Well that hex-nut I turned and tapped on lathe, then wrote little program for Bridgeport to do the hex, I think its ok for now and if it won't work I can always get that Morton-nut... The block itself is not done I still have to bore 1.5" hole for the cam and two 1.125" holes for the pistons. I think I just throw that block in the lathe and bore them out quickly. About that Bridgeport, thing is, since I'm using its "CNC" prototrak I don't think I can lock that table, also I make all my cuts on Y feed so its using the saddle move, however I do use X feed to face or fly mill.
Cutting dovetails, how hard can it be...
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Trickymissfit
Well-Known Member
I cannot ever recall seeing that name! I once worked in a shop that still had a bunch of machines that ran off the old line shaft. Extremely efficient to say the least. I was involved in converting about thirty of the small presses over to motor drive from the line shaft. In that shop we had an old lathe that we used for spray metal work. It used an old time Ford "crash box" for a transmission with a 15 horse electric motor going into it. At one time it was a line shaft machine. That leather belting material used to come in rolls of different widths and thicknesses. I've probably made two hundred belts in my lifetime. When I made a new belt all the machine operators would be hanging around waiting for me to throw it the trash. They made really nice strops for sharpening knives. We are probably in a very slim minority here that even knows what a line shaft system is; let alone ever saw one in use!
Now I feel really old!
gary
Trickymissfit
Well-Known Member
The thing about a Morten nut is that they are precision nuts that are hard and have a thick flange to spread the pressure out. They really hold up well, and almost never mess the threads up on a stud. The radiused ones are self aligning, and once you use them your ruined. You being the only person using that tool block will not have problems. But if you have one guy that drags out a big combo wrench, and you got problems. I also set the blocks up with a large hardend and ground washer underneath the blocks to keep them from screwing up the lathe compound slide
gary
Bullet bumper
Well-Known Member
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I don't agree with that advice especially for small weak cutters. The only dovetail cutter I ever broke was when climb milling just to see how it went and it did not go well. Small light mills have little control of table drag during climb milling so the cut can suddenly increase to overload if the back lash allows the table to jump . Try conventional milling and see what you think . I tried both and don't climb mill dovetails anymore on a small machine with light cutters .
might want to check the gib on the table?? x&y .002 worth! thought i had them locked down, (oop's let the Gato out the bag!) once,maybe 2 but it looked somewhat like your cut,and the chatter was audible. at Clerke Arms we flooded them, no dribbleing coolent, same thing with fluting.again .002x. no lessons needed but a really Fine gunsmith instilled in me that to shear metal it takes aprox. 12 tons. any viberation is to much.
Trickymissfit
Well-Known Member
Gary, the flange on the nut I made is .210" thick, so it might hold up for a few runs. Well this project is almost complete, probably will finish it on weekends if I'm up to it..
nice work my friend. Never saw anybody ever attempt to make the block before. One question though; why did you not cut dovetails on all four sides of the block? Although I've never had more that two sets of tool holders on one block at the sametime. Also I like the way you did your tee nut on the bottom. Most guys will use a short one which tends to dig into the cast iron on the under face of the compound. Your even spreads the pressure. I made large diameter hardened washers to set under the block to also decrease the wear on the top of the compound, and also bring the tool block in towards the spindle centerline.
gary
Trickymissfit
Well-Known Member
one of the major weak points of Bridgeports table design is the unsupported over hang of the table. This means that the gibs tend to wear faster and they tend to loosen up rapidly. The guilty party is not the table, but a weak knee / saddle design. A Willis Machine clone has a wider knee with ways that are about 4" wide. They are harded rectangles with Turcite at a -.001" crush fit. This system will last almost twice as long as the convention dovertail system used on a Bridgeport. But the gibs on the table will still go first.
I've seen good men cut dovetails in both directions, and I'm a believer in "if it works for then so be it!" Still the best way is to cut them with the table locked down solid, and use a cutter path going towards the ram
gary
Thank you Gary! The operation of the push pistons is based on the cam design, portion of which is turned by offsetting one side by 32 thousands in the 4 jaw chuck, the rest of the cam is on center, so having 4 sides would not be very useful. Also I guess this one would be prototype, after all its 1020 CRS and I learned few things making this one, but if I decide to remake this again I use toolsteel or something which can be easily harden.
