Mill rotary table best size

[Goldhunter_2]

Ok I am not the best with proper names of stuff some times so please bare with me. I have a old Kempsmith #4 horizontal mill that has been converted to a vertical mill .
I am looking for something to allow me to mill aluminum parts at a angle and found a "rotary table" (hope that the correct name) I am wanting to replace the steel rods in some of my airboat engines with aluminum rods so I need more movement (angles) of the mill table to make these parts the Rotary table looks like the best tool but if anyone has better or cheaper choice please let me know

the rods are 9" long and 3 3/4" at the widest point ...now the question is what size rotary table do I need to look for to hold materiel this size?

[jalessi]

http://tinyurl.com/yh9tuqs

http://www.shars.com/product_categor...g_Angle_Plates

[Goldhunter_2]

I was thinking more when I said angle movement as twist like a horizontal rotary table like the link below , sorry I did not even comprehend the tables like you showed. My mill the table now only move straight left to right or in and out

http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

that Shears link does have a 8" & 12" horizontal rotary table at a better price but don't know if that is big enough to hold the engine rods as I have never used one of those before

[Goldhunter_2]

I know some of my other stuff like engine case half's hang off the table but I can still secure them to work would it be the same with smaller parts on the rotatory table.

so what is the general opinions of the size table required to hold it , will a 8",10",12",15" rotatory table be required to hold my project? just trying to decide what to look for

[whitis]

Best tool for the job is CNC. You can cut any angle in the XY plane (and in many other directions as well) using linear interpolation. But if your machine is manual only, the rotary table allows you to do this. Try to get one that can easily mount horizontally or vertically (or better yet, tilt), even though you don't necessarily need vertical mount for this job. A horizontally mounted table becomes more or less redundant when you upgrade to CNC (though it can be used for parts that won't fit on the table) while a vertical one lets you cut at angles you can't easily do otherwise.

Yes, you can machine off the end of the table as long as you have a way to clamp the part. If you are way off the end, then you may be putting a lot of force on the gears inside and the backlash on the table will be multiplied to produce some play. With a small part on a big table, backlash and cutting forces are divided but with a big part on a small table they are multiplied. However, a more modest size table with good quality fit and finish and good metalurgy may outperform, with regards to backlash and cutting forces, a larger used table that is clapped out or one which was made to low price point at the expense of quality. You may be able to take up some of the play if you have the ability to adjust the worm gear position.
Backlash causes not only an angular error but a shift in X and/or Y position.

Even a 4" rotary table may be sufficient for this particular project, depending on the tolerances and cutting forces involved but a bit bigger may be more appropriate. If you lighten up on off the cutting forces as you get
further from the center of rotation, you may be ok. Clamping the table also helps. You can also reclamp the parts for each end so you aren't machining way off axis. Also, if the table is suitable for a higher horsepower machine, then you don't need to worry about the cutting forces as much. As long as there isn't too much play and the part itself is rigid enough (or supported by a jig or tooling plate larger than the rotary table for your tolerances, you should be ok. And the close you are machining to the axis of the rotary table, the less of an issue you have with play.

For general use, bigger is better, within reason.

Bear in mind that big tables can be very heavy (as well as more expensive); some need a hoist to move without risk of back injury, etc. The 15" table you linked to weighs around 170lbs (and it is pretty light for its size). Unless you have a jib crane or similar, it will probably sit on the shelf unused. Depending on the Z travel of your machine, a big table mounted vertically may have the center too high or you may not be able to get the spindle close enough. If the table is too big, you might not have enough Y travel to use it in the ways you might expect to be able to and it may hang over the table and bump into the column or the Y handwheel, limiting your travel. If that 15" table was mounted vertically, the axis might be 8" above the table. Add, say, 2" for a 4" diameter part and 4" for your tool and tool holder and your spindle may need to be 14 inches above the table and the part may need to be extended out from the table a good distance or your spindle collides with the rotary table when you are trying to get the tool to the work.

The Y width of your table might be a good size for your machine. If you go much larger than that, the larger rotary table may exclude as many or more setups as it enables additional ones. If you are considering one larger, make a mockup with similar dimensions position it on the machine (horizontally and vertically) and check for collisions. For a given quality, price doesn't vary that much with size below something like 10" but above that the price climbs rapidly with size. Doubling from an 8" to a 16" roughly quadruples the price but halving to a 4" only reduces the price roughly 30%. Even at 10", weight can be an issue. I have a small 4" sherline rotary table (unusually light as some of the parts are aluminum) which weighs 10 pounds (including stepper motor and 0-90 degree tilting table) - I can lift it with one hand. A 10" horizontal/vertical table would probably be in the neighborhood of 140lbs. That is likely to exceed NIOSH safety limitations for even an occasional lift. Though, the same might be said for a large milling vice, which you may have to move to make room for the rotary. A 16" rotary table can be about 350lbs - as much as many small machine tools. Even a 6" can be around 80lbs. I used shars for the weight/price comparisons.

