Lapping pivot hole in blade

Ron Bendele

Ron Bendele

Well-Known Member
In another thread Les Voorhies said:

"If you're worried about your pivot hole being square, make sure your drill press is square and do the pivot hole smaller than the finished pivot will be, then after HT clean up the flats and then ream the pivot hole to final size and use a barrel lap with 400g valve lapping compound until the pivot just slides in, I got this method from Todd Begg and it's working very well."

I didn't want to hijack that thread so I started this one. I have a couple of questions. These questions are not just directed to Les, but I would love to hear his answers :)

- Is the ream you use after HT carbide or something else? Where do you get it?
- When using the barrel lap, how do you do it ... by hand, by machine?
- Do you move the lap in & out of the hole or spin it (or the blade) keeping on one spot on the lap?
- Should the final ream be .001" or so undersized to account for the lapping?
- Does the 400g mean 400 grit? (Sorry for being dense.)

TIA,
 
- Is the ream you use after HT carbide or something else? Where do you get it?
Carbide

- When using the barrel lap, how do you do it ... by hand, by machine?
I use a hand drill and Todd said he did.
- Do you move the lap in & out of the hole or spin it (or the blade) keeping on one spot on the lap?
In and out, and be careful not to over adjust, it really works pretty fast.

- Should the final ream be .001" or so undersized to account for the lapping?
Your not really going to measure it, you'll clean out the hole and try ther piviot, turning as you push until it slides in.

- Does the 400g mean 400 grit? (Sorry for being dense.)
Yes.. not dense, I should have been more clear.

I think maybe I need to include more info. there is more to what Todd told me but I'm not a typist. I'm going out shortly so I'll edit and start to explain and then finish up tonight:

Todd also said to us a ball end mill to start things of, about 600 rpm (carbide) and just brake the edge then turn off the drill holding the handle down to keep it's place in the hole and clamp the blade to the table in that exact spot.
Once the blade is secured lift the spindle and put in your carbide ream, at 60 rpm with good lubricant start "dabbing" at the hole with even strokes until your through, then got to the barrel lap.

GTG, I'll tell you how I adapted this later.
 
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I think I managed to squeeze most everything in that last post except that it's probably not absolutely necessary to clamp the blade down for the reaming. The idea is to knock off the edge of the hole 1st with the ball mill then your reamer will center in that hole, the ream will want to stick in the hole when you pull it back out and that can screw with the square of the hole, so what I've been doing is just starting the reaming operation, stop the spindle then lift the blade up a little with the spindle and put a couple drops of super glue under the blade and bring the spindle and blade back down to the table so the blade sticks just in the right spot. It works at least as good as a clamp but you need to think ahead of time how you are going to unglue the blade. I do this on a mini mill so I have a slotted milling table and it's east to pop the blade loose afterward.
 
can some one show me or post some links to barrel laps?

I'm guessing there are several kinds being used.
 
Thanks for the help everyone. One more question:

For the carbide reamers, are you using carbide tipped or solid carbide?
 
Ron Bendele said:
Thanks for the help everyone. One more question:

For the carbide reamers, are you using carbide tipped or solid carbide?
Click to expand...

Solid carbide, I know they are expensive but I don't know if the carbide tipped ones will work (I'm not even sure I've seen a carbide tipped ream) Make sure you use a good lubricant, Todd mentioned Emuge but I'm using some stuff that Jake bought from Tracy and it seems to work well.
 
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