tolerance needed for angle plate for milling gun parts

[Whiterabbit]

Hi guys,

I'm in need of an angle plate and am shopping. Economy parts are acceptable to me right now, and that does not mean that harbor freight anything is acceptable! Just that if it has the Kurt brand name on it, well, I probably cant afford it.

Anyways, I want an angle plate as a fixture for some parts, and I found an import site (I assume import, anyways):

http://www.victornet.com/subdepartments/Angle-Plates/250.html

So, these angle plates claim accuracy to .002 over 5 inches. I'm no grand machinist (I'm not even a poor machinist, I'm just starting out) but my vise right now is about half that, .001 over 4 inches (that's side to side, I assume the angle plate means up and down).

But still, do you think that .002" over 5" is acceptable tolerance? The price is right on these parts, so that's what I'm looking at.

Or should I scour ebay for something nicer but used?




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Finally, any recommendations for clamps to clamp parts to the plate? Needs to be soft enough to not mar Aluminum, but strong enough to secure steel.

[Whiterabbit]

also, it seems that C-clamps aren't Totally unacceptable on the mill....

http://ww3.tiki.ne.jp/~hwata/Images/C53photo/200907/JobOnJig.JPG

Still not often seen. do the machinists here say visegrip clamps and C-clamps (when used in this way) is always a no-no, and that these machinists "are doing it wrong"? or is it OK when keeping the clamp WAY clear of the table?

[W.R.Buchanan]

Kurt vises rear jaw tolerance is +/-.004/ inch in squareness. That means you put the thing on a surface plate and sweep the vertical side of the rear jaw up and down, the indicator should not move more than .004 in 1" of travel.

This particular tolerance was complete BS and way too loose, and when I called Kurt and they told me of it, I asked them if they actually did runs that bad.

They got all insulted since they are from Minnesota (home of really good machinists [smilie=p:) and told me that no they didn't, and sent me a new rear jaw for my new vise.

Where this really shows up is when you set up a long part to drill a hole in the end, and you edge find the vise and then find out your hole is out of position .015-.020 because of the angle of the vise jaw. .004 at 1" is .020 at 5".

IF they are claiming that their angle plates are Square to .002 over 5" then I would say that is going to be close enough for just about anything you will ever do. That's .0004 per inch which is pretty damn close.

Randy

[Whiterabbit]

You're the man, Buchanan.

Next up: that C-clamp thing. Nowhere NEAR the mill table. Not even close. But clamping to the angle plate. A-ok? Even if not ideal?

[MBTcustom]

I typically expect near perfection from an angle plate. I want less than .001 bottom to top, on all six sides.
I take precision of basic setup parts like this very seriously, because they determine the accuracy of your shop. You're shop is only as accurate as the finest measurement you can make, the squarest surface you can cut, the most parallel surface you can cut, etc etc etc.
It all boils down to your measurement tools, and your basic setup tools.
If I have a true square, and a true straightedge, then I can measure anything I want to as long as I don't need anything as close as those tools are capable of measuring. In the same way, you can't make accurate setups with janky setup fixtures.
However, if your measurement equipment and fixtures are correct, you can do amazing things with really ratted out equipment. I am fortunate, to have had access to surface grinders, and I ground all of my parallels and angle plates so closely that I can't measure them with a .0001 test indicator. But in order to grind an angle plate like you show there, you have to have one that is already true, because you can never grind any more square than the master that was holding the thing you are grinding.

As far as the clamps go, you do what you have to, but I never had good luck using C clamps. I have done quite a bit of work with Kant-Twist clamps, but even they are trumped by a good set of strap clamps. Usually, you can find a way to hold anything you need to with strap clamps.

[country gent]

There used to be a company Called Suburban that sold "kits everything roughed in and hardened for vises sine plates and sine vises. They were reasonably priced all that was left to do was finish grind and assemble. We did several when I worked at campbells as we had no heat treat available. I am a journeyman Tool and Die maker ( 35 years) and angle plates sine bars/plates and on some parts c clamps went together. I perfered the cant twist clamps over c clamps though. In machining it is set-up and how well you get the parts true and square. Indicators are your friend. anything that had to be accurate the first thing was to indicate the vise in to true and square. On bridgeport style mills head needed to be squared with the indicator also. ( Trammed in). Set up is everything when wanting accuracy

[W.R.Buchanan]

But in order to grind an angle plate like you show there, you have to have one that is already true, because you can never grind any more square than the master that was holding the thing you are grinding.

And there in lies the rub.

It is not impossible, but certainly very hard, to grind anything any closer than the machines capabilities or the fixtures you are using.

It obviously can be done or else we would never be able to better ourselves, however it takes a level of skill and patience that is not common in our society.

You also must consider what "level of accuracy" you are trying to achieve. This doesn't mean you should skimp or try to pass off bad products.

I reality on every job you do you must "try" for absolute perfection.

Since this is never obtainable you must decide what you are willing to settle for. This is why there is such a thing as a "tolerance." It gives you some wiggle room, and defines what the customer is willing to settle for.

