Air impact wrench repair?

[julianf]

At the bootsale yesterday, i purchased a couple of air impact wrenches.

One has a known fault (which ill look at later), the other may be 'operator error' on my behalf!


Basically, i powered it up, and there was no action from it. It was only on looking inside that i saw the spring -

Do the units with the sprung clutch need force applied to the tip to engage the clutch, or is the sprung mechanism what creates the 'impact'? (ive never used an air impact wrench before) I can see the parts, but cant get it clear in my head what actually happens. Theyre described as a clutch, but then the parts are called 'hammer' this and that..

Ive just (as in now) found another diagram which makes things clearer -

(you may have to open that one in a new tab to see the part numbers?)

Its the interaction between parts 18-23 that i dont really get.


My plan is, basically, to clean it all up, make sure the 'vanes' are free, and reassemble, but i want to be sure i understand the job also.

 

[julianf]

A point of confusion -


The diagram above seems to show the ball bearing (22) locating in the smaller channels of the pins (23)


The picture below, however, shows the opposite. The hammer cam is located in the channel on the pins, and the bearing is behind the whole assembly -

I thought, when i dismantled mine, that the hammer cam (20) located in these channels, not the bearing. However, then i cant really see the point of the larger recess in the pins.

Can anyone clear this up for me?

 

[Fintray]

Looking at the diagram I expect that the spring keeps part 18 away from the cam part 20 and the cam provides the impact (hammer) action. The impact won't be noticed until you put force against the cam by pushing the gun against something.

 

[julianf]

Looking at the diagram I expect that the spring keeps part 18 away from the cam part 20 and the cam provides the impact (hammer) action. The impact won't be noticed until you put force against the cam by pushing the gun against something.

Thank you.

Yeah, on first glance, that's what it looks like, but the splines on part #18 would not engage easily with the the cam part #20. Part 18 and 20 must be locked, relative to one another, but part #20 slides on the splines of part #18. The splines are actually keyed (ie not symetrical the whole way arround) so as part #20 can only locate in one position, rotationally, on part #18.

When i tried out the unit, the shaft was not rotating at all - it was not just lack of impact.

Today im doing 'clean' work, so i wont look at it again until this evening.

 

[Fintray]

M'mm in that case it is more likely that part no. 24 rotates along with the pins and when you push the gun against something it engages the dogs on part no. 18 with the pins. This is of course pure assumption and is more than likely incorrect......

 

[Wendelspanswick]

I bought a dead air impact wrench from a car boot and it was just the vanes were gummed into the slots with rust and gunk, once cleaned it was fine and is still going strong.

 

[Bill Edwards]

All the impact wrenches I have used will spin freely with nothing on, when enough of a load is applied (i.e to tighten/loosen) they start with the impact mechanism.

 

[daleyd]

All the impact wrenches I have used will spin freely with nothing on, when enough of a load is applied (i.e to tighten/loosen) they start with the impact mechanism.

Yes, same here.

 

[julianf]

Have got the mechanism back together again now. Construction was as per the latter picture i posted.

Cant test right now, as my smaller compressor still needs a few bits sorting before it runs again, and ive lent the large one out...

I recall, from my brief test before, however, that the trigger was leaking too, so i may look at that tomorrow.