On Aligning the Vertical Bed of Sherline Mill

[Karl A]

I received a Sherline 5400 this month. I am in the process of checking and and adjusting it. So far, I have checked the flatness of the mill table. I measured 0.0001 inch over 2. 5 inches along the y-axis, and 0.0002 inch over 6 inches along the x-axis. Those values seem good to me. The next step is to align the vertical bed.

Here are the instructions for aligning the vertical bed from Tabletop Machining, by Joe Martin:
"To align the vertical bed with the X and Y slides, mount something to the table that you are sure is square. With an indicator mounted to the head, move the head up and down a couple of inches with the indicator reading a known square that is set up to read in the X-axis direction. With the four screws that hold the steel bed to the column block, adjust the bed until there is a minimum indicator movement. The Y-axis direction can be corrected with a shim between the column block and a mill base using the same method."

A photo of the page for the book is attached. I shows a square on the mill table. It appears to be a machinist square. I don't have "something ... that you are sure is square" -- a reference square. What square and and level of accuracy shall I buy, for this purpose and for general use with the mill?

Karl

 

[bradells]

Do you have something that is parallel?

It will take longer, but you can measure both edges of the parallel (held in a clamp or fixture approximating a 90deg angle).

Take both readings and say you have .005 and -.005 those would cancel out to 0.000

If they were say .005 and -.009, you would be leaning -.002 away...

Using something square would be best, as you reduce any error in the bed/fixture as you move it about the Z Axis


Brad

 

[mikey]

You are going to be tramming the column numerous times over the life of the mill so 1) get used to it, 2) buy an accurate reference, and 3) check tram often.

How accurate the reference needs to be is really up to you. Consider that if the column is off a thou at the bottom, it will be much more off at the top over the length of the column. My suggestion is to use the most accurate reference you can afford.

Options are:

• A solid square as shown in your picture. Mine is a Tesa tool maker's solid square accurate to 3 microns over 4" and is what I use for this job. Good enough. A tool like this is NOT used to do layouts and stuff; it is a reference square and expensive.
• A 1-2-3 block. This is the least accurate unless yours is verified to be accurately ground. Imports are not usually that accurate.
• A cylinder square. A cylinder square is potentially the most accurate if you can find one that is lapped accurately on the bottom. You don't need a big one. My Murken's magnetic cylinder square is dead on zero over 3" and is more than tall enough to align the column. I don't use it because the table is aluminum and the magnet won't stick. I think a 4-6" tall cylinder square is more than enough.

If I could suggest one of these to you, it would be to buy a decent enough cylinder square. It need not be high end, like a Taft-Pierce. Something imported would be okay, like this one from Travers. It is accurate to =/- 0.0002"/5 microns over a 6" length, which is good enough for this job. It will likely last you a lifetime if cared for and will work to check squareness of other precision tools. Think about it.

 

[mikey]

I forgot to mention that if you can, buy a tooling plate for your mill. It will save your table top from a lot of damage over the years. I have one that is from a company that is no longer in business but I also bought Sherline's plate for a friend's mill and it was dead flat. Put that plate on the table, lock it down and tram from there.

 

[Karl A]

Brad,

I can see from you instructions how something that is parallel can be used. No, I don't have something that is parallel.

Mike,

I now realize that 0.0001" is 2.54 microns. I am used to thinking in terms of microns in a different field. My employer manufactures, packages, and sells membranes that have polymeric selective layers with thicknesses that range between tenths-of-microns and tens-of microns.

A high-precision 3.5 x 4.5-inch Starrett solid square (model 20-4 1/2) at McMaster-Carr costs $295. It's accuracy is .0001"(2.5 microns) every 6" (150 mm). I can afford that cost, but it would slow down my acquisition of other items. Sherline's tooling plate is on my list of accessories to buy.

I hadn't considered a 1-2-3 tri-block. I found that Suburban Tool is offering a single block, with no holes, in size 1 x 2 x 3" plus/minus 0.0001" and square within 0.0002" total. They claim that it is made at their facility, in the US. Cost is $92 plus shipping.

PRECISION TRI-BLOCKS / 1-2-3 BLOCKS by Suburban Tool, Inc.

www.subtool.com

The accuracy of 0.0002"/5 microns over 3" would be least in the kingdom of heaven (the options that you provided).

Your reply is my first exposure to a cylindrical square. I looked at the one from Travers for which you provided a link. Compared to a Sherline 5400, it's big and heavy: 3" dia x 6" long steel cylinder with 18-lb shipping weight. I can see that a cylindrical square would provide a reliable reference for tramming the column (aligning the vertical bed), if its weight doesn't affect alignment. Is that a possibility?
I can see that it would be nice to have the combination of a granite surface plate and a cylindrical square, as a reference square.

