If the proper geometry is important then you may want to consider using full profile inserts: http://www.iscar.com/eCatalog/Family.aspx?fnum=126&mapp=TH&app=78&GFSTYP=M
> -----Original Message----- > From: Marcus Bowman [mailto:marcus.bow...@visible.eclipse.co.uk] > Sent: Friday, June 02, 2017 12:39 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Question on thread geometry > > If this is a 3/8 x 24 then I assume it is a UNF thread. > As I understand it, UNF (and UNC) threads are part of the UTC system, but the > specification for UNF and UNC threads is that UN threads typically have a flat > root, with the option of a rounded root. The rounded root simply gives more > clearance at the root, so is a benefit, but not a necessary feature. The root > could be truncated H/4 from the theoretical vee at the bottom, to give the flat > bottom, but the rounding extends beyond that, giving more clearance. > Male UTC threads have a truncated flat top at the peaks, with a width equal to > P/8 (or 1/8 of 1/24 of 1 inch, which is about 5 thou in imperial units. The > reduction in theoretical OD is twice H/8. H is 0.866025404 x P, so about 72 > thou. > Your insert will cut beyond the flat root, so is fine in a normal duty thread. The > pitch diameter measurement will guide you as to depth of cut. > > UTC threads are metric, but expressed in imperial units, so the A60 insert, > which I use myself, is a general purpose insert and may be a compromise > between both systems, as well as across the range of pitches the insert can cut > accurately. I have had no trouble with fit or finish using the A60 insert (or the > A55 insert either). > > Marcus > > On 2 Jun 2017, at 16:36, tom-...@bgp.nu wrote: > > > There is a custom adjusting screw that I buy commercially and when I get > them the threads have a text-book geometry to them. That is, they have a > small flat top on the major diameter and small flat bottom at the minor > diameter or root. They are made to class 2 or perhaps even class 3. I know that > these screws I am getting commercially are made using single point carbide > insert tooling on a cnc lathe. > > > > I want to make a few of these myself and am cutting them using G76 canned > cycle on my Emco lathe (I have encoder on spindle, etc) using an Iscar carbide > insert 16ER A60 (link below). These are 3/8-24 thread and that falls in the > range of the TPI supported by the insert. We have spent time making sure we > have the tool lengths, etc dialed in as precisely as possible and are trying to be > very careful with our major diameter and thread depth, etc. When measuring > the threads we are within specification in terms of pitch diameter and major > diameter, etc but the geometry of our thread is very pointy. That is the major > diameter peaks are pointy (almost to the point of being sharp) and the root > appears to be quite pointy as well, seems to be exactly like the pointy tip of the > insert. So, the threads work fine for the purpose but the geometry is bugging > me. By the way, this seems to happen for nearly every thread I have cut on the > machine, but I haven't cared as much in the past as the screws have been for > my own purposes, but this one will be used in a product sent to customers. > > > > I am wondering if I am doing something wrong with the insert I am using or > what. Any thoughts? > > > > Iscar insert: > > > http://www.iscar.com/eCatalog/item.aspx?cat=5901944&fnum=113&mapp=T > H&a > > pp=193&GFSTYP=M > > > > -Tom > > > > > > ---------------------------------------------------------------------- > > -------- Check out the vibrant tech community on one of the world's > > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > ---------------------------------------------------------------------------- -- > Check out the vibrant tech community on one of the world's most engaging > tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
