Thread: Knurling

Can you give a step by step description of what you are doing.
How long is the knurl?
Are you running off the end of where you want to knurl?
What feed rate are you using?
What speed?
Are you running coolant?
What material?
Are you using a centre?
How long is the job?
Are you applying sufficent pressure?
Are you keeping the Knurling tool engaged with the job at all times?

David,

Make or buy a scissor type knurler. Makes the production of nice crisp knurling dead easy.

Bob.

Originally Posted by pipeclay

Can you give a step by step description of what you are doing.
How long is the knurl?
Are you running off the end of where you want to knurl?
What feed rate are you using?
What speed?
Are you running coolant?
What material?
Are you using a centre?
How long is the job?
Are you applying sufficent pressure?
Are you keeping the Knurling tool engaged with the job at all times?

For Anorak Bob, I am using a scissor type knurler.
For pipeclay answers to questions as follows
Length of knurl varies but typically, say, 25 mm
Not running off the end of where I want to knurl
Feed rate is 1.5mm
Speed is 48 rpm
Running heaps of coolant in mild steel
Using a drive plate and live centre in tailstock
applying a fair bit of pressure getting a good deep imprint in one pass
Keeping tool engaged at all times

Having never used the type of knurl you are using,I have no idea of any particular things to monitor.
Are you Knurling in one pass or multi passes.

David,

I use oil, not coolant and I knurl in a number of passes. I dont use power feed. Like you, I run the machine at the lowest speed. My knurls are fairly expensive, made in England by WDS. They form a nice knurl.

Bob.

I use a scissor type diamond knurl. I don't use coolant, run multiple passes and feed manually. You have to make sure the diameter is correct and that you don't disengage the tool at any point (once you have the diameter correct), but otherwise it's pretty simple.

I start by doing a very light pass with the knurling tool. Look at the results and if the pattern doesn't match up I take a smidgen off the diameter of the piece. I repeat this exercise until the pattern matches and I then proceed onto doing multiple passes, tightening the tool a little bit before each pass. That's it really.

Thanks to Anorak Bob...I too will have expensive knurling kit one day...I am on the look out on Ebay.

Vernon has the answer I have been seeking. That is, Vernon adjusts the diameter by a smidgin until he gets a clean pattern and then he knurls. I will run out to shed now and give it a go. I will also heed advice and use manual feed, use cutting oil and do multiple passes. I will report results.

Why don't the books mention need to have diameter consistent with your particular knurling wheel? I have read many knurling articles including my own Hercus book and my hefty TAFE Fitting and Machining Book (a very good ref source)...none of them mention this but I suspected all along that if you have knurling teeth follow in the grooves left on the previous revolution, the teeth spacing must divide into circumference as a whole number?

David

There's a section in the Machinerys Handbook (page 1214 on in my copy) which deals with the maths of this - but it's heavy going.

Also there's an article online at Machine Shop Trade Secrets - Knurling Made Simple which might help you.

There was a thread here before that basically proved that it doesn't matter if your material diameter doesn't divide wholly into your knurling wheel diameter. This is because the knurling process gives repeated deformation.

Unfortunately, I don't have a scissor knurl, but what works for me is to wind the cross slide in pretty hard, with the lathe running, until the knurl looks perfect, then put on a modest autofeed (0.4-0.8mm/rev?), stop at the end. Done. Perfect knurl. Go inside.

Edit: Important: for the swivel-head type knurling tool, get it perfectly on centre, otherwise you will have to press the knurling tool VERY hard to get both wheels to press properly. (You will notice immediately if the tool is lightly touching the work that you're not setup properly as you'll only get lines in one direction.)

My little Hercus groaned badly when I tried knurling with a single wheel knurler. I felt that uncomfortable about it that I made my twin wheel clamp knurler.

The knurler works well on 4140 but it requires a hell of a lot of pressure on the wheels to acheive a nice deep knurl. For me, way too much load on the spindle if I was trying to do it with a one wheeler.

I use engine oil as a lubricant and a brass or plastic bristled brush to clear away the swarf while I'm forming the knurl. I also have the tool mounted in a rear tool post. Can't beat seeing what you are doing.

Bob.

I'm going back 40 years now to when I last used a knurling tool, but I don't think things have changed much in that time - except my memory of course, which I will rely on here. 1. We used lubricating oil, not cutting oil because you want to push the steel around, not cut it. 2. Set the tool at a slight angle to the work piece, so it is a little open at the front, 3. Run the tool both ways across the work piece, 4. Hand feed it and 5. use multiple passes.
Hope this helps. Cheers.