Obviously every customer would like perfection, however that's just Too Fumping Bad, You can't have it! Cuz I can't make it!

I can however, get real close.

Randy

[MBTcustom]

Whoever is closest consistently defines perfection. True perfection is an illusion, but its relative. If the precision of your shop, and the quality is head and shoulders better than the next best thing, then you are for all intents and purposes, "perfect".

[country gent]

There is the "rule of 3". When hand scrapping 3 angle plates marked against each other and rolled from surface to surface when scraping them in will become square and true with out an master. There are several manuals/books that give this technique. I hand fit and resurfaced equipment by hand scraping for many years. The steel surface plates I resurfaced were more accurate than the granite plate used to mark them due to the rotation of the part on them each time. Scrapping is a means of extreme preccision but is slow and labor intense. A angle plate can be shimmed into square to the spindlde of a machine with an indicator. It can also be set up to parrallel to travel with the indicator. Most used tool in my box was the 8 ounce dead blow "bumper" i made. I used it for almost every set up every day. Most times the set-up was more time than the machining was. On certain machine parts I could hold .0005 square and parrallel in 2 feet of length. What gets interesting and try this on your mill. Tram head in square with spindle up. Clamp a true hole onto table and indicate it in oooo dead center. Lower table the distance of spindle travel re indicate hole with out moving x y axisses. Most used mills have enough wear that the table will float in out on y axis several thousandths. We had a bridgeport that was ground in at work table shifted .011 in 5" travel of table down. Knee dovetail wasnt square to head. On this machine centerdrilling a hole then going to a drill would put the hole off axis by .008-.010 just raising or lowering the table knee. Can remember the old tool maker I apprenticed with telling me anyone can make a good part on a good machine it takes a crafstman to make a good part on a worn out machine. Craftsmanship is everything.

[MBTcustom]

There is the "rule of 3". When hand scrapping 3 angle plates marked against each other and rolled from surface to surface when scraping them in will become square and true with out an master. There are several manuals/books that give this technique. I hand fit and resurfaced equipment by hand scraping for many years. The steel surface plates I resurfaced were more accurate than the granite plate used to mark them due to the rotation of the part on them each time. Scrapping is a means of extreme preccision but is slow and labor intense. A angle plate can be shimmed into square to the spindlde of a machine with an indicator. It can also be set up to parrallel to travel with the indicator. Most used tool in my box was the 8 ounce dead blow "bumper" i made. I used it for almost every set up every day. Most times the set-up was more time than the machining was. On certain machine parts I could hold .0005 square and parrallel in 2 feet of length. What gets interesting and try this on your mill. Tram head in square with spindle up. Clamp a true hole onto table and indicate it in oooo dead center. Lower table the distance of spindle travel re indicate hole with out moving x y axisses. Most used mills have enough wear that the table will float in out on y axis several thousandths. We had a bridgeport that was ground in at work table shifted .011 in 5" travel of table down. Knee dovetail wasnt square to head. On this machine centerdrilling a hole then going to a drill would put the hole off axis by .008-.010 just raising or lowering the table knee. Can remember the old tool maker I apprenticed with telling me anyone can make a good part on a good machine it takes a crafstman to make a good part on a worn out machine. Craftsmanship is everything.

Words of wisdom there.
I work with an old gent who is a self taught machinist, but he's one of the best I have ever worked with. The new guy gets the new bridgeport, I get the 10 year old Sharp, and Hershel (the old machinist) uses the old and busted Bridgeport. The old Bridgport is one of the most ratted out, sloppy, cussinest mills I have ever turned a crank on. I have real trouble making parts that will pass inspection on old "Molly", but Hershel cranks 'em out day after day just barely in tolerance. He just smiles and says: "now don't give me no **** about old Molly. She does just fine if you know how to run her!"
The point is, we each know our mill like the back of our hand. Mine has gotten worse and worse over the years, but since I'm keeping tabs on it's trouble spots, I know how to work around them. My mill at the gunshop is a different story. It has a short table, and is fixed up with ball screws. For all intents and purposes, the table movement is as predictable as the sunrise. The spindle is a different story. It changes when you lock it down, so I have to make sure to find center in the same condition that I will be using it. ie, if I'm going to be drilling a hole, I don't lock the spindle when finding my start point, but if I'm milling, I lock it when finding home position.
Each piece of machinery has it's quirks, and that's OK, you can work around them, but trying to work around janky measuring equipment or setup fixturing is a waste of time, and is worth the time and expense to correct.
For instance, you buy a new Kurt vice and check it for squareness and parallelism, and it looks great. Well, strap it to your mill and use it for a month, and then check it. It will have changed. At that point, I disassemble it, and grind in each piece to .0001 and use it for a year. Then I do it again. From there, I regrind every two to three years but it changes very little after that first grind, and I'm pretty much just knocking off the dings. Being able to lock down a workpiece and be assured that it is square is irreplaceable.

