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Thread: Taper pin installation
05-17-2007, 07:12 AM #1
I am making a new knob for my lathe and wondering how to get the taper pin back in. The recommended procedure requires drilling a taper hole with a taper drill bit through the collar of the knob ,followed with a reamer. I already have a taper reamer, is it possible to drill with regular straight drill bits and ream the taper to correct size ? If not, anyone knows a source for cheap taper drill bits ? (This is a one time project) . Mc Master listed one for 70 bucks Thanks
05-17-2007, 07:27 AM #2
Is the use of a taper pin critical? If not then maybe a spring pin will suffice?
05-17-2007, 07:37 AM #3
I have used a hand taper reamer with success in mild steel, aluminium and brass. IIRC I drilled the minor diameter of the taper pin measured half an inch from the small end to ensure penetration. I then gently reamed with cutting paste (trefolex) occasionally testing the pin for fit and pentration.
If you have to fit the knob to the shaft already having a tapered hole this may be the best method. A tapered drill might overcut and you'll end up with some backlash when you fit the pin. If the shaft is 'reamable' I'd do both together to get both parts to match.
05-17-2007, 08:54 AM #4
I don't really think the recommended procedure calls for a taper drill, just drill to the small diameter with a straight drill and use the taper reamer.
05-17-2007, 09:10 AM #5
Straight drill bits work fine for this purpose. I have always used them. I bought a set of tapered drill bits for cheap somewhere long ago, but have never used them.
It is very difficult to match a new part to an old so that a taper pin will fit correctly. First determine if the hole in the old part is perfectly centered. If yes, then you can locate the hole in the new part on center. If not, it may be best to drill both parts with a new hole at 90 degrees to the old hole. In either case, you have to ream both parts together. Pins are longer than needed, so you cut off both ends and finish after fitting the pin in the reamed hole.
05-17-2007, 09:21 AM #6
Back in the day, at National Cash Register, Dayton, they drilled the holes to the small end of the pin, reamed the hole and inserted the pin in the hole (holes) and while they were still warm, set the pin (pins) with a punch and a small hammer. If the hole is still warm, don't blast the pin too hard or you will never get it kout.
05-17-2007, 11:22 AM #7
Bit to small diameter and ream. Over #6 taper pin, I'll counter bore a reasonable depth with an appropriate larger drill, the diameter and depth of counterbore determined by micing the pin.
05-17-2007, 05:07 PM #8
I hate taper pin fittings. On my lathe one of the knobs is only a good fit because its "nailed" on with a taper pin. When I came to re-fit the pin the knob rattled around all over the place to the extent that I broke my taper reamer. On any of these jobs that I will do in the future, I'll find a good tap to cut a thread in the bottom 1/3 of the shafts tapered hole. Cross drill the knob with the tapping drill, but only just dimpling the other side of the shafts hole. Tap the thread in the knob, put it on the shaft then using a plug tap run it right through the shaft. Remove the tap and put in a pointed grub screw. Takes about 5 minutes longer then the taper pin, but it comes out 10 minutes faster.
05-18-2007, 01:27 AM #9
What size do you need? I have a few. They are pretty light, cheap to mail, you pay both ways, if I have it, I will lend you one.
Remember, these are hand reamers, don't stick it in an air drill and crush the trigger, unless it is a large low speed drill. You'll just burn off the cutting edge. Ruin 'em!
05-18-2007, 08:49 AM #10
I have a taper reamer that I will try this weekend. Looks like everyone had good results with using a straight drill bit. I really appreciate all of your input. Cheers