The Home Machinist!

Hi folks, I just bought what was advertised on E- Bay as a criterion boring head but think it is a Chi com imitation because ;1) It has no Criterion logo on the body ,2) it has no modle no. on the head, 3) the heads of the set screws that tighten the 2 parts together in the dovetail are 3mm. 4) if you turn the adjustment .050" it moves the head .050. I never used a boring head before so I'm posting this before leaving feed back on E-Bay. Thanks for your comments. In a later post I would like to discuss the project that I am working on with this tool. It does seem to work fine and if my "chi com fraud theory" is true it is no big deal, just another of life's lessons.

oscer

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"...that they are endowed by their creator with certain unalienable rights,that among these are life,liberty and the pursuit of happiness." Thomas Jefferson
"When the people find that they can vote themselves money, that will herald the end of the republic." Ben Franklin

I'm pretty sure it's not a Criterion, but I only have older ones that are direct reading, have english speaking set screws, and a logo and model number on them.

It's a shame that some items get misrepresented, but if the price was right, it will probably work fine for you.

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Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

Hi fellas, the project I mentioned in the previous post is an old work arbor that I bought from a local Amishman for $2. it had bronze bushings that didn't fit tightly in the journals and I don't know if it was being used this way or if this was an unsuccessful attempt to repair it. So I measured the shaft and the journals and made 2 bushings with about .001 to .002 interference fit in the journals and .002 clearance on the shaft. When I pressed them in the journals and slid the shaft in through the one bushing it didn't line up to the other one. I then slid it into the other bushing and it came much closer to lining up but you could see that the journals weren't bored on the same axis. I thought maybe it was originaly made for babbit material and maybe the the fact that they don't line up is why the bushings that were in it, when I bought it, were such a sloppy fit.
So I pressed one bushing back out and set it up the mill with the help of a rotary table. I'll try to post a picture of the set up. I put the journal with the bushing in it on the bottom and slid the shaft through the empty top journal and into the bushing in the bottom one,using an indicator in the spindle I aligned it at 3 and 6 o'clock running the button on the shaft between the journals, got it within a little less tha .001" using shims under the bottom flange for the 3 o'clock and and rotating the table to align it at 6 o'clock. then I put a center reamer in the spindle and used it to center the shaft under the spindle and took a couple of light cuts with the boring head.
Next I knurled the bushing that was removed and put it over the shaft and tapped it into place in the journal with a brass punch. I can turn the shaft by hand but it's a little too tight to run that way so I'm thinking of getting a touch on the bushing and taking a real light cut through it hopefully making this all come out usable, after all it did cost me $2.
I posted this to see if I went the long way around the barn for what I thought should have been an easy repair. It took a good bit of time. If it works and I learn something it's all good. I also want ask if you guys mill a flat spot on your boring bar shanks where the set screws engage them? They fit preety tight and I thought I wouldn't get it back apart without a litte clearance for the burr. I just used a file as I had this all set up on the mill.
Thanks for your thoughts. oscer

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"...that they are endowed by their creator with certain unalienable rights,that among these are life,liberty and the pursuit of happiness." Thomas Jefferson
"When the people find that they can vote themselves money, that will herald the end of the republic." Ben Franklin

I am not experienced enough to comment on your method but bushings like that are commonly "line bored' or reamed with a long reamer that pilots in one bushing while reaming the other. I don't think it is uncommon for parts like that to have misaligned bores.

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Don Young

I thought about the method a bit as well, but that's how a DeVlieg Jig Mill is intended to be operated. Bore one side, rotate it 180 degrees on the RT, and bore the other side. That's why DeVliegs have less Z axis and platen travel than most other HBM's and no foot stock. You had to get the setup correct though with the Z axis aligned to intersect the B axis, or make accurate table movements to compensate. It worked for them!

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Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

The problem is it's not a jig borer, and the degree of accuracy that is required in order for the bores to be on the same plane is not generally available from a milling machine and its accessories. You can trust me on that one. I've done some very difficult work with a mill, and it isn't easy. Any error in the setup is compounded when the part is rotated. Suddenly, a thou becomes two. Far more misalignment than can be tolerated for a running fit.

