# Knurling Question



## prasad (Oct 17, 2015)

Guys

I attempted my first knurling operation. I measured the knurl pitch accurately by running on a paper and measuring the marks with caliper, etc. Made all related calculations for the desired diameter I must use before trying to plunge the knurl. And finally plunged the knurl in after setting the roller to be parallel to the piece mounted in the chuck and speed was set to the lowest available (130 rpm). The result was no good. Please see the picture below. 


	

		
			
		

		
	
 Where did I go wrong? 

Lathe used: G4000 by Grizzly, set at 130 rpm
Tool used: Straight single roller knurling tool,type H5936 from Grizzly. See below. 



Thanks
Prasad


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## higgite (Oct 17, 2015)

Did you flush the work with oil to remove the cuttings during the knurling operation?

Tom


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## dlhoulton (Oct 17, 2015)

To my eye that looks like a good "Straight Line" knurling. Were you trying for something else?


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## prasad (Oct 17, 2015)

higgite said:


> Did you flush the work with oil to remove the cuttings during the knurling operation?
> 
> Tom


Yes, I did. I used WD40.


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## prasad (Oct 17, 2015)

dlhoulton said:


> To my eye that looks like a good "Straight Line" knurling. Were you trying for something else?


Tom, 

Thanks and I am glad if you really say so. Yes I was trying straight line finish.  I am not happy with the appearance of the grooves. They look kind of rough to me. I thought something went wrong and I could not detect it. I have seen similar knobs and they look much finer in finish. 

I guess I will try again soon and see if I can change some process. 

Thanks again, 
Prasad


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## Bill C. (Oct 17, 2015)

Be sure to use a lot of cutting fluid.  When I was cutting threads I used a wire brush to clean the grooves might give that a try.


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## T Bredehoft (Oct 17, 2015)

Try going deeper, and feeding back and forth, to let the tool cut in as it moves sideways.


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## Wreck™Wreck (Oct 17, 2015)

Knurling in a lathe is not a science in my experience, a great deal of measuring, calculating pitch diameters and adjusting part diameters does not seem to help. If you require 1 knurled part make 3 or more and one is likely to turn out nicely. In a production environment one may scrap dozens of parts before getting it right.

From past experience I may offer but one bit of advice, when using a bump tool as pictured, run the tool into the part as fast as you can, and by this I mean Scary Fast, this gives the knurl less time to double track which is the problem that you are having. If you do not have a physical stop on the cross slide for such purposes then make one, you are a machinist after all.

I did these parts several months ago, ran a test part on the same piece of stock and it worked fine, ran the first actual part and it double tracked which is unacceptable to the customer, the second part was perfect and the 5th was awful so I kept bumping up the infeed rate until 1 in 10 were right. This is on a CNC lathe so changing infeed rates is a matter of changing numbers with a key pad.


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## mikey (Oct 17, 2015)

Bump knurlers usually require a good deal of rigidity in both the lathe and the set up due to the way the tool is used - you're pushing from one side only and deflection is going to be a problem. The normal solution for this is to always use a live center for support, and if you were not using it in this case then try it again with a live center in place. Then you can increase pressure so the edges of the knurl don't look all chewed up.

I would also recommend you use a good cutting oil, even on Aluminum. Knurling is not cutting; it is displacement and generates higher temperatures than you might think. Even your hardware store sulfur-based tapping fluid will work for this.

Bump knurlers normally require higher speeds than you're using to track well. I normally knurl at 50% normal turning speed for the material. I haven't used a bump knurler in a long time but I know I was turning at higher speeds than what you're using here. Maybe give it a try?

I prefer a scissors knurler. It allows for much higher knurling pressure, does not stress the spindle bearings, does not deflect the work piece, can be used at higher speeds and produces a really nice knurl whether you calculate diameters or not (in most materials). Below is a knurl done with a shop-made scissors knurler on the end of a 3/8" OD piece of aluminum without a tailstock support:




I'm not sure what this would have looked like with a bump knurler, though!


