general machining questions

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hi all,I have a few general questions#1 if your makeing a bushing or a sleeve lets say for going on an axle and into a bearing . 5/8''axle OD and 3/4'' ID bearing hub. should I make oversized or under or dead nuts on?#2 bolt holes.  if your bolt two parts together. lets say with 3/8''  bolts what size holes?3/8'' or go up to 25/64?  #3 dowl pins and spring pin roll pins.  how much under size?  I know the materials play a big factor.#4 extra credit.  tap thread % . I have read this seraval times and Can't rap my head around it. I need the fisher price explanation.any other general rule of thumbs would be cool.thanks Daye
Reply:Originally Posted by tigmuskyhi all,I have a few general questions#1 if your makeing a bushing or a sleeve lets say for going on an axle and into a bearing . 5/8''axle OD and 3/4'' ID bearing hub. should I make oversized or under or dead nuts on?#2 bolt holes.  if your bolt two parts together. lets say with 3/8''  bolts what size holes?3/8'' or go up to 25/64?  #3 dowl pins and spring pin roll pins.  how much under size?  I know the materials play a big factor.#4 extra credit.  tap thread % . I have read this seraval times and Can't rap my head around it. I need the fisher price explanation.any other general rule of thumbs would be cool.thanks Daye
Reply:I would say if you are using a 3/8” bolt drill a 3/8” hole. The threaded area of the bolt is not 3/8” but the shoulder part is.  If you drill bigger you will have slop in the alignment of the parts when bolted together.  A trick I have used is when making parts. Where 2 are bolted together I tack weld the parts together then drill the holes. This will give you a greater alignment when the project is finished.On spring pins (roller pins) check out these sites for specs.http://www.engineersedge.com/roll_pin.htmhttp://www.driv-lok.com/springpins.aspSpring pins and tapered pins have a different use/function.  I believe spring pins would be easier to use.  And would be easier to install and remove then tapered.  Spring pins go in and out from either side.Threading Like he said get a chart so you use the correct sizes.  Major thing is making sure the treading is done dead on.  By that I mean no leaning one way or another on either inside or outside treading.  Hint, make a thick block with holes drilled for each tap size. Place the block over the hole insert the tap through the hole and clamp it to the part and thread the hole. On inside threading drill the correct tap size hole in the shaft. And then drill a short section at the start of the hole to the finished bolt size then tap the hole.  This will help to start the threading operation in proper alignment and the threads will be straight.
Reply:I got a few tap charts the one in a drill index differ from other charts.. The only time I ran into trouble is with 303 and 304 stainless. 1/4-20 calls for a  #7 I think I had to use a #4 .to get it to tap.thanks for the input guys.heres a picture of another question.  how to drill a hole in a pair of dikesDaye Attached Images
Reply:Tigmusky,303 should cut like butter, 304 is a pain in the butt. Use your #7 for the 1/4-20 but buy some moly Dee cutting fluid made by Castor Oil. I use it when tapping tough materials like Inconel and other bad stuff.Get yourself a machinerys hand book and you can look an the min and max of you major and minor diameters, it makes life easier. LarryMiller XMT 304 CC/CVSyncrowave 180 SDLincoln PowerMig 255XTTermalDynamics 52Lincoln 305GComlpete machine shop to back it up
Reply:Originally Posted by LarrysmachineTigmusky,303 should cut like butter, 304 is a pain in the butt. Use your #7 for the 1/4-20 but buy some moly Dee cutting fluid made by Castor Oil. I use it when tapping tough materials like Inconel and other bad stuff.Get yourself a machinerys hand book and you can look an the min and max of you major and minor diameters, it makes life easier. Larry
Reply:I don't like tap magic, it will actually bind up in 304, Moly Dee is expensive, but I have tried all brands and all types and it works best in all types of materials. The one draw back is that it is messy.LarryMiller XMT 304 CC/CVSyncrowave 180 SDLincoln PowerMig 255XTTermalDynamics 52Lincoln 305GComlpete machine shop to back it up
Reply:I don't know what tap magic used to replace the 111 trichloroethane carrier in the original formula, but it was more for high speed tapping and peck drilling with small drill bits.It mostly worked by cooling the tool as the carrier broke down.Heavy pressure stuff like moly-dee work by not allowing materials to weld together.tigmusky, I imagine you won't be able to find it, but white lead (painters' lead) mixed with alcohol works  well for peck drilling up to 50Rc with high speed tooling. If you mix a little dry ice with it and have some time you can peck drill through a ball bearing and maybe win some bets.Matt
Reply:Originally Posted by tigmuskyI got a few tap charts the one in a drill index differ from other charts.. The only time I ran into trouble is with 303 and 304 stainless. 1/4-20 calls for a  #7 I think I had to use a #4 .to get it to tap.thanks for the input guys.heres a picture of another question.  how to drill a hole in a pair of dikesDaye
Reply:Originally Posted by Matt_Maguiretigmusky, I imagine you won't be able to find it, but white lead (painters' lead) mixed with alcohol works  well for peck drilling up to 50Rc with high speed tooling. If you mix a little dry ice with it and have some time you can peck drill through a ball bearing and maybe win some bets.Matt
Reply:Originally Posted by LarrysmachineTigmusky,303 should cut like butter, 304 is a pain in the butt. Use your #7 for the 1/4-20 but buy some moly Dee cutting fluid made by Castor Oil. I use it when tapping tough materials like Inconel and other bad stuff.Get yourself a machinerys hand book and you can look an the min and max of you major and minor diameters, it makes life easier. Larry
Reply:Originally Posted by greenbuggyForgive my machining n00bness, but how does the dry ice help to peck drill thru the hard steel of a ball bearing?  Is it just the temp drop or another effect that helps accomplish that feat?