Diamond Toolholder

Somehow the Diamond Toolholder (a.k.a. Tangential Toolholder) came to my attention and I thought it sounded like a great idea. Uses a standard 1/4 inch HSS bit, easy to sharpen, easy to adjust height. So I put my money down.
The reality was a big disappointment: here it is on my 7×16 MiniLathe. The cross slide is fully retracted and I can only cut at radii less than 1/2 inch.

When I use a conventionally ground tool bit, I can reach the OD of this 3 inch faceplate.
Maybe if I had bought the left hand holder, I could get to a somewhat larger radius, but still not to the 1.5 inch radius of this faceplate.

I am not saying that this is a bad tool or a bad design, only that it is not suitable for the popular MiniLathes. If you buy one for use on your Southbend lathe, just be aware that the overhang from toolpost to cutting point is about 1.25 inch. What ever diameter you could cut with a conventional bit will be reduced by 2.5 inches. This is the “R8” model toolholder; the penalty is probably greater with the larger toolholders.

Interestingly, it works out better on my Sherline lathe.
Here I have it in Sherline’s standard holder for 3/8 inch bits and I can adjust the cutting point to center. I do not intend to use it here, however; the long overhang is likely to cause chatter.

Posted in Cutting, Turning | Leave a comment

Magnetic Base

This is my new magnetic base for indicators, and I am finding it to be very useful.
It is just the right size for use on MiniLathe and MiniMill and has plenty of articulation. All the joints tighten when you twist one knob. It is readily available at the big auction site.

It even clamps to the quill on my mill.
Here I am using it to center a rotary table.

I had earlier bought this larger magnetic base, but found it to have too little articulation to be of any use.

Posted in Alignment | Leave a comment

Thrust Plate for Compound Slide

I have had a MiniLathe for several months now, but am still having trouble making it function well enough to replace my Sherline lathe for routine reel making operations. One particular problem is that the dial of the compound slide will slip relative to its acme screw, thus losing my zero reference for an axial direction cut.

To understand the design flaw that lets this happen, we have to examine the parts of the slide drive screw.
Front to back here are
– clamp screw and lock washer
– crank
– washer
– dial and its loading spring
– screw guide
– acme screw
Notice on the acme screw the largest diameter portion (only about 1/8 inch axial length) which I will call the thrust collar.

The cross slide drive, which does not have the dial slip problem, has a similar acme screw with thrust collar. Its thrust collar is trapped between two parts of the apron assembly and thereby takes thrust reactions for both tension and compression of the screw. But the thrust collar of the compound screw is not trapped. The collar takes the thrust reaction (against the back of the screw guide) when the screw is in compression. But when the screw is in tension (as it is whenever the compound slide is advanced) the thrust reaction passes through the washer and the dial onto the guide plate.

The dial is subject to three sources of frictional torque:
– from its loading spring
– from the washer
– from the guide block
The problem with this is that the friction from the guide block can overcome the other two frictional torques. When this happens, the dial slips in angular position relative to the acme screw. This is a disaster for someone like me who depends on the dials. It would be much better if the the thrust collar was trapped so that the dial was not exposed to axial thrust.

So here is the part that I made to trap the thrust collar of the compound acme screw.
The flat on the top provides clearance from the bottom of the slide, and the notch at the left clears the gib.

This part screws to the back side of the guide block.
The axial travel of my compound is now reduced by about 1/4 inch, but this is a small price to pay for a dial that actually works.

For adjusting the MiniLathe, see the 3 videos “Cross Slide & Compound” on this Youtube channel:

My efforts to adjust the cross slide and compound gibs were relative ineffective until I lapped the slide dovetails. My lapping procedure:
1. Remove all the parts shown in the top photo of this post.
2. Slather valve grinding compound (500 grit) on the dovetail and gib surfaces.
3. Manually push the engaged slide back and forth several dozen times.
4. Clean off the grinding compound (now contaminated with metal).
5. Repeat steps 2, 3, 4 several times.

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Right Angle Bracket

Little Machine Shop offers this cast iron right angle bracket for use on MiniMills.
I bought one and immediately drilled it to accommodate my Sherline rotary tables.

It is much heavier than the aluminum bracket offered by Sherline.

I have used the cast iron bracket while roughing out the shape of a one piece spool, and find that the mill runs with noticeably less noise and vibration.

Posted in Fixtures, Milling, Work Holding | Leave a comment

More MiniLathe Tooling

I have used a Sherline lathe for about 9 years to make reel parts. In that time I developed many fixtures to facilitate lathe operation. Now that I am converting to a MiniLathe, new tools are needed.

Here its a turning bit based on a 3/8 round carbide insert. I will use it to finish the inside surfaces of spools.
Note 15 April: This cutter did not work, too much compliance. It dug into a bronze end plate and popped it out of a 3 jaw chuck.
27 May 2017: I will take that back. The cutter is OK; the problem was play in the cross slide and compound gibs. If you buy a minilathe, be sure to view a 3 part video on YouTube by Frank Hoose, “Cross-slide & Compound”.

I never used a magnetic base to hold indicators on the Sherline because the cross slide is made of aluminum. Now with a cast iron cross slide a magnetic base is handy.
I bought one, but found the stock arm (laying flat at right) to not have enough articulation. So I bought an additional swivel clamp and made two new arms.

The nut for my ER32 collet holder is grasped with a hook type spanner. To hold the flange, I bought a strap wrench.
But the strap material is too slick; it does not grip the polished flange. So I made a pin type spanner that fits unused holes on the spindle flange.

