A Method for Assembling Flex Shafts using Loctite

[Darin Jordan]

I was putting together some flexshafts this past week and thought maybe someone here could benefit from some explanation and pics.

I'm using Loctite 638 this time around. I normally use the thinner 603, but Steven recommended I try this. It's definitely thicker and seems to flow well enough to get down into the cable winds.

I also use the Loctite 7471 Primer, but I know of others who just use Acetone. I'm using both, in this case.

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First, you'll want to cut your cables to the appropriate length. I simply cut mine about 1/4" longer than I want the completed length with a set of heavy duty wire side cutters, then I sand the ends of the cable down on a sanding disc to get it as square as possible:

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[Darin Jordan]

You also want to be sure the clean out your stub-shafts. The process of drilling out the cable end leaves residue and cutting fluids. I use a Q-Tip soaked with Acetone and clean them out well, until the Q-Tip comes out clean and dry. As you can see from the picture, I chuck the Q-Tip up in a cordless drill and use that to assist the process.

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Clearly a lot of residue left behind! Clean this all out.

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Finally, I use some wed-dry 220-grit to clean up the end of the cable. I chuck the cable up in my drill, then rotate it and sand the end until the gold/bronze is gone and the end of the cable is cleaned up.

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Clean up the end using some Acetone to remove any residue and dry it well. You can even use a little bit of heat from a heat gun or ??? to make sure you completely dry out the windings of the cable. When it's all cleaned up, it'll look something like this:

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[Darin Jordan]

With all the parts cleaned up, you can now start assembling.

One topic that came up recently was how to keep everything lined up while the Loctite is setting. The way I do it for a .150" cable and a .130" flex, is to use a piece of 7/32" and a piece of 3/16" tubing, one to hold the stub, the other to hold the cable. They two pieces of tubing slide into each other and will hold them VERY closely inline.

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Put a controlled amount of Loctite onto the last 1/2" or so of the flex, all the way around. Also, put a drop or so into the stub-shaft.

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When you push the cable into the stub, it may "hydraulic" a bit. Make sure you rotate the flex and push in until it's fully seated. Do this slowly so you don't force all the Loctite out, but rather into the cable windings.

You WILL get a little bit of squeeze-out. Gently wipe this off, trying to leave a little right at the top of the stub. It will soak in as the Loctite sets. Just make sure you get it off the sides of the stub-shaft.

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[Darin Jordan]

Finally, making sure that there isn't any overflow of Loctite on the sides of the stub or the cable, slide the stub into the larger piece of tubing and support it vertically using a shop clamp or ???

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Slide the smaller piece of tubing over the flex and partially into the larger piece of tubing to support and center the flex. DO NOT push the flex-shaft support tuning all the way to the top of the stub. Leave it up 1" or so, just to keep it from possibly getting bonded to the assembly.

Set aside and let it setup. I let mine sit at room temperature for a 24-hour period, just to make sure the Loctite if fully cured.

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If all goes correctly, you'll be able to just slide the brass/aluminum tubing off, run some Scotchbrite over the stub and cable, and you'll have a completed Flexshaft, ready to install.

Hope this helps.

[JimClark]

Nice tutorial especially for those of us who are visual learners.

[TRUCKPULL]

Someone should put a sticky on this one

Very well done Darin.

Larry

[JimClark]

Stuck it is

Someone should put a sticky on this one

Very well done Darin.

Larry

[martin]

Darin acetone will indeed clean grease or oil out but I prefer stuff that is made for that job, Loctite 7061 superclean or 7063 superclean.

[Darin Jordan]

Darin acetone will indeed clean grease or oil out but I prefer stuff that is made for that job, Loctite 7061 superclean or 7063 superclean.

That's fine. Probably just a version of Brake Parts Cleaner or ??... The idea is simply to degrease and dry the area and leave no residue.

[monojeff]

Nice job Darin very easy directions to follow.

[Tamelesstgr]

I was curious, I purchased a .187 flex cable with 3/16 propshaft from OSE. I ended up cutting a little more than half of the cable off, I am wondering if I can make a backup cable if I purchase another 3/16 propshaft? I only see 3/16" propshaft for a .150" cable.

[martin]

You use the 3/16" propshaft with the .150" hole, you have to remove the outer winding on the 3/16" flex. The outer winding is removed the depth of the hole, the flex & propshaft is then brazed together. When you remove the outer winding of the flex it leaves the flex at .150" that goes into the hole.

[T.S.Davis]

The benefit of 603 is that its oil tolerant. Meaning that if there is any residual oil left behind in the cable it won't screw u the whole assembly.

Darin, you should maybe do a 3/16 cable with a 3/16 stub. Kind of a PIA.

[T.S.Davis]

Ah, never mind. Martin is on it.

[ray schrauwen]

You use the 3/16" propshaft with the .150" hole, you have to remove the outer winding on the 3/16" flex. The outer winding is removed the depth of the hole, the flex & propshaft is then brazed together. When you remove the outer winding of the flex it leaves the flex at .150" that goes into the hole.

If you do this, is there any benefit to using 3/16" cable when it terminates with .150" anyway??

[Steven Vaccaro]

If you do this, is there any benefit to using 3/16" cable when it terminates with .150" anyway??

Yes because if you notice all the 3/16 assemblies the flex cable is hard soldered the last 1/4 to 1/2" to the prop shaft.

[ray schrauwen]

I'm sorry. I was under the impression that someone was trying to use Loctite for this.

[Steven Vaccaro]

I agree, as far as I know loctite can't be used with those.

[CraigP]

If you do this, is there any benefit to using 3/16" cable when it terminates with .150" anyway??

Of course there is if you braze the two pieces and re-join the outside braids with molten material. It is then centerless precision ground back to 3/16”. I wouldn’t trust a glued assembly in this application. Many do it, but I put my faith in metal!

[martin]

When you braze a 3/16" flex in the method I outlined above both the 150 part of the flex is brazed into the stub hole & the butted part of the 3/16 joint is brazed as well. You simply cant use Loctite on this type of joint where it is 3/16" flex going onto a 3/16" stub. Chopped up pieces of brazing rod along with flux is put down into the bored hole in the stub before inserting the flex prior to heating the assembly, further rod is added at the butted joint to complete the brazing job.

[CraigP]

The chopped pieces is interesting... I use the hole as a molten metal pot, then bring the flex in from the top, slowly heating it as I insert into the hole. There is extra in there that will flow out around the sides, and some of that is what attaches to the outer cut strands. The procedures sound pretty close to me...

[martin]

Yep same sort of idea, you must also keep the torch flame towards the stub & let the heat travel to the flex otherwise you risk getting the flex to hot if you put to much flame directly on the flex for to long & annealing the flex.

[ray schrauwen]

I'm a bit confused, nothing new.

I see three tubes not two for keeping the cable centered.

Can you fill in the blank void in my melon head?

[ray schrauwen]

If Loctite gets higher than the stub it seems to stay tacky. Should I clean it off or leave it? Just one cable I messed up.

[Steven Vaccaro]

clean off any outside of the stub

[rearwheelin]

I have extra piano wire if you need some to make me drive cables lol I actually just threw away brand new wire that I didn’t need lol

[rearwheelin]

I plan on soldering my own just to experiment. I might be Steve’s new supply chain lol