Tool Post Holder

This morning before having to go to town on errands I was able to get all of the holes marked. I used CAD aka cardboard aided design to make a template to mark the holes. This form of CAD has been around long before the advent of computers. Tomorrow I hope to start drilling holes.
 
I finally got the first holder done. I made a holder for my 5/8" and 1/2" boring bars. I made this one first because I needed a holder for these boring bars and it will get used to make the rest of the holders.

It's not pretty. In fact it's down right ugly. Twice when making light cuts on the mill, one a .005 & the other just a skim, the end mill somehow caught the edge of the holder and walked it partially out of the vice. I have no clue as to why this happened.

Super easy to set on center. It does take a good deal of torque to tighten the clamp nut. Learned a lot making this one. The others should be easier and quicker to make.

IMG_3622.JPG

IMG_3623.JPG
 
Started on the holder for the 3/8 and smaller boring bars today. Got the large center hole bored out. Took me 3 hours to bore a 1 1/4" hole. The first 3/4" goes fast because I am able to use my drills. Wish I had a 1" drill. After that it is .020 per pass to start with and then down to ,010 to .005 to .002 to .001 and finally .0005 passes as I sneak up on the final size. And with each decrease in cut I take a couple of spring cuts. And then there is the measuring. I need lots of practice measuring holes. I am getting better at it. I can now get consistent measurements within .001 to .0005. I take 3 measurements and do a mental average. Tomorrow I will measure bore and compare it to the size of the post. That was today's afternoon project. My morning was spent long boarding the body of my 66 MG Midget. Not a very fun project but it has to get done.
 
Hi Guys,

I can't find the original references to the "Norman Tool Holder" But the original didn't use a bolt to clamp the holder to the post. That drawing in the PDF is modified to use a clamp bolt.

The original design used a split pinch clamp that actually closed on the post directly. Yes it had a screw through it which pulled the two half's of the clamp together. This also allowed a further modification of a handle to clamp the holder without any tools.
 
Got another holder done. This one is for my small boring bars. This holder came out better than the first one. The first one is on the top and the second is on the bottom in the picture.

IMG_3624.JPG


Two down. Five to go. It takes me forever to make one. The next five will all be the same. Hopefully that will make it quicker to make them.

I used the first holder to make this one. Amazing difference in rigidity compared to using a lantern tool post to bore the 1 1/4" center hole.
 
Hi Mick,

Looking good. Curious as to why you used two screws for hight adjustment.
 
I was concerned that the holder may rock on the post and the first holder that I made does rock a little before it is tightened to the post. So I put in two screws. Maybe overkill. Once tightened it is rock solid with no movement whatsoever.
 
Hi Mick,

That is one of the reasons that the original design used a split pinch clamp. The pdf article modified the design, presumably to make it easier to make, or avoid copyright.

I used to have a scan of the original drawing on one of my HDD but I'm stumped to find it now.

I have a new drawing which I have done from memory and the pdf converted to metric dimensions.
Norman-001.jpeg
 
The slight rock when loose on my first holder is not because of the clamp method. It is from a slightly oversize hole in the holder. There is no rock in the second holder. The second holder is a very, very tight fit on the post. Might be too tight. I am not very good at measuring the diameter of a hole. I tend to measure the hole smaller than it actually is. Per my likely inaccurate measurement the second holder is .0005 to .001 smaller in diameter than the post. I can just barely get it on the post.

If I understand your drawing correctly the pinch bolt when pulled to one side clamps against the post preventing the holder from moving. I wonder if it would work where the hole in the holder is slightly oversize like in the first holder that I made. I might try making one of my holders like your drawing. I would bore hole for the pinch bolt first and with the bolt in it's hole then bore the large hole for the post. Interesting.
 
Sometimes pinch bolts are cut in two at the top of the arc. thread one end, clearance drill the other and float the assembly in the hole. to tighten, tighten the cap screw through the clearance hole. This will 'expand' the pinch bolt onto the post. Hope this makes sense.
 
You must log in or register to reply here.
Back
Top