Thursday, April 24, 2014

Lathe: Tormach 0XA QCTP

I've had a A2Z CNC type QCTP on the lathe for about a year now and it's been a huge improvement over the stock tool post. However, I didn't like that it was made from aluminum nor that locking the tool holder in place pushed it away from the tool post itself, so only the two dovetails were in contact.

I happened across the Tormach 0XA QCTP on Little Machine Shop and immediately ordered one. Not only is it made of steel, but it's also an AXA or sliding wedge style tool post. In this design as the tool holder is locked to the post, it's pulled in against the post, so you have a lot more contact area between the two than with the A2Z CNC style; the 0XA is just a better design. I also really like that it comes with a knurling tool, which saves me an extra $25. Also, tool holders for it are cheaper than the A2Z CNC as well, which is nice since you'll want a lot of tool holders.

After installing it last night, I'm very impressed with it. The quality is excellent, and the added weight of the post and the holders is very evident. The back of the holders have a ground and polished finish. There's a very nice, tight fit between the post and holders.

Brand new the A2Z CNC QCTP costs $99 while the 0XA costs $129. However, in my opinion the 0XA is absolutely worth the extra $30, especially since you also get a knurling tool with it.

Tuesday, April 15, 2014

Lathe: Bike Computer Tachometer

Please read the complete article:

After testing, it appears that most bike computers lose a lot of accuracy over 1,000 RPM. I suspect this is probably because the reed switch used to sense the magnet simply can't operate that fast.

I had been planning on installing bike computers on both the mill and lathe, but the 1,000 RPM limitation doesn't make it worth my time since a lot of my cutting it done on aluminum which uses speeds often well over that.

As of now the plan is to continue using my non-contact laser tachometer and I'll mark graduations around the speed control knob. Crude, but it should be effective enough.

Sunday, April 13, 2014

Lathe: Leadscrew Play

My lathe had play in the leadscrew. I've heard of people shimming the leadscrew at the pillow block, but to make is easier I just removed the pillow block, threw it in the mill, and made the bolt holes into ovals so I could adjust the clearance between the pillow block and leadscrew by just loosening the bolts and sliding the block. Using this I was able to remove all the play from the leadscrew.

Saturday, April 12, 2014

Lathe: Spindle Extension

I wanted to put a spindle extension on the back of the lathe for a couple of reasons. First I wanted to make sure any swarf which made its way into the spindle bore fell out of the machine instead of into it. Second, I wanted a convenient place to mount a magnet for my bicycle computer tachometer. The spindle thread is M27x1.5 and I was able to find a corresponding nut on Amazon. It's actually designed for compression fittings, but it works great. It's available in two sizes, 18mm and 35mm. Being cheap I opted for the less expensive 18mm. Once I received it I turned down 9mm of its end until the wrench flats disappeared, and then a little more. I then had to enlarge the opening in the gear cover which was easily done with a Dremel and a sanding drum. Finally I threaded the nut onto the end of the spindle and snugged it down. Neither lock ring on the spindle needs to be removed to install it.



Lathe: Gear Cover Hand Screws

I decided to replace the gear cover screws with thumbscrews to make its removal easier.

I bought a section of M5 threaded rod and two 25mm M5 threaded standoffs from McMaster. 9mm of one end of the standoffs were turned down to 8.5mm diameter, and then were red Loctited onto a 60mm long section of threaded rod.

Tuesday, April 8, 2014

Lathe: Carriage DRO

Please read the complete article:

I was finally able to install the DRO on my lathe's carriage. I used a 12" iGaging digital scale with a remote display, the same type I used on my mill.

When I do threading on the lathe I'll just back out my bit and run the lathe in reverse to rest the carriage, so I have no need for a threading dial and had removed it a while ago. That left a great threaded hole to mount the DRO bracket to. I suppose if you still have the threading deal there you could always just sandwich the bracket between the apron and dial. The bracket was easily made from 1/8" 1" aluminum angle. It's a bit overkill and I'll probably trim it down a little more later, but it's not really in the way as is.

The design I ended up with places the DRO below the lead screw, so it's fairly well protected from swarf. The mounting for it is quite stiff, so I only have the scale attached at one end. That was particularly helpful since I didn't want to try drilling into the lathe' body at the head since it houses the motor right there.

I still haven't found a good place to mount the remote display though, and I may end up doing an Arduino DRO display like I did for the mill.

Both the carriage and cross slide DROs are visible.

Carriage travel at the extreme right of the bed is limited slightly.

Monday, April 7, 2014

Lathe: Changing Gears

It took me a minute to figure out the proper way to adjust the lathe's gears when converting to and from threading operations. There are two adjustment, one locked in place by a 14mm bolt, and one by a 10mm nut. Use the 14mm bolt adjustment to set the clearance between the idler gear and the lead screw, and the 10mm to adjust clearance between the idler and spindle. Proper clearance should allow just the slightest amount of play between the teeth of the gears.

Lathe: Shimming Carriage Gibs

The gibs on the carriage went out of adjustment again, bringing the project I was working on to a temporary end. Highly annoying. Instead of just adjusting them, I took the time to shim them.

The mini lathe's carriage gibs are held in place and adjusted by opposing screws. Two of them push the gib away from the carriage, while three of them tighten the gib to the carriage. In theory, by balancing the screws against each other you can adjust the gib/carriage/bed clearance. In reality it's a crappy system. It's hard to adjust, puts a lot of stress on the gib, and bends the two ends of the big toward to the bed, making it even hard to adjust properly.

To switch to shims remove the small locking screws and leave the socket head cap screws. Starting with the back of the carriage, slide a shim between the gib and carriage, tighten down the three screws and see what it does. If the carriage won't move it's too tight, if there is any movement it's too loose. On mine the back gib ended up with a 0.035" shim. Once that's done, repeat on the front. When testing for movement, make sure there is there isn't any play between the carriage and the bed's prism.

Once the shims are in place, apply blue tread locker to the screws, tighten everything down, and lube the ways.

Mill: Mill Column Tuning Device

I jokingly call this my Mill Column Tuning Device, or MCTD.

It's very difficult to get the column exactly perpendicular to the base using just shims. Additionally, temperature can make the column lean more one direction or another. What I did was fabricate a bracket which is bolted to the base using the column's mounting bolts (longer bolts were required), and then connect the bracket with the top of the column using turnbuckles. Both the side and back of the column received a turnbuckle. Now, as I tighten or loosen the turnbuckle, it will push or pull the column slightly to account for any slight misalignment.

The turnbuckles actually bend the column, so the amount of movement becomes greater the closer to the top of the column you get. Therefore you can't use this system to get the column exactly perpendicular to the base at every position on the column. However, once you've done the best you can with shims, this will let you get it a little closer still, and I'm happy with an incremental improvement.

The rod ends were stock items purchased from McMaster. The turnbuckles themselves were created from 1/2" mild steel rod. The ended were turned down and then threaded on my mini lathe. One end is right hand thread, the other is left hand thread. A M14 nut was slide down the turnbuckle and then welded in place, giving a convenient way to turn them.

The power box was spaced away from the column using simple standoffs to make room for the turnbuckle.

As an added bonus, the bracket was is an ideal location to put my mill's DRO's control box and let me clean up the wires.

The system installed on the mill.

The bracket the bottom of the turnbuckles attach to.

Top of the turn buckles, and the power box spacers.

The DRO control box on the bracket and the wires corralled.

UPDATE: I ended up taking it back off the mill. In practice it proved pretty hard to use, and my column is already close to perfect that it just didn't make sense to keep it. Removed it also allowed me to move the spindle light and power feed control back to the top left of the column.