# Camjack Knurler



## Hawkeye

Okay, guys. A couple of months ago, I mentioned a Project-in-Waiting  that I called a Camjack Knurler. When you invent something, you're  allowed to make up words, too. It came about because I had checked out  several sites on clamp knurlers. Most seem to use a 6 mm threaded shaft  to apply pressure, but some commented that it didn't have enough force  for steel. This tool has plenty of pressure, easily controlled.

Members of this forum may use this principle to build their own, but, of course, may not profit from my design. 

Here's a look at the finished product in use, mounted in the QCTP. The bar on the top with the 1/4" jack screw is the camjack. When the tail is raised with the jack screw, the camjack pivots around the opposite end and pulls up on the 1/2"-20 main screw. It provides more than 5 to 1 mechanical advantage. The knurl arms are pivoted farther away from the roller ends than normal. This unit is designed for up to 2" knurled work.



Jumping back to some of the construction details. The bottom bar and the camjack are clamped in the vise with a piece of 3/8" aluminum between them to plunge-mill the depressions for the 3/4" main screw pivot blocks.






The axles for the knurls were turned from a pair of 5/16" grade 8 bolts.



The complete tool is set up for the test cut. The 1/2"-20 main screw works well with a lug nut as the adjusted. This is turned hand-tight once the crossfeed is centered on the work, with the camjack all the way down. Then the jackscrew is tightened with the work oiled and the lathe running at knurling speed. Enough pressure can be applied by hand that I may just add a knurled top on the jackscrew.



I'm quite pleased with the way it works. This will, of course, be the main screw nut. It has to have a knurled one, doesn't it? (See the top photo.)


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## hq308

Nice job Mike.

I especially love the wheel nut you used temporarily on the main screw.


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## Highpower

Mike, that is one _heavy duty_ knurler! I know that puppy applies some serious pressure to those rollers, because I have a different tool that uses that principle for separating the taper on ball joints. When they let go, they do it with a BANG!

Great job, and great idea.  Well done Sir!

View attachment 667


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## Hawkeye

Sorry, Mayhem. No plans. Just a basic CAD sketch to work out a few ideas. Funny thing was, I zoomed in on the layout I wanted and printed Display onto an 8 1/2 x 11 sheet. When I laid the L-shaped mounting arm on it, it fit exactly. All I had to do from there was measure off the drawing. Nice when a 'plan' comes together.

For reference, the arms are 1" x 5/8" bar stock 5" long. Material is MU (Magnetic Unknownium - not to be confused with the nastier Ferrous Unknownium). The knurls were taken from my cheapy bump knurler.


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## joesmith

*Congrats*

Nice design and execution.  I intend to copy it.  I have worn out the bump knurlers that came with my toolpost sets,  The knurls don't like stainless.
Joe


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## Hawkeye

Okay, Mayhem, here's the individual pieces of the knurler. It's a bit more work to post without the buttons, but I'll try.

All of the pieces are shown. I did try a spring on the main threaded shaft, but it kept getting jammed up in the slots, even with washers in place.



The threaded parts. The jackscrew is not shown in this one. The main shaft is 1/2 - 20. It's swivel is threaded and held in place with strong threadlocker. A smaller shaft diameter would likely work, but I wouldn't go any smaller than 3/8". Fine thread is recommended.



The mounting arm was the first part made, some time ago. Most clamp knurlers are completely on the work side of the toolpost. I figured longer arms pivoted from behind the post would give better control.



The arms are 5" long. The bottom one has a 3/4" diameter swivel groove. Both have 1/2" slots to allow the main shaft to swing to suit diameters of work up to 2". The upper arm has a 3/16" diameter slot for the camjack fulcrum.



The key to the power of this knurler is the camjack. The fulcrum is a piece of 3/16" music wire welded into a milled slot at the end. The end of the jackscrew is rounded to allow it to move on the flat surface of the upper arm.



Final parts include the knurled (of course) main shaft nut, diamond knurls and the upper shaft swivel.



Have fun making your own version of this tool. I'm very pleased with the way it works.


