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Good material for rear rail on magnetic chuck

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Diamond
Joined
Sep 25, 2011
Location
Garbsen, Germany
I made a rear rail for my magnetic chuck, and side-ground it:

attachment.php


The rail is designed to slide down out of position, and has a groove so that the inside corner is free and there is a drain path for grit and swarf:

attachment.php


I made this out of construction (low carbon) steel, but needed to be careful to provide "mounting pads" which are fairly small so that they don't short out the magnetic field of the magnet poles. The next time I make a rail like this, I want to make it from some kind of metal that is non-magnetic, so I can make contact all along the chuck.

Could someone recommend a type of stainless that is (1 ) non-magnetic (2) easy to machine (3) fairly inexpensive (4) available in ground stock of the right general size, say 8 x 30mm?

Cheers,
Bruce
 
Very nice job Bruce…I have made them by splitting heavy steel angle iron to desired size grinding flat the face the chuck side and notches for bolts ..good to use long good quality bolts to save the thread as long as possible then with tighten with two fingers so not over tight, center bolt first. Good to have a right angle flat parallel to set parts 90 off the rail and to have a bump rail at the go end so a heavy grind job might not slide.
Haven t considered the mag loss but that is good thinking.
 
Hi Mark,

Any 300 series/austenitic stainless steel or brass will do the job.

I'd like something harder than brass, but don't know any metallurgy. Looking at this table of type 300 stainless https://mdmetric.com/tech/ssgradetable.htm could you please recommend a specific stainless type?

I picked this chart because it shows the German and DIN equivalent types.

(One type that seems available and inexpensive in Germany is 1.4301, which is type 304. Is that a good choice? I seem to remember that it's a PITA to machine, because it work-hardens in a flash and then eats tools. Is there a better choice?)

Cheers,
Bruce
 
I want to avoid cast iron because it will "short out" the poles of the chuck, unless I make support pads as I did on the one shown above. My grinder has a good flood coolant system, so I am not so worried about heating and warping.
 
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I want to avoid cast iron because it will "short out" the poles of the chuck, unless I make support pads as I did on the one shown above.
I have a few Walker chucks that have cast iron rails. Yes, they have standoffs.. I have had other chucks with rails made of angle iron (OEM).. It is a real pain to grind the steel rails, they heat up and jump into the wheel. Really tough to get an accurate true surface on those rails. Grinding the cast iron rails is easy...
 
Hi Mark,



I'd like something harder than brass, but don't know any metallurgy. Looking at this table of type 300 stainless https://mdmetric.com/tech/ssgradetable.htm could you please recommend a specific stainless type?

I picked this chart because it shows the German and DIN equivalent types.

(One type that seems available and inexpensive in Germany is 1.4301, which is type 304. Is that a good choice? I seem to remember that it's a PITA to machine, because it work-hardens in a flash and then eats tools. Is there a better choice?)

Cheers,
Bruce

304 is is fairly easy to turn or mill, 316 is a pain. 304 can get gummy at times, feeds and speed have to just right. Someone recommended using silicon carbide wheels for grinding it. Both 316 and 304 will work harden in a pinch. 316 is readily weldable so it used most often for architectural and structural weldings. My only experience is with turning and milling 304. I had some 316 and gave up on it. With 304 just take as deep a cut your machine will allow. I have no clue how it would grind.

http://www.aksteel.com/pdf/markets_products/stainless/stainless_steel_comparator.pdf
http://www.practicalmachinist.com/vb/general-archive/grinding-stainless-83473/


dee
;-D
 
I do not believe that a magnetic rail has any effect on the holding field. Based on observation the magnetic field is at 90 degrees to placement of the mag bars, the ends of the mags have very little field strength, and this field does nothing, to add or subtract from the central field.

Every magnetic chuck manufactured by the companies that would know, has a steel rail on the side when purchased new. If there was a issue with magnetic rails, don't you think the rails would be made of something non magnetic.
 
Hi Mark,



I'd like something harder than brass, but don't know any metallurgy.

When you use the fence, you are only pressing the part against it. The only wear it ever has is when you grind it to make it parallel with the grinder ways. So hardness is not a problem. With a modern fine pole chuck that has the poles going all the way to the edge, a non-magnetic material is neccessary. With an older coarse pole chuck, with the poles not going to the edge, there is no magnetic field to 'short out', but these are not common now.

I do not believe that a magnetic rail has any effect on the holding field. Based on observation the magnetic field is at 90 degrees to placement of the mag bars, the ends of the mags have very little field strength, and this field does nothing, to add or subtract from the central field.

