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Floating reamer holder

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PekkaNF:
Yesterday I managed to make decent 16mm H7 holes, but it breaks always a cold sweat. Odd barrel hole and oversized holes are fact if you chuck the reamer or hold it in a tap wrench.

Looking for a practical design to make one.

I have found Hemingways design that used Odlhamn coupling principle.

Suggestions?

Thank you,
Pekka

PekkaNF:
Also found this design




http://www.practicalmachinist.com/vb/printthread.php?t=306442&pp=20&page=1


Looks pretty simple, but I spot two (potential) problems with this design:
1: As far as I can see tilt (for angular misaligment)  not very smooth, bears on pins or flat faces. Normally there is a ball
2: Looks clearance holes on the shell perimeter will cause pins to center the reamer holder, probably not ideal. Holes could be slots to counteract on this tendency, needs keepers though to prevent it falling apart.

Am I wrong or (least partially) right?

Roger B:
I made some investigations into floating reamer holders on MEM:

http://www.modelenginemaker.com/index.php/topic,6562.0.html

I think that you have to be a member to see the pictures. One source that may be of interest to you is the gun makers:

http://www.brownells.ch/epages/Switzerland.sf/de_CH/?ObjectID=55053

PekkaNF:
Thank you

I only see three last pictures of reply #12 and can't understand it or previous ones :scratch:

Have to read it again, you use external linkage?

Pekka

cwelkie:
Given that the pictures referred to in "reply #12" are mine, I'll try to example how it works ... first off my holder is an adaptation of a design shown in Model Engineers Workshop magazine some years back (can't remember the issue number).

The tool in the photos consists of a changeable tool holder so that small dies or an ER16 collet can be used.  The collet can be used to hold small taps or reamers.  The tool holder has three spring loaded "pins" that maintain some tension between the back face of the tool holder and a flat flange on the end of the arbour that is inserted in the tailstock.  A threaded collar allows the head to be removed.

In use the holder is intended to keep the tool (e.g., tap or reamer) parallel to the lathe centre line while allowing a small amount of shift side-to-side.  The holder also slides towards the work as the cut or threads are being applied.

Is it perfect - probably not.  It was a interesting tool to make though and surely more accurate than some of the other ways (I've) used.
Charlie

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