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Tool Post Holder

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kd4gij

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I hope everybody considering a four way will check out the inexpensive wedge type QCTP and holders available from many sources, say for example,, CDCO tools. The capability and ease of use, coupled with the low cost of more holders and styles (boring, knurling, etc.) are hard to beat.

Why do you discourage using a 4 way.
 

jdedmon91

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Why do you discourage using a 4 way.
I don’t know what OP thoughts was. Mine is the simplicity of getting the tools set and kept set. I have so many tools that are set on center and it is too handy


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mickri

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I wondered that too. I like my 4 way even if it is really a 2 or 3 way when you get right down to it. I was actually researching how to make a 4 way to fit the atlas/craftsman tool holders that came with my lathe when I ran across the plans to make a norman style qctp. The tool post holder I am making didn't seem any harder to make than a 4 way. So here I am. Of course this is just a hobby for me and it doesn't really matter how long it takes me to do something. Would be a different story if I was trying to make a living.
 

kd4gij

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I have an aloris QCTP on one lathe and a 4 way on the other. In production the 4 way is faster and more ridged. Either one is a great choice.
 

Winegrower

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Yes I could imagine for some repetitive operation the 4 way could be pretty efficient. But for me, I don’t find that situation very often, and the “normal” QCTP holders are inexpensive and set for the specific tool, just pop it in. I must have 15 of them loaded with different tools. And a few empties for what new need arises.
 

T Bredehoft

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the inexpensive wedge type QCTP ... capability and ease of use, coupled with the low cost of more holders
I concur with Winegrower, above. However, funds for the Aloris type tool holder and tools have eluded me. I was trained with a Lantern Post, back, before the dark ages, then as progress overtook my employer, the entire tool room built for themselves an indexiable four square tool holder. We each had one, and spacers to make them fit the lathes in the toolroom. When retirement allowed me my own machines, I build the four square I remembered from my apprenticeship.
 

TakeDeadAim

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Found a you tube video where a guy made one of these for his mini lathe.


And I found a you tube video that showed how the indexing on a 4 way tool post holder worked. So I have figured out how to make one of these tool post holders indexable. I have some of the steel that I need and will order the rest.
Was it just me or was watching the video of that guy making the toolpost scary? Wanted to look away and not see the thing fly out of his wooden and home cast aluminum lathe.
 

jdedmon91

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I concur with Winegrower, above. However, funds for the Aloris type tool holder and tools have eluded me. I was trained with a Lantern Post, back, before the dark ages, then as progress overtook my employer, the entire tool room built for themselves an indexiable four square tool holder. We each had one, and spacers to make them fit the lathes in the toolroom. When retirement allowed me my own machines, I build the four square I remembered from my apprenticeship.
That sounds like a concept. In my younger days that is what was on the lathes. The only 4 way was on Turret lathes.


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mickri

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I have finished cutting the tool holders out of a 1.25x2.25x18 hunk of 1018 and have finished off the rough ends left from the the saw cuts on my mill/drill. I cut these with my sawsall. Not pretty but it got the job done. Took awhile. I ended up with seven 1.25H x 2.25W x 2.50L pieces.

Of these 7 pieces my plan is to make four to hold my atlas/craftsman tool holders which are 3/8x3/4 or 3/8x13/16. I will make these 3/8x13/16. These holders could also hold 1/4 to 3/8 HSS tooling. I am thinking of making one holder to hold 1/2 HSS. Or make this holder to hold a drilling attachment like I recently saw on another thread. The final two pieces I plan to make to hold boring bars. My largest boring bar is 5/8 diameter and will make one holder to hold this boring bar. I would also use this holder with my 1/2 boring bar. The final holder I would make to hold 3/8 and smaller boring bars. I have a bunch of these.

All of these holder will have the same hole layout except for the holder for the 5/8 boring bar. My question is how thick should the wall be between the end of the holder and the boring bar and between the boring bar and the center post? I can make these walls up to 1/8 thick.
 

mickri

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Here is a top view sketch of the holder for the 5/8 boring bar holder with 1/8" walls as in my previous post.

tool post holder layout boring bar.jpg
 

mickri

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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.
 

mickri

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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
 

mickri

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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.
 

BaronJ

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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.
 

mickri

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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.
 

BaronJ

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Hi Mick,

Looking good. Curious as to why you used two screws for hight adjustment.
 

mickri

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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.
 

BaronJ

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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
 

mickri

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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.
 

