Knurling Stainless Steel

I need some advice on knurling some 304 stainless. The job is architectural, so looks are paramount. The biggest issue I’m having is small fragments breaking off and fouling the rest of the knurl.

Any advice will be gladly accepted.





Be safe




Jeremy

jermfab said:

I need some advice on knurling some 304 stainless. The job is architectural, so looks are paramount. The biggest issue I’m having is small fragments breaking off and fouling the rest of the knurl.

Any advice will be gladly accepted.





Be safe




Jeremy

Click to expand...

What coolant ?

for SS , i'd use a cut-knurl rather than extrusion.

I suppose 304 is the only SS flavor allowed?

Denis

For coolant I’m just drowning in dark cutting oil.

304 is what the customer spec’d.

I started with a cut knurl and immediate knocked the edges of of the roller.

Most of the knurling I’ve done previously was formed and on softer materials, typically aluminum and brass.


Jeremy

It could be that the knurling wheels are not tracking properly and therefore shred the peaks already formed.

Tip: start the knurl off the end of the part so perhaps only 1/4 of the width of the wheels are engaged. Start the spindle at very low rpm because you don't want the part to make a full revolution before you've set the tool to depth. Crank that mother in hard and fast, and it should track. Now, it will likely be excessively deep at this point and you will have to back off the pressure a little to proceed. The paramount feat to achieve is to get a good first revolution to teach the wheels the proper path to follow.

I most often set my knurling wheels at a bit of an angle, with the leading edge farthest into the part (so you can knurl nicely up to a stop). IMO, a full width broad faced setting of the tool doesn't produce enough focused pressure to get the job done.

BTW, you can dial the spindle speed back up to whatever you want as you proceed with the operation.

We did a lot of SS knurling a few years back and I don't recall what grade of SS was used, but we used dark thread cutting oil, flooding straight into the cutting wheels. Some bits will break off but the oil should flush it out. The job was on long (18"?) 1" diameter shafts and was done on a 15" Clausing Colchester lathe. We just took several passes until the knurl fully formed. A few of the shafts had a very heavy knurl too, like 1/8"-3/16" wide diamonds.

jermfab said:

I need some advice on knurling some 304 stainless. The job is architectural, so looks are paramount. The biggest issue I’m having is small fragments breaking off and fouling the rest of the knurl.

Click to expand...

One of the problems with conventional knurling on 304 is that it work hardens under deformation very quickly.

To knurl 3xx series stainless steels, I've used cut knurling with success, and having to experiment to find the optimum speed/feeds. Deformation knurling has never worked for me on 3xx stainless alloys. It can work on some 4xx stainless alloys (eg, 416, 420).