Ream Bushings or Grind Shaft

C

CARP104

Plastic

Joined

Apr 15, 2013

Location

Dublin, Ohio

• Jan 31, 2019

• #1

I have a somewhat unique situation, in that I am spinning an object on a 1" ETD150 dead shaft. The object that is spinning on the shaft is two pieces, the main bar and a pulley which are bolted together. Both the bar and pulley have an oilite bushing pressed into them. The problem is they both seemed to have closed in different amounts. I can get a .996 gauge pin in one bushing and a .999 in another.

My shaft is measuring .9978", so it won't even go into one of the bushings. Given these are oilites my initial thought is to grind the shaft down so I don't risk closing up the pores in the bushings. However the uneven bore sizes now has me a bit concerned, as the object spinning will be under extreme shock loads at times and won't evenly distribute the load to the shaft or bushings.

After checking the oilite data sheet apparently you can ream these with a very sharp tungsten carbide reamer without causing too much pore closure. The problem is I'm not a machinist and I don't have a new sharp reamer to do this.

Does anyone have any suggestions to fix this? My gut tells me to have someone ream them.

 

Finegrain

Diamond

Joined

Sep 6, 2007

Location

Seattle, Washington

• Jan 31, 2019

• #2

Have the the parts (with the bushings installed so you know what size you are getting in-situ) bored out on a lathe. A sharp boring bar should cut cleanly and not harm the Oilite functionality.

Regards.

Mike

 

C

CARP104

Plastic

Joined

Apr 15, 2013

Location

Dublin, Ohio

• Jan 31, 2019

• #3

Sounds like a good suggestion. The part is fairly dangerous to spin on a lathe however, it has a 12" diameter at the tips with sharp hardened steel cutting teeth - might make some machinists uncomfortable?

 

Finegrain

Diamond

Joined

Sep 6, 2007

Location

Seattle, Washington

• Jan 31, 2019

• #4

CARP104 said:

Sounds like a good suggestion. The part is fairly dangerous to spin on a lathe however, it has a 12" diameter at the tips with sharp hardened steel cutting teeth - might make some machinists uncomfortable?

Click to expand...

Depends on the machinist

Regards.

Mike

 

H

HuFlungDung

Diamond

Joined

Jan 19, 2005

Location

Canada

• Jan 31, 2019

• #5

It takes a sharp reamer to ream brass or bronze anything. I'd ream it and be done with it. There is no way it is going to close up the pores, that is a fallacy. A dull reamer will be unable to cut it, so don't waste your time trying with one.

 

C

CARP104

Plastic

Joined

Apr 15, 2013

Location

Dublin, Ohio

• Jan 31, 2019

• #6

Sounds like I may have to buy a reamer and just go for it. I occasionally can get access to a 4-axis makino horizontal mill through a friend, I wonder if extrapolating the hole out with a sharp end mill would also work?

 

H

Hodge

Stainless

Joined

Jul 30, 2008

Location

spartanburg sc

• Jan 31, 2019

• #7

I would also look into ordering new bushings if it's not a one off piece of equipment. If you do have the bushings reamed/cut i would have the machinist look over both shaft and bushings before proceeding. You also mention that the bushings are pressed on, if that is correct be careful about opening up said bushings.

 

M

Milland

Diamond

Joined

Jul 6, 2006

Location

Hillsboro, New Hampshire

• Jan 31, 2019

• #8

I doubt the surface hardness of the ETD 150 shaft is appropriate for direct running of oilite bushings. You may get scarring, and depending on loads could risk fracture given the shocks you say this assembly receives. That doesn't sound good considering the heavy spinning sharp edged disk...

Tell us more about what this thing does, and whether it's a new item or based on an established design/materials.

 

C

CARP104

Plastic

Joined

Apr 15, 2013

Location

Dublin, Ohio

• Jan 31, 2019

• #9

Hi Milland,

It's actually not a piece of machinery, but rather a spinning weapon for a combat robot (Battlebot). The spinning arm will be spinning at approx 5K rpm on the dead shaft. I know this isn't ideal for bushings, however given the bushings are only run in 3 minute intervals and replaced after every competition they will typically only see a total of less than an hour of run-time before being replaced. Several competitors have successfully used them at these speeds for these short periods of time.


My previous shaft was 6al-4v Titanium and had problems galling with the bushings, so I chose ETD150 this time mainly for it's overall tensile/yield strength and switched to oilites over non-impregnated. The standard case hardened shafts you can get on mcmaster don't have the yield of ETD-150, but the ETD150 comes in around 30Rc.

 

A

adama

Diamond

Joined

Dec 28, 2004

Location

uk

• Jan 31, 2019

• #10

^ that will be fine and you won't need to change them for even several hours of run time if you give them a splash of some decent oil after every run!

Don't be too worried about closing the pores in the oilite, its largely a theoretical problem and not one in reality or the second it spun on a shaft they would burnish shut and that would be it. Correctly loaded you can spin oil light bushings for thousands of hours with just the odd drop of oil! A HSS reamer will work fine for that job, its really only production were the carbide is key.

Scariest thing i have done in a lathe is a 4' long 2' diamiter muck spreader rear flight (well pressure washed off i might add) with its teeth on to skim a bearing, that fucker was hypnotic due to the spiral, it really screwed with your brain! After that everything is pretty tame.

 

fciron

Stainless

Joined

Oct 14, 2009

Location

Louisville, KY, USA

• Feb 3, 2019

• #11

If your going to be replacing the bushings regularly I'd think you would want a procedure that fits the bushings to the shaft and you'll probably want to own the tool to do it.

I think that equals buying the reamer.

 

J

john.k

Diamond

Joined

Dec 21, 2012

Location

Brisbane Qld Australia

• Feb 3, 2019

• #12

Sooooo...the thingy is dangerous to spin on a lathe,but not dangerous to spin at 5k revs with a hundred nerds watching .......Still,suppose not much harm would be done.

 

Spruewell

Hot Rolled

Joined

Sep 8, 2015

Location

Northern California

• Feb 4, 2019

• #13

I’m a nerd. I’ll watch that! Personally however, I would get a reamer to size the bushings. The difference in ID is likely due to inconsistent bore diameters in the part they are being pressed into. The shaft size is more likely to be consistent and would make much more sense to match. It is also way easier to run a reamer than to try and re-size the shaft.

 

D

DDoug

Diamond

Joined

Oct 18, 2005

Location

NW Pa

• Feb 4, 2019

• #14

CARP104 said:

Hi Milland,

It's actually not a piece of machinery, but rather a spinning weapon for a combat robot (Battlebot). The spinning arm will be spinning at approx 5K rpm on the dead shaft.

Click to expand...

Oh goody....

 

M

Mcgyver

Diamond

Joined

Aug 5, 2005

Location

Toronto

• Feb 4, 2019

• #15

Spruewell said:

I’m a nerd. I’ll watch that! Personally however, I would get a reamer to size the bushings. The difference in ID is likely due to inconsistent bore diameters in the part they are being pressed into. The shaft size is more likely to be consistent and would make much more sense to match. It is also way easier to run a reamer than to try and re-size the shaft.

Click to expand...

or a reamer to size the hole the oilite is pressed into. There's notes in machinry's handbook explaining the calcs, the resulting ID of the oilite is a function of the bore dia they are pressed into. Get that right and you've engineered the ID of the oilite to fit the shaft