# Work around for inconsistent sizing of square 5C collet blocks



## John Conroy (Oct 20, 2021)

I have been making and selling some parts from 1/2" CRS rod that have a rectangular feature . Using a 5C collet block in the mill vise along with a vise stop makes consistent set up fast and easy. I decided to add a second collet block to my set up so the milling on 2 parts could be done with one set up. I previously bought a collet block set from KBC that contains a square and a hex block as well as the nuts to mount the collets into the blocks. I just ordered another square block of the same part number from KBC to match the one I already had. After it arrived I quickly found out that the outside dimensions are different than the one I had. I called KBC and asked that they check the others they had in stock and sure enough they were all inconsistent in size. The collet is dead center in the block but outside dimensions on the 2 I have vary by .010" from each other.









With the 2 blocks mounted side by side in the vise the rod is .005" higher in one of them.









The blocks are very hard so correcting this in the mill was not an option and I don't have a surface grinder. I made up a stepped plate to fit under the 2 blocks. One block sit on a pad that is .005" higher than the other. The overall width of the plate is .010" less in width than the 2 collet blocks side by side.









Running the indicator over both of then now shows the same height  with a minimum amount of work. I have engraved marks on the plate and the thinner block so it's easy to orient them correctly.









This is my vise stop set up.





Just another example of how import tooling can be disappointing.


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## 6.5 Fan (Oct 20, 2021)

On the bright side, you now have a reason to buy a surface grinder.


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## PeterT (Oct 20, 2021)

That's a common complaint I hear about the collet blocks. Either the square section is rectangular by a couple thou, or the block is square but the hole is not on the axis. I use them for 'good enough' work but it is important to know how they stack up in the accuracy department.


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## Susquatch (Oct 20, 2021)

John Conroy said:


> I made up a stepped plate to fit under the 2 blocks. One block sit on a pad that is .005" higher than the other. The overall width of the plate is .010" less in width than the 2 collet blocks side by side.



Too bad anyone has to do that to fix a problem that shouldnt be there in the first place. 

But very simple and very effective solution. Well done! My hats off to ya!


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## RobinHood (Oct 20, 2021)

I agree, surface grinder time.

Christmas is only two months away…


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## Tom Kitta (Oct 20, 2021)

I ground mine... on a surface grinder.


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## Susquatch (Oct 21, 2021)

RobinHood said:


> I agree, surface grinder time.
> 
> Christmas is only two months away…





Tom Kitta said:


> I ground mine... on a surface grinder.



Yup, here we go again. Spending more time and money buying and making tools for our tools than making stuff. 

Alas, Santa will never bring me a surface grinder. The reindeer would never get the sleigh off the ground.


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