Tools for Machining Dowel Pins

I am currently trying to machine hardened dowel pins. I have to turn the dowel pin down and round the end and part it off. Will Carbide tools work for this or is there a better type of tool?

How many and what size? Any chance of making them from scratch then heat treating and centerless grinding afterwards?
If not I would cut them off to length with a CBN cutoff wheel, may temper the end back enough that it is not so hard to machine. I have used some inserts that worked well on Allen screws but I doubt the same inserts would work on dowel pins. Insert techs with the big suppliers may be able to steer you in the right direction.

Depending on size and quantity cutting them off on a grinder with that CBN wheel and form grinding could work.

Hi J_Tay14:
Is there a particular reason you want to start with hardened dowel pins?
You are making your life more difficult, maybe enough so that it's worth making them from some other material and hardening them after machining.
A-2 is a good choice for a lot of this kind of stuff.
It's air hardening, very stable and gets very hard...65 Rockwell if you want it that hard.
Buy it from McMaster Carr.

The dowel pins I'm familiar with are not always hardened through, so if you have a lot to remove be aware of this.
Also, the machines you do this on will influence if you can do this...a hobby lathe is typically not rigid enough for any amount of stock removal when hard turning, and certainly not for parting off hard stock.
The carbide grade you use will influence what you can do too, and your ability to sharpen it will determine how much carbide you have to buy and sacrifice to do the job.

Parting off will be your biggest nightmare...I doubt you can do it economically on a lathe... in fact I doubt you can do it at all unless your lathe is a beast.
You're better off cutting the dowels to length another way...abrasive chop saw, spin grinder, wire EDM; depending on what you've got in the shop, how many to do and whether it's worth it to farm the cutting out to someone else.
For example; I just cut 60 pieces of 17-4 PH condition H900 (45 Rockwell) on my wire EDM because it was the most efficient way to get all the lengths identical within 0.0005"
If you need to do something like that, it's a great way forward, but if you don't, another way will be far simpler and cheaper.

So consider making the parts in the soft state and hardening them; also consider cutting them to length first and then turning the shape on them.

Cheers

Marcus
www.implant-mechanix.com
Vancouver Wire EDM -- Wire EDM Machining

There isn't a particular reason. I was given the dowel pins and asked to make the parts on them. My first thoughts were Dowel pins aren't meant to be machined, but wanted to get some advice before going to them and telling them it would be better to get Steel and heat treat it.

Thanks for the information!

the hardened dowel pins i get are hrc60+. no way to machine them with carbide. cbn or grind. thre are cbn inserts up to 72hrc.

I have a couple of specific parts that I need to make in small, like 4, quantities at odd intervals. I have found the most efficient raw material for these parts is 3/16" and 5/16" steel dowel pins. I use a Hardinge manual bench lathe with 5C collets and about 3000 RPM. I have no trouble machining a step on one end and cutting-off with carbide tools. One part needs to have the length controlled closely and no pip on the ends, so I do a facing cut on the ends of those.

I usually use a TPG-221 C6 insert in an APT 3/8 bit in a Hardinge QCTP for the steps. The cutoff is a Luers-style P1 carbide blade in a Hardinge QCTP. I have proper grinders for keeping the tools sharp and yes, I do touch up the inserts once or twice to get extra life out of them.

Turn fast and use solid equipment. But carbide works OK on dowels.

Here are pictures of the stepped dowel pin. I also face off the mating set screw. These are for Hardinge taper spindle chuck adapters.

Larry

Not my first choice of materials to make parts out of, but, as above, carbide should work. Just watch your stick-out. Rigidity is your friend.

J_Tay14 said:

There isn't a particular reason. I was given the dowel pins and asked to make the parts on them. My first thoughts were Dowel pins aren't meant to be machined, but wanted to get some advice before going to them and telling them it would be better to get Steel and heat treat it.

Thanks for the information!

Click to expand...

What machine ?

dian said:

the hardened dowel pins i get are hrc60+. no way to machine them with carbide. cbn or grind. thre are cbn inserts up to 72hrc.

Click to expand...

I didn't know I couldn't machine hard dowel pins with carbide. Is there a law against it or??

I turn the splines off a 2" diameter curburized 8620 shaft and cut new splines into the hard layer.

I also part appx 5/8" gauge pins in half.

Been doing those for 10+ years with carbide.

Haven’t had to do it recently, but I’ve cut to length or put a step in plenty of 60 to 65 HRC steel parts, typically A2, with carbide tooling. Most were 1/4” to 1” diameter and this was done on a 15” Colchester.
I wouldn’t want to run penny pinching production that way, but if your tolerances allow, I wouldn’t hesitate to do a dozen that way.
Turned the teeth off of a few 5” diameter sprockets of the same hardness range as well, but insert life wasn’t pretty.