Need help identifying this toolpost

fratskop

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Hi all,
I’ve tried this on another forum already with no luck but here goes: so i recently bought a colchester mascot 1600 for a reasonable price given the state of it, problem is that it came with no tool holders i have no idea what kind of post it is thats sitting on there now here’s a picture: A03AFED4-9D58-41D3-8B4B-7172E140CD88.jpeg
I have only ever worked with the dickson type toolposts so this is very unfamiliar to me. Some measurments: the total width of the block is 106 by 106 mm, the height is 80 mm and the Outer end of the dovetail is 73mm ( metric lathe, so sorry for no values in inches)
I have searched the web far and wide for something that resembles it, but to no avail. Hoping to have Some luck here since i just wanna buy Some holders for this or else i gotta buy a new post.
 

NortonDommi

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Or make some toolholders. How close is it to an AXA 250-400 or one of their other sizes?
 

fratskop

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Or make some toolholders. How close is it to an AXA 250-400 or one of their other sizes?
I guess it comes closest to a CA at 4 inches (or 101.6mm) but i cant find any dimensions of the dovetail itself, only Total width and height. I could try to make Some myself but i dont really trust myself that much with stuff like that since ive never done it before
 

WCraig

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For the quick change toolholders that Shars sells, they have a diagram showing the key measurements of the dovetail attachment:

Eg:



For a CXA toolholder, the dimensions are:
H: 0.555"
L1: 2.202"
L2: 1.681"

Get the same series of measurements from your toolholder and that should have determine what you've got.

See: https://www.shars.com/products/toolholding-workholding/quick-change-tool-post-holders/turning-and-facing-holder-1-type-301-cxa

Offhand, it does not appear to me that the angle of your dovetails is 60 degrees, however.

Craig
 

fratskop

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For the quick change toolholders that Shars sells, they have a diagram showing the key measurements of the dovetail attachment:

Eg:



For a CXA toolholder, the dimensions are:
H: 0.555"
L1: 2.202"
L2: 1.681"

Get the same series of measurements from your toolholder and that should have determine what you've got.

See: https://www.shars.com/products/toolholding-workholding/quick-change-tool-post-holders/turning-and-facing-holder-1-type-301-cxa

Offhand, it does not appear to me that the angle of your dovetails is 60 degrees, however.

Craig
image.jpg
Here is a more up close image, looks to me to be somewhere around 60 degrees, unfortunately i dont have a protractor at home (yet) so ill just have to take Some more measurments and calculate it
 

Bob Korves

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Pay attention to what Tom posted, they are 45 degrees or very close to it. Edit: The angles look different because you are not looking straight down on the part. Check the slots for parallel sides with a caliper, and don't let the internal corner radii mess up the test. If those slot walls are parallel, then the dovetail angles must be 45 degrees.
 
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fratskop

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If those slot walls are parallel, then the dovetail angles must be 45 degrees.
Makes sense, problem is i am now even more clueless as to what type of holder this is. ive never encountered a 45 degree dovetail before and cant find any information about something similar to this. guiss i'll have a go at making some myself.

side note: i also find it very weird that the clamping pistons are only on one side and not central, what makes even less sense to me is that they are on the 'back' side of the dovetail because to me it seems logical to put them on the front side so the clamping force is closest to where the cutting forces will take place
 

Latinrascalrg1

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Thats a 45°ish angle as measured by overlaying a protractor over the overhead picture. If that picture is not perfectly taken directly above the tool post will change this of course.

Im guessing its a home made tool post.
 

fratskop

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Thats a 45°ish angle as measured by overlaying a protractor over the overhead picture. If that picture is not perfectly taken directly above the tool post will change this of course.

Im guessing its a home made tool post.
tried this and it is indeed a 45° angle. you could be right about it being home made since i have never encountered a post like this one and cant find anything similar on the web. so, if i were to make a holder myself, what material could you reccommend? (i guess something that could be hardened seems logical)
 

T Bredehoft

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I'd use half hard (28-32 RC) 4140. Its' readily available, easily worked (with patience) and holds up well in service. It makes O1 look like ledloy as to work-ability.
 

fratskop

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I'd use half hard (28-32 RC) 4140. Its' readily available, easily worked (with patience) and holds up well in service. It makes O1 look like ledloy as to work-ability.
thanks for your help. here in europe we know 4140 as 42CrMo4 (the DIN standard) ive worked with it a few times. not super hard but also not very soft but machines great and shines nice. it seems the next project for my mill is sorted.
 

