Lathe Tool Holders Part 1

I seem to be spending a little more time with my 'puter lately. Let's see if I can turn that into some productive writing. (I will do my best, despite Blogger working against me by randomly moving pics when I try to add captions and just making me want to throw shit...so sorry for any strange formatting that takes place)

Current project is new tool holders for my lathe. Sure, I can buy them for about $15 each, but then I wouldn't learn anything. Also, it's a good opportunity to learn 3D modeling with Fusion 360 (more on that later...maybe?).

This is what we're aiming for. How are we going to get there? Ignore the rough finish on the end...that's the result of a roughing mill and will be smoothed out later.

Before the fancy dovetails get cut...we have to do the grunt work. If you were to just start plowing out with a DT cutter, you'd wear it out right quick. Once your base piece is dimensioned, it's best to cut the basic slot away with an end mill (or even better, a roughing end mill). Roughing mills can remove more material faster than a standard end mill. The trade off is the poor surface finish. Run the roughing mill to within .010"-.020" of your finished dimension. Change over to a standard mill and finish it up. Roughing mills aren't cheap, but they can take beatings that your standard end mills can't.

Cut that dovetail!!

There are a couple of ways to measure dovetails. Let's focus on this way (because, honestly, it's the only way I know). First off...you can NOT just measure a dovetail. You'll need some gauge pins. The size of the pins depends on the size of the dovetail. In this case, we'll be using .125" pins. I cut the first side of the dovetail to a known dimension over a pin to the datum side. (I'll have to post some drawings next, I guess). Anywho...you need to know your target. Once your first side is cut, you can move over and do the other side.

Cutting the second wall.

There are multiple ways to measure inside the DT. First, and least accurate, is to place your gauge pins into the dovetail and use a caliper. For this type of dovetail, this method is probably accurate enough. This isn't a sliding DT, and it's only an inch long when finished.

More accurate is to place the two gauge pins and use an adjustable parallel between them to measure the distance,..

...then you just mic the adjustable parallel in order to get your measurement.

More accurate still, is to use gauge blocks between your gauge pins to get the measurement. That just seems like a lot of screwing around to me. I will roll with the adjustable parallel for now. Til next time...