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## Splat

Mike/Hawkeye(MASH, in my top 3 tv faves! )  thanks for posting this! Once I get my lathe I need to do some serious knurling so I'm going to try to build this. It's a Franken-knurler!


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## bcall2043

Hawkeye said:


> Okay, guys. A couple of months ago, I mentioned a Project-in-Waiting that I called a Camjack Knurler. When you invent something, you're allowed to make up words, too. It came about because I had checked out several sites on clamp knurlers. Most seem to use a 6 mm threaded shaft to apply pressure, but some commented that it didn't have enough force for steel. This tool has plenty of pressure, easily controlled.
> 
> Members of this forum may use this principle to build their own, but, of course, may not profit from my design.



Hawkeye,

Thanks for the design. It's a great idea. I put it on my list of want-to-builds. I don't know how I missed it when first posted.

Benny


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## swatson144

Hawkeye and I discussed me releasing a set of drawings for this and he was gracious and generous enough to say go ahead with a few common sense exclusions !not for commercial use! Use at own risk.

I'm not quite ready to release the drawings yet. Things are moving a little slow in testing them since I had a hernia repaired and my gall bladder removed 2wks & 3 days ago. The doctor allows me to lift 15#s now but that still leaves me using the HF drill press vice. I just want to make sure that if someone orders material and the parts don't fit it's their own dang fault and not the drawings.




It is so much like clamping work on the table with that vice.




Here's is what I have done so far sitting on full size drawings.

Steve


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## churchjw

Really nice job on this.  I bought one of these a few years back.  Big mistake I should have just made one.  Maybe your post will inspire me to make a new one.  I like your design better than the one I bought by miles.  

Jeff


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## Hawkeye

I'm looking forward to a few guys building their own. I'd like some feedback on how they work for you. I was impressed with the fact that I could force the knurls into the steel by turning the jack screw with my fingers.


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## swatson144

I got far enough along that I do not feel there are any insurmountable problems with the drawings. they are currently available here . As yet untested use at own risk etc. I will put it in the downloads section here on the forum when I have it in final form.

Hopefully my shoulder bolts will arrive today and I can finish it up and test it out and make updates to the drawings, finish the notes and post it. The 3/16" ball end cutter arrived. I probably should have just used bolts like Hawkeye (perhaps why he did?). Definitely should have procured the odds n ends before starting. It's just that I didn't consider them that odd to be NC, or NIS everywhere local.

It is sorta astounding what pieces one may need for a small project that can't be easily found locally in a city as industrial as this one. A lot of I can order it for you, or they come in a box of 25. 

Steve


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## swatson144

It's finished. The first test didn't go so well but it is assuredly my fault as the tool behave perfectly. Actually it behaved as if it was 4X strength of what was needed to do the job. 




The knurling is not right but it is deep and there was no problem to the tool. I haven't much practice or experience at knurling as it just wasn't called for a lot in the navy. Most likely something stupid I'm doing. Frankly I just stuck it on the lathe to let the green loctite set up and then got carried away. 




Seen from the centerline you can tell the tool is still a little high and the tool holder is bottomed out on the compound on my 12x36. when I get around to it I'll likely change the mount to be more of a sideways T than a sideways L. 

Even though I'm only using an AXA and the 1/2" mount is plenty strong using a 5/8" plate will give enough clearance for the height adjusting wheel on the holder. 9/16" also. I shimmed it out .030" for clearance 

I went with a 5/16" x 24 TPI on the cam (jack screw) simply because it looked more to scale with the other pieces.

I tend to make tooling and not spend a lot of time on the aesthetics. I never know when they will work as desired, and I figure once they prove to work well, I'll go back and make them pretty. Perhaps some day I will. So far not so much.

