How To Mod Your Impact Wrench for More Torque

[vegasjetskier]

NOTE: Try this at your own risk. We assume no responsibility or liability if you or someone else gets hurt or you cause property damage by following these instructions.

About 20 years ago I bought a Campbell Hausfeld 1/2" drive impact wrench that is rated at 240 ft-lbs. I thought I was set, but it didn't take long to realize that it wouldn't take the lug nuts off my car. It quickly became a paperweight.

As I was taking off my Volvo wheels with my breaker bar for the 50th time the other day, I thought it sure would be nice to have an impact wrench to do this job. I remembered the old wrench and thought if only there were some way to increase its torque I might have a use for it again. So I decided to take it apart and look for ways to improve it. It turns out the air flow through the tool is very poor - the passages are convoluted and small. Time to open them up.

I tested the wrench on my car before and after the cylinder and endplate porting. I used my S80 lug bolts torqued with a torque wrench to 105 ft-lbs. Before modding the wrench would just rattle on the bolt. After modding the bolt instantly came flying out of the wheel and fell on the ground. Success! I already had the tools and supplies needed. Total cost - ZERO.

Here's what I did. You don't need to do all of it to improve the torque - most of the gain is in the cylinder and front endplate porting. If you want you can do that and skip the rest and will probably still get satisfactory results.

This is for the Campbell Hausfeld TL1002 impact wrench. There are other brands that use the same design. I believe Harbor Freight sells a clone for $20 (less when it goes on sale): http://www.harborfreight.com/cpi/ctaf/d ... mber=95310). I'm sure the principles apply to other similar designs also.

The "before" parts you see in some of the pics are from a different gun, but are very similar to the TL1002 so that you will get an idea of what it "used to be like."

Tools you will need:

Dremel tool and grinding bits.
5/32" Allen wrench.
3/32" Allen wrench (optional).
Adjustable wrench (optional).
X-Acto knife (optional).
Drill and bits (optional).
Disc brake cleaner or soap and water.
Rags or paper towels.
10 weight air tool oil.

Start by using the 5/32" Allen wrench to remove the rear cover plate:

Impact Wrench Mod Remove Rear Cover.jpg (90.11 KiB) Viewed 26282 times

Be careful not to damage the paper gasket when you remove the cover.

Now lift out the front endplate and bearing, then pull out the rotor with the vanes, and finally the cylinder.

Here's a before and after pic of the cylinder:

Impact Wrench Mod Cylinder Ports Before and After.jpg (123.88 KiB) Viewed 26347 times

Use the Dremel to grind the cylinder ports into this new shape on the front.

Impact Wrench Mod Ground Cylinder.jpg (117.46 KiB) Viewed 26337 times

I made a mistake on mine and removed too much metal in one area. I suggest that you grind your ports to approximate the blue lines shown in this photo:

Impact Wrench Mod Cylinder Port Revision.jpg (116.15 KiB) Viewed 26302 times

Use the dremel tool to grind the cylinder like this on the back:

Impact Wrench Mod Ground Cylinder Back Side.jpg (104.11 KiB) Viewed 26308 times

Open up the exhaust ports on the cylinder til they look like this:

Impact Wrench Mod Enlarged Exhaust Ports.jpg (108.11 KiB) Viewed 26317 times

Here's a before and after of the endplate:

Impact Wrench Mod Inlet Port Before-After Comparison.jpg (115.38 KiB) Viewed 26300 times

Grind the end plate until it looks like this (you can use a drill to remove most of the metal first if you want):

Front view

Impact Wrench Moc 014.JPG (225.86 KiB) Viewed 26284 times

Rear view

Impact Wrench Moc 013.JPG (207.84 KiB) Viewed 26279 times

If you want you can stop here and cut the gasket to fit the new ports, then clean everything up and put it back together. You should have a sufficient amount of torque to remove the lugs now. Be sure to lube the parts with 10 weight air tool oil.

I kept going with more mods because I want to develop enough torque to remove the crankshaft pulley nut when I need to change my timing belt. You don't have to do all of them as each one will enhance the airflow somewhat. Just mix and match if you want. Here are the rest of the mods:

Remove the power regulator:

Impact Wrench Mod Remove Power Regulator Knob.jpg (97.05 KiB) Viewed 26310 times

And enlarge the biggest (#4) hole. Also cut out the two ribs on the sides of the cover plate. (The pin in the center of the photo will be covered later):

Impact Wrench Mod 021.jpg (107.58 KiB) Viewed 26304 times

Use the adjustable wrench to unscrew the inlet fitting and remove the valve components:

Impact Wrench Mod Valve and Inlet Parts.jpg (83.85 KiB) Viewed 26302 times

Use the X-Acto knife to cut out the center of the rubber seal to the same diameter as the hole in the metal seat it sits against. Also, use the Dremel tool to remove material from the trigger pin in the areas shown in the photo (this improves airflow through the valve):

Impact Wrench Mod Seal and Trigger Rod Modifications.jpg (105.33 KiB) Viewed 26293 times

From here on you will need to completely disassemble the wrench so you can clean out all the grinding debris before reassembling it.

