View Full Version : Tap Grinding Attachments
This one is probably for Ken:
I need to regrind a bunch of hand taps.
I have a Tool and Cutter Grinder but no
tap sharpening attachment. I do have a
KO Lee work head that will index and a motorized work head. I don't understand the
principle of a tap sharpening fixture and the
importance of the cams that are needed.
Could I use my workhead and make a cam or
use a whirly-gig and modify as needed. I
have probably 100 to 200 different size
taps to resharpen. Most are just dull throw
aways from work.
02-16-2003, 09:07 PM
The cams for the tap grinding fixture create drop or relief. Relief is need to create a cutting edge. The cams you will need are reflective of the flutes the tap has 2, 3, 4 flutes. The KO Lee fixture is rather expensive new. You may check out ebay for the Weldon tap grinding fixture. I would recomend using the tool grinder rather than a surface grinder. You will need to dress wheel angle for the style of tap you want. bottom, plug, starter.
02-16-2003, 10:01 PM
But why would anyone want to actually try to do this? If you want to use the taps, sharpen them with an air grinder with an appropriate size wheel. Yep, grind out the flutes. They may be slightly out of spec, but the screws won't care.
You could probably do this with your tool grinder and do a better job of it.
02-16-2003, 10:13 PM
Correct me if I am wrong but if you use the relief grinding cams won't that close up the h-limits?
02-16-2003, 10:52 PM
I have the KO Lee tap grinding head, works quite well for two and four flute types, ghave hack with three fluters - does anyone have a hint?
I like it, but it is all in the wheel setting that makes it work best. I use cup wheels for tool grinding over round face wheels (surface ginder type), so I have better luck. The camming puts the tp forward and "up" into the wheel, just about like sharpening a drill bit action.
A spin jig will work in certin conditions but you would have to use a "hollow type" of wheel, and cut at the proper angle to the inside on the periphery on the inside of the wheel, and the wheel would have to be the right size. There is a company "TDS (I can get the actual company name)" that uses this method for drills and taps, and I also have this unit. Works well for drills, but very suspect for taps.
The "H" limits are not in the relief, but in the finish size of the tap itself at the start of the flute point for the first full thread (diameter at that point). Much like a drill bit that is sharpened perfect, the size is the size of the actual drill, but taps don't "wobble" of chisel point. Maybe a reamer is the better example, a properly sharpened reamer on the cutting end. The only way to change the "H" limit other than a bad sharpening which will increase the H size is to grind the flute at the sharp end of the thread - along the tap, not on the taper end. Most tap sharpeners work on the general idea of providing relief at the "taper" end of the cutting.
I am still on the "novice" side of using my KO Lee sharpener. Would like info on those pesky three fluters as a shop just donated about 100 of them dull (they knew I had a tap sharpener, thus the dull donation).