New (old stock) Impact Drive not working

[wxm]

I picked up an old Craftsman 3/8" drive impact gun on a garage sale, and it appears to be never used. However, went home connect to the air line, it is not working. I tried to dump a lot of oil, it was blown straight through the vent; soaked in the oil for two days still not working. Any suggestion?

 

[Tools R Us]

I picked up an old Craftsman 3/8" drive impact gun on a garage sale, and it appears to be never used.

Type, model#, pic?

However, went home connect to the air line, it is not working. I tried to dump a lot of oil, it was blown straight through the vent; soaked in the oil for two days still not working. Any suggestion?

Better define "not working"? Under power nothing turns? Without air connected, when you manually turn the anvil, what happens?

 

[wxm]

THe model number is Craftsman 875.199460

Sorry for the incomplete problem description. The air blew and came out from the vent next to the trigger, but anvil was not turning. I even opened it from the back - it seems not much you can see or do there, but at lease I confirmed the seal was good. I am not sure how to disassemble it from there.

I also tried to turn the anvil manually. It turns freely as if there is no load, though occasionally it seems to hit or bind on something then loosen up right a way (not sure I discribed it clearly. )

Here are some pictures:

 

[Tools R Us]

That is a private label Astro 135, good gun. Not the most powerful (IIRC ~80ft/lb), but fast and durable.

It is a rocking dog clutch. When you turn the anvil, the clutch engages and it stops, likely the problem is in the air motor, broken vane, bad bearing, stuck from rust, etc.

To take it apart; put the anvil against the bench and push on the handle housing, the anvil should push in and air motor end start to come out. Hold the air motor in and turn it over so the anvil is up (I prefer to put the cover back on so the parts stack on it). Using a tool (punch, etc) push down on the anvil and pull up on the housing, the housing should pull off. The air motor should be a slide fit, but sometimes requires some persuasion, if so, be careful with alignment, it needs to come straight out, if it becomes cocked will be much more difficult. If tight, best bet is to apply some oil, push it back in, repeat until it comes out smoothly.

Once it is out, the impact clutch just connects with splines, so can be lifted off and set aside. The air motor front end plate should lift off, then the cylinder. Now should be able to see the problem, is a vane broken, stuck, they should move smoothly, rust, bearings turn smoothly, etc? Shoot, post pix.

 

[wxm]

That is a private label Astro 135, good gun. Not the most powerful (IIRC ~80ft/lb), but fast and durable.

It is a rocking dog clutch. When you turn the anvil, the clutch engages and it stops, likely the problem is in the air motor, broken vane, bad bearing, stuck from rust, etc.

To take it apart; put the anvil against the bench and push on the handle housing, the anvil should push in and air motor end start to come out. Hold the air motor in and turn it over so the anvil is up (I prefer to put the cover back on so the parts stack on it). Using a tool (punch, etc) push down on the anvil and pull up on the housing, the housing should pull off. The air motor should be a slide fit, but sometimes requires some persuasion, if so, be careful with alignment, it needs to come straight out, if it becomes cocked will be much more difficult. If tight, best bet is to apply some oil, push it back in, repeat until it comes out smoothly.

Once it is out, the impact clutch just connects with splines, so can be lifted off and set aside. The air motor front end plate should lift off, then the cylinder. Now should be able to see the problem, is a vane broken, stuck, they should move smoothly, rust, bearings turn smoothly, etc? Shoot, post pix.

Mine was very tight, I was trying to push the anvil out the way you described but it would not budge at all. I even put the body in a vise with anvil up (well padded on the side of course) and tried to hammer the anvil with a plastic hammer, it showed no sign of outward movement. I started wondering whether I needed to remove the trigger or anything else. Now I know I does come out that way I will try harder tonight... Unfortunately I don't have access to a press, otherwise, I could see pressing it out instead of hammering (feel like I am going it brake it if I apply too much brutal force. )

Thanks again, I will post pictures if making any progress.

 

[Tools R Us]

Likely rust, corrosion. Often heat helps, remove the rubber bumpers and use a torch, keep it away from the trigger area, more on the top side.