SidecarFlip
Well-Known Member
I konw Gary preaches about the weak design of a Bridgeport in regards to table and saddle dovetail to gib relationship, but that actual reason for the wear is most mill hands operate the table in a constant centered position. When you don't use the outer ends and just the center, all the sliding wear...........is in the center.
I'm puzzled about his 'Gary's' comment about having multiple toolholders on a post at one time. I'd like to see a picture of that. Possibly 180 degrees opposing but in my view and experience, that's it. I'm always open to novel ideas however.....
I'm puzzled about his 'Gary's' comment about having multiple toolholders on a post at one time. I'd like to see a picture of that. Possibly 180 degrees opposing but in my view and experience, that's it. I'm always open to novel ideas however.....
Trickymissfit
Well-Known Member
if you decide to make another, order in a bar of ground finish 4150 pretreat steel from Baldwin out of PA. This is the best pretreat steel I've ever worked with, and seems to take a nitride hardening (Gassified) better than most of the other generic brands of steel. You'll pay about ten to fifteen percent more for their steel, but you get what you pay for. The only brand of steel that I've ever seen that will at least run with their stuff if not be a little better is Timken. I'd make the cam out of A2 machined to size and then hardened. All you gotta do after heat treat is polish it.
Baldwin sells a stainless steel that's a pretreat, but has the properties of the old 300 series (won't rust). It's called MAR-10, and this is absolutely the best stuff you could cut a barrel out of. It's a little tough, and a little expensive. It's also the only steel I've seen other than 310 that won't rust in deionized water. It's pretty much the samething as 17PH-4 rearc melt, but better quality. I've gun drilled holes as long as 24" in the stuff, and once you learn to work with it, it's not all that bad.
gary
Trickymissfit
Well-Known Member
my comments about multiple tool holders is just in the way some folks like to set them up. And example would be in threading and cutting a very square shoulder. But myself I always just used one tool holder at a time like most of you.
The original Bridgeport design was with a short table (36"?), and used a step pulley head. That is still their best design to this very day. Look at some of the other mahines and you'll notice that the table (x axis) is fully supported in all it travel. Now to really see what that table is like, remove it and set it on a surface plate (on three points). It will scare you to death! Their tables flex all over the place (I had one measure almost .008" once). The shorter ones are far more ridgid, and do not wear the gibs due to less over hang when in use. But just as bad is that the table will also become a lever forcing excess wear on the dovetails in the saddle (that's why they did the hard chrome option). Now you compair the bridgeport with a Willis Machine clone, and the first thing you'll see is that the saddle ways are about 4" wide, and further apart. Everything on the machine rides on hard ways and Turcite at a crush fit. It's not perfect, but still far more ridgid. Then you move into the spindle head. Both use a "J" type head, but one is much moe massive. The quill on the Willis alone is about 2" in diameter larger. Bigger bearings and a larger spindle diameter means it will handle heavier cutting loads. Most folks opt for the Bridgeport taper tool holders these days (I always liked the R8 holders). The Willis uses number 40 Ericson tool holders. Much heavier construction, and are machine at a fraction of the talorence that the Bridgeport tapered holders are (course they cost more). But the real advantage here is the many styles that Ericson sells (or the clones). The other major issue with the J head is in the drive pulley and the plastic sleeve they use. There is a fix for this (heard it was being copywrighted). When the sleeve goes the drive key screws up the spindle. This area on some other machines is built much heavier, and at least one uses a double depth twin key setup that has the drive keys locked down with cap screws.
If I were shopping for a Bridport type machine, I'd either buy the Willis or a Southwest Trac. The SWT uses ball screws and hard ways. But uses the same basic J head. Seems to position a little more accurately, and for sure cuts a little more square. Better yet would be a Fidale out of California. It has a much wider table and a better frame design. If I were buying a milling machine in that basic class today it would be a Fidale without a second thought.
gary
shortgrass
Well-Known Member
Now, fix those gibs on that table!
