Introduction: A Simple Gauge for Setting Tool Height in the Lathe.
I made it at TechShop!
This is a simple gauge for quickly setting tool height in a lathe. If you're using a lantern or four-way style toolpost these can be invaluable, but they are very convenient even with a quick change toolpost! Just place the tool on your cross slide and set the height of the tool point by leveling it with the top surface of the gauge. I like to just gently rub my finger across the top so I can easily feel whether the tool is high or low.
What you need:
- A lathe! :)
- Appropriate lathe tools for facing.
- A Bandsaw/Cold Saw/Chop Saw/Hacksaw/etc. to cut the stock.
- Any piece of round stock long enough to do the job.
I'd prefer a piece of pipe or tubing for this. That way it's less likely to get a chip stuck under it.
Step 1: Get Your Stock.
Here I have a 1.25x12" pipe nipple in Lowe's. I chose this one because I DIDN'T get a coarse measurement from the lathe first, and was thinking the gauge would end up longer than it did.
Firstly, a GIANT WARNING!!! The piece I chose was GALVANIZED. When heated beyond a point the zinc vaporizes creating VERY dangerous fumes. This is why you should never weld galvanized steel. The boiling point of zinc is ~900dF, which is plenty of headroom in machining terms, but all the same I kept my cuts away from the aggressive end and used spray coolant to keep temps in check, just to be safe.
Secondly, learn from my mistake. I didn't measure the lathe first and assumed the gauge would end up longer than it ultimately did. Because of this, I was favoring the 1.25" pipe which Lowe's only carries as galvanized. A 1" diameter piece of "black iron" pipe would have served fine and allowed more aggressive cuts. ::smacks forehead::
You can get a coarse measurement of your lathe by simply sliding the tailstock over to the carriage and measuring between the top surface of the cross slide and the point of a dead center in the tailstock. Add a little to your measurement so you don't accidentally leave yourself with too little to properly face.
Try to plan for a length:diameter ratio below 6:1 or so to keep your gauge from being too tippy. ;)
Step 2: Rough Cut.
Here's the piece fresh out of the bandsaw. I cut off the threads, and chose a length of 4 and 5/8's.
(After measuring the lathe) :)
I now also have a short piece of pipe for future projects. :|
Step 3: Chuck It Up and Face One Side.
First make sure your tool height is very nicely set, as you will be using it set your gauge length. Any tools you set to this gauge in the future will be this same height.
Chuck your piece in the 3-jaw and make a nice cleaned up face on this end. You can add chamfers (beveled edges) like I did, but remember to keep the outer one very small. I skimmed a little more off the face of the one in the second picture here because I overdid it a little.
Also, remember to double check that your tool height is very closely on center. ;)
Step 4: Facing to Length.
Now turn your part around and cut a nice face on it. You cut the stock slightly long, right?
With both sides faced, you can now start comparing the gauge length to the tool height. You need to have both ends cut clean before the gauge will sit square on the cross slide and give a clean edge to compare with your tool. Be sure there aren't any chips or burred edges throwing off your comparison.
Got a bit more to go in the pic above. :)
Step 5: Final Cuts.
You'll find yourself taking several of these skim passes as you sneak up on the final dimension.
You remembered to TRIPLE check your tool height, because if it's slightly low you'll be banging your head later. Right? :)
Step 6: DONE!
You can now use this gauge to rapidly confirm the height of any tools you pop in your quick change, as well as set the height of new ones. If you have a 4-way toolpost this tool will help immensely in your war with the hated shims.
If you are using a lantern toolpost you are crazy, but I respect you all the same. This tool will save you immeasurable time in your struggles. You might also consider creating a version of this with a lip cut into the side, rather than a top surface. That way you can simply lift the tool tip until it contacts the gauge and tighten.
I cleaned mine up with the shop soap the same time I did my hands. A pot scrubber plus the the pumice loaded soap cleaned all the sticker crud and coolant off and had it looking like the intro pic in about a minute.