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Chip Breaker Inserts on a Sherline

Rockytime

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#1
I have used HSS tooling on my Sherline lathe for years. I keep seeing 1/4" and 3/8" sets of carbide tools extremely inexpensive albeit from China. I know about Valenite and the other makers but I am interested in the Chinese because they are cheap as am I. I use chip breakers on my MaxiMat7 and they work well. I'm wondering if anyone has experience with these. I have heard somewhere that they have been used disappointedly. Is that a word? I have a friend that uses brazed carbide almost exclusively but he first sharpens them on a diamond wheel. I am happy with HSS but am curious if it is worth testing the $25-$30 tools.
 

mikey

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#2
I have used 3/8" SCLCR tools on the Sherline. These take CCMT or CCGT inserts and they work fairly well. If you know how to use carbide tooling then you'll be fine. Your roughing depths of cut will be severely limited by the lack of rigidity in the lathe but they finish good at top speed. I would not hesitate to use a CCGT AK insert on aluminum - they work well.

With that said, a properly ground HSS tool will outperform carbide in almost all cases on a Sherline lathe, at least in my experience. I get very little deflection with a good HSS tool on a Sherline; this is definitely not so with carbide on this lathe so beware of them when accuracy is paramount.
 

Rockytime

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#3
Thanks for your response. I think I will order the 3/8" sets. I have the boring bars with CCMT inserts. I just got them and have not tried them. I turn some 12L14 but mostly brass and aluminum.
 

mikey

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#4
Thanks for your response. I think I will order the 3/8" sets. I have the boring bars with CCMT inserts. I just got them and have not tried them. I turn some 12L14 but mostly brass and aluminum.
You'll be fine. The CCMT inserts work fine for most steels. I need to experiment more with the chipbreakers but I don't use this tool much so it may take me some time to gain experience enough to comment on them.

Be sure to order some CCGT AK inserts at the same time. These AK inserts have an aggressive positive rake and will do well in aluminum. Look for Korloy in an H01 grade - uncoated but ground and polished to a very sharp edge. These inserts will also cut 12L14 fairly well, although they won't last as long. It only has a 7 degree relief angle but it still makes pretty good cuts in stainless if you can keep up with the feed.

The most common inserts will be a CCMT 25.51 or 25.52 (0.015" and 0.0312" nose radius, respectively). I have found that the smaller nose radius works well when your tolerances are tight and you're taking fine finish cuts (0.005-0.007" deep) but for roughing or when tolerances are looser, the larger radius works better and gives a better finish.

Note that the Sherline lathe will only get up to ~2800 rpm unless you have a 10K spindle. This is pretty slow unless you're cutting at the maximum diameters your lathe can handle. Cutting speeds for aluminum is about 900 sfm and we cannot get anywhere near this speed (4600 rpm for a 3/4" OD piece, for example) so I find I have to run as fast as I can and slow my feed. As a result, I get long stringers but it can't be helped. Still, the tool works okay. By the way, max depth of cut is about 0.125" or so and your Sherline can take it if everything is tight.

For brass, I have found a zero-rake HSS tool to work the best for me. The CCMT insert will work for brass but I get a much better finish and tighter tolerances with HSS. Might just be me.

Good luck with this. It's fun to play with these tools on a Sherline and it sure beats having to grind tools. Lucky for me, I have all the HSS tools I need and it takes me a few seconds to hone an edge so I don't use these inserted tools very much but it was fun figuring out how to use them.
 

Rockytime

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#5
Thanks for your info. I have several carbide insert-able lathe tools which I used on a larger lathe before I downsized everything. I no longer remember what the inserts were. I should have labeled them. At the time I was younger and was sure what they were. They, however, will not fit the Sherline. I'll have to google an insert chart as there are a myriad of different inserts. I had a neighbor who was a sales rep. for Valenite for a long time and answered all my questions. Unfortunately he passes away several years ago. In the meantime I appreciate your taking the time to give me a heads up.
Regards, Les