Knurling Question

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.
 
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
Click to expand...

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.
 
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.
 
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
 
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.
Click to expand...
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
 
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.
 
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
Click to expand...

Knurling with a forming tool still makes chips from fracturing. That is why I said "chips do break off..."
 
joshua43214 said:
Knurling with a forming tool still makes chips from fracturing. That is why I said "chips do break off..."
Click to expand...

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.
 
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.
Click to expand...
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
 
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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