I'll update the plans and notes  http://www.totallyscrewedmachineshop.com/projects/camjackknurler/camjack.html 

Steve


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## ScrapMetal

swatson144 said:


> I got far enough along that I do not feel there are any insurmountable problems with the drawings. they are currently availablehere. As yet untested use at own risk etc. I will put it in the downloads section here on the forum when I have it in final form.
> 
> Hopefully my shoulder bolts will arrive today and I can finish it up and test it out and make updates to the drawings, finish the notes and post it. The 3/16" ball end cutter arrived. I probably should have just used bolts like Hawkeye (perhaps why he did?). Definitely should have procured the odds n ends before starting. It's just that I didn't consider them that odd to be NC, or NIS everywhere local.
> 
> It is sorta astounding what pieces one may need for a small project that can't be easily found locally in a city as industrial as this one. A lot of I can order it for you, or they come in a box of 25.
> 
> Steve



Thanks to both of you for making the plans available.  I've got too many things on my plate right now but I will surely make one of these in the near future as I really like the design.

-Ron


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## Hawkeye

It doesn't matter what type of knurler you use. It still comes down to matching the work piece diameter to the pitch of the knurls. Get the diameter off and there's no way you will get a good finish. Get it off just the right amount and you will make a good fine pitch using a medium-pitch knurl set.

Steve, your camjack looks nice and solid. It should work very well for you.


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## swatson144

N = (pi ) (dia) (tpi) 

N is the number of lines your knurl will make on the circumference of your part. TpI is the pitch of the knurl. In the unlikely event N is a whole number knurl away.

If N isn't whole say 14.4

diameter change = n (right of decimal .4) / (pi)(tpi)

Seems to be the common method. 

There also seems to be thoughts that if it is slightly off a whole number the knurls will follow if set deeply and well lubed, probably about like mine did since I did no math, nor dust blowing or lube.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=1759&PMITEM=01295203&PMCTLG=00 and go to page 1752 for MSC's reference on knurling

Steve


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## November X-ray

Steve - I think you will get better results when you do use lube (or something) to flush the knurls clean with. I know with mine it makes noticable difference with flushing vs without!


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## swatson144

I finished my paying job so I got another run at it.




Turned out good enough for the 2nd try. Seems to need a little practice getting the tension right since you can put so much on it. seems to be nothing set in granite about this, just like playing music you just monkey around and practice, eventually the station will be in nice and clear.

Steve


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## Hawkeye

If you're wondering about the pitch of your knurls, take one out of the holder and slip a shaft through it. Roll it in a straight line along a piece of paper on a flat surface. there will be enough oil on it to leave a print of the ridges. Next, draw a straight line along the path you printed, parallel with the direction of travel. Mark one knurl line where it crosses this line and another 1", 2", 5", 10" (or whatever) further down - longer is better, until you meet up with a clear intersection where knurl, horizontal line and inch mark come together. Count the knurl lines, not including the first one. Divide by the number of inches to get lines-per-inch.

If you divide 1 by the lines-per-inch number and record it, you can make up a table to keep in the shop with a number of workable diameters on it. Here's the chart I keep in the shop for my particular knurls. It will only work if yours have the same pitch as mine.


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## jayman

Nice job! Nice idea! Looks pretty cool! Have you tried it with straight knurls?


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## swatson144

No Sir I haven't. Truth be known I haven't had a need to knurl anything since, but the tool is there, the math is there and I am sure this will meet my knurling needs.

I speculate on pure conjecture that to do good straight knurls one would require knurls of the right pitch for the diameter of the work or vice versa. However to straight knurl to increase the diameter of a shaft to turn down to a bearing size would be simple. This tool would work well.

Steve


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## Hawkeye

I haven't tried straight knurls either. Some day, I'll order a set and try them out.


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## jhamm

Hawkeye said:


> I haven't tried straight knurls either. Some day, I'll order a set and try them out.



The  Accu-Track website at http://accu-trak.com/holders_bump.html shows the following diagram, which says to use a single knurl die instead of a pair, when straight-knurling.  Seems to me you could either not worry about it (ie go ahead and use two straight knurl dies in the scissors knurling holder) or use a plain (smooth) roller on one side. Or perhaps somehow synchronize the dies. Has anyone tried the holder for straight knurling?


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## Jim2

I've done a couple of straight knurls using two knurl wheels.  It's worked fine the handful of times that I've done it, but I've only ever tried it in brass.  I don't really do much knurling, so it could be just dumb luck!

