Accurate location of two concentric cylinders 6

[JediJew]

I'm in the process of designing a small bar end grinder. The device has two casings: one which holds a gearbox and another which holds the bar to be ground. These could not be machined from one piece of material and so I need a way to fix them together so that they do not move relative to one another (i.e. thread is inappropriate)

I've uploaded pictures of the parts. The outer housing has an outer diameter of 150mm, and an inner diameter of 140mm. These are not fixed but I'd prefer them not to be too much larger for weight saving purposes.

Any suggestions appreciated

 

[DesignerGuy16]

What about a sleeve with a tight sliding fit, then drill and press some shear pins into them at assembly?

James Spisich
Design Engineer, CSWP

 

[hydtools]

You do not need a thread to use a Loctite product meant for slip fits.
See info here:

http://henkel.dirxion.com/skin/entrymap/entrymap_noanimation.asp

Ted

 

[MikeHalloran]

No, but you'll need a thread and wrenching features to jack it apart.

I _really_ don't like the idea of disassembling the gearbox housing for a change of abrasives... which guarantees proximity of, and probably contamination with, abrasive grains.



Mike Halloran
Pembroke Pines, FL, USA

 

[JediJew]

Ah. I haven't been clear. Forgive me.

The gears are separated from the grinder by a plate. The grey cylinder (in my first image) holds the gearing and is sealed on both sides by a plate. The grinder protrudes from a hole in this plate. The blue cylinder is used to hold the bar stationary and act as a guide during the grinding process, so separating the two cylinders will not cause the gearbox to be exposed.

hydtools: I had a look at that website and, as MikeHalloran mentioned, separating the cylinders after bonding will be tricky.

Jspisich: I like the idea of shear pins! My only concern is that after disassembly it may be tricky to line up the holes again. But that is a minor concern. Thanks!

Keep the ideas coming guys. I really appreciate it!

 

[lfmarini]

JediJew,

I'm designing a hopkinson bar and I'd appreciate to share some information about it. Hence, I can't understand the usage of the gearbox you say in hopkinson bar experiment. Could you clear up my mind?

thanks
lfmarini

ITA - Instituto Tecnologico de Aeronautica
SP, Brasil

 

[JediJew]

lfmarini

I can understand why you're confused. I was designing a machine to grind the surfaces of the bars themselves. A hopkinson bar test rig wouldn't require any sort of gearbox.

Sorry to confuse you

 

[unclesyd]

I would look at using a collect and collect chuck for you application. If you can vist a mill supply store or get hold of tool catalogue I'm willing to bet that you can find a combination that will work.

http://www.jtsmach.com/jtswebshop/Workholding/CH038.asp

What is your material and sizes?

There are numerous companies that can provide you with very precision ground bar stock

http://www.bostoncenterless.com/AccuRod.htm

http://www.dowelspinsshafts.com/catalog2.html

 

[mrpi]

How about a keyless bushing, like unclesyd above mentioned? I've used the Fenner Drive brand with good success:

B-Loc high-torque couplings:

http://www.fennerdrives.com/keyless_bushings/b_loc_keyless_bushings.asp

Trans-Torque

http://www.fennerdrives.com/keyless_bushings/trantorque_home.aspx

Also have a look at these CMT Maxi-Torque split bushings. These can be used over a key, I believe. We use a keyless one and it works great.

Keep in mind that all the taper-locking couplers have a hard time repeating axial location since they move axially when you clamp them.

If that doesn't work, how about just a cylindrical alignment boss to hold concentricity, then a bolt flange around it? The bolts will hole rotational alignment pretty good.

Beat to fit, paint to match.

 

[mrpi]

Oops, forgot the CMT coupling:

http://www.cmtco.com/maxitorque.html

Beat to fit, paint to match.