Every magnetic chuck manufactured by the companies that would know, has a steel rail on the side when purchased new. If there was a issue with magnetic rails, don't you think the rails would be made of something non magnetic.

Mine came with brass rails. I have an older electromanetic chuck with an iron rail, but the poles of that chuck do not reach the sides, so they cannot be shorted out by the rail.
 
Hi Mark,

Mine came with brass rails.

Your arguments make sense. If my back rail gets damaged I think the next one might well be brass. A few minutes of reading indicate that there is a type of brass (beta) which is both harder and stronger than the other types. That should be a good material to use, if I can get a piece at reasonable cost.

(What about using 7075 aluminum? It is harder than brass and non-magnetic. Yeah, it's thermal expansion is more than steel, but on my grinding machine everything is flooded with coolant.)

Cheers,
Bruce
 
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I think Aluminum is not hard enough to resist nicks and bangs and does not touch up grind as well as iron or steel. Tend to agree with Toms Wheels that the loss should be minimal.

OT: To set all parts on the rail tends to wear a hole in the chuck surface at that place. Jobs that squareness does not matter should be set all about the chuck. jobs that do matter should be often spacer set away from rail. Grinding the chuck least often is good.

Adding a rail at the Go side (left) can be a great aid to holding parts from tipping and/or sliding.

A simple bar C clamped to a block and touching a tall part high up can often save a tippy job from tipping.

Push a tippy job hard hand shoved with two fingers often can tell if it might tip.

A tippy job is best served with one way grinding..coming in to stock feed (removal) from the grind side only (not the climb side.

Block-ins are best set to bump the part at the highest place..and on the go side.

Some put block-ins all about the part.. Then as the part expands from heat it may come lose. If coming lose to the go side it may tip..Good to put block-ins to the go side and perhaps the back side only..Adding a clamp to the back side block can also be an aid.

Mild-hard and soft block-ins mag hold better that hard.

Good to think parts expand and slide.

A Norbide stick can nick a radius or a bevel to a wheel quickly by hand. Yes only when you are comfortable and safe having you hand close to the wheel..(you can clamp a Norbide stick to a block but they can break.) one can do the same with a stick of carbide.

Rough parts that may damage you chuk surface can be set on a simple sheet of copy paper.

Good that block-ins be dead square.. or the side used for block touches part at high point.

A shim can be set at the high edge of a block-in to assure the support is high on the part.
 
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back rail on a surface grinder

I made a rear rail for my magnetic chuck, and side-ground it:

attachment.php


The rail is designed to slide down out of position, and has a groove so that the inside corner is free and there is a drain path for grit and swarf:

attachment.php


I made this out of construction (low carbon) steel, but needed to be careful to provide "mounting pads" which are fairly small so that they don't short out the magnetic field of the magnet poles. The next time I make a rail like this, I want to make it from some kind of metal that is non-magnetic, so I can make contact all along the chuck.

Could someone recommend a type of stainless that is (1 ) non-magnetic (2) easy to machine (3) fairly inexpensive (4) available in ground stock of the right general size, say 8 x 30mm?

Cheers,
Bruce
Sometime we tend to over-think what is needed. We don't need to worry about shunting the magnetism along the outside edge of the chuck. Take 1/8" or 1/4" angle iron and mill away the inside radius. Cut the slots for mounting, mill the top of the rail to about 7/16" to 1/2" wide and grind the inside that fits next to the chuck. Mount the back rail about 1/16 " above the surface of the chuck. Dress the wheel 38A100K8BVE and relieve the side of the wheel down very close to edge of the periphery of the wheel. Dial down with the wheel a few tenth at a time. Don't move in from the side of the wheel.
Best Wishes,
Roger
 
Chuck tops are mild so a good method is to tighten back rail with two only fingers… staring with center bolt and then tighten out from their. Good to use longer bolts (yes that don’t bottom out.) keep thread holes clean so less abrading threads.

Back-stop rail is ground in place so if finding a out of square chuck I would indicate the front end so the front rail can be set on the chuck for dusting…..I have not yet found an out of square chuck, So with that indicating the back side is fine.

Good to have some set-off parallel so work can be set off back rail and about the chuck so not always wear at back-center.

Selective oil stone honing can keep a chuck .0001/.0002 for a very long time. Perhaps run an an indicator across once in a while to note .0001 high and then hone that a little more.
 
QT RogerTool: [Take 1/8" or 1/4" angle iron] We had some Canada Steel angle iron.. about 1/4 x 2". I would parting wheel it to about 1" x 1/2" grind one inside leg flat, grind in screw notches ..and so make back and end rails.

Very nice job Bruce..and your top grind looks perfect.
Buck
 








 
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