Most recently did these 1/2" diameter nuts for my new knurler (no, not a camjack--sorry!).






Jim


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## jhamm

Jim2 said:


> Most recently did these 1/2" diameter nuts [using 2 straight knurl wheels] for my new knurler (no, not a camjack--sorry!).
> Jim



It looks like they turned out fine.  BTW, did you invent that method of locking the axle pins in place, or was it on a set of plans?  I assume the aluminum or steel bar stays down and in place during operation even if the brass nut loosens up.  Have you noticed any other pros or cons to that pin-locking method?


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## Jim2

jhamm said:


> It looks like they turned out fine.



Yeah, I don't know as they'd look any better any other way.




jhamm said:


> BTW, did you invent that method of locking the axle pins in place, or was it on a set of plans?



Well, I'm not exactly sure!  I know someone else had the idea of cutting the gash in the pin and tightening a small flat to hold it in place.  I don't know as that person had an angle on the end, but it seemed like a good way to do it so that the flat would be easy to hold in place while tightening the knurl-nut.  

I looked at a lot of knurlers before I made mine.  I like to give credit where it is due, but I just can't remember where I saw it now.




jhamm said:


> I assume the aluminum or steel bar stays down and in place during  operation even if the brass nut loosens up.  Have you noticed any other  pros or cons to that pin-locking method?



I haven't really used it much yet--just finished it a few weeks ago.  The bars don't really seem inclined to move.  It seems like a relatively simple, trouble-free way to hold the pins in place.

Jim


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## jhamm

Jim2 said:


> I've done a couple of straight knurls using two knurl wheels.  It's worked fine the handful of times that I've done it, but I've only ever tried it in brass.  [...]
> Jim



I see that the question of straight knurling with a scissors clamp has come up before, in a August 2011 knurling thread,  http://www.hobby-machinist.com/showthread.php/2637-Knurling-thread-by-George-Wilson?highlight=knurl.  Some people tried using hard-rubber wheels in one side of the clamp.  But at the end of the thread, George Wilson points out: 





> I cannot recommend trying to use any kind of rubber wheel in knurling.  You really need 2 matching knurls in a scissor type knurling tool,or  just run the 1 wheel against your metal-which is the best option unless  you have a real small lathe  [...]


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## old toolmaker

Hawkeye,

You have made a wonderfully nice job of the camjack knurler!!

Dick


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## jayman

I use straight knurls for my QCTP height adjusters to lock the stop and nut together lock-nut fashion. That way I don't have to reach for a wrench to do it. Coarse knurls in steel work best for me. I am making the Camjack to get the leverage I need for coarse knurls in steel. Will post results when finished.

jayman


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## Silverbullet

My list has a new addition yupp


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## jayman

WOW! Has it really been seven months since my promised post? SORRY! I LOVE my Camjack Knurler. I have done some extensive testing with it using 96DPI straight knurls from Accu-Trak on 3/4 inch dia. 12L14 steel. My light 7X14 minilathe has been accurized and rigidized, but is still too flimsy to support axial movement under lathe power without the dreaded doubling. Doubling requires a lot of rolling to work out of the stock which creates needle debris that embeds in the workpiece and the user's fingers (think of how thin sheet metal fractures when folded back and forth across a crease.) The knurl\workpiece interface is so shrouded by the arms holding them that debris cannot be brushed out as the work rotates. 

I have worked out a procedure I call "Knurling by the Knumbers" which I do manually and which produces sharp, fully-formed knurls with zero debris. I will post the results as soon as I learn how to post pics, hopefully the 10th.

Jayman


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## jayman

O.K. Here goes. To save time (I'm at my local library) I formatted the results at home as a picture. Hope it loads. Failed. Try pdf format file. Looks like it loaded OK.


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## jayman

jayman said:


> O.K. Here goes. To save time (I'm at my local library) I formatted the results at home as a picture. Hope it loads. Failed. Try pdf format file. Looks like it loaded OK.


