Author Topic: Pratt and Burnerd LC lever type collet chuck  (Read 807 times)

Offline Biggles

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Pratt and Burnerd LC lever type collet chuck
« on: June 14, 2018, 11:22:37 AM »
Hi All, I have recently come into possession of a lever type collet chuck advertised as a Crawford. On further inspection I have found it to be a Burnerd multisize of lever type with EC collets. The collets supplied were in fact Crawford but the chuck did not have any ID, probably worn.
I have now taken it apart and found a exploded diagram of the LC type chucks as below. The chuck is missing item 18 on the drawing, can anybody help firstly with the workings of the two key type items 16, 18 as I haven’t a clue as to what they do. Secondly what is item 18 and any help on dimensions, drawings for the purpose of making or purchasing would help in restoration. If anybody has one; it doesn’t need to be the same size as reading in the notes the LC 10 to xx’s have the same item dimensions inside. Photos and measurement will definitely help.
 :nrocks:



Offline JohnC

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Re: Pratt and Burnerd LC lever type collet chuck
« Reply #1 on: June 20, 2018, 12:52:23 PM »
Hi Biggles,
I have the same chuck, and guess what - no item 18 either!  So maybe not that important - the chuck works just fine as it is. 
Hope that helps,
John
John C
York, UK

Offline Biggles

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Re: Pratt and Burnerd LC lever type collet chuck
« Reply #2 on: June 21, 2018, 10:23:01 AM »
Hi John, it seems to work after a fashion but the locking mechanism obviously will not. Since there are two keyways in the lever mechanism I can only assume that item 16 is stationary and 18 sits in the other keyway. When the lever is pulled round item 18 overrides 16 which make for a long pushing plunger in addition when the lever is pulled forward this plunger forces the collet out. Anyway that is my assumption.
George

Offline Biggles

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Re: Pratt and Burnerd LC lever type collet chuck
« Reply #3 on: July 01, 2018, 02:01:10 PM »
I have been in contact with a few people who have the same type of Burnerd collet chuck and they all say that they have one key in there chucks. Therefore going by the majority, I can only assume that contrary to my previous thought the extra key way is for alignment purposes of the lever and the expanded drawing shows an alternative key, not an addition. Sometime back in 2011 in Practical Machinist, the same problem cropped up with no resolution but with a photo of the offending with the extra keyway visible.
Thread: https://www.practicalmachinist.com/vb/general/burnerd-collet-chuck-problem-234832/
Therefore I think I will put this one to sleep. Many thanks to all that replied.
George

Offline vtsteam

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Re: Pratt and Burnerd LC lever type collet chuck
« Reply #4 on: July 01, 2018, 06:28:39 PM »
Glad you solved the puzzle, George. Sorry I couldn't contribute, but no experience with these.  :beer:
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline Biggles

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Re: Pratt and Burnerd LC lever type collet chuck
« Reply #5 on: July 04, 2018, 11:16:54 AM »
Thanks Steve, not realy solved more put on the back burner. If anybody else has anything to contribute please PM.  :scratch:
George