Karl

 

[mikey]

I just chose that Traver's cylinder square to show you what I meant. These cylinder squares can be expensive but they can be very useful. I think a 1-2-3 block is okay but you have to back it with something so it doesn't move; they aren't all that heavy.

The important thing is to understand the concept. You need an accurate vertical reference to align the column. How accurate the reference is is really up to you.

I highly recommend the tooling plate. Bolt it down and sweep the surface; it should be as flat as the Sherline table. If it is then anything you put on it will be accurate, including your vise.

Speaking of vises, if you can spare the cash, look into a steel screwless vise. A 2" vise would suffice on this mill. Vertex makes good ones. Look for one with a long slot on the sides to lock the vise down; they are much easier to make hold downs for. Sherline's aluminum milling vise is okay but nowhere near the accuracy of a screwless vise that is ground and hardened.

 

[Aaron_W]

I have this set of machinist's squares. They are a fairly cheap set which I just got to get me started, but they are square to each other and my 1-2-3 blocks so I've been satisfied with them. so far. These are what I've used to square my mill, and then dial it in further with an indicator.

https://littlemachineshop.com/products/product_view.php?ProductID=5874&category=

They sell singles as well for even less but on a mill the size of the 5400 I have used all three sizes so the set of 3 has been worthwhile for me.

Little Machine Shop has been a good resource for me, they offer decent quality import tools. Not as cheap as some on ebay, but I've not been disappointed with anything I've bought from them. As the name suggests they focus on small machines.

 

[Karl A]

Mike,

I found that Suburban Tool also makes and offers cylindrical squares. Model CS-6 is 3" diameter x 6" tall. It is square to 0.0001". Price is $370.

STEEL CYLINDER SQUARES by Suburban Tool, Inc.

www.subtool.com

Shipping weight is 18 lb.

I am concerned about the weight of a heavy cylindrical square on the Sherline 5400 causing sufficient deflection to affect the alignment reading obtained with the cylindrical square. Do you think this is a valid concern?

Thank you for the recommendations on a vise. Does making the hold downs for the slots on the sides of a vise require a vise, or can they be made using a lathe chuck as the holder?

Karl

 

[Aaron_W]

Thank you for the recommendations on a vise. Does making the hold downs for the slots on the sides of a vise require a vise, or can they be made using a lathe chuck as the holder?

Karl

I bought a similar vise on Mikey's recommendation. The rotary table hold downs that came with my Sherline rotary table fit the slot on my vise.

Sherline sells a set separately as 4 jaw hold down clamp set, this is also the set Sherline includes with their vise.

https://www.sherline.com/product/3058-4-jaw-chuck-hold-down-set/

 

[mikey]

Mike,

I found that Suburban Tool also makes and offers cylindrical squares. Model CS-6 is 3" diameter x 6" tall. It is square to 0.0001". Price is $370.

STEEL CYLINDER SQUARES by Suburban Tool, Inc.

www.subtool.com

Shipping weight is 18 lb.

I am concerned about the weight of a heavy cylindrical square on the Sherline 5400 causing sufficient deflection to affect the alignment reading obtained with the cylindrical square. Do you think this is a valid concern?

Thank you for the recommendations on a vise. Does making the hold downs for the slots on the sides of a vise require a vise, or can they be made using a lathe chuck as the holder?

Karl

That is a lot of money for a cylinder square but Suburban Tools make really, really good tools. 18# is not a lot of weight because it will be centered over the center of the mill and it isn't enough to distort the structure of the mill. It is heavy enough to sit there without having to be clamped down and it will be accurate. I think a 3" OD square is great - small enough to use on a Sherline or any other mill. I am NOT recommending that you spend that kind of money on an alignment tool. I am just making you aware of the options.

This is a good time to discuss what we're doing here. You have to ask yourself just how accurate your mill needs to be to do the work you're doing because as you're discovering, it gets expensive to chase tenths. If you are just starting out then it might be okay to just use a reasonably priced machinist's square or 1-2-3 block to align the column. Later on, as you gain experience and if you need to work with greater accuracy then a cylinder square is the way to go.

As for vise hold downs, you can use Sherline's hold downs initially as Aaron said. Then you can make better ones if you wish.

Before I forget, keep in mind that the Sherline mills is potentially really accurate because it has adjustable gibs, headstock angle and column; these same things can also make the mill very inaccurate if they are off. Learn to adjust the gibs well; it makes a difference. Find a good tool holder and use a dowel pin or accurate rod to align the headstock.

If you are not sure how to do these things then sing out.