The Shop > Tools
Do you lap your female centres ?
PekkaNF:
Interesting....I never even knew this. Now I'm considering it.
Found this pretty informative "How to lap a Center on a lathe"
Now my questions: Where do you find small carbide "laps" in europe? Can carbide burr used instead? Those can be used only on soft material, but maybe there are harder:
https://www.shop-apt.co.uk/carbide-burrs-60-countersink-type-j.html
I envision carbide being very useful for small centres. 120 grit stone can't be dressed very small and survive.
My next related question would be about how to dress dead centres....but let's wait for it. I don't have this setup:
Pekka
Some silly videos too:
Turn the voice down...next one has exceptionally irritating muzak
Manxmodder:
A toolpost grinder does a very good job on centres. It also has many other uses and is relatively simple to build one from scratch if you don't fancy buying one.
Toolpost grinding a lathe centre:
OZ.
PekkaNF:
Thanks.
I wonder how Andrew et.al. finishes centres.
I'll try most simple stuff first and see where it takes.
I did a little reading on 1915 book "Modern toolmaking methods" and there was a little descriotion of conical lampping and lappin on centre holes.
Apparently some sort of nutating or orbital component is needed to prevent rings or distortion of the conical form.
I'm not planning of making any orbital mechanism like on jig grinders that has planetary (orbital?) and reciprocating motion (oscillating) movements. I tried to google those mechanisms for hours, but could not find any illustrations.
Pekka
awemawson:
Male centres I can do easily on my Jones & Shipman 1300 EUIR cylindrical grinder, but I've still not got any way of lapping female centre holes other than a suitably pointed wooden dowel and lapping paste.
PekkaNF:
How does it works out? I read somewhere that rings are nuicance and paste has tendency to accumulate at the wider part of the hole (and make taht part bigger). Some texts suggest using brass lap and to make it 0,5 - 1 degree more acute to comesate somewhat that tendency. Other book said that you should "peck" very briefly repeatedly and use slow rpm. Probably the same reason.
Pekka
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