HELP! Lathe questions!

A C Richards said:
Turning it on a mandrel, one side is normally chucked up and the other is supported by a center. Turning between centers requires a lathe dog and 2 centers. One in the chuck and one on the tailstock. One advantage is you can turn the center in the chuck and it will be perfectly aligned. This is as long as it is not removed until the job is complete. Now if you are going to bore the bearing seats then neither of these methods will work. Both require you to have a shaft running through the workpiece. You will need to bore the bearing seats in a chuck. If the machine has a 4 jaw chuck you can dial the work in. By the looks of your lathe it does not look like an adjustable 3 jaw. If you turn the bearing bore then turn the OD between centers this can remove much of the run-out. There are a few ways to go about this. You could almost do the whole wheel in the chuck if you cut the bore then turn the OD without removing from the chuck. The only problem with this is you need a large enough piece of stock to hold and turn without removing it.
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I was told that when turning between centres, a lathe dog is not necessary because the work is pinched enough not to slip. It sounds like I need a mandrel anyway to do it.

Our school (I think I forgot to mention that it is at my high school) has a larger 4 jaw chuck that I can put on.

Could I do the rough OD and one side square to it, then cut one of the bearing bores, hold in the inside jaws and dial it in, cut the other seat and the bore going through for the shaft, pinch between centres and do the final OD?
 
If you are able to hold a bar between centers and turn a workpiece you have things way too tight. There is nothing but the two points and a very small area providing friction. You need the lathe dog to keep things running smooth. Yes you can do one side, turn it around and do the other. The key, as you mentioned is dialing it back in. If you have the capacity to do this, either a 4 jaw chuck or an adjustable 3 jaw, then this is the way to go. Do you know if the 3 jaw you have is adjustable?? From the pictures it did not look like it. The way you tell is there is a series of 4 allen heads around the circumference of the chuck. You loosen one and tighten the apposing to adjust. It works similar to a 4 jaw but does not have nearly as much adjustment range. Also if you are using the inside jaws to hold your workpiece then just cut the OD in the same setup.
 
Definitely use the 4jaw. You can dial this in to within .0005 easily. That is well within acceptable parameters.
 
I cut the chunk for the drive wheel today, the bandsaw blade had a bent, dull spot and kept popping off, so I just cut it with a hacksaw :)

I still am not sure on how to keep both bearing bores lined up on the tracking wheel,I figured I could turn the rough OD then dial off of that, but I could only do less than half at a time in the chuck, so I am not sure on that one. :confused:

My teacher doesn't want me putting the 4 jaw chuck on saying that the 3 jaw ones are made to be perfect and that, even though I have a dial indicator, I would take forever centering the work. Maybe I can talk him into it later.

I also got my bearings today, they are rubber sealed ones, 3.50 each, I also ordered some cast iron step pulleys ($50 each :eek:) but was thinking that I should order some bearings for platen wheels, but I don't think I have time to do a platen.

Another question, I guess I need to drill for a set screw to hold the drive wheel on, how so?

Thanks, again!
 
And what is the angle of the crown and how deep is the counter bore on the drive wheel? Thanks again!
 
Keith,

3 Jaw chucks are not perfect!!! Some I have seen have been as much as .05" out. That would set up a pretty mean vibration on your wheel. If you have limited time and the teacher does not want the lathe tied up then I can see were he is coming from, but a 3 jaw is no were near as accurate as a 4 jaw, with the exception of an "Adjust True" style 3 jaw. I do not know what the crown should be. 1-3 degrees should be adequate if your set up is running true. Yes you will need to drill the drive wheel for a set screw. I think you would be better off boring clear through the drive wheel and use the set screw to keep it in place. The fit should be pretty good anyway.

Good luck
 
Thanks, Chuck.

I have been using the 3 jaw chuck to make my drive wheel. Because everything is done on one setup it really doesn't matter how accurate it is. For the idler, I am going to insist on putting in the 4 jaw.