 

[wxm]

OK, I have a good news and bad news - after failed to take it apart with pushing, hammering, I decided to give a try with the HF bearing press kit that I acquired a while ago for bearing replacement for my Nissan Maxima, and it worked - I will let the picture speaks for itself...

Now comes to the bad news. As it turned out, the problem does not appear to be due to the rust or corrosion. Instead the rear drive shaft (not sure I am calling it right) is really stuck and hard to spin. It is the piece that has the spline shaft on front end and connects to a bearing to the rear end. The bearing seems to be the culprit. I have a feeling that this might be a defective item from the beginning which explains why it appears to be never used. The question now is whether I should try to buy a spare drive shaft (not sure Sears still selling it as parts), or try to get a bearing (labeled NSK 626z) and somehow press it in. Unfortunately, the either case might cost me more than what I spent on the wrench in the first place. But on the other hand, I'd really hate to waste a otherwise perfect wrench. What would you do?

 

[Tools R Us]

The "drive shaft" part is called the rotor, is it bad? Most often it is just the bearing and 626 bearings are very common, IIRC skate board wheel bearing. The rotor should push out of the bearing with a few taps on a punch, then tap the bearing out of the rear end plate.

 

[wxm]

Oops, I screwed up. While pushing the rotor out of the bearing, I got carried away a little. As a result, I cracked the rear end plate (I think that's what it is called). Fortunately, it is a $9 part from Sears. Just ordered both rear end plate and bearing. After all the "investment", hopefully it will eventually work properly once put back together. Speaking of re-installation, I have a question regarding to the orientation of the cylinder. The cylinder has channels on the top and two small holes. I think one of the hole is for the pin that aligns the front end plate properly with the rear end plate, correct?


Many thanks.

 

[fzj75macka]

why didn't you just bring it into sears for warranty work? Say you don't have the receipt anymore.

 

[wxm]

why didn't you just bring it into sears for warranty work? Say you don't have the receipt anymore.

It is an old stock, don't think Sears sell them anymore, the power tool this old has long passed its warranty period (I think).

 

[Tools R Us]

... Speaking of re-installation, I have a question regarding to the orientation of the cylinder. The cylinder has channels on the top and two small holes. I think one of the hole is for the pin that aligns the front end plate properly with the rear end plate, correct?
...

The two holes are to feed air, one forward, one reverse. When assembling, they need to lineup with the inlet ports on the rear end plate and the kidney ports on the front (towards the impact section). The channel/grooves are for the alignment pin, the one used depends on model, most often it is the one centered between the air feed ports.

The cylinder has differing outside profile in the exhaust area. IIRC one end is full OD, a ridge around the end? That end usually goes towards the front end plate.

My method for assembly is, build/stack all of the parts on the rear cover, lube well with oil, then push the housing on. Everything should slip fit, may want to find what bound and do some deburring/polishing so everything fits smoothly.

 

[Tools R Us]

why didn't you just bring it into sears for warranty work? Say you don't have the receipt anymore.

Most power tool warranties are relatively short, expired long ago.

 

[wxm]

The two holes are to feed air, one forward, one reverse. When assembling, they need to lineup with the inlet ports on the rear end plate and the kidney ports on the front (towards the impact section). The channel/grooves are for the alignment pin, the one used depends on model, most often it is the one centered between the air feed ports.

The cylinder has differing outside profile in the exhaust area. IIRC one end is full OD, a ridge around the end? That end usually goes towards the front end plate.

My method for assembly is, build/stack all of the parts on the rear cover, lube well with oil, then push the housing on. Everything should slip fit, may want to find what bound and do some deburring/polishing so everything fits smoothly.

Got you. Thanks you, Sir! I'll report back once the parts arrive.

 

[wxm]

Success at last.

Got the parts on Friday, pressed the bearing into the rear end cap, put everything together, but still not working. It did not come easy. I had to do a couple of tries to get it work finally. The thing is nice when it works. Comparing to the my 3/8" HF, it is a lot quieter... It might sounds silly, the parts plus the initial purpose price probably cost me more than buying a new one :whoops:, though, I got a lot better understanding on how air gun work and that is priceless... Thanks again for everyone's help, especially Kevin. You are the man!

 

[Tools R Us]

Success at last.
...

Turd polishing!