Start with a Harbor Freight Chain Breaker.

Take it all apart and get your drill press out.

Drill out the parts shown:



Toss the bits that have the X next to them into your junk drawer.

Put it back together as a cotter press. Don't forget to grease the threads:


You will have 2 pushers that go in from the inner side. One is a spare in case the thin part breaks. I doubt it. It's got to be stronger than the cotter threaded part and because of the way it is built should not twist inside the tool.

Place tool over cotter/crank and tighten outer bolt until the pusher touches down:




Press out cotter using inner bolt:

Sweet!

Just to be sure I wasn't clear above, the hole that is drilled out to 31/64" is NOT the part that the larger bolts thread into but the part that the little cup threaded into at the far side of the chain breaker. This has to be drilled out so that the cotter dumb end fits into it and has somewhere to move into when it is pressed out.

I drilled mine out to 31/64 because it it looked "about right."

The mouth of the big bolt has to be drilled out to 21/64 because that is the size of the collar of the "pushers" which will get put back into the outer bolt from the other end. If the hole is left small the pusher will not go in far enough because of the collar and there isn't enough room to fit onto the crank.

DO NOT try and just use the pusher in the way the chain breaker uses it. It will fall off the threaded part of the cotter and destroy the threads. I tried doing this while I was messing around and almost ruined the cotter in one of my bikes before I noticed what was happening. One you drill out the receiver cup threads it is ruined for use as a chain breaker anyhow. Might as well finish out the mod and drill the big bolt too.

The pusher has a dimple in it because it is designed to use that little ball bearing with the chain breaker. It happens to fit over the cotter perfectly and many of the better cotters have a dome built into them so they work with a cotter press with a dimpled end on it.

Brilliant!!

Very cool, I might have to get one even though I don't need one.

Nice, thanks for sharing!

Excellent!

Best re-use of a tool I've seen in a long time.

If you can't afford Mark's tool, this is the way to go.

-Kurt

I did this a while ago.

Just a caveat - there wasn't enough clearance to get it over the cotter of a Peugeot mixte I was working on. Yet another reason to hate the French.

What did you use to drill out the chainbreaker?

I needed a reason to run to Harbor Freight.

I don't need a reason...

I think that it would be possible to grind a bit of a notch on the bottom to allow the cotter a little more clearance -it would make this tool look a little more like the bikesmith version. I'm sure the jaw length is big enough for most any crank, it's just teasing the bits onto the crank and over the bits of the cotter that stick out. It's probably necessary to unscrew the pusher part entirely to get it over some cranks/cotters and then screw it back in. Kind of a PITA since the pusher will want to fall out of the end of the bolts as nothing is holding it in. I wouldn't say that this version is quite as nice as the BikeSmith one but I bet it works just as well once you get it teased onto the work.

Just a thrift tip toyounew Harbor Freight shoppers. Always download a 20% off coupon and a free item with a purchase of at least 19.95, even if you don't want the free item, donate it to the thrift store of your choice. HF accepts computer printed coupons. I keep a stack of them in my car.

I used a 1/2" hand drill moter in a vise. I wouldn't suggest you do this unless you have some experience running a drill for fabricating stuff. I'm an electrician so I've done more of it than I'd like to admit out in the field -often using my feet as a vise. I did have the help of a step-drill (unibit) to help me get it close and then I cleaned it up with the appropriate bit the rest of the way.

A drill press with a good press vise would be best but it CAN be done without it. I don't take any responsibility for broken/bent bits and/or wrists if you don't heed this warning

+1 on the free coupon item. They usually are pretty nice items like decent leather gloves or those little LED aluminum flashlights. I'm a card-carrying insider-club member too because I bought an air compressor and the savings paid for the membership that first purchase.

More good business from the Chi-com Outlet - Love it and thanks for the pics...

Great idea, looks super strong.

I've been on the fence for quite a while about buying the bikesmith cotter press. Now I would be absolutely stupid not to get/make this.

The last time I went to a retail store the price of this chainbreaker was $19.99 but HF prices go up and down almost daily. I bought mine for $8.99 or 9.99 on a whim. I've seen it as high as $24.99 I try to only buy stuff HF when it is on sale. Then again I end up buying a lot of junk that I probably don't need just on the theory that it is on sale NOW and if/when I do need it it'll be expensive the day I go to get one. The HF I go to is about a 40-minute drive out into the burbs from my house with traffic and at least one toll on the "free"way so when I go I usually end up spending at least an hour searching for stuff that I might need or is on sale and rarely get out of there without spending at least $50 -usually closer to $75. So I guess that strategy works.

The chainbreaker I used for this conversion was bought and promptly lost in a pile of crap and was still in its original packaging as I had never even opened it up. I had been thinking of this conversion for a while now and was looking for the thing off and on for weeks if not months. I have a really nice professional motorcycle chain breaker (that also works well on cotters although it is a pita to set up as it comes in a plastic case and only fits inside the case when it is all disassembled) so I really didn't need to buy this although it WAS cheap. Now I have a dedicated cotter press that can be stored with my bike tools

I have not tried this but someone, I think Jur, reports that cotters can be pressed out with a C-clamp and a socket. I use BikeSmith's but I got this before I read about the C-clamp and socket.

If you come up against a recalcitrant cotter, the c-clamp will yield first. (been there done that).

The C-clamp method works with an older quality C-clamp. I wouldn't try it with some of the newer cheapo chinese cast C-clamps. Those will snap if you just drop one unloaded onto a wood workbench from more than 12" inches. Drop one on a concrete floor and they shatter into multiple pieces.

the other problem with a C-clamp is the thread pitch. A C-clamp has a very coarse thread pitch of like 6-8 threads per inch where a good press like the wheelsmith or even this Harbor Freight conversion will have something on the order of 25-30 tpi or more. That is just leverage. With more TPI you have a ton more leverage for each thousandth of an inch you need to move the cotter until it gives way.

Update:

I just used this press on a '72 lady Sports with a TON of rust on it. The cranks and spindle were a bit rusted and (I really don't see this that often) rusted cotters. The bike was left outside for years and the rims were so badly rusted that OA isn't even putting a dent in them.

The cotters came right out using this press without any effort or fuss at all. I don't think I put more than 40-50 ft/lbs into the 3/8" ratchet wrench I was using with a 14mm socket to operate the inner bolt on the "cotter press."

The time to set this press up is minimal compared to my Motion-Pro chain tool.

Because of the modifications and the way it works the "pusher" will just fall out of the outer bolt when the tool is not mounted so I store it inside the tool installed backwards (the way it went into the tool before it was modified to be a cotter press.) The only set-up required to use this tool is to remove the bolts and pull the pusher out of inside of the two. Place the press over the crank & cotter. Reverse the pusher and screw the bolts/pusher back into the tool being careful not to let the pusher fall out onto the ground. Once the pusher and the outside bolt seats onto the cotter you can tighten the inner bolt by hand until it hits resistance. At this point the tool is ready to use. Turn the inner bolt with a 14mm socket (or combo box/open-end wrench) about 4-5 turns and the cotter pops right out.

The converted tool works even better than I had hoped. Maybe I'll make a video the next time I pull off some old cotters. I've got the 60's-era Flying Jet to do next. That should be another good test of the tool. So far I've removed 3 cotters and all of them were smooth as butter.

What did mechanics use in the heyday of cotters? I am under the impression that they used hammers, but maybe not.

Every shop I worked at had some sort of ancient cotter press
But we did use a hammer and a punch to remove them. We never reused pins.