My Shop-Made Slotted Cap Twister

[Wood Doctor]

Each year the loggers I work with break the fuel and bar oil tank caps on their larger Stihl saws by using the T-scrench to twist the slotted caps on and off. These caps are still standard on the MS660 and were used on practically every "0-series" saws of times past. Thousands of these saws run today with these slotted screw-on/off caps, although most new models have been replaced with flippies (much to the chagrin of many new saw owners).

I have concluded that the slotted caps have been broken usually because a T-scrench (or scrench) has been used to tighten and loosen them. This tool works fine for the spark plug, decomp valve, and chain tensioner, but the flat blade is way too small for the fuel and oil caps. That plus the leverage afforded by the T handle sets up huge stress inside the cap. The cap either cracks or the slot gets completely dug out. Once cracked, it leaks like a sieve, regardless of how much it's tightened. Here's my proposed solution:





I started with a 3/16" x 3/4" length of strap steel stock and cut it to 7" long. That extra thickness and width needed to be shaped at the tip to fit the cap snugly, minimizing play. The slot on the bar oil cap is a bit smaller, so I used that as a guide. The handle is actually two pieces of 5/8" thick hardwood, about 1-5/16" wide. I cut a 3/32" deep dado through the center of each half, the same width as the steel blade. Then I drilled a pair of countersunk holes about 2-1/2" apart into the blade and used a pair of 3/4" flathead screws to hold it tight to one side, 4" into the handle. With the blade sandwiched between the halves, I glued and clamped them together. A loose tenon on the end of the handle sealed it all up prior to shaping and sanding. Here's the final fit to the slotted cap:



This handle supplies all the torque I need to twist the caps, and I think the plastic will really appreciate the snug fit--over twice the mass of the scrench's tip. After using it a few times, I have to wonder why Stihl did not offer something like this as an option to the scrench, which has probably destroyed (and sold) more slotted caps than any tool ever conceived. WDYT?

 

[Warped5]

Doc, I like it!

Still not buying a Stihl, though.

 

[Big_6]

The new style slotted caps have hard plastic in the slot, unlike the older caps. As described, the plastic breaks and the caps leak. If you used a wrench on the outside or fitted the spark plug side to the cap, there would be no issue.

 

[old-cat]

Here's the one I made.

 

[Wood Doctor]

The new style slotted caps have hard plastic in the slot, unlike the older caps. As described, the plastic breaks and the caps leak. If you used a wrench on the outside or fitted the spark plug side to the cap, there would be no issue.

I have also used both channel locks and large slip-joint pliers on the caps. However, the drivers shown here (and especially Old Cat's) seem more portable. I may make one of Old Cat's using 1/8" thick scrap stock to carry in my pocket.

I should show you some picks of butchered caps that I have kept through the years as souvenirs. Some actually look like the operator used the scrench to drill a 3/8" hole right through the center.

 

[old-cat]

I saw one on an 028 that was broken from too much force.

 

[Marshy]

So now I have to carry a file, a scrench, and a gas/oil cap tool now too to operate a Stihl?? No thanks, I think I'll stick with Husqvarna. BTW, I've never has a cap leak that had a good oring, and Ive never had to tighten them more than hand snug unless the o-ring was bad... see where Im going?

 

[Wood Doctor]

Old Cat has motivated me to post my first attempt that was even simpler. This one uses a 2-1/2" length of 1/2" angle iron sandwiched between two halves of hardwood:




LOML said she liked this one the best, but I was afraid that it would supply too much leverage. However, it also boasts a much larger tip mass than the scrench, so it will likely work well also. It's a little easier to make, but not much. Likely the angle iron could be replaced with strap steel stock for easier joinery.

 

[sawfun]

The Husky 346 caps break even easier. Mine did in just a few months and it wssn't over tightned.

 

[Wood Doctor]

So now I have to carry a file, a scrench, and a gas/oil cap tool now too to operate a Stihl?? No thanks, I think I'll stick with Husqvarna. BTW, I've never has a cap leak that had a good o-ring, and I've never had to tighten them more than hand snug unless the o-ring was bad... see where I'm going?

Problem is, Stihl stuck about 100 thousand decals on their saws that showed a scrench tightening the caps. Operators see that decal and assume that's what they are supposed to do. Many of these operators have big biceps and strong wrists. The caps can't take that when the scrench's tip is only about 5/16" wide. It gets worse when the scrench's tip is off center when the torque is applied.

 

[Marshy]

Problem is, Stihl stuck about 100 thousand decals on their saws that showed a scrench tightening the caps. Operators see that decal and assume that's what they are supposed to do. Many of these operators have big biceps and strong wrists. The caps can't take that when the scrench's tip is only about 5/16" wide. It gets worse when the scrench's tip is off center when the torque is applied.

Husky was smary enough in their early design to mold the hex pary of the scrench into the cap that way you cant really strip it. However, it becomes easy to overtorque it and break it with the extra leverage. I've replace those older caps with the ones that come on their consumer saws being sold at home depot and found those caps have a little extra material on the cap and you can take them off easier. I still dont have an issue where I need to use a scrench, regardless.

