What is needed to learn the fine art of knurling on a mini-lathe? Is it possible?

[WobblyHand]

Looking at @mikey's thread, I think it's possible for me to make nearly every piece on a lathe, or drill press, except milling the slot in the arms. If I buy ground stock, then at least the pieces will be darned close in size. The side pieces will be very close. I can clamp pieces together and drill them. Still puzzling over the best way to do the slotted arms, but I sure can drill them together, with overlapping holes, and file them together. Not as precisely as with a mill, but it's possible. The half moons won't be able to be a true half moon, but I could get close machining them using a 4J chuck. Should be good enough. Not quite sure about rear mounting, but I think doing so would be a very good thing. I have a big enough chunk of aluminum to do that.

For some more detailed questions on straddle knurler, should I ask here, or on the other thread? I'd hate to clutter up that beautiful post. My questions are on topic for this post. For instance, for the knurling pins, what is special about the Precision drill rod? Instead, could I use hardened O1? Or M42 rod? If I used the M42 rod, I should be able to cut it with an abrasive saw disk without worrying about softening it, right? I mean, it's cobalt steel.

 

[mikey]

First, your questions are appropriate in either thread but since this one is yours, ask your questions here.

If you work very carefully, you probably could make that knurler without a mill. Before I had a mill, I had a hacksaw, files and a strong right arm.

If you buy ground low carbon steel, much of the machining will already be done for you. The plates and arms will be precision ground, straight and flat. None of the dimensions in that tool are so precise that you can fudge the pieces one way or the other.

For the half-moons, use round rod that is accurate; O-1 rod works well for this because it is somewhat hardened as supplied and it works fine for the wear it will see in that state. Hardening is not necessary. The problem will be cutting them in half to form the pivots - maybe ask one of the forum guys to do this for you? Whatever you do, do not grind this stuff in half; it will be harder than Hades and you won't be able to drill or tap it.

For the pins, nothing special about the brand (PTD) but I suggest you use a drill blank. It is precisely sized and hard enough to use as a pin.

For cutting the slots in the arms for the wheels, you can do this several ways. You can scribe the slot on both sides and bandsaw or hacksaw out most of the bulk, then file it to your layout lines. I remember doing fairly precise filing this way. Or you can ask one of the guys on the forum to end mill it for you, which would be the easiest way.

Otherwise, I don't see a major obstacle if you have a lathe, a drill press and the will. If you do build it, maybe take pics and start a thread. I'm sure there is some other hobby guy out there in your shoes, too.

 

[WobblyHand]

@mikey Thanks for the encouragement. Been scratching my head trying to make this happen. Even made out a shopping list. Yes, I was planning on using ground stock, that would help me get over the milling to exact size problem.

For the half moons, do they exactly have to be 1/2 circles? How about being a clipped circles? (Almost 1/2 moons.) I was thinking of laying the tight tolerance O1 rod on its side and holding them with a 4J and cutting a flat on them. I'd use carbide, I guess. Would that work? Or would that harden the daylights out of it?

For the knurl pins, could I use D2 steel? That's a tight tolerance tool steel. Drill rods confuse me. Looking on McMaster, they have comments that O-1 could be used as drill rod, as well as D2, M2, well you get the idea, too many choices. They also have some M42 tight tolerance rod as well. It specs at -0.0002" to 0" ground finish. ($14 for 4.5") I know M42 will maintain its hardness! What kind of hardness is desirable? I could get hardened O-1 for instance.

I'll try the layout lines, hacksaws and files. After all, it's only low carbon steel, not tool steel. Filing shouldn't be that hard. Almost any filing is better than filing tool steel with a diamond file! The filing will keep me off the streets, which is a good thing these days. There's a 4x6 horizontal bandsaw in the garage, but I just don't trust it enough to do this kind of work. The vise is terrible.

One last question, what did you use for the spring? How long does it need to be? It has to have an ID greater than 1/4" to fit over the tension screw, but beyond that I'm not sure. If I had a box of springs laying around, I wouldn't even ask. Since I need to order stuff, might as well get something close!

As for a project thread, should I start one in the Members project area? Yes, some of us hobby guys starting out don't or can't have a full shop, so we have to substitute resourcefulness for raw tons of iron. Maybe it would encourage another beginner.

 

[mikey]

@mikey Thanks for the encouragement.

Brother, if you have the will and determination to see this through, you can do it. I don't know about you but the best way to make sure I do something is to tell me I can't!

For the half moons, do they exactly have to be 1/2 circles? How about being a clipped circles? (Almost 1/2 moons.) I was thinking of laying the tight tolerance O1 rod on its side and holding them with a 4J and cutting a flat on them. I'd use carbide, I guess. Would that work? Or would that harden the daylights out of it?

