Author Topic: Floating Reamer Holders  (Read 6736 times)

Offline Roger B

  • Full Member
  • *****
  • Posts: 3278
Floating Reamer Holders
« on: November 03, 2016, 11:27:55 AM »
I am aware of the need for floating reamer holders to get the best possible accuracy and finish when reaming in the lathe. Industrial ones are too big and will probably cost more than my lathe. Hemingway offer a kit:

http://www.hemingwaykits.com/acatalog/Floating_Reamer_Holder.html

This is also too big for me  :( By the time I have fitted a chuck and a reamer I have almost no space left for a workpiece  ::)

The working principle is to offer a small amount of axial and angular freedom whilst transmitting torque. Most available units seem to use something like an Oldham coupling to transmit the torque and some form of thrust ball.

As the amount of torque required when reaming is quite low (or should be) I am looking at a different principle. To keep the unit short the floating Morse taper will not be full length, the remaining part of the chuck or reamer taper will be inside the taper of the tailstock quill. The floating action will be by two pairs of links at 90░ connected by a ring that fits around the floating Morse taper. One pair of links will fix to an adaptor that clamps to the outside of the tailstock quill, the other pair will be attached to the floating Morse taper. There will be a small clearance (~0.25mm) between the floating Morse taper and the ring and adaptor to limit the movements. The links will pivot on hardened steel bushes held in place with M3 caphead screws.

Will this work? I can see a few potential problems  :headscratch:

1) The links will tend to twist with the torque. Close tolerances should reduce this.
2) Will the weight of the chuck tend to deflect small reamers, exchanging one problem for another? By small I am thinking of the ~1.5mm reamers used for my injection system.
3) The torque reaction on the links will tend to withdraw the reamer, possibly starting a chatter problem.

All thoughts, ideas and suggestions welcome  :ThumbsUp: :ThumbsUp:  :wine1:
« Last Edit: November 03, 2016, 11:59:41 AM by Roger B »
Best regards

Roger

Online Admiral_dk

  • Full Member
  • ****
  • Posts: 862
  • S°ften - Denmark
Re: Floating Reamer Holders
« Reply #1 on: November 03, 2016, 08:50:57 PM »
Hi Roger

A very interesting problem. My first thought before opening your drawing was a coupling like the ones on my CNC router between the steppers and the shafts. One of these might support a micro chuck and could potentially do what you need in the very small sizes.

The cheap and cheerful :
http://www.banggood.com/5mm-x-6_35mm-Aluminum-Flexible-Shaft-Coupling-OD19mm-x-L25mm-CNC-Stepper-Motor-Coupler-Connector-p-993600.html

The really good quality :
http://www.lovejoy-inc.com/products/disc-coupling.aspx

And the in between quality :
http://www.cncrouterparts.com/oldham-zero-backlash-couplers-p-223.html

I really should think about one for myself too  :old:

Offline Lew Hartswick

  • Full Member
  • ****
  • Posts: 210
  • Albuquerque, New Mexico, USA
Re: Floating Reamer Holders
« Reply #2 on: November 04, 2016, 02:28:09 PM »
I've been curious about this "device/concept" for a long time. The above links to the "idea" in the OP is beyond me. Is there a description to be found somewhere on how the principal works. In a bit more detail than what has been said above. ????
   Thanks.
   ...lew...

Online Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 11131
  • Hampshire, england.
Re: Floating Reamer Holders
« Reply #3 on: November 04, 2016, 03:26:33 PM »
This is a commercial one.  Taking it apart there are three main parts:

1, The bit that mounts in the tailstock has a slot in it for using a morse taper extractor in and note the dome screws line up with that slot.
2, The interesting floating/fixed middle bit - more later  ;)
3, The floating bit the tool mounts in which has the morse taper socket in it and you will notice the mounting screws are at 90 degrees to the slot on the morse taper for extracting.

The clever bit is that middle bit  :naughty:: The floating bit the tool mounts in is clamped to the first outer ring by two allen screws. At 90 degrees to those screws on the ring is two pins that allow the central tube to move left and right. To the other end of the central tube: is another outer ring with two pins at 90 degrees to the first pair. this give the up and down movement. That ring is clamped by the two domed head screws to the first part. So if you put all three bits together you get two movement axes left/right and up/down.

Now it gets posh: the central part also has a big spring round the outside of the tube and a plate. The plate screws on the front of the bit that goes in the tailstock using three csk screws and is the surface that the floating tool holder floats on. The spring lives behind this plate and pulls the tube and the attached floating tool holder back against the surface.

The result is you have a morse taper socket that is free to move in two planes while maintaining its parallelism with the axis of the mounting taper.

I hope that is clear as mud  :headscratch:

Jo

Usus est optimum magister

Offline Roger B

  • Full Member
  • *****
  • Posts: 3278
Re: Floating Reamer Holders
« Reply #4 on: November 04, 2016, 03:35:32 PM »
The idea, as I have understood it, is that a reamer will follow an existing hole opening it out accurately to size and leaving a good surface finish. If the reamer cannot follow the existing hole, for example if the tailstock of the lathe is not very accurately aligned with the headstock the side pressure on the reamer will cause the hole to be tapered/bellmouthed, the tendency to cut on one side of the reamer only will cause chatter and the surface finish will be degraded.