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## Doubleeboy (Oct 17, 2015)

Just an aside, bump knurling is hard on your lathe, If you worked in a shop on a high precision lathe like a HLVH or similar and the shop owner saw you bump knurling you would be gone in a heartbeat.   I have a couple bump knurlers, neither have been used in decades, scissors are much kinder to your machine.  

michael


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## kd4gij (Oct 17, 2015)

What material is the knob?  Also I do like grizzly but things like that knurling tool isn't the best of quality . And isn't going to perform well.
I replaced the knurling wheel with a bearing and use it for bumping things to run true in the lathe. It works great for that.


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## prasad (Oct 17, 2015)

kd4gij said:


> What material is the knob?  Also I do like grizzly but things like that knurling tool isn't the best of quality . And isn't going to perform well.
> I replaced the knurling wheel with a bearing and use it for bumping things to run true in the lathe. It works great for that.



Martin, 
Material was aluminum, I am trying to make two knobs for my Crayford Focuser. Bump knurler is the only type of knurler I have. I also have diamond knurler which is also a bump knurler. 
Thanks
Prasad
AB3EH


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## prasad (Oct 17, 2015)

Doubleeboy said:


> Just an aside, bump knurling is hard on your lathe, If you worked in a shop on a high precision lathe like a HLVH or similar and the shop owner saw you bump knurling you would be gone in a heartbeat.   I have a couple bump knurlers, neither have been used in decades, scissors are much kinder to your machine.
> 
> michael


Wow, never thought of that. Lucky for me, I am the owner. I guess I wont fire myself for using a bump knurler. I bought it because it was cheaper. I also have a diamond knurler from Grizzly which I guess is also called bump knurler. I have not tried it so far. This is my first knurling attempt.


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## kd4gij (Oct 17, 2015)

I bought this scissor knurling tool because it is cheap it did better but I still wasn't happy with the outcome. So I picked up some good knurling wheels of eBay and it works like a champ.

http://www.lathemaster.com/DUALHEADKNURLINGTOOL.htm


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## Bill C. (Oct 17, 2015)

I hate to ask but just what is "Bump" knurling?  I have cut diamond patterns before. I recall rolling/cutting them in training.  Don't recall any in production, they are usually time consuming.

I do remember using a live center for support. One can always cut off the center if the part doesn't allow one.

Thanks,


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## Wreck™Wreck (Oct 17, 2015)

Bump means that you push the tool straight into the work from one side, making a diamond pattern as shown above takes 2 knurling tools, 1 left handed and 1 right handed at the same time. if you insist on having knurled parts buy a scissor tool as mentioned. Eagle Rock makes excellent tools that I have used in the past, they may be a bit out of the Harbour Freight/Grizzly price range however.


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## wawoodman (Oct 17, 2015)

And there are any number of plans for a scissors knurler on line. A pretty good starter project. I even made one myself!


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## prasad (Oct 17, 2015)

wawoodman said:


> And there are any number of plans for a scissors knurler on line. A pretty good starter project. I even made one myself!


That is good idea. I will look for one. I am interested more in straight knurling. How does scissors type work for straight knurls? I understand scissors will not have a problem if it is diamond style but I dont understand how it will work for straight. 

Thanks
Prasad


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## mikey (Oct 18, 2015)

The pattern is a function of the knurl type you use, not the knurling tool itself. Straight knurls are generally matching, while diamond knurls have a right hand and left hand pattern so they cross each other as the pattern is made. A scissors knurler can use either type.

If you do make a scissors knurler, consider mounting it to the rear of your cross slide bed. This greatly improves rigidity and gets the tool out of your line of sight.


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## kd4gij (Oct 18, 2015)

Good HSS knurling wheels are the trick. I found the wheels on the cheap imports to be soft and not very sharp.


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## mzayd3 (Oct 18, 2015)

prasad said:


> That is good idea. I will look for one. I am interested more in straight knurling. How does scissors type work for straight knurls? I understand scissors will not have a problem if it is diamond style but I dont understand how it will work for straight.
> n
> Thanks
> Prasad



I imagine that to use straight knurl wheels in a scissor type knurler that you would replace one of the wheels with a bearing.  Otherwise, both wheels would cut resulting in a non-sychronized knurl.


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## prasad (Oct 18, 2015)

mzayd3 said:


> I imagine that to use straight knurl wheels in a scissor type knurler that you would replace one of the wheels with a bearing.  Otherwise, both wheels would cut resulting in a non-sychronized knurl.


Thanks. But would't the ball bearing exert pressure and flatten the tips of the serrations produced by the single straight knurl mounted on the other side of the scissors?


