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Model Forum / General / Models / May 2008Slittling very small screws
In the process of making Watch screws (14BA and smaller) from carbon steel, I have been experimenting with slitting them. Normally I use a screw head file, but this can be somewhat time consuming so I tried a slitting saw in the lathe. I mount the screw in a tapped brass block clamped to the vertical slide and run in gently at centre height to the slitting saw. This sort of arrangement I find works well when making larger screws (4BA and larger), but with a 8 thou slitting saw and slow backgear performance was somewhat hit and miss; sometimes a beautiful slot was cut, other times the slot was very Vee shaped with ragged torn edges and in one case the slitting saw lost a tooth (but the screw was undamaged)! I have a feeling that this may be because I am using a cutter of too coarse a pitch (the finest saw I could find had a tooth spacing greater that the diameter of my screw head and normally I try to ensure that at least two teeth are in contact with the work. I should be interested to know if this is a plausible explanation? Alan > In the process of making Watch screws (14BA and smaller) from carbon > steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 16 lines] > > Alan sounds plausible to me, IIRC when selecting a hacksaw / pierceing saw blade the guidance on TPI is to select one which will keep 3 teeth in the cut. I guess slitting saw blades would be similar. Have you thought of using dremel / clone cutting disks? Im not sure how thick they are, but might be able to thin them a bit anyway. Dave > In the process of making Watch screws (14BA and smaller) from carbon > steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 14 lines] > that at least two teeth are in contact with the work. I should > be interested to know if this is a plausible explanation? Yes, very plausible. Three teeth is standard. http://cgi.ebay.co.uk/4-Diamond-QUALITY-Lapidary-Saw-Blade-1-2-Hole-20mm_W0QQite mZ300203774152QQihZ020QQcategoryZ4843QQcmdZViewItemQQ_trksidZp1742.m153.l1262 -- Peter Fairbrother > In the process of making Watch screws (14BA and smaller) from carbon > steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 5 lines] > This sort of arrangement I find works well when making larger screws > (4BA and larger), but with a 8 thou slitting saw and slow backgear Backgear? Why? What dia is the saw? The center height of the lathe? > performance was somewhat hit and miss; sometimes a beautiful slot was cut, > other times the slot was very Vee shaped with ragged torn edges and [quoted text clipped - 4 lines] > greater that the diameter of my screw head and normally I try to ensure > that at least two teeth are in contact with the work. something smaller than my last suggestion: http://www.jlindustrial.co.uk/CGI/INSRCH?ns=1&oldNtt=&oldNtk=&oldURLVar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scrNtt=0.008&x=25&y=15&Ntk=Keyword+Search&withinResults =true but the teeth are still 1.5 mm apart. -- Peter Fairbrother >> In the process of making Watch screws (14BA and smaller) from carbon >> steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 24 lines] > > -- Peter Fairbrother There are 1" diamond slitting discs on 2 mm arbors available. I don't have access to mine at the moment so I can't give a thickness, but it is far thinner than the Dremmel type of resin-bonded slitting disc. Cliff Coggin. >>> In the process of making Watch screws (14BA and smaller) from carbon >>> steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 30 lines] > > Cliff Coggin. Dremel cutoff discs come in (approx) 0.05" and 0.025" flavours. The small diamond disc I have is also approx 0.025" [cut] [cut] >> There are 1" diamond slitting discs on 2 mm arbors available. I don't have >> access to mine at the moment so I can't give a thickness, but it is far [quoted text clipped - 4 lines] >Dremel cutoff discs come in (approx) 0.05" and 0.025" flavours. The small >diamond disc I have is also approx 0.025" Thanks for this suggestion; I hadn't thought of grinding type tools and googling around finds http://www.eternaltoolshorology.com/diamond-discs.htm which offers a 7 thou diamond slitting disk; looks ideal, thanks for the idea! Alan >> In the process of making Watch screws (14BA and smaller) from carbon >> steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 7 lines] > >Backgear? Why? What dia is the saw? The center height of the lathe? The saw is 3" diameter. Lathe is 4" centre height with gap bed. Backgear was probably around 50rpm, so that makes a speed of 40 surface feet per minute and a quick look in tables suggests about 55sfpm for silver steel with an HSS cutter. Anyway that was my reasoning, it is was wrong then I would be interested to know! Many thanks for the suggestions and pointers, Alan > I have a feeling that this may be because I am using a cutter > of too coarse a pitch (the finest saw I could find had a tooth spacing [quoted text clipped - 3 lines] > > Alan Have a look at the Precitool range of carbide slitting saws.Not cheap for a home shop but very good and last a long time.We use them for slotting Stainless screws. Mark. > In the process of making Watch screws (14BA and smaller) from carbon > steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 16 lines] > > Alan > In the process of making Watch screws (14BA and smaller) from carbon > steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 16 lines] > > Alan Hi Alan I think that the others have covered te main things, namely that the teeth on the cutter ned to be finer, also the cutter could be smaller with support cheeks. J&L list an .008" wide x 3/4" dia with 1/4" hole with 40 teeth, I am using a .010" one to slit brass 3 times at 120 degrees running at 10,000 rpm dry, not silver steel I know but it shows they work! I would also avoid plundging the cutter into the end of the job and pass the screw head under the saw, ie put the cutter in the lathe chuck and hold the screw shank in a holder on the cross slide and then wind the slide in to cut, plenty of coolant and you will get a perfect result. You will also get a flat bottomed slot. Peter > In the process of making Watch screws (14BA and smaller) from carbon > steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 16 lines] > > Alan > In the process of making Watch screws (14BA and smaller) from carbon > steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 16 lines] > > Alan The speeling in the title reminded me of a related mistake. Quite sometime ago the department secretary typed up a "Business Case for a Slitting Saw". Unfortnately she typed an "h" instead of an "l". Took quite a while before she was allowed to forget it. >> In the process of making Watch screws (14BA and smaller) from carbon >> steel, I have been experimenting with slitting them. Normally I use a [quoted text clipped - 21 lines] >Slitting Saw". Unfortnately she typed an "h" instead of an "l". Took >quite a while before she was allowed to forget it. Speeling? :)  SignatureMike Whittome |
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