The question is how accurate must the alignment be? I think that the answer must be better than the tolerance expected in the hole after reaming.

The floating reamer holder is supposed to allow the reamer a small amount of freedom to follow the existing hole and to transmit the cutting torque. How much freedom is required? Again I think that the answer must be more than the inaccuracy of the headstock-tailstock alignment. Typically this will be a couple of degrees angular and a couple of tenths of a mm axially.

I hope that this clarifies things a little  :headscratch: I am certainly not a machining specialist, but this is what I have found from various books and websites.
Best regards

Roger

Offline Roger B

  • Full Member
  • *****
  • Posts: 3278
Re: Floating Reamer Holders
« Reply #5 on: November 04, 2016, 03:38:46 PM »
Thank you for the pictures Jo  :ThumbsUp:

How big is that one, MT2? Who was/is the supplier?
Best regards

Roger

Online Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 11131
  • Hampshire, england.
Re: Floating Reamer Holders
« Reply #6 on: November 04, 2016, 04:09:58 PM »
You are welcome Roger,

That is a Clarkson floating reamer holder. Currently fitted with a 2MT but by the looks of things the socket in the end can be replace by other sizes.

As for the supplier: It turned up at my model engineering club at our white elephant sale and I think I was the only person who put a bid on it  ::)

Jo
Usus est optimum magister

Offline Lew Hartswick

  • Full Member
  • ****
  • Posts: 210
  • Albuquerque, New Mexico, USA
Re: Floating Reamer Holders
« Reply #7 on: November 05, 2016, 02:03:43 AM »
This is a commercial one.  Taking it apart there are three main parts:

I hope that is clear as mud  :headscratch:

Jo

Thank you. That helps  a lot. The angular "float" is not quite clear yet but I'll work on it. :-)
   ...lew...

Offline Roger B

  • Full Member
  • *****
  • Posts: 3278
Re: Floating Reamer Holders
« Reply #8 on: November 06, 2016, 07:26:55 AM »
This is the 'Swiss' version. An MT1 - ER11 version exists. I may pluck up courage to ask how much  ::)

The description of operation and the diagrams are good. Looking at Jo's version and this one I think that I would need to add some centering springs between the floating Morse taper and the tailstock quill on my design.
Best regards

Roger

Offline Roger B

  • Full Member
  • *****
  • Posts: 3278
Re: Floating Reamer Holders
« Reply #9 on: November 08, 2016, 07:34:08 AM »
The MT1-ER11 Angst floating reamer will cost me CHF 700  :o Actually it is not as bad as I thought it might be  ::)

Now I have 3 options so I need to decide how much my workshop time is worth:

1) Continue my own design with uncretain success. Cheap but will consume quite a few hours.
2) Use the Hemingway design as a basis but shrink it a bit. Costs a bit more but should work. Will also consume quite a few hours.
3) Spends lots of money and spend the workshop time building engines.

 :headscratch:  :headscratch:
Best regards

Roger

Online Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 11131
  • Hampshire, england.
Re: Floating Reamer Holders
« Reply #10 on: November 08, 2016, 07:45:54 AM »
3a) Buy some model engine castings  :naughty:

A copy of the Clarkson floating reamer would not be difficult to make  ;)

Jo
Usus est optimum magister

Offline Rivergypsy

  • Full Member
  • ****
  • Posts: 186
Re: Floating Reamer Holders
« Reply #11 on: November 08, 2016, 01:20:20 PM »
An interesting problem, and one I've spent more than a few hours on to try to 'float' a leadscrew, so that the rotary motion doesn't affect the linear travel (long story), but what I stumbled across was a flexure based system what allows float in 4 degree of freedom, but is rigid in the two required - perhaps this could be modified to float a reamer?

Offline cwelkie

  • Full Member
  • ****
  • Posts: 133
Re: Floating Reamer Holders
« Reply #12 on: November 08, 2016, 01:35:26 PM »
FWIW here are some photos of a holder I put together a while back. Sorry, no drawings. It uses interchangeable "heads" so I can use it for different size dies and taps.







Hopefully the photos are self-explanatory.
Charlie




Offline kvom

  • Full Member
  • ****
  • Posts: 1567
Re: Floating Reamer Holders
« Reply #13 on: November 08, 2016, 03:30:24 PM »
Nothing I build would benefit from whatever advantages such a holder could offer.  Interesting discussion however.

Offline gerritv

  • Full Member
  • ****
  • Posts: 438
  • St Catharines, ON
    • Gerrit's Hobbies
Re: Floating Reamer Holders
« Reply #14 on: November 08, 2016, 05:20:07 PM »
Charlie, that is a very neat Implementation.
Don't confuse activity with progress