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## prasad (Oct 18, 2015)

kd4gij said:


> Good HSS knurling wheels are the trick. I found the wheels on the cheap imports to be soft and not very sharp.



Good point Martin, the knurl I have is an import and could be of poor quality. I have search for a bunch of knurls I had picked up at Cabin Fever Expo earlier in April this year. I know some of them were US made but previously used.  

Thanks
Prasad


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## wawoodman (Oct 18, 2015)

mikey said:


> The pattern is a function of the knurl type you use, not the knurling tool itself. Straight knurls are generally matching, while diamond knurls have a right hand and left hand pattern so they cross each other as the pattern is made. A scissors knurler can use either type.
> 
> If you do make a scissors knurler, consider mounting it to the rear of your cross slide bed. This greatly improves rigidity and gets the tool out of your line of sight.



Mikey,
How would you mount to the rear of the bed? I'm interested!


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## prasad (Oct 18, 2015)

wawoodman said:


> And there are any number of plans for a scissors knurler on line. A pretty good starter project. I even made one myself!


Mike
I googled and found plans for scissors knurlers. Isn't it necessary that the knurl holder, etc., must be hardened? I am not sure I would be able to do it. I am not sure if they can be used without hardening as they may buckle under pressure. The straight knurler I bought from Grizzly is hardened.  
Prasad


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## prasad (Oct 18, 2015)

wawoodman said:


> Mikey,
> How would you mount to the rear of the bed? I'm interested!


I think he means the tool would be on the other (rear) side of the object to be knurled from the back side and the two rollers would face the operator. The lathe operator would then be able to view the rollers. 
-Prasad


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## wawoodman (Oct 18, 2015)

prasad said:


> Mike
> I googled and found plans for scissors knurlers. Isn't it necessary that the knurl holder, etc., must be hardened? I am not sure I would be able to do it. I am not sure if they can be used without hardening as they may buckle under pressure. The straight knurler I bought from Grizzly is hardened.
> Prasad



I didn't harden mine. I don't know how to do that.

Right now, I'm working on the Tom's Techniques knurler. It calls for hardening some of the parts, so I hope it's covered in one of the videos!


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## wawoodman (Oct 18, 2015)

prasad said:


> I think he means the tool would be on the other (rear) side of the object to be knurled from the back side and the two rollers would face the operator. The lathe operator would then be able to view the rollers.
> -Prasad



But how would you do that? I don't think my cross slide goes that far. Do you have to make a different mounting method?


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## prasad (Oct 18, 2015)

wawoodman said:


> But how would you do that? I don't think my cross slide goes that far. Do you have to make a different mounting method?


On my G4000 lathe with cross slide mounted on the second hole and moved all the way to the back I think, it can be done. I dont have a scissors style knurler yet though. Let us wait till we hear the real answer from Mikey


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## mikey (Oct 18, 2015)

Good morning, guys - you've been busy!

First, straight knurls used in a scissors knurler are a matched pair - both wheels will track in the same pattern. The coarser the straight knurls are (fewer teeth per wheel), the less the potential for mistracking. 

Rear mounting a knurler requires a cross slide with T-slots, which the G4000 has. If you don't have T-slots you cannot do it without major surgery. If you do, however, it is the most solid way to mount the tool. Knurling produces pretty high forces, most of which are taken by the tool instead of your spindle bearings. That force has to go somewhere and it is passed on to the mount. In the case of a rear mounted tool this force pushes down on the cross slide where it is handled by the gib that is designed to handle that force. This translates into a cleaner knurl. The other major advantage is that rear mounting the tool clears your line of sight and gives you more room to work.

There are plans for making a knurler on the net - choose one you like. The only parts on mine that are hardened are the axles and you can use drill blanks for that; the rest can be mild steel. The most important thing re the tool itself is that there be no lateral play in the arms; on mine, there are plates to limit this and it was machined with zero play. The plates were then filed so the arms just moved freely ... but no more.

I'm having trouble posting pics. I'll get them posted when I figure it out.

Good knurls are important, as is a radius on the knurls if you are going to do any axial running (making a knurl longer than the knurl is wide). I like FormRol knurls. AccuTrak makes convex knurls made for axial running, as well.

More later - gotta' run.