Push the impact mechanism and rear endplate out of the housing by pushing on the square end (where you connect sockets) of the anvil.

This is what the impact mechanism looks like:

Impact Wrench Moc 028.JPG (211.96 KiB) Viewed 26280 times

Here's a view of the impact mechanism parts:

Impact Wrench Mod Hammer Mechanism Parts.jpg (101 KiB) Viewed 26290 times

Use the 3/32" Allen wrench to remove the screw at the front lefthand side of the tool. Be sure you don't lose the spring or plunger that are in the hole. Push the reversing valve out the back of the tool:

Impact Wrench Mod Removing Reversing Valve.jpg (112.61 KiB) Viewed 26283 times

Grind away the top of the two air pressure holes to match the bottom edges of the endplate and cylinder:

Impact Wrench Moc 016.JPG (85.26 KiB) Viewed 26281 times

This is what it looks like when all the parts are matched up:

Impact Wrench Moc 023.JPG (203.38 KiB) Viewed 26287 times

You can drill out (enlarge) the two air pressure holes. Just drill down to the current depth or you will break through into other ports:

Impact Wrench Mod Enlarge Air Pressure Holes.jpg (102.67 KiB) Viewed 26290 times

Use the X-Acto knife to cut the paper gasket to match the new porting:

Impact Wrench Moc 031.JPG (217.55 KiB) Viewed 26274 times

The route for the exhaust air is very restrictive and contorted, so I decided to drill through the casing right above the cylinder exhaust ports to vent the air straight to atmosphere. Be aware that if you do this mod dirt will have a direct path to get into the cylinder so you might want to keep the wrench in a toolbox or cover the ports with tape when it is not in use. Also, when using the wrench, make sure that you aim the ports AWAY from any people or animals so they don't get hit with shrapnel if the rotor frags. It will also be VERY loud. Here's a pic of the holes I drilled (I know, it doesn't look great, but hey, I'm not a machinist. ):

Impact Wrench Moc 019.JPG (198.46 KiB) Viewed 26283 times

Here's a pic that illustrates why the porting works to increase torque (this shows the "reverse" direction, which is where we want the most torque for removing those stubborn nuts and bolts):

Impact Wrench Moc 032.JPG (119.02 KiB) Viewed 26317 times

Make sure you debur all your cuts, then clean the parts with disc brake cleaner or soap and water to make sure you get all the grinding debris completely out of the tool and parts. If you use soap and water, immediately dry and put a thin coat of oil on all steel parts so they don't rust.

Reassemble the tool, putting a thin coat of 10 weight air tool oil on all moving parts. Pour several drops of oil into the inlet while holding the trigger open.

Here's a diagram and parts list if you forgot where something goes:

Note: DO NOT run the wrench wide open with no load on it because it could overspeed the rotor, causing it to disintegrate.

That's it for the mods to the wrench.

In addition you can do the following to improve airflow to the gun:

1. Use a 1/2" diameter hose (http://www.harborfreight.com/cpi/ctaf/d ... umber=3107).

2. Use "highflow" quick-connects (http://www.harborfreight.com/cpi/ctaf/d ... mber=65894, http://www.harborfreight.com/cpi/ctaf/d ... mber=97631).

This pic shows the difference between a highflow fitting and a regular one. The highflow is on the left. Both of them have 1/4" NPT threads on the other end. Since the loss through the fitting is inversely proportional to the fifth power of the increase in diameter, doubling the size will mean that the highflow fitting will only have 3% of the resistance of the standard fitting:

004.JPG (200.56 KiB) Viewed 26274 times

3. Connect the hose directly to the compressor regulator or air tank (no quick-connect at the compressor, just put a quick-connect on the end of the hose). This eliminates one set of fittings that increase resistance and reduce airflow.

Have fun with your "new" gun!

Edited 6/24/2009 to include "before" photos.

[matthew1]

Wow, very interesting Vegas. I don't have a gun, but when I get one I'll try this.

Can't help but think I'll want to do this when the mod is done:

[FCPEURO]

Wow! Excellent write up!

You know you are a true car guy when you think to modify your tools too.

[midyrp]

Brilliant !!! Thanks !!!
It was the only tool I regretted buying. I only did the first part, and now at least it handles 'normally' torqued wheel nuts.