When the carriage is moved by its rack and pinion drive, there is no dial on the handwheel. So it made a holder for a dial indicator. It clamps to the lathe bed.
This holder can also be used as a carriage stop.

The same holder can be clamped in the tool post in order to read axial runout on a flat part.

Posted in Alignment, Fixtures, Turning | Leave a comment

MiniLathe Tooling

In 2015, I replaced my Sherline mill with a MiniMill (Little Machine Shop 3990).
The switchover was simple; I only had to make some special hold down clamps to continue using my Sherline rotary table with the new mill.

Now I have gone a step further and bought a MiniLathe. I chose MicroMark 84631 because it has 20/inch leadscrews on the cross slide and compound.
I locate the cutting tools by reading the dials at the handwheels, and I cannot work with a dial that has 62.5 divisions.

During lathe assembly, my attention was drawn to the system for adjusting the carriage gibs. It uses a combination of screws to push and pull the gib. None of these screws can be properly tightened because there is no solid stack of parts to tighten against.
So I removed the “push” set screws and put round shims under the gib and around the “pull” cap screws.

The tool post can clamp a bit as large as 5/8 inch, but you would have to do a lot of grinding to get the point down to the right height. I have many 1/4 inch bits from my Sherline lathe that I will continue using.
The brass shim here brings a 1/4 inch bit up to working height, and the shoulder centers the bit under the clamping screws.

It is obvious that the 3 inch chuck for the new lathe is more robust than the Sherline 3 jaw chuck.
But this extra heft comes at a price. Changing chucks is a matter of fiddling with studs and nuts in a confined space, rather than just spinning the chuck onto a spindle nose thread.
Further, I am heavily invested in Sherline chucks.
Significantly, the 4 jaw chucks can serve as milling vises, and can be quickly transferred to the rotary table on my mill. So I am highly motivated to continue using my Sherline chucks.

My solution is to buy an ER-32 collet chuck from Little Machine Shop. This allows me to chuck stock of up to 3/4 inch diameter through the hollow spindle.
When I first installed the collet chuck base on the spindle, I found the TIR on the taper to be about .0001 inch. Then I chucked a gage pin and read about .0002 inch TIR. (Note 9 April: Apparently this was luck. The second bolt-on measured .002 TIR on the taper. Later same day: I made several installs. One position consistently has .002 TIR, another .001, but the best position is under .0003 .)

The key to using my Sherline chucks is to leave the ER-32 chuck in place and make an adapter with the Sherline 3/4-16 thread.
This adapter is Duronze. It has 3/4 inch OD and a bore of a little more than 1/2 inch. Sherline sells a similar adapter but it does not have a bore.

Here is the adapter installed.
And here is a Sherline chuck mounted.

To keep chips from falling where they may, I tape transparency film to the stock chip guard and I have installed a piece of acrylic sheet in front of the carriage.
Note also a piece of Tygon tubing (split) around the exposed lead screw.

From LMS I bought several accessories: Jacobs chuck, live center, die holder, hand crank, and cut-off tool.
With all this, I believe that I have replaced all the Sherline lathe functions except for knurling.

Posted in Tools, Turning, Work Holding | 1 Comment

Cool Water

He’s a devil not a man,
and he spreads the burning sand with water.
Cool, clear water.
“Cool Water” recorded by Sons of the Pioneers (and many others)
Songwriter Bob Nolan

Got my anodizing process restarted after the move to New Mexico. This involved adding some plumbing to a garage utility sink for the cooling water loop.

One of the desired conditions for sulfuric acid anodizing is a bath temperature of 20C (68F). The DC supply is injecting power into the bath and the production of aluminum oxide is exothermic, so the bath is likely to rise in temperature during the 1 hour process time. If I would make a bath of 1 gallon or more volume, the bulk of the acid/water solution would limit the temperature rise. But I use only 1 quart of solution, making forced cooling necessary. My blog post of 22 Aug 2012 details the water cooled cathode.

In Lovells MI, my well water came out of the ground at 4 to 12 deg C year around (pump setting 50 ft, water table 1 ft). Overcooling was quite possible, so I had to supply the cooling water intermittantly while watching a thermometer. Probably made an on/off cycle every 5 minutes. Running the process took constant attention.

Here in NM we have been having warm weather for the season, 75F for several days. I am on city water, and the houses here are built on a slab. I do not know the building practices, but it seems that there is not much insulation between the cold water pipes and the concrete. When I first open a cold tap, the water may run at 24C for a while, gradually dropping to 18C. So there is not much temperature difference available for cooling. With a steady flow through the tubes, I could only keep the bath temperature down to 23C. Having more tubing in the cooling loop would probably allow lower temperature.

As for the resulting anodize layer, I cannot observe that it is adversely affected by the slightly higher temperature. And, I spend much less time watching the thermometer.

Another process consideration is that here at 5800 ft elevation, water boils at about 200F. So sealing the anodize layer has to be done at the lower temperature. My data sources say that anything above 170F should be OK, see blog post of 3 March 2012.

Update 23 May 2017: Resolution is to put a submersible aquarium pump, frozen blue ice packs and water into a small insulated container. Use the pump to run a closed cooling loop. With cooling water at 14C, I was able to maintain cell at 20C. I did stabilize the cell solution near 20C before starting.



Posted in Anodizing/Plating | Leave a comment