Help!! (reposted)
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Re: Help!! (reposted)
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Posted by: randykimball ® 12/07/2005, 17:12:01 Author Profile Mail author Edit

OK, being an on hand at this, and having run aircraft machine parts shops for the majority of my past, I'll chime in. Sorry for the delay. Modern carbides come in several grades and usually are purchased in very precise shapes. These fit onto tool holders that are "qualified" to precise shapes. With these quilified shapes and sizes, and with the various grades and coatings, there are enormous advantages in the following ways. 1. You can set up a machine on a repeat job with the same tools off a set up sheet and expect to get the same results using modern qualified tool posts and turrets. 2. You can program or plan a job in advance by selecting tools and "inserts" (the carbide part) from a known library. This allows a job to be "planned" somewhere else or far in advance ... or better yet, as part of the bidding process. Planning is the key to profit and quality control in a well organized shop. 3. Carbide inserts are much more productive. (note that there are many other new substrates and coatings out there besides carbide). Why, I'm glad you ask. Carbides allow you to cut at surface speeds (the velosity the material passes by the cutting edge) in which high speed steels never dreamed of reaching. Carbides can cut with surface speeds above 700 feet per minute. Tool steels are only going to be able to handle surface speeds of less than 200 feet per minute in ideal conditions. The reason is mostly two fold, carbide can handle enormous heat and carbide is much harder that any tool steel. When you get a tool steel hot you remove the hardness. 4. Carbides with proper substrate and coating selection can be used to cut abrasive steels and allows. 5. Carbides can be used to even cut hardened tool steels. 6. Carbides will cut synthetic materials such as high carbon phenolics and fiber glass at a reasonable and profitable rate. 7. Used within the proper cut load, surface speed curve, and substrate/coating selection carbide will cut many times the cubic inches of metal removal per dollar/per edge, in both price per tool edge and labor. 8. Yes, I know you can get fairly good chip control with a well ground high speed tool steel cutter. Being able to run at much higher surface speeds modern carbide inserts have an array of built in chip breaker designs that allow a skilled operator to get excellent chip control in the vast majority of cutting configurations. ... perfect # 6's and 9's. There is nothing that will convice an old tool steel grinder about the advantage of carbide than to see a lathe with a carbide tool remove several pounds of steel in about two minutes into a pile of chips that can be skooped up like gravel while the tool steel has only taken a couple of passes on a competing lathe. Years ago there was a dept of cut advantage to tool steels. This has vanashed. I've seen carbide inserts burried 3/4" deep into a lathe cut, turning a 12" diameter at 400 RPM and feeding at .018" per revolution. ... that's productive !! Making a profit in a machine shop is still all about removing metal as efficiently as possible. In conclusion, there is one disadvantage I know of: This disadvantage is that you can not use a carbide cutter in an older or vintage machine which does not have the ability to run the cutter or chuck at speeds that are in the carbide cutting surface speed curve. Why? ... because if you cut too slow with a carbide you will break it. However there are still applications in which it is more productive to use a high speed tool steel insert. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Wed, Dec 07, 2005, 17:35:24

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Re: Help!! (reposted)
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Posted by: tspco ® 12/07/2005, 07:25:05 Author Profile Mail author Edit

Well simply put, and assuming you are talking lathe work, bear in mind I have been out of he loop for a few years, the big advantage to using carbide is you don't have to hand grind your bits there is a carbide insert and holder for just about any application, granted carbide is brittle and I remember mt machine shop instructor making quite a fuss when he broke an insert, my personal experience with carbide inserts is they do make a cleaner cut than cobalt, just don't try to cut too deep at a time , but things may have chnged is the fast several years. In short if you don't like grinding tool bits, and want a cleaner cut but don't mind spending a little more time on a project use the carbide inserts and holders. Did this help? If not do a google on carbide cutting tools, you will mind many suppliers that offer info.

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