DIY lap and tapered reamer

Sorry about the number of questions here

I want to have a go at making a barrel lap as per this discussion **LINK**

and associated links.

What I'd like more info on, please, is

a) the degree of taper on the lap spindle..it looks from the pics around 4-5 degs

b) if I have a go at making my own taper reamer for the lap expander then is this best made as a tapered hex, as a midline fluted round taper or fluted off centre from the round? I'm guessing for say a 15mm lap it's tapering reamer would have 1-1.5mm grooves? If they're cut off centre then endmill size is academic.

c)Is the lap itself best made with it's own internal taper or as a sleeve on a separate lap expander which then adds the question of depth of the slits. Since the lap carrier (or one piece lap) has varying depth to internal taper I'm guessing the slot and slits need to follow that?

Can one just slit an expander and then slot and slit a lap sleeve?

d) If lapping with diamond powder then the best carrier..oil or water?

As ever I appreciate your wisdom

pgk

That one I showed has about 1.5 deg on the topslide so 3deg included angle.

I bored the taper at the same setting as I turned the male taper, but for a small one then just a D bit type reamer will do eg cut away half the diameter

I think you could do it either way provided you have enough diameter to get a sleeve and lap.

Just slot along the length don't worry about the taper.

Never used the diamond due to the risk of embeding but use oil for the SiC powders

excellent, Jason, thanks

pgk

Hi Jason

In the engine build article when using the cylinder lap you say the lathe is running "slowly", can you please advise the spindle rpm ?

Emgee

The reading I did suggested speeds of 100-300rpm

Yes something in that sort of range say 200rpm for a 20mm cylinder bit slower on a 25mm.

PGK you may find this thread by Ramon interesting

Yes, an excellent series. I had found that a while back but remembering stuff isn't automatic any more...

I use wooden laps in the lathe, and use the bottom straight speed of 240 rpm, regardless of bore, usually 40 mm or less, but has been up to 2 1/4", the bigger one just got a bit warm, a bit quick, the one time to wear a glove as I hold the cylinder in my hand, and let it slowly rotate as I move it back and forth. News Paper on the lathe bed .

Ian S C