Where do I drill the set screw hole, and is it threaded into the aluminum?
 
and another question, Is a reamer fine for the drive wheel, or is it best to find a boring bar that is small enough?
 
ib2v4u said:
Scott, I did not mean the OD that the outside of the race presses into. I know that has to be the correct size. I was referring to the OD of the rest of the hole. Does it matter if the shoulder the side of the bearing sets against is .10 or .05? The bore thru the center on mine is .875 and the cut for the bearing OD is 1.1248 or 1.249 (can't remember but a slight press fit) for a shoulder of almost .125. If my center bore OD was 1.00 and it made the shoulder .0625 what would it matter as long as the OD and depth were correct?
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Sorry for not replying sooner. I've been busy. That is one of the reasons that I requested the part number. Sometimes the backing diameter can be too large which doesn't appear to be the case with yours. However, sometimes it can be too small, depending on the bearing part number. If it's too small, it can interfere with seals, cages, etc. Usually with a ball bearing, it really can't be too small, but without knowing the part number, it's impossible to know.
 
Scott, they are a sealed ball bearing that has an OD of 1.125, a center hole of .500 and a width of .3125. They are what is in my KMG. I can't see who makes those. The biggest use for them seams to be skateboard and inline skate wheels.
 
So long as your set-up has not changed you are fine. There should be some type of hub on your drive Normally the set screw goes there. If you do not then you will need to do a deep hole through the wheel and yes threade in to the alum. This can be a pain but doable. If you do not want to drill the set screw hole then a couple of collars can be used on either side to capture the drive wheel. Since you will be using a key spinning should not be an issue. If you are comfortable with the accuracy of your center hole then a reamer would be ok. If you are not then it should be bored.
 
Keith_H said:
and another question, Is a reamer fine for the drive wheel, or is it best to find a boring bar that is small enough?
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Reamers are to get things round and a specific size, but it does not guarantee an accurate hole. They follow the hole that is already there.

The correct order of operations is to center drill, drill, bore, then ream. It is trivial easy to take a skim cut with a boring bar before reaming to get things concentric before sizing the hole.

If you can't find a small enough boreing bar sometimes you can use an endmill from the tailstock to get things more or less concentric.
 
Ok, thanks. I found a box of boring bars, so I will use those (they really are not very exciting :D)

the bearings are most likely made in China

I considered making the inside of the hub on the drive wheel radiused, but I think I will just make it square.
 
I have a question, not related to lathes, but it concerns me.

How should I go about making the receiver square to everything else? How should I accurate set up my wheels so that all three are on one vertical plane? You guys are a great help!
 
If you set up your bearing mounts for your drive shaft square to the receiver that wheel should be fine whether you use pillow blocks or flanges also keep them the same height. If they come out a bit off you could shim them with thin pieces of steel. run a straight edge on the outside of the wheels and get them ligned up with each other before you lock down your shaft. You can shim your contact wheels or platen out a bit also. Washers on the contact wheel and if you have a platen a washer or 2 behind the wheels. It would be beter to adjust everything to the platen wheels though. On your Idler once again get the mount in plane with the length of the receiver. Its vertical plane is of course adjustable to control tracking. This wheel should be wider also to make up for adjustment movement. You could shim it out a bit or make the shaft for it to get it so that its centerline is near the C/L of the others. Are you making an exact copy of a KMG of what. My "clone" uses a simple adjuster that I can slide the tracking wheels shaft in and out and then clamp down.
 
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This grinder was originally a home made 2x48. I used this piece and modified the swing arms a bit to mount it on my clone. The tracking wheel is mounted on a short shaft. The shaft. It is held by a piece of pipe with a cut in it and 2 tabs are welded beside the cut, It also has be drilled and tapped for a 1/4 20 allen screw. The tabs go up thru a slot and are bolted together, there is a thick washer on the outside of each tab and the washers ride on the edges of the slot so the shaft mount can rock on them, Then there is a adjustment bolt that presses down on the end of the shaft to move the angle of the tracking wheel. I added a locking nut with a short arm to lock the adjustment down better. The slot and adjustment bolt are on a short piece of angle welded to 2 pieces of flat bar. the flat bar s are drilled and pivot of a piece of stock welded vertically to the receiver. On the bottom of the 2 bard I welded a pad with a small 1/2 round stock stub to hold the top of the tensioning spring in place. Just shows there are lots of ways to skin the adjuster cat
 
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