Here is the link to the sherline table and tilting angle plate mentioned above.
http://www.sherline.com/3750pg.htm
http://www.sherline.com/3700cncpg.htm
You might want to read the user manuals. One flaw in their design is that there is no bore hole all the way through so you can't feed bar stock through (like you can on a lathe) when mounted vertically.

You can also make a large round tooling plate for clamping on a not so large rotary table. This gives you some, but not all, of the advantages of having a larger table or two different sizes of table.

A rotary table is a very useful accessory for a lot of different operations. So it can be a good investment. For your particular project, however, there are some alternatives.

You didn't specify what type of rods you are making, so I will assume straight connecting rods to connect the pistons to the crankshaft.

The cheap method is to unclamp the parts and reclamp them at an angle or use the swivel base on a milling vice. You will have to figure out how to position the cuts after reclamping. That problem doesn't entirely go away on a rotary table, though, since the table rotates around its center not the corner of a feature (unless you have clamped that corner on center). But with a rotary table, if you have aligned some feature on the part in a known position with respect to the axis of the table you can use trig to calculate the required X and Y offsets. Otherwise, you need to do something like indicate in known features on the part and calculate from there each time you rotate the part.
Here is an example of a (cheapo) milling vice with a swivel base.
http://www.shars.com/products/view/5...th_Swivel_Base
You can make a custom jig that holds the parts by known features and holds them an an appropriate angle to make your cuts. For a connecting rod, this might be a vertical rod to fit in the shaft hole, various pin locations to set different angles (coordinates calculated using trig) when the shaft is swung around to touch the pin, and some hold down clamps. Or, two vertical rods one for each shaft hole.

The adjustable angle plates linked to by jallesi let you tilt an object +/- 45 degrees for things like drilling non-vertical holes or chamfering an edge with a flat bottom/side end mill. You could flip your connecting rods over on their side clamped on one of those plates (or a vice mounted on top), and then tilt over 45 degrees to cut 45 degree angles around the holes for the shafts in your conecting rods. Or you could just use a 45 degree angle block as a guide and clamp the rods in a vice at a 45 degree angle from horizontal/vertical.
http://www.shars.com/products/view/2...id_Angle_Plate
http://www.shars.com/products/view/2...0_Angle_Blocks
Other angle blocks can be combined to produce different angles. For example, a 25degree plus a 2 degree to make 27 degrees. A typical set might include 1-5 degrees by 1 degree and 5-30 by 5 degrees, which can add up to any integer angle from 1 to 120 degrees and some include fractional degree increments.

Another trick I have seen pictured for rounding off the ends of connecting rods was to mount a shaft vertically (clamped in vice, for example), slip the rod over it, bring a milling cutter into contact and then turn the rods by hand. This was for very small rods for a model. With a larger one, you have the danger of the cutting forces yanking the rod out of your hand or pulling you in, although with a long cheater bar you might get away with it. If you have 200lbs of cutting force (about 1HP) and are cutting a 1" radius with your hands 25" away, the force is only about 8lbs (more if the tool grabs).

Usually, there are a lot of ways to skin a cat. Especially if you don't need to crank out 100 parts per hour.

[whitis]

Here is where the low-tech rounding over technique for connecting rods came from:
http://www.cnccookbook.com/CCBlogJul2008.htm

[Goldhunter_2]

whitis that is a lot of info and answered my question thanks

I would love to go to a CNC but don't think I can realistically do it, manual stuff I can figure out myself or see it once and I am good to start but setting up a CNC I would pretty much have to read and learn as I go witch hasn't proved to work for me in the past so for now manual will have to do

My kempsmith mill actual has the drive line and box for a power feed table on it but I have never used it it was discounted when the mill was converted to vertical before I bought it , but appears that it could be connected to a power source and used again I have been considering doing that but have not as of now. I'll have to get some pictures of my system posted for ya'll to see a real antique ..lol

I do have a good size mill vise witch can help me understand the weight issue about taking off the larger rotary table I normally slide it all the way out on the end so I have room to put the engine cases on the table but with the rotatory table either the rotary or the vise would have to be removed for big jobs so that is something I did not consider before

A tilting vertical/horizontal table sounds interesting I'll have to look at something like that more to but first concern would be height as my mill only has about 13" max form the table at its lowest point to the boring head so the taller the table is would limit the projects I could use it for , though if I had it I am sure I would find more projects

I was afraid of going to small for a rotatory table before but after reading your info I think the 15" it to big for my needs maybe ideal would be a 10-12" or if I find a deal on a 8" table . I guess a 4" I just be to afraid that hanging 2.5" off each side would allow to much play but it is interesting to know something that size could be made to work. this was the main question I needed answered and you posted helped me decide thanks

Robert