View Full Version : d bits / 1/2 reamers
11-05-2001, 12:49 AM
several designs ...perhaps easiest is start w/ 01 oil hardening drill rod , w1 (h20 hardening ok but will warp more in heat trt.),silver steel in u.k......turn slight radius on end of appropriate size( no more than .015 cut left for any machine reamer, .005 for hand reamer) so reamer will enter hole...mill /file grind /gnaw/ for a length of 1 1/2 to 2 diameters ,1/2 the diameter,less abt .010 on a 1/2 inch reamer...this gives a flat w/ one cutting edge w/ slight negative rake.....hogs in less & scrape cuts smoother.....,,heat up to 1450+/-..cherry red in subdued light ...i think closer to color of cooked carrots,at which time it is no longer magnetic....but i wait for shadow lines to disappear& lighten up to one shade, at which time,dunk it vertically in #10 wt. oil /a/t/fluid,....it will become "file hard", wont bite....draw temper in oven @ 400 deg. /i hour ...shut off & let oven cool...if wife wont let u in kitchen , heat away from edge a couple inches, SLOWLY, when cutting edge gets to straw color ,circa 410deg. dunk it again.....if u mess up anywhere reharden again.. i get less warpage hardening in drill press @ 200 rpm & bringing oil up to cutter ...be ready to blow out flame.... now stone the flat to sharpen will cut accurate size hole .........u can also make by filing a 30 deg. slant on end & heat trt. good for small holes /brass will cut .0005 to .001 large......u can make own counterbores , c/sinks ,end mills ,flat driils like spade bits ,only 120 deg.angle on end& back off cutting edge & sides w/ file (magic mark to see where u are filing).file flutes ..dont have to be indexed dead on , in fact chatter less if not..old time machinists made owntools ,,hacksaws ,pliers , wrenches,files ,rasps (cold chisel the teeth at angle & harden)anneal old car flat springs & go to work.... . MUST use at 1/2 cutting speed of high speed steel.. turn of century methoods ideal for HSM's...free urself from the tool supplier!!!!t u can make a special size in 1/2 hr& not have to wait 2-3 days .... this stuff no longer taught because industry demands high productivity to be competetive ..w/ high speeds /multiple cutting surfaces,,,but i guarantee if u ever use a single edge c/sink, u will never go back to a fast ,chattering 6 edged one....shop wisdom of frank mclean ( on this site)has lots of good stuff along this line ....even if u purchase commercial ,u still feel better knowing u did not HAVE to....
11-07-2001, 08:21 PM
ok i think i have got it. I have read/ re-read your post several times. Now i am getting the hang of it. One question though. You are talking about oil hardened drill rod. Can i use any metal and then temper it? Actually i have 2 questions. How about using a BBQ for the heating treating of the edge (400). We use BBQ's at work to warm up bearings to slip them onto shafts.
11-07-2001, 11:46 PM
pictures would help a lot , but i am too ignorant to post some ......u really do need a 1920 mach tool text.......NO.....steel must have sufficint carbon contsnt to harden ...abt 90 points to 125 ( .9 % to 1.25% ) for lathe cutting tools .....drill rod available any industrial supply housein oil hardening & h2o hardening ,$4 to $6 .50 for 1/2in. by 3 feet...1/4 ,maybe $2...these are off the top of my head ,but close ......any steel will harden if it has 35or more pts carbon , but wont get hard enuf ..u can anneal old car springs ,flat /coil( heat to cherry red & jam in bucket of lime or sand till cool )then shape & harden/draw...ordinary machine/angle iron etc. has insufficient carbon .....u can harden / temper w/ anything u can handle ....if u let it get over 410-425 (straw color) , it will dull more quickly ....goes to dark straw,brown, purple ( screw driver temper),.... blue ( spring temper abt570),....keep in touch
11-07-2001, 11:57 PM
forgot to mention ...old files great for flat drills ,reamers (turn a chamfer on edge ,back off chamfer edge, back off sides ,leave end flat & u have large flat reamer(anneal it first ,then harden) actually ,if ur really good , just grind teeth off & grind chamfer& clearances using lots of h2o.( for rough work)..if gets too hot ,brown/purple , u will have to reharden....files have abt 1.25 % carbon
Regarding the use of "any metal" ...no. To harden, steel has to have at least a certain minimum percentage of carbon in it, about 0.40%, I think for good results. If it's much less than that, you can heat treat the steel all you want and it will stay soft. Drill rod is readily avilable, pretty cheap, and designed to be fairly tolerant of heat treatment so you don't need to get it "perfect" to get an acceptable tool out of it.
There are 3 key steps to hardening steel:
1. Heat it above its critical temperature. You can tell when it reaches that point when it will no longer attract a magnet. This is about 1550-1650 degrees, though it varies depending on the kind of steel.
2. Quench it quickly in oil or water, as appropriate. At this point the steel ought to be glass-hard and about as brittle.
3. Temper by heating to 350-400 degrees or so and holding it there for a while. This is all the business with colors -- heating to "light straw" or whatever. I do it in the kitchen oven, a lot more predictable. Tempering softens the steel slightly so it won't shatter when you use it.
Travers Tool (and probably others) sells pre-made D-bits, so you could buy one and see what shape it is.
11-08-2001, 02:11 PM
So when ever i grand and file new tools out of HSS should i draw temper it like you are suggesting? I haven't so far and my bits seem to be cutting fine. Maybe the metal i am cutting isn't very hard. And now i have to find some where that sells drill rod steel. Correct in order to make the reamers
HSS is a totally different breed of cat altogether. It has its own set of procedures, which are pretty much beyond the range of home hardening/tempering abilities. I'm talking about plain carbon steel.
11-08-2001, 11:41 PM
Lapdiary people have had the answers ye seek for years. Thats right, Computer controlled, fully programmable ovens to 2ooo*C. You could if you so wish hook a hose up to it and flood the chamber with Argon (inert), or Nitrogen (Nitrate the surface a tad). Air hardening steels suddenly become a "good" thing. The Computer control can taper off the temp as required and go through many different stages of tempering, normalizing, or what ever you desire. $1000 (US)