Not suggesting it can't, or won't work---just that it's a lot tougher to accomplish the mission, in particular if you're hoping for a straight shaft to fit both bearings properly.

Harold

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Wise people talk because they have something to say. Fools talk because they have to say something.

Thanks for weighing in fellas, it may be even worse than you are thinking. I'm not going to rotate the table 180* and bore the other side. I am just using the rotary table for an angle plate and to shift the set up side to side as needed to align the shaft, that is resting in the lower bushing, to the mill spindle ( the shaft had been removed when the pictures were taken) So I tried to align the mill spindle by indicating the arbor shaft that was installed in the lower bushing, then I bored the upper journal and pushed it's bushing back into it, after nurling it to enlarge the O.D.( I bored so little out of the top journal that I was able to use the same bushing that I previously removed when I discovered that the journals were not in alignment. Next I put the arbor shaft through both bushings and it acually fit, a little tighter than I would prefer,but it fit. Then I ran a very light cut through the top bushing and now it turns relatively freely. The first goal was to save the bushings that I machined before I realized that the arbor journals weren't in line with each other, just to see if I could. I guess the second goal was to try to learn something in the process.
I think my imitation Criterion boring head will serve me well even though I paid too much for it.

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"...that they are endowed by their creator with certain unalienable rights,that among these are life,liberty and the pursuit of happiness." Thomas Jefferson
"When the people find that they can vote themselves money, that will herald the end of the republic." Ben Franklin

Not rotating the rotab to bore both holes is a step up, as that's where alignment is overly critical.

Having said that, unless the bore was in direct alignment with the spindle, the location of your indicator on the shaft would have provided concentricity at that specific point (with the spindle), but it would not take in to account the fact that the arbor itself is most likely not perfectly perpendicular in two planes. Thus, when you bored the upper hole, you would be concentric with the area indicated (assuming the shaft was a respectable fit in the bushing) but may not have been perpendicular. The net result is a pair of bushing that are not in a common plane, although they must be quite close. They can be out in more than one direction, and where the shaft marks the bushings when slid back and forth will identify the error.

That you managed to fit the shaft after boring, assuming you allowed reasonable clearance (no more than a thou), you should be commended for your efforts. That's not an easy thing to do and have it work out as desired, for the reasons I mentioned.

One thing I'd like to mention. When you have a bushing that is too loose, knurling isn't a great idea. It may displace material so the bushing will press, but the amount of surface area in contact may not be adequate to prevent the bushing from coming loose in due time, assuming there's a respectable load on the shaft. It may or may not serve as you hope, but now that it's done, I'd recommend you give it a go. Just keep an eye on it to see if it begins moving. Might even consider a drop of penetrating Loc-Tite if you have any doubts.

Well done!

Harold

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Wise people talk because they have something to say. Fools talk because they have to say something.

Agreed! I was just expounding on the concept of boring from both sides.

That's why I use a honing machine!

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Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

A honing machine, what a way to cheat .

If you can't cut it to size, hone it .

I'd set it (casting) horizontally on the mill table, with bores parallel with the x axis.

Bore from one end with a right angle head, and boring head, index the right angle head 180 degrees

and bore the other end.

Granted the mill head has to be trammed as close as possible,

and the right angle head indicated dead nuts on the indicating bands.

Care also has to be taken to reset the y axis when you move to the other

end of the part.

Of course the casting bottom needs to be flaaaaat,

or all that work is for nothing.

Kap

If you have access to a big enough lathe, you could do it the way the old-timers did it when they only had a lathe.

Use a long boring bar between centers and mount the work on the carriage.

That's how Curley would have done it!

Here's a guy line boring two holes on a tiny Taig lathe:

You can read about it here:
http://www.deansphotographica.com/machi ... indle.html

Steve

Thanks again for the replies fellas,

Harold, those slight misalignments due to the movement of the shaft in the lower bushing were my concerns from the begining as well. I'll take your avise on the locktight.

SteveM, That was plan B However I don't have a table for my carriage...yet

Kapullen, I haven't got a right angle head for my bridgeport either

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"...that they are endowed by their creator with certain unalienable rights,that among these are life,liberty and the pursuit of happiness." Thomas Jefferson
"When the people find that they can vote themselves money, that will herald the end of the republic." Ben Franklin