No, the half-moons do not have to be perfect halves; mine are not. However, the flats need to be pretty flat. I don't know if cutting them on the lathe will harden them excessively; you have to try it and see. I don't see why it would be much harder than using an end mill if you use a lot of cutting oil and take small bites but having never done this before, I am not sure. Try it and see.

For the knurl pins, could I use D2 steel? That's a tight tolerance tool steel. Drill rods confuse me. Looking on McMaster, they have comments that O-1 could be used as drill rod, as well as D2, M2, well you get the idea, too many choices. They also have some M42 tight tolerance rod as well. It specs at -0.0002" to 0" ground finish. ($14 for 4.5") I know M42 will maintain its hardness! What kind of hardness is desirable? I could get hardened O-1 for instance.

I just used a drill blank. You can buy these cheaply on ebay. I used PTD brand because they are known to be a quality brand but you can use whatever you like. Size them for the ID of the wheels you use.

I'll try the layout lines, hacksaws and files. After all, it's only low carbon steel, not tool steel. Filing shouldn't be that hard. Almost any filing is better than filing tool steel with a diamond file! The filing will keep me off the streets, which is a good thing these days. There's a 4x6 horizontal bandsaw in the garage, but I just don't trust it enough to do this kind of work. The vise is terrible.

Filing is not hard. Filing accurately is hard!

One last question, what did you use for the spring? How long does it need to be? It has to have an ID greater than 1/4" to fit over the tension screw, but beyond that I'm not sure. If I had a box of springs laying around, I wouldn't even ask. Since I need to order stuff, might as well get something close!

The spring is not critical. If it helps, mine is 1-1/2" long.

As for a project thread, should I start one in the Members project area? Yes, some of us hobby guys starting out don't or can't have a full shop, so we have to substitute resourcefulness for raw tons of iron. Maybe it would encourage another beginner.

Yup, start a thread there. I guarantee you that there is some silent guy out there with fewer tools and experience than you that will benefit from everything you share. I think this is a good project for this kind of effort because most of the dimensions are non-critical. In fact, none of them are critical but you need to try for good fits where you can. In the past, guys who made things mostly by hand were called Craftsmen ... not a bad label if you ask me.

 

[WobblyHand]

@mikey Alright, one last question on drill blanks. The link you provided has a lot of listings. What's in common is they say 3/16", which to me is 0.1875". However, they seem to be all different diameters? Right off the bat, I see, .1770, 0.1600, .1760, 0.1910, 0.1660, and 0.2010. Why are they different diameters and not just 0.1875? How does this work? Confused.

Are they machined or brazed onto other tooling? Why is 3/16 drill rod not 3/16? What kind of tomfoolery is this?

Don't get me wrong, I understand that I'd get something that was dimensionally closest to what I need. I'm just used to ordering things with a tolerance that I understand. Mind is flabbergasted that 0.1600 is called 3/16. Is this weird dimensioning also in other parts of machine technology? Or is this eBayese?

 

[mikey]

It is Chinese-ese. Look for blanks made in the US or with a stated tolerance. Drill blanks are normally +0.0000, - 0.0003" or something like that. If in doubt, order from McMaster Carr; they will give you dimensions and you'll get a quality product.

 

[WobblyHand]

Oh, thank goodness, thought I had gone insane! There weren't any PTD drill rods in good sizes today on eBay. Might have to shop on $$$ McMaster. I'll get something.

One thing I don't quite understand is if one should get a hardened rod, or just "drill" rod from a reliable supplier. McMaster really confused me with multiple steels qualifying as drill rod, especially since they were available as either hardened or annealed.

Edit: Formroldie sells carbide pins, so clearly they think hard is good. Might go with hardened pins then.

 

[mikey]

You are looking for drill BLANKS, not drill rod. Drill blanks are hardened to about Rc60 and are precisely sized.

 

[royesses]

My LMS straddle knurler wore the original pins a lot so I made some out of 4130 - fail lasted a couple of knurls and started wearing. So I made some out of 4140 and heat treated and tempered to 52 Rockwell and they are doing much better. I may also go the carbide pin route. I wonder how well the drill blank pins will last. That might be a good way to go also. I think Mikey just answered my question 60 Rockwell.

Roy

 

[WobblyHand]

You are looking for drill BLANKS, not drill rod. Drill blanks are hardened to about Rc60 and are precisely sized.

Oh, I missed that. Thanks for whacking the 2x4 on the side of my head! So RC60 and harder. That helps a lot! Still a few choices, but it narrows down the field. Thanks for your patience. All the 'rod' I was looking at was precisely sized, I was missing the hardness spec. Now that I have that, the shopping begins...