Sherline Boring Depth Question

[tharperidaho]

Hello, I am new here and pretty much new to machining. I have been going through the Harold Hall books in the Workshop Practice Series and have decided I am willing to tackle the dividing head project in the Milling: A Complete Course book. I have looked over the project and have a concern about boring the cast iron spindle bearings. I have a Sherline 5400 mill. In order to bore both bearings in the same setup, the depth needs to be 2". The Sherline info says that any boring work should stay under 1.5 inches. I am inclined to believe them, but thought I'd ask what sorts of experiences folks have had with their Sherlines.

If this sounds like too much for the machine, I suppose I could scale down the dividing head, but wonder if I would run into usage problems that I do not foresee. Alternatively, I could make the body and bearings, fit them, and take the unit to a machine shop and let them do the boring. Being a confirmed do-it-yourselfer, that idea does not seem completely satisfactory though. Any thoughts will be greatly appreciated.

Cheers,
Tom

 

[mikey]

Hi Tom,
This is the first I've heard that there is a limit to what the Sherline mill can bore to. If it can only go 1.5" then I've broken their rule multiple times. As far as I know, bore depth is not the issue; bore diameter is. When a boring head is extended too far then balance becomes an issue, especially if you use the tiny OEM Sherline boring head. You can go bigger with a bigger, stiffer boring head like a Criterion but even that has a limit before vibration stops you. I've gone big enough to rock the machine on it's base.

What bore diameter are you trying to hit?

 

[tharperidaho]

Hi Mikey,
Thanks for the reply. Sounds like I am worrying about the wrong axis. The cast iron bearings need to be bored out to the neighborhood of .945. His plans are all metric and call for a 24mm diameter. Does that sound like too large a diameter with a better boring head?

Cheers,
Tom

 

[mikey]

Even the tiny Sherline boring head can cut a 24mm ID. Cast iron is not hard to cut so using that head will work - just take smaller cuts and work your way out to final ID.

I use a Criterion S-1-1/2A on my 5400. It is a square head that is solid, well-balanced and accurate. It is tiny but just the right size for this mill. Using an adapter, it screws right onto the spindle and it can be extended farther than the Sherline head before vibration becomes a problem. I've only used this head and the Sherline head so cannot attest to how well others work but the S 1-1/2A is a really good one and I really like it.

 

[itsme_Bernie]

Hey Tom-

I have the 5400 Mill. A few thoughts and experiences here-

First, the machine can do what you observe it can do. In other words, give it a try, observe what you can make it do, and whether you see anything bad happening.
That said, I see no reason you can't do that and more. I used the Sherline boring head, and another even bigger boring head I conjured up.

The Sherline Boring head is the ONLY accessory that Sherline made that doesn't honestly work as promised and expected out of the box. Here is why:
The 4-40 (if I remember correctly) nut, with the graduated dial for adjusting the depth of cut, does not have an improved surface on the end that makes contact inside.

You can resolve this in a few ways, but the easiest is to take the screw all the way out, and turn the end as flat as possible. Slightly rounded is the best way.

You can use the head, just don't trust the numbers- adjust the head and measure it's depth of cut with a depth mic on the opposite side or something.
What I did was buy a small "made in India" head, removed the 7/8-20 tapped arbor, and drilled and tapped the 3/8-24 thread inside it for the Sherline MT1 threaded arbor.

It fits PERFECTLY in there. The 7/8 thread slides right over the Sherline Spindle thread. Pics below. Of you want more specs, pics,mor info on this, I'll be happy to post.

You can do A LOT more than you expect with that little mill!! I cut much larger pieces than I expected (6 inches diameter) like a vertical lathe, and toolpost on the table!

Bernie

 

[tharperidaho]

Thanks Bernie and Mikey,
That info definitely gives me some options and a better understanding for approaching such questions. Bernie, thanks for pointing out the need to observe. I am pretty new to this and feel like I am wading around in the shallow end of a very large body of water. It's exciting, but I am wary of not knowing what I don't know. The last thing I want to do is mess up my lathe or mill. I've never failed to surprise myself with the clever ways I can manage to do stupid things when I don't know much about what I am doing. Okay, off to make some decisions. I am looking forward to starting this project, but have to go on a vacation first. Life is tough sometimes. . I'll post some shots once I get started.

-Tom

 

[D.C.Clark]

Bernie makes some excellent points. Here's how I adjust my boring head.



David Clark in Southern Maryland, USA

 

[Rick Leslie]

I have a 5500 (I believe) that I converted to CNC a while back. The little machine never ceases to amaze me. The only drawback is ,as you see, limited work area. The Z axis has a good amount of travel and I've drilled 2.5 to 2.75 inches before with no problems. I don't have a boring head for the Sherline at the moment (CNC negates the need for what I use it for) so I have no experience with those on the mini mill.

My suggestion is a general one: watch some Youtube videos of general machine work and practices, then experiment and get a 'feel' for your machine. Know how the material is supposed to feel when cut properly. Each material has it's own feel. Tubalcane (tubalcain?) has some great videos for general operations. I still watch them after 30 years of 'hacking'. Above all, be safe! Eye protection, no loose clothing, etc. Even a small machine can ruin your day.

One other thought: could you rough in the bore and finish with a metric reamer?

Hope you have a safe and happy Independence Day.

- - - Updated - - -

Almost forgot, in case you haven't already found them:

http://www.sherline.com/index.html
https://www.littlemachineshop.com/

 

[tharperidaho]

Thanks Rick and David. The reamer is an interesting idea and I like the way to use an indicator to watch how the boring head attachment is adjusting. That's a lot better than hit or miss. I think I will use that setup on my Sherline head.

Current thoughts are to attempt to make a larger boring head as a pre dividing head project. I have a copy of Jose Rodriquez's boring head video. It looks like something that i am capable of. I''ll test it out on a a few things before committing to the real thing. Those Criterions sure look nice though...

Rick, thanks for the safety reminder. I built bicycle frames back in the 70's and managed to put a steel sliver in my eye while using a burr on a tube - no safety glasses. No damage, just a very good scare that I treasure as a very cheap lesson. I live in the country and it's an hour to town for medical help if its needed. So I always think about safety and always appreciate someone reminding me about it. I'm not very good looking, but I still have great appreciation for my body parts!

Oh, I have subscribed to Tubalcain. I think the internet accounts for something like 90% of my brain these days.


-Tom

 

[HomeMetalMan]

Good to see Tom that you are intending to make the dividing head, you will be in good company as it is amongst the most popular of my designs. I am though concerned that you may be thinking of making the boring head in the book. This is rather too big for your mill and will need to scale it down, as others are saying vibration may be a problem. Unfortunately, when I first produced the article, over 20 years ago, mini milling machines were not that common so produced it with the machines available at the time in mind.

As an alternative you may like to consider the mini boring head detailed on my website. This is an item mostly made on the lathe and is a good exercise in using the faceplate. Faceplates, not liked by many, but the methods used are fully detailed. See here for details http://www.homews.co.uk/page199.htmlhttp://www.homews.co.uk/page199.html

Regarding the bearings, you will be boring them out almost to the required size on the lathe so there will be very little to remove on the milling machine.

Harold Hall