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Sorry BDB I just found out what tapered means in english ,I thought tapered was something related to tempering of the iron process.

The pins were just like these days pins threaded and with smaller conical tip and smaller wrench tip to use

Ado, here are some other options if you have the flexibility.

A pin that is too tight and jumpy can often be fixed by removing the wire, winding the pin out, give a light brushing with a wire gun brush to the hole, blow out with compressed air, and then hammering back in the original pin.

The surface of machined thread area on the pin actually has tiny serrations/tears on it if you were to look at it with a microscope. These act like fine sandpaper on the hole. This is one of the reasons the pins are typically not wound in, but rather, hammered into place. It minimizes the wear/sizing on the hole.

Gun bore brushes can be gotten according to caliber. I keep several different ones on hand but .270 brushes work well. Stainless steel ones are more rigid for larger sized pins, bronze brushes are more flexible for smaller holes. The brushes do not resize the hole. They will clean off glazing caused from high speed drilling and remove epoxy/glue residue from multi laminate pin blocks.

Reamers are handy for truing up the roundness and slightly taking the size larger. On the reamers which are adjustable, note that on most of them, the first 1/3 of the reamer is slightly under sized and serves mostly as a guide. Some people will get several of them, set them to work in a certain narrow size range and then hack saw off the excess adjustment thread out front. This lets you true up the blind hole parallel down much deeper.

In my experience, the "spoon" reamers offered by piano supply places are garbage. I had a few 5/16" front cutting reamers ground to custom size for me by a buddy who runs a tool grinding shop. I use these instead of the side cutting adjustable type. I just need to be more careful on the initial line up angle when entering the hole with these but I find they work supreme once you get the hang of it.

All good advice from Emmery about reamers.

Make sure when you are setting the reamer diameter that you set the cutting edge at the rear rather than the leading edge at the front.

Measure twice, cut once. This is always the rule in the metal shops. Yes the pin block is wood but when sizing tuning pin holes, this is a machinist application using machine shop tools and precision.

Regarding the part about blind holes, the reamer I have shown in the photo earlier would not work well in an upright for example, as the excess threaded stem of the reamer would not allow the reamer blades to get to the back of the hole walls.

A reamer with excess stem off the end is used for grand’s with the pin block drilled through the bottom.

Now if the threaded excess is cut away then the reamer will work in all holes, blind or drilled all the way through.

Another thing I have remembered about adjustable reamers if you go that route. When using an adjustable reamer turn ONE WAY ONLY, to the right.

Never turn back or reverse the direction of an adjustable hand reamer. If you do the nut that adjusts the blades diameter will undo and you will never get the reamer back out without destroying it and damaging the hole.

Thank you guys for very useful info.
So 0.2795...(7.10mm)pins and holes finally reamed out to 0.270 (6.85mm)
I will be doing some testing on some 5cm hardwood before touching the pinblock .

I might probably use one size reamer if I can find the correct size

Ado, testing a reamer first for its effects on sizing is common practice in metal machining also. You want to find a wood material as similar in hardness/density to the pin block as you can. Next, you want to predrill it to as near size as what the pin block holes are. Pay particular attention to how fast you are feeding it through and duplicate that same speed. Pay attention to the resistance you feel on the cutter, if it increases too much, then slow the amount you are feeding it per revolution.

There is a bit of a learning curve with the intial reaming experience. Once you get the hang of it, it is an incredibly accurate way to get consistant sizing and torque on the pins. To add to what Dan mentioned...a reamer (especially for metal) is never rotated in reverse while in contact with a part. Even when removeing from a hole, keep rotating in the cutting direction so you don't leave long vertical slice marks from the cutting edges.

Forgot , I will probably have to drill before with something like 6.5 or 6.7 drill.

If you haven't done a lot of drilling, use a fairly steady feed and enough speed on the bit to do the hole in about 5 or 6 seconds max. Some materials I do even faster. Too many people dwell and go to slow on the feed. The bit gets very hot from this and can expand by a few thousandths of an inch, not to mention, it allows more time for the alignment to wander. Having a steady stream of high pressure air on the bit and the hole can actually help in keeping the drilled size consistant.

That reminds me of my techschool workshop and as I remember was kind of tricky to get to ream after drilling if the object was moved and the result if not aimed correctly was ovalish holes and broken reamers,even though that was metal and big mashines I imagine wood and handreaming will be a chalenge .

Thank you Emmery
What about manual drilling with 6.7 or 6.8 drill and not using reamer ?