To follow up my post on my Camjack Knurler knockoff, here is my Cut Knurling Adventure.


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## Hawkeye

Thanks for posting your excellent write-ups. I'm glad the knurler is working for you. I recently found the same thing regarding the right amount of pressure to cause or prevent double-tracking.


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## Silverbullet

Thanks


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## ttabbal

So, I started building one using the plans, thanks for sharing them. 

I noticed that I don't have a 3/16 ball mill for the fulcrum. I do, however, have 1/8 and 1/4. Any reason not to use one of them and the matching size fulcrum?


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## savarin

I have been wrapped in my copy since I made it.
Most of my knurling is in stainless so really needs a bit of pressure.
The high tensile bolts I originally used wore down considerably from these pressures so hardened pins are I believe a necessity.
I also added an arm support on the middle between the  two arms with a large flange to help prevent the arms from deflecting sideways from the pressure I've been knurling at.


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## ttabbal

Thanks for sharing the design! I got mine finished up and, per the rules of DIY tools, used it to make a part for itself. I couldn't believe how little force I needed, the thumb screw was plenty. 

The knurling came out great, even with the wheels that came with the QCTP set. I'll order some nice wheels if I use it frequently.


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## Hawkeye

Nicely done. I'm glad you like it. I can see that your thumb screw would have plenty of authority. Mine uses a SHCS, but most times, I just turn it by hand.


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## KBeitz

*Knurling Calculator*






						CGTK - Knurling Calculator
					






					www.cgtk.co.uk


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## KBeitz

A spring like this might work...


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## AmericanMachinist

This design seems very smart - thank you for sharing.  I'm going to make one.   I don't have a 3/4" end mill.  I'm contemplating using a drill and figuring it'll be close enough for this purpose.

But I'm also debating buying the endmill and having it... I know the $70 is an investment...


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## Hawkeye

If you clamp the two pieces with the 3/4" groove together in the right locations, with a piece of, say, 1/8" or 1/4" scrap in between, the drill bit will likely do a good job. Centre the hole on the scrap.

My knurler is still doing good service. I'm quite pleased with the design. Used it several times in the last couple of weeks.


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## AmericanMachinist

Thanks.  I'm thinking with a sharp bit and an uninterrupted cut it ought to be precise enough for its role in this tool.

I'm going to be adapting the design very slightly at the tool holder portion to make it work with a T-nut in place of a lantern toolpost.


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## AmericanMachinist

Finally getting around to building one of these knurling tools.   I am considering how to bolt the base into my T-slots on my lathe (no QC tool post).   Alternatively, I am wondering if the forces on the tool are light enough that I can insert the base into my lantern tool post which normally holds a 3/8" wide (1/4" bit) Armstrong tool holder.   With the cross slide and compound backed out, I'd still get about 5" arms from the rear arm pivot points to the center of the lathe bed. 

Assuming the tool is built accurately, I'd imagine there isn't all that much force on the tool base and by extension on the compound, and in my case the lantern tool post.  Is that a reasonable assumption?     I may use a 7/16" x 1" piece of steel in my lantern tool post if I'm not way off base here. 

Thanks!


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## AmericanMachinist

I finished my knurling tool tonight.  *Thank you *for sharing the designs and plans.

Two additional notes:

1)  I did this entirely on a grizzly mini-mill (and horizontal bandsaw).  *So if all you have is a mini-mill, like me, you can do this!*   Just take your time.

2)  I adapted the idea for the QCTP mount to instead slide into a lantern tool post (about 3/8 x 1-1/4").   So far this is working fine, I did one test knurl and then knurled a thumb nut for the knurl itself.  *So if you have a lantern tool post and no QCTP, you can do this! *

Edit:  Adding note 3)  I believe the original design welded the pivot pin for the cam jack.  I could have built didnt want to weld, then grind smooth, etc.  So far I've just placed the pin in the slot, and run with it (no fastening).  I did apply red loc tite tonight to see if that'll hold the pin - merely for convenience sake.   An expoxy like JB weld would surely work.  *So if you don't have a welder, don't let that step intimate you!*

Edit:  Adding note 4)  Although I did purchase and use a ball end mill to cut the slots for the cam pivot pin, in retrospect I'm not sure this was necessary.  I believe *with a sufficiently long square end mill, the same technique shared by the original author to create 3/4" radii for clamping nuts, could be used to create these small slots.  *In the event it saves a tool purchase beyond budget.  Perhaps with a solid spacer to avoid an interrupted cut a sharp drill could even be used as Hawkeye stated above.