[country gent]

Yes it is and being able to lock the piece down true and secure in a vise is nice. Being able to set up an angle plate and work of it with strap clamps and be square from start is great. Gunsmithing is all small parts. I have 6 screw jacks many 1 2 3 blocks and step blocks for when a machine member needs to be set up. Some times the set-up requires a lift truck or crane to pick up the part. Then set up and clamped down adjusted with a die bar screw jacks and blocking Indicated into square and work done. Knowing how to set up a part is the actual skill at times. Another trick when working this parts. Put a plate in the vise dust of true with a mill or fly cutter. Put a layer of double face tape down and stick the part down on it. I have made small thin berrryillium springs for govenors like this. You cant work hard or very fast but you can get the job done. A little alchlol and the tape will release the part when done.

[W.R.Buchanan]

Country: if you can scrape ways and get it right you are definitely among a dying breed. I know one guy personally who can do it. I doubt there are ten guys left in all of California who know how and can actually improve on a ground way surface.

Today new CNC machines are made with roller bearing ways which don't need scraping. Even surface grinders have these ways now. An Okamoto surface grinder is a joy to use simply because of the low amount of effort you use to run the table back and forth on the ball bearing ways.

It would be interesting to see how much machinery will have changed in another 50-100 years. I doubt much will be done manually.

The new 3D printers are about 1 or 2 clicks away from the Replicators in Star Trek.

I guess they won't need us at all then. Unless their toys break! Then you always seem to revert back to basics.

Flintlocks for all!

Randy.

[Whiterabbit]

Where this really shows up is when you set up a long part to drill a hole in the end, and you edge find the vise and then find out your hole is out of position .015-.020 because of the angle of the vise jaw. .004 at 1" is .020 at 5".

I just put a scrap of aluminum in my drill press vise and ran my DI up and down the scrap. Vertical tolerance is about .02 at 5 inches.

So my new angle plate is shipped an on its way :) They claim .0005 over 6 inches or so. I'm expecting BS on that but even if it's a fraction of that it will be better than .02 over 5 inches!

new rule in my shop. No more drill press vises on the mill table.

[country gent]

WR the skilled crafstmen will always be need to keep the "new and Improved" running. LOL Scraping is a long slow tedious process learning to "read the blue patterns and know what is high what is just coming in and what is going to be there. Also a hand scraped surface supplies something a ground ways or surface dosnt have, Valleys for oil and lubrication. A scraped surface provides this and if you back over it cutting the gulls wings then theres some real oil pockets. You see these "gull wings patern" on some of the bridgeports ways and others also. In my tool box at work are several granite straight eddges and a Biax power scrapper and a bi ax power flaker ( cuts the gulls wings much easier than by hand) along with an assortment of hand scrappers and cast iron straight edges. Also a couple sets of osborne bearing scrappers. I would ussually be asked to scrape several cast surface plates tru after the yearly refinish of the granite plates at work.
White Rabbit the trick is to set up the part to the machine a small bumper and a little carefull work can tap that part to .0000 in 5" to your spindle. How does your vise set in relation to machine? swing in the bottom of vise bolted down to see if spindle is square. also swing table to see if spindlwe is square to it. Indicate back jaw to spindle travel to insure square. Another trick is to use a piece of round stock between moveable jaw of vise and part, This keeps the moveable jaw from over powering the fixed jaw. A issue with most screw adjustable vises drill press and grinder vises is the flex induced by screw pressure applied. Indicate your vise bed at rest on a flat true surface mark readings start middle and end with a marker. clamp a piece on parrallels in to your normal pressure and re indicate the bed under the part when clamped. Bet its changed now. Kurt angle locks and drill press ginder vises with the screw at an angle pulling down are better at not flexing. The indicator is your friend You may not like the information but knowing it and working accordingly is how its done. Just like indicating a 4 jaw chuck on the lathe accuracy is in the person doing it. Also like the 4 jaw a part in the mill may need to be indicated in. A quick easy way for square and accurate parts is to start with the stock above the vise and work 5 sides in in one set up. cut off and finish last side. the more you can do in one set up the better. Vises can be a real help or hindrence.

[Whiterabbit]

I'm not machinist (more like a metal butcher), but it doesn't take a craftsman to see the problem with adjustable jaw lift on the drill press vise, or even "machinist" vises that are not angle-lock. The next one will absolutely be an angle lock vise, even if I can not yet afford a Kurt.

And I certainly agree with "WR the skilled crafstmen will always be need to keep the "new and Improved" running." I fix robots and light industrial machinery in Silicon Valley. Here, the skilled labor is no longer producing components, it is producing the automated machines that produce components. It seems to have been that way for awhile now in factory towns everywhere I go in the US.

[country gent]

Before i went on medical I was seeing a trend in the trade that was really worring to me. The simple hand tools Hacksaw, files, chiesels, stones were no longer being considered as hand tools. We had tool makers that if asked to take .002 off of a key had to take it to the tool room and a surface grinder. The skills of hand fitting and hand tools are no longer being taught.