HSS Inserts?

[Bradells]

Saw a video on the YouTubes that was using HSS inserts (opposed to Carbide inserts).

These might be handy for me with my tiny machine ... I've been able to use carbide but not to all of its advantages, but the HSS might be a better option.

In my quick google searches, I'm just ending up with HSS blanks, not inserts ....

Any suggestions?


Brad

 

[francist]

Have you looked at a Little Machine Shop?

 

[Tom Kitta]

Yeah but at these prices who can afford that! I usually pay well under 1 CAD per insert - here cheapest one is a whopping 8 USD and its not even carbide. I mean small inserts even not on sale are ultra cheap - https://www.aliexpress.com/item/329...8.0&pvid=8e158dc9-6fe2-4fb9-aba7-6559816e0057

For interrupted cut get a grade of carbide that is for soft stuff and has lowest speed setting. Also get maximum radius you can get (i.e. no sharp corners).

Here is some discussion of HSS inserts: https://www.practicalmachinist.com/vb/general/hss-direct-replacement-inserts-293476/

 

[PeterT]

Agree with Tom. What specific application were you thinking of? I've seen HSS occasionally for threading but seems to slowly be phasing out. Less so for straight turning, albeit I wasn't aware of the ones shown at LMS. But yeesh 8.95 USD for one. You can get a 10 pack of carbides with same geometry & many more flavors of material cutting applications, coating, nose radius, chip-breaker etc.

I'm guessing the selling point is the usual HSS vs Carbide discussion: HSS has toughness so theoretically better for lower speeds, interrupted cuts, dissimilar density like breaking through skin even though its usually not quite as hard as carbide. Unfortunately loose lathes or less rigid or real low power machines may fall into this category inadvertently. HSS may help but its not a miracle cure in those cases either. For straight turning, cheapo Ebay/Ali carbides have served me well in a variety of materials. The uncoated ones for aluminum are razor sharp & go for miles before degrading. The coated ones I use for steel, same deal. Most chipped corners are operator induced unless its an ugly material.

For example I ventured into carbide threading inserts last year & was pretty impressed despite running at much lower than recommended SFM. They cut clean with no degradation. These happen to be fine threads (therefore teeny tip radius), stainless steel parts (more challenging material that likes to heat & work harden). On a manual machine sometimes you don't have any other option than to run slower, especially threading, without running the risk of disengaging late & bad things happen. So no, not removing material as efficiently vs. CNC, but those machines are much more robust, have optimized variable rpm & feed control. But that doesn't mean carbides wont still work well for us. You may have to experiment to find the best settings on your setup, but that's almost a given in hobby machining.

 

[Bradells]

For me, my machines are tiny and not high on the HP, my deepest cut I can take on 6061 is roughly a slow 30thou... kinda where most inserts like to start showing their strengths but at much faster speeds and aggressive.

I do get decent results with the few that I’ve used so far (except for my single cutter face mill).

With HSS better suited for light cuts, and that I don’t have a grinder make these seem like a good match....


Brad

 

[Dabbler]

@Bradells You can learn to grind HSS blanks, which will give you a great cost/use ratio. However, the secret to using carbide on small machines is to Positive Rake inserts. They require up to 1/3 less cutting pressure, as compared to negative rake inserts like CNMG ones. (I'm considering moving in the oppoisite direction for my bigger lathe)

look for something in the TPMT or similar type. you can get more radical, but $$$. Look for inserts ground for cutting aluminum - they will work fine in steel, but have a much sharper cutting point - lasts shorter time, but cuts with much less force.

Ya see, there's carbide and the there's carbide... (takes straw out of mouth and spits chawing tabbakie)

Seriously with a ground insert, the cutting pressure will be very close to cutting with HSS - but - your best option is grinding your own HSS,

 

[DPittman]

I used hss inserts from A.R. Warner on my little Atlas lathe and liked them, especially for threading. I liked that the cutting edge could be easily honed sharp again using a flat stone.
I was even less experienced then when i had that little lathe....so take my advice with a grain of salt.

 

[Bradells]

@Bradells You can learn to grind HSS blanks, which will give you a great cost/use ratio.

Still using my HSS tools I made 20+ years ago! Just give them a run with the stone to keep them sharp and clean!

However, the secret to using carbide on small machines is to Positive Rake inserts. They require up to 1/3 less cutting pressure, as compared to negative rake inserts like CNMG ones. (I'm considering moving in the oppoisite direction for my bigger lathe)

look for something in the TPMT or similar type. you can get more radical, but $$$. Look for inserts ground for cutting aluminum - they will work fine in steel, but have a much sharper cutting point - lasts shorter time, but cuts with much less force.

Ya see, there's carbide and the there's carbide... (takes straw out of mouth and spits chawing tabbakie)

Seriously with a ground insert, the cutting pressure will be very close to cutting with HSS - but - your best option is grinding your own HSS,

Indeed, but a tiny 10oz-in motor (.85A output) can only do so much! https://www.sherline.com/standard-dimensions-of-sherline-tools. I've got a few TNMG inserts in holders at the moment.


Brad

 

[Dabbler]

you'll see a huge improvement using TCMT over TNMG tools, or better yet these:

https://www.banggood.com/7pcs-10mm-...73201502H&custlixnkid=440236&cur_warehouse=CN

the included inserts are for aluminum, which means they are diamond ground. They won't last as long as tnmg, but give a better finish, and most importantly, take far less cutting power.