Tool Post Holder

a 5/16 bolt is 1.5 times stronger than a 1/4 bolt. if you went to a grd 8 bolt, and went 5/16 it would help. 3/8 would be more than twice as strong, if there's room. If they are made with 1/2" steel, you can safely go to 3/8 which will be a lot better.
 
The the large boring bar holder is the only holder with a 1/4 bolt. It looks like I have room for a 5/16 bolt if I can offset the hole. I don't think that a 3/8 bolt will fit. I will measure it again. All of the other holders have a 3/8 bolt. If I can't successfully offset the hole then I will make another holder for the large boring bar.
 
Hi Mick,

Just a thought, I've been back and looked at your pictures, if you put a saw cut in the holder one on each side of the post hole, say 50% of the material thickness, it just might allow the holder to flex more and give a slightly greater grip area.
 
I thought about making the saw cut wider when I made the holders. I also thought about milling more of the material away so that the sides would be thinner and have more flex. I saw one picture where one side followed the curve of the center hole and looked to be 1/8" to 3/16" wide. Without a rotary table I didn't know how I could do that other than rough cut most of it away with whatever and then use a grinder to smooth it out.
 
Something I did on mine was offset the slitting operation so one side has more material than the other.
 
I thought about offsetting the slot. I just went with what everybody else was doing with the slot centered. I am going to make a holder where the holder follows the curve of the post.
 

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I enlarged the existing hole and threaded it for a 5/16 x 18 bolt. Picked up a grade 8 5/16 bolt which tightens the holder to the post. No more slippage. Looks like I got the problem solved.
 
When I made the base of the tool post I left it flat with nothing fitting into the T slot. I have had issues with the base and post twisting under heavy cutting loads. I don't like how tight I have to tighten the base and post to keep it from twisting. I don't have any stock on hand thick enough that I can use to make a new base. My thought is to weld a piece of steel to the base and machine it to fit the T slot. Is this an acceptable solution?
 
Hi Mick,

Based on your picture in post 24, I thought that you had made it so that it fitted into the "T" slot. A temporary fix might be to put a piece of paper under the plate and tighten down on that. The post on mine is 38 mm in diameter and locks solid.

With regard to indexing, I've never used it or needed to. If I want to square the holder or the tool bit, I just use the chuck face.
 
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