Thinning W/ pressure

[Tower]

1st of all I would like to say up front that this is how I do it. I would like to see how others thin their points. I will show 3 pics . Side A, B, & side profile. The first pics are of a preform I made yesterday. Its a piece of raw Georgetown, a Texas rock. This is how I want my preforms to look after final percussion. That's not to say I might not take another during the pressure thinning process. If the need arises. I stop percussion at this point because its fairly thin & flat w/ a little convexity. Also I think that the quality of the stone is good enough to be thinned w/ pressure. The next stage in my process is to build platforms out of the deltas & ridges left over from percussion. When I attack the platforms I pay close attention to the surface of the stone. I try & take the high spots out 1st. If there are any hinges left from percussion this is when I try & remove them.when I am finished with this stage there should be no high spots left. Low spots are another story. Its OK at this stage , because they can be addressed in the next stage. I am looking for a blank that has a uniform surface.

[Tower]

Pics to the above post

[iowabow]

Wow you realy got that thin before the pressure flaking began!

[gstoneberg]

It's how flat it is that I find amazing.  My preforms always have somewhat of a dome/ridge down the center.  No wonder I can't get the point thin, I'm starting to make the point with too thick a preform.

Thanks for doing these guys.

George

[Gus]

Yes Sir,

Excellent threads!!

Thank You Very Much!

-gus

[Tower]

Next, I lightly shape the blank. I use the alternate bevel method for this stage. I have found numerous points this method was used on. I only use the alt. Bevel because if I bevel both edges to the same side it can make it hard to keep the tip of the point straight.It tends to have a slightly bent look. The reason I lightly shape the point instead of shaping the point all the way is that this allows for another thinning pass. Meaning that every time a thinning pass is made a little width is lost. This helps me keep a buffer zone for an unwanted flake malfunction. PLENTY of room to fix it. I approach this thinning pass much the same as before.  I hit the high spots , grind & try to take consecutive flakes down the length of the blank. I go tip to base because its easier for me to keep the flakes running across the blade.  After this pass alternate bevel it. Again this time do it opposite from the last .  Make a thinning pass again.  After this pass most if not all of the percussion scars should be erased from the blank. Next alt bevel the blank & take it to the desired shape. Leave a little extra width & keep the tip a little wide. Remember the width will fall into place with the next set of passes.  I didn't touch the base. Because I will reshape it & send some thinning flakes later.

[Tower]

This it the w/ the above post

[bowtarist]

Wow that's cool!  I'll have to read and reread this one.  Thanks for the post Tower.   

[iowabow]

The percussion pre-pressure is real good and thin.  I also do a lot of percussion thinning before the pressure flaking but did not show that on the other thread. I use an copper end cap with a little lead poured in to give it some weight. What are you using for the percussion work? You seem to thin the preform much better?

[Tower]

I try to thin the preform as much as possible W/ percussion. I don't like leaving a median ridge in my preforms. If one starts to appear I eliminate it before it has a chance to grow larger. Like everyone else the size of my tools depend on the size of stone I'm working. This was a spall w/ a percussion bulb. The entire percussion thinning was done with a 3/4 copper cap w/ lead in it. When I'm to the point that my percussion flakes need to remove a little more to flatten the blade, but its pretty thin I change the way I use the bopper. Instead of holding the wooden handle I hold it at the cap. Kinda like someone would hold a small hammer stone. Using my thumb, pointer finger,&middle finger. The end of the wooden handle rests in the palm of my hand . Its held in place w/ the ring finger & pinkie.holding it this way gives me great control over the preform. I have to alter my swing , instead of having an arch to my swing I take a sharp, swift. 75 deg angle swing but do it delicately.  At this point your hand holding the preform is as important as the other. Aside from stabilizing the point, my middle & ring finger are used to stop flakes at a determined spot. They can be used to make flakes dive under hinges. Sometimes I use them to push against the flake & this can help to blend two opposing flakes together. Just like pressure thinning. Take the high spots first & work down until its flat. Its kinda hard to explain but I hope it helps. Oh by the way if its not thinning the way I want during percussion I put a little heat to it. No point in working a blade that's not cooperating with me. Tomorrow I will try to finish the point & notch it. 

[bowtarist]

Wow that's cool!  I'll have to read and reread this one.  Thanks for the post Tower.   

dido...

[mullet]

 Good thread Tower, I thought it would be good at the top so we can find it easy.

[gstoneberg]

I don't like having a median ridge on the preform either, but I'll be darned if I can stop doing it.  Sometimes I have a central hump, even worse than a ridge.  I wonder if my tools are not the right weight after reading your post.  My 3/4" copper bopper has more than an inch, maybe 2 of lead in it so it is real heavy.  Does great spalling out flint chunks.  Too heavy for percussion.  Then, my 1/2" sized bopper is probably a little light.  Perhaps I'll go make some more.

Thanks for these kinds of posts.  Very helpful for us newbies.

George

[Tower]

The next thing I do is look at the point & the terminations of the flake scars. If I have small hinges because one edge is slightly higher than the other I will flake the higher edge 1st. I'm trying to meld the flakes together. I take my small pressure flaker w/ a sharp tip & delicately start at the tip . I send my flakes inward into the blade, not across . Flaking across might cause an overshot I don't want. Flaking inward at a 45 deg angle will allow me to thin a little more & it help stop the tip from snapping. BUT not everytime! I pressure down the edge using the ridge from the last flake. For the next. Before I take this next flake I use the tip of the flaker to dress up & slightly grind the thin 1/2 a delta I will use as a platform for the next flake. I pay close attention to the surface of the point when doing this.  Sometimes a flake may need to be taken at a different angle.  After flaking down the 1st beveled edge I flip the point & do the same to the other side.  The edge after that pass will look ugly with lots of small deltas. I lightly grind the edge lightly! Then I flake the deltas. I'm not trying to thin them I'm just trying to clean the edge & shape it again. I do this to both edges. Now I have a continuous platform down the length of the point. Its below centerline but it can be a little strong .  This is where. Angling the flakes help. An angle flake will remove some of the strenght from the next flakes platform. Again I start at the tip because its the weakest part of the point. Its easier to flake the platform & start a sequence of flakes. I still use a 45 deg angle into the point. I do this to both edges.  Now the edge will have many tiny deltas & if everything went good I will be at centerline. If for some reason it isn't its OK if its not too bad.  Hopefully the last thing I do is lightly brush the edge with a fine abrading stone. This rids the edge of weak stone & builds a weak almost non existing platform. Now I start at the back of the point & micro flake up & down to sharpen the edge. I use a fine copper nail for this. Now the edge should sharp, clean & straight.  Next will be the base. 

[Jimbob]

Very helpful, thank you.