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## mikey (Oct 18, 2015)

I cannot seem to post pics for some reason. I'll keep trying but I don't think its a problem on my end.

I saw this pic on the net one day: http://www.astronomiainumbria.org/a...anica/easyweb.easynet.co.uk/_chrish/r-t-7.jpg

From this one picture I figured out what had to be done and blatantly made one much like it. This tool has a lot going for it - it has beefy arms (mine are 1/2" steel) that are constrained on the sides by thick plates. Those arms can move up and down, even when under pressure, so getting on center is not a major issue. The knurls have enough clearance to turn freely and allow them to track but only just - maybe 0.003" total clearance in the slot that the knurls sit in. Both arms have no discernible side play but move freely. The tool can knurl anything from near zero OD up to about 2-1/8" or so. The main screw has a T-bar that fits in the head but I normally don't use it. Due to the location of the screw, a great deal of pressure is applied with just hand pressure.

This tool normally lives on my Sherline lathe but can be moved to my 11" lathe by swapping the mounting block. I normally don't do that and use an Alorix AXA-19 instead. However, I will say that this smaller tool works better than the -19; its smoother and makes nicer knurls. If you don't want to make a tool then consider the Aloris -19 - it does the job rather well.


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## Bill C. (Oct 24, 2015)

prasad said:


> Good point Martin, the knurl I have is an import and could be of poor quality. I have search for a bunch of knurls I had picked up at Cabin Fever Expo earlier in April this year. I know some of them were US made but previously used.
> 
> Thanks
> Prasad



Its been awhile but if I recall correctly the cutters should feel sharp.  Maybe not as sharp a HHS tool bit but shouldn't feel smooth to the touch.


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## Bill C. (Oct 24, 2015)

I was thinking the other day when I did knurl a diamond pattern I squared the cutter wheels to the diameter then angled the leading edge of the wheels about two to five degrees so that the leading edge would lead the rest of the tool into the material.  Be sure to tighten all the bolts including the toolpost so nothing slips.   Just a thought.


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## joshua43214 (Oct 24, 2015)

I see two things wrong here.
1) the knurl is not complete, you need to knurl until the points are sharp. If the sharpness is not wanted, then run a file over the finished knurl to make it more comfortable to handle.
2) The finished knurl is very rough, probably because of the oil used. WD40 is not a knurling oil. Knurling is not a cutting operation, it is a swaging operation. WD40 is for cutting aluminum. For knurling you need something that that works like a high pressure lube. I use standard cutting oil for lube. You need to keep the knurl flooded, chips do break off the work and they need to float away before they cut pulled under the wheel a second time.

What all the others have said about bump knurlers is spot on, but even the most rigid clamp knurler will not knurl well if the knurl is not complete and the wrong lube is used.

-Josh


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## Wreck™Wreck (Oct 24, 2015)

joshua43214 said:


> I see two things wrong here.
> 
> 2)  You need to keep the knurl flooded, chips do break off the work and they need to float away before they cut pulled under the wheel a second time.


This type of knurling is a forming process not a cutting process, if you are developing chips something is already off.
There are cut knurling tools which work a charm and require less load on the machine itself. The cost will scare off most hobbyists I suspect.
http://www.mscdirect.com/product/details/03298635


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## savarin (Oct 24, 2015)

I made one of these http://www.hobby-machinist.com/threads/camjack-knurler.3533/ works a treat.
All mild steel with no hardening.
I used high tensile bolts for holding the wheels and arms.
The original knurls that came with a cheap bump knurler always caused problems but once I changed them out for good quality ones the difference was like chalk and cheese.


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## joshua43214 (Oct 24, 2015)

Wreck™Wreck said:


> This type of knurling is a forming process not a cutting process, if you are developing chips something is already off.
> There are cut knurling tools which work a charm and require less load on the machine itself. The cost will scare off most hobbyists I suspect.
> http://www.mscdirect.com/product/details/03298635



Knurling with a forming tool still makes chips from fracturing. That is why I said "chips do break off..."


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## Bill C. (Oct 25, 2015)

joshua43214 said:


> Knurling with a forming tool still makes chips from fracturing. That is why I said "chips do break off..."



I agree, it been years since I last knurl, there are fine bits of material left on the finish.  The operation needs more cutting fluid to wash them off.