Toolmaker51

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fratskop says "I guess it comes closest to a CA at 4 inches (or 101.6mm) but i cant find any dimensions of the dovetail itself, only Total width and height. I could try to make Some myself but i dont really trust myself that much with stuff like that since ive never done it before "

I've singled out certain parts of that statement.
No one here can say they never said or thought one or more of those. Every single job looked at gets that same perusal, regardless level of expertise.
Learning is composed of not less than 2 elements, one is initiative.
The other depends on the person. . .
There is good news. There are numerous helpful members here, and other toolholders WAY harder to replicate!
 

fratskop

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No one here can say they never said or thought one or more of those. Every single job looked at gets that same perusal, regardless level of expertise.
Learning is composed of not less than 2 elements, one is initiative.
The other depends on the person. . .
There is good news. There are numerous helpful members here, and other toolholders WAY harder to replicate!
it's not that i dont trust myself in making one, its just that i get scared easily when making parts like this.but hey, there's a first time for everything right? at work i am a CNC miller and have done way more complicated stuff than this but no matter how simple the part i handle it with a certain caution, ya never know what could go wrong
 

WCraig

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Can you show how the clamping piston works? I would guess it is retracted in the pictures above. What does it look like when it is extended?

Craig
 

Superburban

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side note: i also find it very weird that the clamping pistons are only on one side and not central, what makes even less sense to me is that they are on the 'back' side of the dovetail because to me it seems logical to put them on the front side so the clamping force is closest to where the cutting forces will take place
KInda neat that it has separate clamping pistons for each side. Think about this. The piston wether it locks by moving inward, or outward (I'm voting on inward), it will force the whole height of the dovetails on the front edge, to lock together, giving a strong clamping force on the front edge. The rear end will just have the area of the piston, providing the clamping. Except for the challange of finding holders, I think I like the design.
 

MontanaLon

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That seems to be a very well thought our design and a simple way to create dovetails requiring only a V-block and a straight mill.

Thinking about it just a little I bet the sliding dovetail lock is a parallelogram wedge type that pushes the dovetail wedge into the body and keeps it aligned no matter how much it is tightened. It also pushes it out when loosened. If you get a chance to take it apart, I would love to see what makes it tick. It took some serious planning to set up but was likely done with very limited machining steps.
 

fratskop

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That seems to be a very well thought our design and a simple way to create dovetails requiring only a V-block and a straight mill.

Thinking about it just a little I bet the sliding dovetail lock is a parallelogram wedge type that pushes the dovetail wedge into the body and keeps it aligned no matter how much it is tightened. It also pushes it out when loosened. If you get a chance to take it apart, I would love to see what makes it tick. It took some serious planning to set up but was likely done with very limited machining steps.
I planned on taking it off anyway because as you can see in the picture it could use some cleaning
 

fratskop

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Can you show how the clamping piston works? I would guess it is retracted in the pictures above. What does it look like when it is extended?

Craig
When one of the four hex nuts is rotated, the piston moves inward. They dont extend and also there is no ‘end stop’ if you keep turning it one way it will return to the normal position
 

francist

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Cool, an eccentric on the shaft of the hex then and each corner operates independently. Interesting.

-frank
 

fratskop

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KInda neat that it has separate clamping pistons for each side. Think about this. The piston wether it locks by moving inward, or outward (I'm voting on inward), it will force the whole height of the dovetails on the front edge, to lock together, giving a strong clamping force on the front edge. The rear end will just have the area of the piston, providing the clamping. Except for the challange of finding holders, I think I like the design.
they move inward indeed. nice explanation, i haven't thought about it that way but it make sense. cerntainly not a bad design
 

Choiliefan

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I had a similar but larger tool post with Schaeffer Tool Co embossed on the top.
 

francist

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And coincidentally located in Germantown, Wisconsin as well...

-f
 
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