T Bredehoft

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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.
 

mickri

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My intuition is that by splitting the holder like I have and as I have seen on all the plans that I have looked at online provides a larger clamping area around the entire post when you tighten the clamping bolt. That's just a guess on my part.
 

BaronJ

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Hi Guys,

The pinch clamp is, after drilling tapping size, cut in half so that there is a gap between the two half's.
But before that the clamp is trapped in its hole, and the hole for the post bored, so that the clamp gets the radius machined into it.
If its done properly, only a fraction of a turn on the clamp bolt will lock the whole thing onto the post.

The hole for the holder should be a smooth sliding fit on the post. It shouldn't be tight.

Mick:
Splitting the holder distorts the hole and whilst it works, the post is gripped on two edges.
If you blue the post and lightly nip the bolt move the holder slightly you will see this.

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.
Yes that would be how to go about it.

Tom:
Yes you almost have it ! The two half's of the pinch bolt clamp together, there is no expansion.
 

mickri

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Almost had a major screw up today. I was down to the last couple of cuts as I was sneaking up on the correct size of the center hole. I was moving the crossslide in .001 increments to take off .002 at a time when I inadvertently moved the crossslide .011 equating to taking off .022. When I saw how deep the cut was I knew something was wrong and stopped the cut. Luckily I was only in about 1/4." Found my error and finished the hole getting a good fit for the remaining portion of the hole. The oversize portion of the hole is about .014 oversize.

What should I do about the portion that is oversize? One thought is to put some JB Weld in the oversize portion and then machine it to fit. I don't know if the JB Weld would stick long term. I could also use my welder to lay some beads in this area and then machine the beads to the correct fit. Or I could do nothing.
 

BaronJ

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Hi Mick,

1/4" (6 mm) I would do nothing ! It isn't going to make any real difference, 14 thou naw...

I try to avoid sneaking up on a size if I can. Too easy to overshoot as you have found out.

Anyway does this drawing help ?
Norman-002.jpeg
Note that this split clamp pin diameter is not set in stone. The end on drawing shows a diameter of 14 mm, only because I happen to have some drill rod that size. Also the bore is drilled tapping size for M6, but I've shown it as a 6 mm hole.
 

mickri

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Thanks Baron, The drawings definitely help. I am going to make at least one of the holders per your drawing.

I have to sneak up on a hole to get the correct size. I tend to measure holes slightly under their actual size. If I went by my measurements the holes that I bore would all be oversize. At least for now. Maybe someday I will be able to measure a hole to it's actual size. Or get to a point where my measurements are consistently under size by the same amount.
 

BaronJ

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Hi Mick,

Are you boring with the lathe or the mill ?
How are you measuring the bore ?
 

mickri

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I am doing the boring on my lathe. Don't have a boring head for my mill/drill. I use a telescoping gage and a micrometer to measure the ID of the hole that I am boring. I am getting better at it. I now get consistent measurements. My measurements are smaller than the actual ID. How do I know this? As stated in a previous post my measurement of the ID of the hole is smaller than my measurement of the OD of the post yet the holder fits on the post. So the ID has to be bigger than my measurement.
 

macardoso

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I hope everybody considering a four way will check out the inexpensive wedge type QCTP and holders available from many sources, say for example,, CDCO tools. The capability and ease of use, coupled with the low cost of more holders and styles (boring, knurling, etc.) are hard to beat.
100% on board with this. I have the CDCO wedge tool post with 7 holders for ~$100. Nice quality and I can take my tools on and off and they repeat to the same position within a tenth or two. It makes life so much easier. Plus the height adjustment screw means you don't need to ship. Some argue that there is a loss in rigidity to a small extent, but I haven't found this to be an issue even when doing heavy machining of alloy steels.
 

homebrewed

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I made the Norman style QCTP, too. The version with the single slit, not the split clamp. Mine took a lot of "oomph" to tighten on the post as well. To address that I drilled a 1/8" diameter hole on the other side of the holder, located halfway between the bore and side of the holder. Then I cut another slit down to the hole. The rounded section is used as a stress relief. This mod made it much easier too secure the holder to the post.

Here's a photo showing my build. It's installed on a 7x12 mini lathe. I normally do a lot more facing cuts than threading so the compound is set parallel to the ways. The post is CRS, the holder is 6061 aluminum.

my_QCTP.JPG
 

BaronJ

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Hi Homebrewed,

Looks nice !
You have discovered one of the issues with using a screw to clamp in that way.
I think that all the articles showing toolpost designs, using a screw to clamp, in that fashion, have done it that way because drilling a hole and cutting a slit is easier than making a proper spit clamp.
 
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