# Measuring Mill X&Y Dovetail Perpendicularity



## tkalxx (Apr 15, 2021)

Hello, 

I'm trying to come up with a way to physically measure the perpendicularity of my X and Y dovetails on the saddle of my mill while it is disassembled from the rest of the machine. I am looking to verify squareness measurements that I took from the mill while it was assembled and confirm whether the X and Y dovetails were machined out of square, or if there is another source of error (ex. gibs) that I should be investigating. 

I have come up with a method using some precision ground linear rods that I have sitting around in the shop, but I am seeking some advice or a superior method. The straightness tolerance of this rod is .0005"/ft which should be sufficient as I'm attempting to measure upwards of .020"/ft. One ground rod would rest in the X-axis dovetail, and another in the Y-axis dovetail. A test indicator would be attached to the Y-axis rod and a dial indicator would be zero'd on the butt end of the Y-axis rod. The test indicator would then be swept from one end of the X-axis rod to the other while maintaining zero on the butt end dial indicator. See image below:



Maybe this question is better suited for the scraping section even though I'm not planning on scraping this saddle. Any input is appreciated.
-Adam.


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## graham-xrf (Apr 15, 2021)

All the possible static alignment tests and setups for a mill are set out in Connelly's book "Machine Tool Reconditioning".

There are likely some cute quick tricks that can verify squareness. I am sure members will let you know.


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## Richard King 2 (Apr 15, 2021)

You should remove that PDF as the current copyright owner of the book is suing people who copy it and show it online.   The book can be purchased.


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## tkalxx (Apr 15, 2021)

"Sec 28.58 - The Plain Saddle
...
Since the treatment accorded the individual surfaces is similar, and the objectives and alignment tests identical to those described previously in Sec. 27.46 of the Horizontal Milling Machine, it would be unduly repetitious to describe again."

I'll have to get a copy of section 27.


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## Richard King 2 (Apr 15, 2021)

You need to use a precision square to check the bottom X axis dovetail to the X axis dovetail opposite side of of the gibs.  Testing a know blade square or a granite square.  You need to look for this on You Tube  This one shows testing a blade square about the 8 minute mark.  



   The fellow doing these shows is a 6 time student named Jan.   He is an Electronics engineer and a hobbyist rebuilder.  He has dozens of You Tube Shows as does Keith Rucker.   Jan is in Norway.

I found this one on a lathe dovetail scraping and tests.  Think about it as a mill.   Testing the feed screw is not the way to go.

Here is another one made by Keith Rucker,   Like I said imagine this being your mill.   If you need better explanation you can call me.  651 338 8141.





     at about 3 minute mark.


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## macardoso (Apr 15, 2021)

tkalxx said:


> "Sec 28.58 - The Plain Saddle
> ...
> Since the treatment accorded the individual surfaces is similar, and the objectives and alignment tests identical to those described previously in Sec. 27.46 of the Horizontal Milling Machine, it would be unduly repetitious to describe again."
> 
> I'll have to get a copy of section 27.



There is some snarkiness to Connelly - I love it. There are some good graphics in the lathe alignment section, specifically the saddle, which show using a surface plate, ground rods, and a precision square to measure the squareness of an individual component off the machine.

I would recommend the book as a good starting place for learning machine alignment measuring and scraping. I think it teaches the processes well, but I'm sure the technique of scraping best learned with hands on instruction. $100 from DAPRA is about as good as it gets. If you buy from Rich I think he signs it for you if you ask.

I'm a rock climber and I drew parallels to machine scraping right away. When you climb, you can read books on knots and anchors, but when you actually get out on the rock, nothing looks exactly like the examples in the book. It is better to learn the philosophy behind the process, rather than the exact steps covered in the book. While my mill looks nothing like the vertical mill in the book, I was able to understand the philosophy of the process and feel like I at least know where to begin. To me the book was worth it to get that out of it.

Rich will tell you that there are parts of the book which are dated or plain wrong - I trust him. But I have also yet to find an equally comprehensive read on the subject, especially for a neophyte like myself.

-Mike


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## Janderso (Apr 15, 2021)

macardoso said:


> I think he signs it for you if you ask.


I thought I was special 
He signed mine at the class.
He then made a comment about the author 
This is a family forum.


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## Richard King 2 (Apr 15, 2021)

I found out a little history about Connelly.  He was a Bachelor and had no kids. He lived in St. Paul that is about 20 miles from my place.  When I used to buy the books from him inside the box was leaflets about the John Birch society...super right wing group...  I also wanted to meet him and tracked down the PO Box he had me mail the check too.  It was a answering service and they did mail too.  I had written him a few times asking I would like to meet him and I'd buy him dinner.  Never received an answer.   I then called the answering service and ask them to put a note in his mailbox, again asking to meet him and I put my phone number on the note.  

About a week later he called me and said "this is Ed Connelly and MIND your OWN Business!!" and hung up....  Then for a while I could not buy the books, neither could DAPRA.  It was about a year later and I started to get the books again.  I found out Ed had died and left the copyright to his younger brother Ray, who was selling the books again.   Then a year or so later, I called the number on the website and it said "HI it's Dan, leave a message"   I called 2 or 3 time before I got an answer.   I assumed it was a nephew of Ray or someone .   I drove over to Dans house for a case of books.   He told me he was Rays male nurse and Ray also was a bachelor with no kids and he signed over the copyright to Dan. Dan told me this story about Ray and that's all he knew.   He had no idea what scraping is.    He did tell me he had sued a few people and won after he discovered they were copying the book.    Yes I signed Dan's book last week... he was one of the students in my 2nd scraping class at my home here in MN.


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## tkalxx (Apr 16, 2021)

Richard King 2 said:


> You need to use a precision square to check the bottom X axis dovetail to the X axis dovetail opposite side of of the gibs.  Testing a know blade square or a granite square.  You need to look for this on You Tube  This one shows testing a blade square about the 8 minute mark.
> 
> 
> 
> ...



Thanks Richard, the Monarch lathe video really helped. I know I can modify that particular setup to suit my mill. It's tough to know what to search online to find good resources like the ones you linked - especially for such a niche topic. Might have to purchase a copy of Connelly's book from you in the future to feed my curiosity.


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## Dabbler (Apr 16, 2021)

For a brief period of time, there was a copy of Connely's book put in our downloads section by someone from 'another land' where the copyright had run out.  It was brought to our attention that the book was still in copyright in the US, and since we host in the US, we had to remove it from the site.  I hope this clarifies the whole situation.


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