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## prasad (Oct 25, 2015)

savarin said:


> I made one of these http://www.hobby-machinist.com/threads/camjack-knurler.3533/ works a treat.
> All mild steel with no hardening.
> I used high tensile bolts for holding the wheels and arms.
> The original knurls that came with a cheap bump knurler always caused problems but once I changed them out for good quality ones the difference was like chalk and cheese.


Charles

Thanks. I like this knurler. After reading so many responses it is clear to me that my push knurler is no-good. I will dump it and salvage the knurling wheels for making one like in your link. I have too many of such improvement projects on my list.  I was trying to make two knobs for my focuser and I will live with the two I made. I want to stay focused on that for now.  It is slowly taking shape. 

Thanks
Prasad


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## NightWing (Oct 25, 2015)

A couple of things.  Knurling tools cause the material to grow.  The exception is cut rolls which don't displace metal.  If you over-roll, trying to get sharp crests, the material will fracture and flake.  Those flakes will be driven into the profile.  Dwelling the knurling tool on the workpiece will build up pressure and can spoil the profile.  Get on and off as quickly as you can.  I always figured .011 feed per rev when knurling or thread rolling.

You need carbide pins to keep the knurls from bugging up on the ID.


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## wawoodman (Oct 26, 2015)

Carbide pins? Dowel pins aren't hard enough?

If the pins are harder than the knurls, isn't that just as bad?


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## NightWing (Oct 26, 2015)

Carbide pins won't pick up and transfer material to the roll.


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## wawoodman (Oct 26, 2015)

Sorry, Nightwing, but I don't understand. Could you elaborate on that, please?


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## Bill C. (Oct 26, 2015)

Wreck™Wreck said:


> This type of knurling is a forming process not a cutting process, if you are developing chips something is already off.
> There are cut knurling tools which work a charm and require less load on the machine itself. The cost will scare off most hobbyists I suspect.
> http://www.mscdirect.com/product/details/03298635



At that price specially


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## 2ndsteel (Oct 26, 2015)

American tool companies wonder why people are looking for alternatives to their over priced tools!


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## Wreck™Wreck (Oct 26, 2015)

2ndsteel said:


> American tool companies wonder why people are looking for alternatives to their over priced tools!


It appears that most of the US Companies that stuck with producing tools for manufacturing and never dabbled in the consumer/hobbyist market are doing fine. Dumont for example, can't buy their broaches and bushings at home depot I suspect.

A tool that can produce 200 parts per day for weeks repeatably without  fail is worth a bit more to the purchaser then a tool that will fail often or make inconsistent product. Another interesting aspect of American companies is that they only do one thing, they rarely use their  large R&D infrastructure to develop other products. Not disparaging the auto industry at all, many advances in manufacturing processes have come from auto makers in the past.

Yamaha makes pianos. motorcycles, outboard engines, personal watercraft and small boats.
Honda makes cars, generators, motorcycles, outboard engines, lawnmowers etc.
Hyundai makes ships, heavy equipment, large engines, cars and other products
BMW makes cars and motorcycles
Kawasaki makes motorcycles and Industrial robots 



Toyota makes cars and large CNC milling machines under their original name Toyoda 



Mitsubishi makes cars as well as excellent machine tooling, inserts and holders. 




General Motors makes cars and car loans.


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## savarin (Oct 26, 2015)

this looks buildable
http://www.ebay.com/itm/Hardinge-L2...t-Condition-/181907946310?hash=item2a5a8efb46


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## NightWing (Oct 26, 2015)

wawoodman said:


> Sorry, Nightwing, but I don't understand. Could you elaborate on that, please?



A hard steel roll spinning on a hard steel pin will result in the two parts welding together when one component transfers a bit of its metal to the other part due to friction and heat.  The carbide pin is extremely smooth and much harder than the roll, so there is less chance of the parts setting up.


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## wawoodman (Oct 27, 2015)

Ah! thanks.


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## mikey (Oct 29, 2015)

Prasad, I tried to post pics of my knurler before but was unable to do so until Nelson and Robert got to work on the problem. Now it seems to work and I can show you a simple tool I made for my Sherline lathe. It is mounted to the rear of the cross slide and will transfer to my larger lathe by changing the mount. This knurler has produced beautiful knurls in mild steel, stainless, aluminum, brass and Delrin. In most cases, it will create a full-pattern knurl on the first pass if I do my job.






