Short Dabbles

I don't get much time in the shop these days, and when I do, there's little time to record stuff. I made an adapter a few days ago on my smaller lathe,and it was a learning experience...

The project: make an adapter for my manual ironworker...


It started as a piece of donor metal 4300 series shafting, heat treated, 3" in diameter, and ended up with 2.4" and 1.600" OD, about 10" long overall.


The lessons are all in the boring. It needed a 1.680"hole 4" deep in the large end. All this to accommodate .080 in difference.. sigh.


4330 and 4340 are pretty tough materials. I had no way to anneal a 10" long piece without grand measures, so I decided to soldier on with drilling and boring. I drilled it up to 1.035 using a MT3 drill. That's where the fun started! I had 2 insert boring bars available: an inexpensive TCMT 1/2" boring bar from offshore and a SECO 5/8" boring/grooving bar. The inexpensive 1/2 inch boring bar could only make slow progress, around .006 DOC per pass (.012 diameter). It just wasn't rigid enough to take a deeper DOC and it could only reach in about 2". - Extending it any longer was fruitless.

Enter the SECO. I only have a grooving tool for this bar (I bought it used) and new inserts for it are very$$$$. I was able to take cuts up to about .011 deep (.022 diameter) This was taking FOREVER. After 5 hours of boring I decided enough was enough.

PHASE 2 - new boring bar.

I can hold up to 5/8 tooling in my 12" lathe, so I ordered an Accusize 3/4" WNMG432 boring bar from ACCUSIZE. Did this ever make a difference! The sharper amongst you will notice the size issue, but look at this clever profile:


Because of the flats milled in the top and bottom, I can still hold it in a 5/8 holder or a round 3/4" BB holder. A nice compromise for both worlds. I was able to take .030 DOC (.060 diameter) - my limit was the belt drive 1.5 HP drive system. Instead of an additional estimated 15 hours boring, it took about 3.

So right tool for right job.


I spent some $$$ and bought 10 coated aluminum inserts for this job. They were 80$ for 10, but they needed less than 1/2 the tooling pressure to cut, and allowed the deep DOC. with conventional inserts, even tuned up with a diamond hone, I could only take about .020 DOC [update with a conventional insert] The single edge lasted the whole job with no dulling visible using a loupe.

So even in tough materials, using an aluminum insert can make it easier, and didn't break down the edge much at all.
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