Gunsmithing School me on knurling

[jonaddis84]

Made my first attempt at knurling tonight with the #10 aloris holder. I read up on educated guessing the correct diameter so the grooves always line up, found that correct diameter. But where Im lost is my speeds and feeds? All I have read is go as fast as you feel comfortable...shouldnt there be a set rate to feed at?

At first I could not for the life of me figure out how I was going to get the crosshatch pattern in there when it was just making straight angled lines in the part, but it seems that as you go deeper into the part is what actually causes the crosshatch, is that true?

I got it looking halfway decent, went in about .055", does that sound close?

Seems like knurling is a procedure that flood coolant would really help with, looked like a lot of the tiny chips were just getting pressed right back into the peaks of the knurls and made it look a little rough.

thanks for the help
Jon

Oh, the piece I was knurling was a scrap piece of the end of a Savage 17hmr barrel, I only had it out of the chuck enough to where the knurling holder was almost touching the jaws and to give me about 5/8 long knurl.

 

[CountryBoy19]

Re: School me on knurling

If you were only getting an angled line until you pressed the tool in to the workpiece harder then your tool wasn't properly lined up. Only one knurling roller was touching to start with. The cross-hatching started when you pushed the tool into the workpiece harder and the 2nd roller made contact.

As with everything, setup time is likely going to be the largest time spent on this type of thing. You can't just drop the tool on the post and go to town. Check, double check, and triple check that both rollers are making contact evenly.

 

[LRI]

Re: School me on knurling

I struggled with knurls for a long time. Getting the tool to run on center is a big factor.

It seems to work best for me with a conservative RPM and an aggressive feedrate.

Eventually I just went to cut knurls as its much easier on equipment.

Good luck!

C.

 

[colchester]

Re: School me on knurling

As pointed out you need to be careful when you set tool height, advance the tool slowly into the part and watch the knurls. If only one knurl turns adjust the tool height accordingly and recheck. I also try to be sure that the knurl makes contact across its entire face. I feed slow to medium speed and and run spindle around 240 rpm. You are correct about the knurls loading up, use cutting oil or kerosene to lube and flush the knurls. I have a chip brush that is cut down to make it stiffer, I use this to brush out of the knurled surface and apply lubricant. I make a pass to the end of the part without running the tool off the edge, shut off the lathe and clean with the brush, relube, reverse the travel and make a pass in the opposite direction. Advance the crosslide and repeat until the desired surface is achieved Lastly I would advise against trying to clean the knurling while running the lathe Its just top easy to snag the brush. Be patient take your time dont try to take too much at a time.

 

[JJones75]

Re: School me on knurling

Cut knurling is the way to go but if you want to use a typical "bump" knurling tool get one with a self centering head , it makes life WAY easier in the setup department

http://www1.mscdirect.com/cgi/NNSRIT2?PM..._-SearchResults

 

[Clark]

Re: School me on knurling

This video from MIT is only ok cinematography, slow, and has lag.
http://techtv.mit.edu/videos/134-machine-shop-9

At 15:30 to 22:30 in this video has a section on knurling.

The basic concepts on knurling I got from the video are:
1) The tool height must be adjusted so both knurling wheels touch the work at the same time.
2) The ratio between knurling wheel circumference and work circumference is almost never a perfect multiple. This will cause many more hatch lines than desired. If one plunges fairly deep on the first revolution, deep grooves will form for the knurling tool to follow on subsequent revolutions.


My brother tells me that the knurling tool does not cut, but upsets, and the work should weigh the same before and after knurling.

 

[CountryBoy19]

Re: School me on knurling

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">This video from MIT is only ok cinematography, slow, and has lag.
http://techtv.mit.edu/videos/134-machine-shop-9

At 15:30 to 22:30 in this video has a section on knurling.

The basic concepts on knurling I got from the video are:
1) The tool height must be adjusted so both knurling wheels touch the work at the same time.
2) The ratio between knurling wheel circumference and work circumference is almost never a perfect multiple. This will cause many more hatch lines than desired. If one plunges fairly deep on the first revolution, deep grooves will form for the knurling tool to follow on subsequent revolutions.


My brother tells me that the knurling tool does not cut, but upsets, and the work should weigh the same before and after knurling. </div></div>

This is a good answer....

Special emphasis on the last part of item 2. To go into more detail, if your ratio isn't perfect and you take a light pass the tool may make new grooves as it goes around. However, if you make a heavier pass the first time, the tool will often times find the other grooves and eventually work itself out to where it's running in the same grooves. It is not uncommon for one roller to find the groove and stay while another roller struggles and it looks nasty.

My advice to you is if it doesn't line up right, and the OD isn't super critical, turn just tiny little bit of material off the outside. you just changed the diameter and now have a better chance of the rollers lining up. Try again, if it doesn't work this time, get frustrated, swear at it, and throw tools around the shop.

Another note, because a knurling tool forces material out of the grooves and into ridges, it will increase your diameter some. Knurling is one of very few ways to increase the diameter of something because you force material up out of the valley, into peaks.

 

[671RTO9513]

Re: School me on knurling

I do a lot of bump knurling here (one roll). Make sure you have a good quality knurl roll- I like Accutrak's convex ground rolls as the axial feed is so much better.
Setup must be rigid and correct. Speed like for threading. Lots of lube. RAM the tool into whatever it is you're knurling. It is very important to cut the knurl almost full depth on the first revolution to get it to track right. Try to finish it in no more than 20 revolutions and only about 90% depth to reduce the flaking.
If rigidity is a problem you may be best with cut knurls.

 

[WRM]

Re: School me on knurling

My buddy Bob has a spiral knurling video up, and said he'll address diamond knurling in a separate video, but I don't see that one posted, yet. Spiral and diamond are not the same, but it may give you some ideas.

http://www.youtube.com/watch?v=FlHEUp085w4&feature=player_profilepage

Cheers,

Bill

 

[jonaddis84]

Re: School me on knurling

Can you guys embellish a little on the cut knurling? Easier, harder, require new tooling?

 

[Bill Larson]

Re: School me on knurling

Get a different knurling tool.....one that does not require pressure against the chuck/collet....
it tightens itself on the workpiece... exerting NO pressure on chuck.... only on workpiece.sound more sensible...???
snug tool on subject piece... then lok- down aloris holder.
Mine is made by eagle mfg. in MI. I think...
slo-speed cutting oil with an air hose to blo out minute chips...
bill larson

 

[toolmaker]

Re: School me on knurling

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bill Larson</div><div class="ubbcode-body">Get a different knurling tool.....one that does not require pressure against the chuck/collet....
it tightens itself on the workpiece... exerting NO pressure on chuck.... only on workpiece.sound more sensible...???
snug tool on subject piece... then lok- down aloris holder.
Mine is made by eagle mfg. in MI. I think...
slo-speed cutting oil with an air hose to blo out minute chips...
bill larson </div></div> What Bill said, use a self centering sissor type knurling tool. I have the same one made by Eagle Mfg. its a quality tool and works great.