Machinist's Hammer Head on Sherline Lathe (mill?)

[BiggerNoise]

I recently took a stab at another project, a machinist's hammer. Ended up with a bit of hammer shaped metal that I can hit things with and lots of experience.
(brass face omitted because I made a boneheaded mistake that my pride prohibits sharing)

I think I want to remake the head because I didn't do a very good job on the hole that the handle screws into. The head is a 1" diameter cylinder, 2.5 inches long. The handle hole is tapped 1/2-20 and there's a bit of a .600 hole before the threads start to allow the handle to 'vanish' into the head. Material is 6061.

To get a flat bottom on the hole, the suggested order of operations was to:

Drill close to the minor diameter
Use a mill to mostly flatten the bottom of the hole
Use a boring bar to open the hole to the minor diameter
Use the boring bar to open that little bit of .600 hole

The problem was really getting a grip on the thing with the four jaw. because of the head's length, I had to reverse the jaws on the long axis of the head. Unfortunately, this raises the part off the face of the chuck and I couldn't get the jaws on the narrow axis to grip the part.



So, I tightened the long axis jaws and worked gently. The drill was no problem. I couldn't get a mill in there, I was already close to the minor diameter and was able to flatten the bottom a bit and get my minor diameter, but there was no way that setup was going to hold together for the .600 boring operation.

At the end of this experience, I said "this would probably have been trivial on the mill".

The only thing that might have been an issue is that I do not have a boring head for my mill. The Sherline offering doesn't have a good reputation around these parts and I've just caught my breath after looking at the Criterion heads everyone seems to love.

So, after that lengthy setup, two questions:

• I can understand that Sherline boring head is fussy, but is there an envelope within which, it might deliver reasonable results?
• If I stayed on the lathe, is there any way I could have made the setup more rigid?

 

[mikey]

Good job! Not easy to do with just the lathe.

I don't care for the Sherline boring head. I put in several years trying to like it and gave up. A Criterion S-1-1/2 is a vastly superior head. Look for one that uses 3/8" bars and buy cobalt bars from KBC.

 

[BiggerNoise]

The cobalt bar you recommended previously is just wonderful. It's somewhat frustrating that I have only been able to use it in setups that left a lot to be desired for rigidity. Someday I'll use it to bore a hole in something securely held and I'll probably be moved to tears.

 

[EricB]

As I wrote in another thread, Sherline's boring head is the only tool I have from them that did not work as expected out of the box. After a bit of cleanup it does a decent job with light cuts in soft materials using Sherline's boring tools.

That being said, the other day I bored through an iron casting using the Sherline head and an inexpensive brazed carbide bar. It did the job and the bore dimensions are good. The finish was looking good at first but got progressively worse and I couldn't stop the chatter with the lighter cuts to bring it to size.

I've read that boring separates machinists from everybody else. I have a ways to go.

 

[mikey]

Eric, you would not believe how much better and easier it is to bore with a Criterion S-1-1/2 head. It threads directly onto the spindle via a 3/4-16 to 7/8-20 adapter so the connection is quite rigid. The ways of the head are much larger and beefier than the Sherline head and the mass of the head is significantly higher. When used with a good cobalt boring bar, the Criterion head is a VAST improvement over the Sherline head.

Boring on the mill is not difficult, although it is a skill like most things. Still, having the right tools is an important thing and I would encourage you to upgrade your head and bars when you can. If you go for an S-1-1/2, Criterion made them to accommodate either 3/8" or 1/2" bars. I highly recommend you go for the A-model that takes the smaller and lighter 3/8"
bars. For bars, go for the M42 set from KBC.

 

[BiggerNoise]

I did fix the brass face and am reasonably happy with the results:


I did have one issue with the face. I did the large end first, then flipped it around and did the small end (threaded) with the part in the four jaw.

The machining went well, then I set up for the thread cutting by removing the chuck from the lathe and clamped it to the cross slide.

When I was cutting the threads (7/16-20), the torque from the die wrench started to rotate the head in the jaws of the four jaw (causing those marks near the end of the face). I was able to finish the threads by really tightening down the chuck.

So, assuming that's a reasonable way to set up for cutting threads:
- Should I always remember to really tighten the chuck before cutting?
- Should I have a better tap & die set? This is an Amazon no-name set
- Should I have single point cut the threads? Seems overkill for this thread, but I did inherit the thread cutting gears along with the lathe.

 

[BiggerNoise]

Eric, you would not believe how much better and easier it is to bore with a Criterion S-1-1/2 head. It threads directly onto the spindle via a 3/4-16 to 7/8-20 adapter so the connection is quite rigid. The ways of the head are much larger and beefier than the Sherline head and the mass of the head is significantly higher. When used with a good cobalt boring bar, the Criterion head is a VAST improvement over the Sherline head.

Boring on the mill is not difficult, although it is a skill like most things. Still, having the right tools is an important thing and I would encourage you to upgrade your head and bars when you can. If you go for an S-1-1/2, Criterion made them to accommodate either 3/8" or 1/2" bars. I highly recommend you go for the A-model that takes the smaller and lighter 3/8"
bars. For bars, go for the M42 set from KBC.

Boy, those Criterion heads are hard to come by. I'm bidding on a used one, but have seen new for $1,000. That's bonkers.

At any rate, a while back you made reference to this thread adapter. Is something like 12L14 strong enough for that, or would I need to build it with more of a tool steel?

 

[mikey]

ABSOLUTELY learn the cut threads on the Sherline lathe. It takes a bit of getting used to when setting up for threading but it is straightforward and works very well. I have cut numerous class 2a/2b and 3a/3b threads on this lathe and no longer even think about converting to the screw cutting attachment. No slipping of the work in the chuck and you will be able to produce very finely cut threads. Spend the time to learn about thread reliefs, chamfering the end of the work and then how to size and turn the work to the required diameters. From there, screw cutting is simple. If you get stuck, let me know.

You can definitely use 12L14 for a boring head adapter. Sherline uses 12L14 for their end mill holders and other things that thread onto the spindle so you can, too.

I've been looking for a S-1-1/2 for you on eBay. They usually run between $50 for a beat up one to maybe $120 for one in really nice shape. You do not need a mint condition head; you simply need one that is totally intact and has all the required screws. There is a nice one listed but the seller hasn't responded with the bore size yet; I'll let you know.

 

[BiggerNoise]

This is the listing that I've been bidding on, seems to be in pretty reasonable shape. It looks like the various backsides just screw on to that 7/8-20 thread.

 

[mikey]

See the 3 socket head cap screws on the side? Those are supposed to be set screws with ball bearings under each of them. Contact the seller to confirm the bearings are there.

Also, stop bidding. You're driving the price up. PM me and we'll go over bidding.