b'Ream On count the flutes as it spun. doesnt matter if you use coolant or Reamers work best when onlyoilthe reamer just needs some-a small amount of material is re- thing to prevent the tool from rub-on a mill or drill press. When usedmoved, so having the right amountbing the inside of the hole. Softer on a turning machine, the prob- of stock after drilling is critical. Asmaterials are subject to galling lem is alignment. Tailstocks and tur- always, the manufacturer is goingwhen no fluid is in the hole. A good rets hardly ever are aligned closeto provide the best recommenda- flow of coolant is also nice for wash-enough to ream a good hole. Thistions, but you will succeed in mosting away chips, which can become is one of the few times when hold- cases if the finish allowance for thelodged in the flutes, causing bad ing the cutting tool in a rigid man- reamer is 0.002" (0.05 mm) to 0.005"finishes and broken reamers.ner can be detrimental to the oper- (0.13 mm) per side (radial depthLike most things at a machine ation. Successfully reaming a holeof cut). Leaving too much materialshop, if you ask 10 machinists how An old guy once told me that a reamer was runningtoo fast if I could not count the flutes as it spun.on a turning machine often requiresfor finishing results in bad finishes,to do something, you will get 10 dif-some type of toolholder that al- oversize holes and broken reamers. ferent answers, and each one will be lows movement or float. If you areReamers are for sizing drilledthe best solution. That said, these going to ream holes on a lathebyholes, and reamers make goodare the things that I think about which I mean a traditional two-axishole geometry even better. How- when preparing to ream holes. I amgo ahead and purchase a floatingever, they cannot correct a poorlysure that machinists and toolmak-ream holder before you start. Thedrilled hole. The drilled hole needsers would have varying opinions floating holder enables the reamerto be straight and round or elseabout my methods. However, the to overcome alignment issues andthe reamer is not going to cut cor- theories are sound and aligned to find the center of the hole. rectly. In this case, the result is usu- the best practices common among Cutting speed is critical to suc- ally an oversize hole. If the hole ismachinists and toolmakers. Select cessful reaming, and reamers likenot straight when drilled, it will nota good tool, minimize runout, run to cut slowly compared with otherbe straight after reaming. the reamer at the right speed, and tools like drills and endmills. Manu- Finally, lubricate the reamer. Itdont push too hard.CTEfacturer recommendations and Ma-chinerys Handbook are the bestabout the author references for cutting speed, but a general rule is to run the reamerChristopher Tate is manufacturing engineering manager at 50% to 80% slower than a drill. AnUnified Brands Inc. in Vicksburg, Mississippi. Contact him at old guy once told me that a [email protected] running too fast if I could not Scientific Cutting Tools Featured New ProductsDrill Mills NPS Thread MillsThe versatile, multi-operational drillNPS thread mills are designed with amill specialty tool is designed for milling, helical ute which reduces side-cuttingchamfering, and light spotting applications.pressure. Thread sizes range from 1/8-27to 2/12-8 and larger.Drill mills are available in 2 or 4 helical ute stylesOered with 90 degree or 120 degree included angles NPS thread mills are National Pipe StraightCutter diameter sizes range from 1/8 toNPSF thread mills are National Pipe Straight Drysealwww.sct-usa.com [email protected]|805.584.9495 800.383.2244|Technical Assistance is Available 38OCTOBER 2022 Reaming.indd 38 9/19/22 2:23 PM'