GuShH's DevBlog

When having to drill repetitive holes in parts as second operations on an engine lathe, having a means to automate the tailstock could prove valuable.

Not all lathes come with the option of a hydraulic tailstock and some only have limited action.

The following are two basic ideas that can be implemented on virtually any lathe and very quickly as well!

 

First method:

Attach a suitable pneumatic cylinder to the bed using a similar clamping method as used on the tailstock itself. Have it push the lightly clamped (but free sliding) tailstock. A restrictor to control the feed-rate is mandatory. This method requires no modification to the lathe, if you need it to also retract through pneumatic action you can use a bracket or clamp on the tailstock. Otherwise you can push it back by hand as usual. Using a second restrictor on the return valve could help lengthen the life of the cylinder, so you don’t constantly ram it to fully closed all the time.

Second method:

With a long arm and bracket mounted on the toolpost, one can have the tailstock move, when the auto-feed is engaged on the carriage. This method has several limitations but it only requires light fabrication on mild-steel or aluminum for the “pushing arm”. While you can adjust the feed, it won’t be as flexible as the pneumatic cylinder, and you’ll have travel limitations in some cases.

Of course, the obvious alternative is to have the tailstock mounted in front of the carriage, and have the carriage push the lightly clamped (but still free sliding) tailstock.

 

Whichever method you choose, be careful and keep in mind possible crashes or tool ruptures. These are NON-CNC methods, for any type of electrical control you could, in theory, easily mount a stepper motor to the quill feed on the tailstock, but that itself is a modification of the lathe and beyond the scope of these two simple methods.

As for peck-drilling, the second method won’t allow it, this is why I’m starting to work on a clamp system for a pneumatic cylinder, peck-drilling with a pneumatic setup is relatively easy (although it may be expensive for some). The whole idea however is not to modify the tailstock in any way at all.

 

Enjoy!

To quickly align your tailstock:

1. Face and center-drill some scrap steel, round 1/2″ about 5 inches long.
2. Insert a dead center on the tailstock.
3. Mount your dial indicator so it touches a flat section of the dead center, right after the 60°, make sure you are on a flat by moving the tailstock quill back and forth, your indicator dial shouldn’t deviate.
4. Once you’ve setup the indicator, you can now push the dead center onto the center you drilled before. If your tailstock is misaligned your indicator will show a slight deflection as everything slightly flexes toward center.
5. At this point, you can go back and forth adjusting the tailstock setscrews until pushing the dead center won’t yield a deflection on the indicator dial.

You can easily get your tailstock centered within a thou or less using this method in under 5 minutes. Depending on whether you use a test indicator or a dial indicator, you can improve the alignment furthermore based on the available accuracy and resolution of your indicator.

Just keep in mind a test cut is always a good way to know for sure if you’re in dead center. Of course this requires the use of a known good micrometer and lots of time and patience. The alternative is to use a calibrated rod and indicate throughout the X travel for deviation, but the rod has to be held within centers.

Step 1 is very important, the part has to be center drilled on the spot every time for a good reference. You can use the same part twice (working on either side) afterwards you’ll have to face the center marks off or start from another scrap piece.

Once you are happy with the alignment:

Don’t forget to lock the setscrews against each other. Do this while indicating to make absolutely sure you aren’t pushing the tailstock to either side.

If after the alignment you still have issues, chances are you need to look into shimming your tailstock as wear has brought it’s height down from center. This is unfortunate, but it does happen. Bigger machines have removable contact plates that can be remade to deal with this, other machines can be coated or utilize teflon contact surfaces that are replacable. But typically if you have a solid cast iron base, you have to shim it.

The alternative is to machine a new lower plate / base for the tailstock, making it so the contact areas are replacable. Problem with more parts is, more chance of the parts actually moving and causing trouble. Your choice though.

This method relies on flexing of the part and the actual tailstock quill, it doesn’t matter how big or small your lathe is, all parts flex and we can use this to our advantage.

Happy new year everyone!

Intro:

Here’s a small but useful io function, The basic routine is also included for less demanding uses.

This function will read a text file into a string, the Ex (extended) functionality allows for defining size constraints to the return string and positioning of the file pointer for location/seeking purposes.

On big text files and in cases where you want to limit memory usage, this is a very useful routine. Otherwise the basic function works just fine.

The extended routine can also be used with a callback to set a progress bar, based on data size you can also calculate the remaining time, however that’s all beyond the scope of this post.

Code:

Use example:

Keep in mind that with the basic routine the whole file will be read into memory, so you have to beware of this detail.

If you never expect file sizes to exceed a certain range, this won’t be an issue. Otherwise use the Ex function to prevent memory and other performance related issues.

If the file is not found the return string is empty, this is the expected behavior, no error codes are used but you can easily implement this.

Have fun!

Small but sturdy…

This small capstan lathe was salvaged from certain doom, a lot of old machinery ends up sold as scrap metal — If you can avoid it and salvage at least one, do it. They’re well worth it.

First order of business:

Remove all non standard parts, this includes the fume hood and other sheet metal parts that were fitted at the previous factory.

Upon removal of the sheet metal parts, I noticed a small 3 jaw chuck was fitted to the spindle — Unsurprisingly it was stuck, but we had to remove it and take it apart anyway as part of the restoration, so we’ll put that aside for now.

A few missing parts reveal themselves, mainly the X positioning for the slide was missing (no rack, no pinion, no handle). The slide was missing the handle and the push mechanism, no motor, only a single cast iron pulley, no collet chuck.

The turret was stuck, no surprise there. Water did get inside at one point in time.

 

Refurbishing the turret

What’s worse than a machine in bad condition, rusty, dirty, beat up?, a machine that is also missing one or more vital parts of it’s internal mechanism!

I was missing the lock trigger for the turret, this was a huge setback because I have never seen the part, I couldn’t find information anywhere, everyone I asked had no clue or they’ve worked on different capstan lathes, with similar but not-quite-the-same lock mechanism, so I was out of luck!

Decided to go full-on CSI on the lathe, I noticed a horizontal shaft where the trigger may have been pivoting on, I also noticed a wear mark on a stop block underneath, this gave me the depth of the missing part … Now I was “just” missing the geometry of the part.

Started with a rectangular piece of flat stock, steel (unknown alloy from the scrap bin, but with relatively high carbon content based on how it machined) — Marked the height for the pivoting hole — using an informed guess — Center punched, spotted and drilled it, then reamed it up to size.

I dyed the blank trigger, fit it inside the shaft and attempted to run a cycle on the capstan, it gets stuck (not a surprise there) — But this is good news, now we have transferred onto the dye where it hit. After several iterations or removing the part, grinding away some material, dying, fitting it, cycling, etc. I managed to get a full cycle going, success!

The final part looks like like this:

 

Locking mechanism

However the locks were not working properly, a closer inspection showed a missing locating pin that would’ve locked both parts together, I machined one out of SAE1010 1/4″ round stock, should be plenty good for this application.

 

 

 

Now the turret cycles properly, it just needs to be fine-tuned so it doesn’t over-spin, failing to lock automatically on every cycle (requiring the usual “hand nudge” on old, tired lathes that aren’t setup properly).

The lathe is functional in the turret department at last, most of the remaining work on the turret will be to clean up threads chasing them with taps and other basic tasks such as priming and painting.

Focus is now on the spindle, carriage and chuck. Toolposts will be required.

 

So how did it look like when I got it?

It looked like it belonged to a landfill, take a look:

 

To be fair the ways are in good shape, other than the peck-marks from who knows what (parts falling onto the ways or tools being thrown over the ways)

Here’s a close-up after cleaning them:

More to come…