View Full Version : finish bore by lapping - ""Floating" End Mill Sharpener"

02-15-2011, 04:50 PM
the article by Philip Duclos, ""Floating" End Mill Sharpener"

A member, Gary Hart, who I haven't seen on the board lately, says this, "Difference between spindle and bore diameters is .002" but the not so easy part is no more taper then 2 tenths in spindle and bore. Had much frustration turning the spindle and bore without taper."
"Suggest starting with a ground and polished shaft to start with and finish bore by lapping."

What is, or how do, you 'finish a bore' by lapping?

any pictures?



02-15-2011, 06:45 PM
A long tedious process. Better to just hone it. But will need excess to good Sunnun hone.

02-15-2011, 08:28 PM
I've had good luck with purchased barrel laps and also with shop made laps. I like lapping as a method to get a hole (or cylinder) to be the same diameter over its length. The process isn't super fast which in my hands is a good thing because it gives some time to get a feel for the material vs the abrasive and how fast material is being removed. However, it isn't a terribly slow process for modest size holes - I got a 1/2" hole on size in about 20 minutes using a barrel lap. You can feel where the tight spots are and spend more time on them to quickly even out the diameter. Boring to within a couple thou is key, if you leave a lot more it takes a long while to lap it off and if you go under that then some machining marks may be left.

Rollie Gaucher mostly makes his own laps and there is a recorded talk he gave on lapping on the NEMES site: http://neme-s.org/2008_February_Meeting/nemes_monthly_meeting.htm

For steel I make laps from aluminum or brass, either embeds the abrasive well. Cast iron can be used for laps but I haven't tried it. Clover valve lapping compound works well as an abrasive.

Make a practice piece to experiment on, it doesn't take long to get a feel but you don't want to gum up something with a lot of machine time already in it.


A couple of shop-made OD laps, one in the holder. Wear is accommodated by a setscrew to reduce diameter.

http://img507.imageshack.us/img507/9823/shopmadelaps.th.jpg (http://img507.imageshack.us/i/shopmadelaps.jpg/)

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