading. Measure the OD and set the cross slide to remove about half of the still oversize work piece. Measure the OD again, and if everything went well you should have removed half the oversize. If so, set the cross slide to remove the remainder and, presto, you have a nicely turned finish on specification size. If the first pass removed a little more or a little less than half, make an appropriate adjustment before the final cut.

Here’s a picture of some EMT conduit mounted in the chuck of my Cummins 7x12. EMT is welded steel tube and difficult to finish, at least for me. The welded seam can be harder than the surrounding area making it difficult to get a good, smooth finish. The front has been machined with my usual knife tool. The finish doesn’t look to bad but it is rough to the touch.

Here’s that same piece after using the ‘Finishing Tool.’ Hard to tell from the picture but the finish is very smooth to the touch. Because the tool cuts on the front it doesn’t need to be exactly on center height. You can’t cut up to a shoulder because of the geometry.

How to Grind and Use the ‘Contrary Finishing Tool’

Because of the high level of interest in this subject, I decided to show how I grind the tool and then show it in use. Here’s how I do it. Continue reading How to Grind and Use the ‘Contrary Finishing Tool’

Cutting Glass on the Mini-Lathe

Diamond blade cutting a test tube on a mini-latheI needed to cut a piece of glass tube to a certain length and this is how I did it using my mini-lathe, an inexpensive diamond blade, some masking tape and WD-40.

The Stirling Engine I’m building uses a glass tube for the power cylinder.  It calls for one with an outside diameter of 16 mm and a length of 26 mm (1.02-inches), although those dimensions are not critical.  I thought I’d have to order a tube with the right diameter but I got lucky and quickly found a package of three 16 mm test tubes in the science kit section of our local Hobby Lobby store.  They cost $3.99.

I found all kinds of techniques on the Internet for cutting glass tubes and bottles.  One, which I’ll call the flaming string method, didn’t look like it would create the smooth even edge that I wanted.  Another video showed how to cut tubing by scoring it part way around with a carbide tool, putting a drop of water on the scratch and then pressing a red hot glass rod into the scratch.  That seemed to neatly break the tube, but I didn’t have a glass rod that I could heat up.  Others suggested cutting it with a diamond blade and I happened to have one of those.

The blade that I used was from a set of Dremel-size diamond blades that I bought a while ago at my local Harbor Freight for only three or four dollars.  They came with a mandrel which I was able to clamp in one of the tool holders for my quick-change tool post.

The test tube fit perfectly, and I mean perfectly, in the center hole of my three-jaw chuck.  Any bigger and it would not have fit.  To ensure that the tube wouldn’t slip while cutting I put some masking tape around it and just barely tightened the jaws.  The test tube had a lip on it that would interfere with the piston so the first photo shows me cutting it off.

I set the lathe in high gear and turned the speed control to almost maximum and then very, very slowly advanced the cross slide.  Water is usually used as a lubricant and coolant when cutting glass with a diamond blade but I didn’t want my lathe to get rusty, so I used a squirt bottle filled with WD-40.  It didn’t require much and afterward a paper towel soaked most of it up.

To be safe, I wore a face shield and I recommend that you do the same.

The cut edge was pretty smooth but I tried to make it even better by using the side of the blade to grind the edge.  The second cut I made left an even smoother edge so I left it alone.  I have a small diamond sharpener that I use to hone cutting edges and if I were to do this again I would probably try to use it like a lathe file to slightly round the edge of the rim that will be exposed when the engine is assembled.

Photo 2 Finished glass tube for the power cylinder

How a rookie makes a flywheel

I ran across this on the Home Model Engine Machinist forum.  I think it is an ingenious, easy and almost fool-proof way to make a spoked flywheel with just a lathe and drill press.  The flywheel blank is turned as shown and the spokes screwed in.  The back is then cut away and the rim turned down a little bit so the spokes are flush.  You can see more pictures and the finished flywheel by visiting the link.

Random Quote

What you need to invent is an imagination and a pile of junk.

— Thomas Edison