 

[Rockjock]

I have a wider bladed stubby screwdriver that I use much like this one. I would think you could take a larger bladed screwdriver and cut it down to a more user friendly size

I do like wood doctors solution. I find that handmade tools have much more character!

 

[jughead500]

I have a wider bladed stubby screwdriver that I use much like this one. I would think you could take a larger bladed screwdriver and cut it down to a more user friendly size

I do like wood doctors solution. I find that handmade tools have much more character!

Handmade stuff shows that your a pro at what you do.of course i haven't been able to build a better scag or anything but i can make better stuff a little bit better. just like you guys.

 

[Wood Doctor]

I have a wider bladed stubby screwdriver that I use much like this one. I would think you could take a larger bladed screwdriver and cut it down to a more user friendly size

I do like wood doctor's solution. I find that handmade tools have much more character!

I thought about that stubby (as you can probably expect). Ruining a good screwdriver or a 1/2" wood chisel seems pointless. They were never designed for twisting chainsaw caps, and the tip of the stubby is still too small, even if you grind it down in half. And the little handle is too small for twisting. Try doing it with warm gloves on. Stihl just plain blew it when they recommended the T-scrench for their slotted caps.

 

[Rockjock]

I thought about that stubby (as you can probably expect). Ruining a good screwdriver or a 1/2" wood chisel seems pointless. They were never designed for twisting chainsaw caps, and the tip of the stubby is still too small, even if you grind it down in half. And the little handle is too small for twisting. Try doing it with warm gloves on. Stihl just plain blew it when they recommended the T-scrench for their slotted caps.

Naa you go to the dollar store buy a cheap large slot screwdriver and go to town LOL or ya go flippy cap

 

[Wood Doctor]

Naa you go to the dollar store buy a cheap large slot screwdriver and go to town LOL or ya go flippy cap.

Unfortunately, RockJock, you cannot go flippy cap with a saw outfitted with twist caps. Flippies do not work with the case threads. So, thousands of saws have slotted caps being broken with T-screnches on a regular basis.

 

[Nitroman]

Each year the loggers I work with break the fuel and bar oil tank caps on their larger Stihl saws by using the T-scrench to twist the slotted caps on and off. These caps are still standard on the MS660 and were used on practically every "0-series" saws of times past. Thousands of these saws run today with these slotted screw-on/off caps, although most new models have been replaced with flippies (much to the chagrin of many new saw owners).

I have concluded that the slotted caps have been broken usually because a T-scrench (or scrench) has been used to tighten and loosen them. This tool works fine for the spark plug, decomp valve, and chain tensioner, but the flat blade is way too small for the fuel and oil caps. That plus the leverage afforded by the T handle sets up huge stress inside the cap. The cap either cracks or the slot gets completely dug out. Once cracked, it leaks like a sieve, regardless of how much it's tightened. Here's my proposed solution:





I started with a 3/16" x 3/4" length of strap steel stock and cut it to 7" long. That extra thickness and width needed to be shaped at the tip to fit the cap snugly, minimizing play. The slot on the bar oil cap is a bit smaller, so I used that as a guide. The handle is actually two pieces of 5/8" thick hardwood, about 1-5/16" wide. I cut a 3/32" deep dado through the center of each half, the same width as the steel blade. Then I drilled a pair of countersunk holes about 2-1/2" apart into the blade and used a pair of 3/4" flathead screws to hold it tight to one side, 4" into the handle. With the blade sandwiched between the halves, I glued and clamped them together. A loose tenon on the end of the handle sealed it all up prior to shaping and sanding. Here's the final fit to the slotted cap:


Because it sells a part.

This handle supplies all the torque I need to twist the caps, and I think the plastic will really appreciate the snug fit--over twice the mass of the scrench's tip. After using it a few times, I have to wonder why Stihl did not offer something like this as an option to the scrench, which has probably destroyed (and sold) more slotted caps than any tool ever conceived. WDYT?

 

[fearofpavement]

Curiously, I've never encountered a broken Stihl screw on cap. I've seen broken caps on Huskies and Poulans (mostly tabs broken off) and I had one Stihl that the oil cap slot was all boogered out but the cap itself was still fine for hand tightening and loosening. Never had a cracked Stihl cap. Now, the very next Stihl I get will have a busted cap I bet... I do have experience with a lot of leaky and broken flippy caps on the Stihls. Also a lot of Huskies with leaky caps.

 

[Rockjock]

Ok I have the answer drill out the centres of the cap, insert the splined shaft then affix this to it.

They can be painted whatever colour you like No issues with gloves either

 

[Rockjock]

Curiously, I've never encountered a broken Stihl screw on cap. I've seen broken caps on Huskies and Poulans (mostly tabs broken off) and I had one Stihl that the oil cap slot was all boogered out but the cap itself was still fine for hand tightening and loosening. Never had a cracked Stihl cap. Now, the very next Stihl I get will have a busted cap I bet... I do have experience with a lot of leaky and broken flippy caps on the Stihls. Also a lot of Huskies with leaky caps.

I had one just today. I used epoxy to fill the slot and it is as good as new. Hand tightening is all that is needed on that saw. Echo cs 400 oil cap was lost and customer used a stihl one.