Lathe tool choice...

[Davek0974]

Hi all,
i've been looking for some time for some large tooling to use on my colchester student lathe.

I'm finding it really hard to get a suitable set of tools with tips on ebay, new ones in larger sizes seem to be very ££££

I dont want to get lots of different tools with lots of different pattern tips etc.

As i need to get using it soon, what are the opinions on a set of 1/2" shank brazed carbide tools or a set of 1/2" HSS tools?? Both are available for a good price in ebay shops.

It will mainly be doing the larger work including cast iron and such.

Is brazed better than HSS??

I have got a grinding wheel for carbide as well as ordinary so touching either up should not be a problem.

Thanks in advance
Dave

[Fasttrack]

If its ductile castings that your talking about - go with HSS! Once you figure out how to sharpen the bits, they are the most cost effective way to go for general applications, imo.

They are flexible, in that you can always regrind the bits for different operations or form cutters and if they get dull, you just sharpen them. A 4" chunck of HSS will last you a long time.

If you have to work with hard material, carbide is the way to go. Brazed carbide is handy since its already ground correctly for basic operations and they are cheaper than indexable types.

If you have to do production stuff or have to turn hard material, carbide is the way to go. Remember that carbide HAS to be run FAST! If your lathe can't spin 1000 rpm, HSS better be your main tooling.

Plus, you have to be careful with carbide. Most carbide inserts and brazed tools have a minimum DOC for it to effectively cut. This is true with HSS too, but it is dependant upon tool geometry (along with other factors like feed/speed and rigidity) and is easy to change.

Finally, carbide can be sharpened with CBN wheels or to a much less effective degree silicon carbide. However, there are dangers associated with sharpening carbide since the binding agents are toxic.

ALUMINUM OXIDE won't sharpen carbide worth a darn. Neither will silicon carbide. Once you sharpen with silicon carbide, the edge never lasts as long as one produced with CBN/Diamond. If you look at the edge under a microscope, you see that its not very smooth compared to a new edge.

[Davek0974]

Thanks

I'll go fo good old HSS then.

Looks like i need to dump the AL/OX wheel - more duff advice from a supplier!

Probably fit a wire brush wheel or buffer instead.

Dave

[Evan]

I would go with both. Carbide tooling has a very important place even on a small lathe such as my South Bend. Common wisdom states that my lathe isn't large enough, powerful enough or fast enough to make use of carbide tooling effectively but I beg to differ. I was turning this yesterday. HSS just won't hold up to this.



If all you have is HSS tooling you will be out of luck the first time somebody needs to do some hard turning.

[airsmith282]

i would agree that HSS will not hold up to turnning steels of any kind at hi speed.
but at lower speeds it just just fine. I use mainly HSS cutters now that i grind my self iam in no rush to get something done so the HSS works for anything i turn inlcuding SS.

I do have indexable carbid cutters and brazzed on models as well and they have there place thats for sure. You can turn steel at a higher speed when using carbide but i find they tend to dull fast and snap faster. as for DOC i can take a bigger bite with HSS Cutters then carbid and have no problems.

i also have found that no matter what cutter you use the faster you spin the peice the more heat you get and you wont get proper sizeing in your peice either. i get what i want at lower spin rates then i do at faster with and with out cooling the metal.. slower is better in my opnion..i also take lighter cuts per pass as well. alot of the stuff i have been making lately requires free spin... as there is no room for the live center to be use which also forces lighter cuts.

the other thing i have learned as well is to take my peice down so far the let the metal cool for an hour and then go back to it this gives the chance for the metal to shrink from the expansion it goes threw when heating up.. anyhow just a few things i have found and do and i get the results iam after in the end...

i have seen CNC machines really rip threw alot of stuff fast but for the home machinest with much lower end stuff we have to take things alot slower.

i only have about 2 years in on machineing... but i have learned alot in the last 2 years.. iam not always right either but from my own excperiences these are the things i have learned.

[Evan]

In the above photo nearly all the heat is carried away by the chips. The work doesn't become hot. The tool does and that is where carbide wins over HSS. I grind my own carbide tooling from sticks of solid carbide and I agree that you need diamond and/or CBN wheels to do a proper job. Carbide should be ground with diamond as it tends to glaze CBN wheels. There is no comparison between a diamond wheel and a silicon carbide wheel. I have all types and diamond cuts carbide like aluminum oxide cuts mild steel. Silicon carbide is ok for touching up a tool but for real stock removal when custom grinding carbide a 60 grit diamond wheel is invaluable.

One of the most useful characteristics of solid carbide tooling is that it can be stuck out much further than steel tools. Carbide is three times stiffer than steel so it doesn't flex as much when hanging way out there.

In the above photo I am cutting at about 250 SFM.

[small.planes]

Dave,
try JB cutting clicky, if you give them a ring they have a massive range of tips and tooling at quite reasonable prices.

Dave

[Davek0974]

Thanks all,

excellent website dave, i use carbide tips all the time on my smaller lathe using ccmt060204's and have boring, left and right and a tool that uses the odd two corners of the tips.

I will contact JB and see what they recommend in a larger size.

Dave

[SmoggyTurnip]

Originally Posted by Evan

I grind my own carbide tooling from sticks of solid carbide.

Where do you get sticks of solid carbide?

[Paul Alciatore]

I go along with all the arguements for using HSS as a first choice in the home shop. But I also have to agree that carbide has it's uses, in that same enviroment. I always grab HHS first unless there is a real reason for going to carbide; usually when machining a hard steel.

I have had bad luck with the brazed carbide tool bits. It seems like they always chip just when you really need them. I have had much better luck with an inexpensive set of indexable carbide tools. They are available from several suppliers. Each insert has three points so they are economical.

http://www.use-enco.com/CGI/INPDFF?P...MITEM=325-7224

All the usual disclaimers.