I did notice the arms tend to pull to the side a bit.  I believe someone in the thread mentioned adding support to prevent that. May not be a bad idea. Though my first 2 knurls in steel of unknown alloy look great.

I also noticed the need to hold the arms apart to position them onto the workpiece.  Not a big deal. May look into spring options at some point.  Just position the knurler arms lightly on the work piece with the lathe off.  Seems to work.

Thanks again for sharing the designs and plans!


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## mickri

I might make one of these.  Still thinking about it.  After reviewing everything the cam jack appears to add little if any additional force over just tightening the screw on the top piece.  The cam applies force to the top piece at two points.  Any force applied by the cam and how that force is divided between the two points is determined by where main screw is placed between the two points.  In this case the greater force would be applied at the adjusting screw because it is further away from the main screw.   Longer lever arm. So the cam instead of applying greater force at the knurl end is applying the greater force at the other end.   I won't bore you with the math.  The vector diagram gives you a visual on the force distribution.




Eliminating the cam would simplify making it.  The top and bottom pieces would be the same shape.  Also moving the main screw further away from the knurl end would increase the force on the knurl.

This is a great design and well worth making.


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## AmericanMachinist

I think a benefit of the cam is that you get fine-adjustability given the reduction in travel of the two sides of the cam.

I believe the size of the force vectors backward in your drawing.   A point closer to a fulcrum experiences a larger force with less travel.  The object far from the fulcrum must travel a multiple of times further, but can apply a much larger force to the object close to the fulcrum.

In effect, you might tighten the jaws of the knurler near the 1/2-20 main screw 20 thousandths by raising the rear of the cam 100 thousandths.  But applying 1/5 the constant force to the cam screw.  

The alternative being a need to crank on the 1/2-20 screw with a wrench and also finding fine-adjust difficult.

Edit to add:   I've only built one of these, with cam, and its my first knurling tool.  So I can't say with confidence how difficult it would be to use without the cam, BUT the benefits of the cam seem intuitive, and by the time you build the rest, the cam is just a small part of the build.


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## mickri

In my reading of the thread the force was being applied by the 1/2-20 screw.  The OP mentioned how easy it was to tighten with just the knurled piece on the 1/2-20 screw.  The OP also calls the knurled end of the cam the fulcrum which indicates to me that the 1/2-20 screw is providing the downward force.  If you are using the adjustment screw on the cam to add more force then you are correct that a small upward force on the cam adjustment screw would create a larger downward force at the knurl end.  It would also create an upward force on the bottom piece.

All of these interactions would create complex force vectors.  More than I want to try to calculate.  But I still wonder how much you are really gaining with the cam.  Maybe someone who has made one of these could try to use it without the cam and just applying force with the 1/2-20 screw to see what happens.


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## savarin

All I know is it works great and is easy to apply a touch more pressure if it looks like double tracking.
Most of my knurling is in stainless and this knurler works everytime.
I only used a lathe and drill press to make  mine.


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## mickri

How do you make the adjustments to get more or less pressure?  Do you use the 1/2-20 screw or the adjustment screw on the cam?


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## AmericanMachinist

Cam screw once the wheels are engaged.  This lifts the 1/2-20 nut, pulling the two arms together.


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## Hawkeye

You could do without the whole cam mechanism. The 1/2" bolt will provide enough force with a wrench to form good knurls. But savarin and I can tell you that we can get enough pressure by turning the jack screw with our fingers (after the 1/2" bolt is adjusted to suit diameter) to press the dies into the work.

You don't have to use my design. Make your own. That's half the fun of machining.


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