I hope this gives you some ideas if you decide to make one of your own.

Edit: I forgot to add that it will knurl from zero out to 2-1/8" OD and despite having a hex shaped shank on the main screw, it tightens with simple hand pressure. Cost was almost nothing except the knurls - just stuff I had laying around the shop.


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## prasad (Oct 29, 2015)

mikey said:


> Prasad, I tried to post pics of my knurler before but was unable to do so until Nelson and Robert got to work on the problem. Now it seems to work and I can show you a simple tool I made for my Sherline lathe. It is mounted to the rear of the cross slide and will transfer to my larger lathe by changing the mount. This knurler has produced beautiful knurls in mild steel, stainless, aluminum, brass and Delrin. In most cases, it will create a full-pattern knurl on the first pass if I do my job.
> 
> View attachment 113315
> View attachment 113316
> ...



Thank you Mike. Pictures are clear to me. This will be one of my projects. I have printed the photos for reference later. Thanks again
Prasad


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## mikey (Oct 29, 2015)

Yup, you're welcome. Sorry it took so long, and I hope this gives you some ideas for making your own.


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## mikey (Oct 30, 2015)

I tried to find a good pic of a knurl but I don't have many pics and can't find them anyway. I do have an unusual one that comes from George H Thomas. It is called a Square Knurl. I made a true square knurl but the corners of the pattern felt a bit sharp on the fingers so I cut a hex shape instead and it feels nice but with a good grip. The main knurl is a simple straight knurl, which is then cross cut with a 60 degree tool; spacing between the cross cuts is the same as the peak to peak distance of the straight knurl. If you cut to the same depth as the straight knurl you get a square pattern. If you cut less than that depth you get a hex as seen here.




The straight knurl is cut in a single pass to full depth and it is important to do this so you produce a clean pattern with which to work. A scissors knurler will do this quite well. For a less busy pattern, use a knurl with fewer teeth.

Anyway, thought I would share.


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## prasad (Oct 30, 2015)

mikey said:


> I tried to find a good pic of a knurl but I don't have many pics and can't find them anyway. I do have an unusual one that comes from George H Thomas. It is called a Square Knurl. I made a true square knurl but the corners of the pattern felt a bit sharp on the fingers so I cut a hex shape instead and it feels nice but with a good grip. The main knurl is a simple straight knurl, which is then cross cut with a 60 degree tool; spacing between the cross cuts is the same as the peak to peak distance of the straight knurl. If you cut to the same depth as the straight knurl you get a square pattern. If you cut less than that depth you get a hex as seen here.
> 
> View attachment 113343
> 
> ...


Mikey

Great idea. I want to try it. I will share the photo if result is good. 

-Prasad


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## Wreck™Wreck (Oct 30, 2015)

NightWing said:


> A hard steel roll spinning on a hard steel pin will result in the two parts welding together when one component transfers a bit of its metal to the other part due to friction and heat.  The carbide pin is extremely smooth and much harder than the roll, so there is less chance of the parts setting up.


Not exactly true, there are many applications employing hard steel on hard steel interfaces  (rolling element bearings, ball, tapered roller or roller, drill bushings, automotive ring and pinion gear trains for example), a small amount of lubrication is required however. I have never used a knurling tool that used carbide pins, this does not mean that they do not exist.


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## NightWing (Nov 1, 2015)

Wreck™Wreck said:


> Not exactly true, there are many applications employing hard steel on hard steel interfaces  (rolling element bearings, ball, tapered roller or roller, drill bushings, automotive ring and pinion gear trains for example), a small amount of lubrication is required however. I have never used a knurling tool that used carbide pins, this does not mean that they do not exist.


And I have never used a knurling tool that didn't have carbide pins.  Use anything you like.

You can't compare ball or roller bearings to knurling tools because ball and roller bearings have point contact with their respective races and they roll rather than slide, as is the case of a knurl wheel sliding over a pin with almost 100% contact.  Yes, steel pins might work for a while but if you want longevity, then carbide pins are the answer.   I owned a manufacturing company for 22 years and we knurled and thread rolled thousands of pieces on production equipment.  Carbide pins were the only answer.


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