Milling set up question

[WhoWhatNow]

I need to mill the center of a roller chain sprocket gear out. I am doing this on my manual Bridgeport with a rotary table (no DRO). My question is how I go about finding the center of the gear so I can mill the center out. I am sure this is a simple exercise for the machinists here but his is the first time I am using the rotary table so any help is appreciated.

 

[WILD-BILL]

You can get it close by using something that fits the bore of the gear snugly and chucking that into the chuck and move the part until the piece slids down into the bore freely.

To get it dead nuts, you need to sweep the bore with a coaxial indicator or a DTI.

 

[no704]

Pics of the gear would help. Sweep in with an indicator. Just like finding 0 on the rotary table.

 

[Robby321]

Here ya go...sweep indicator

 

[WhoWhatNow]

Thanks guys. Mr. Pete had a great video on it. I'm going to have to get creative with clamping the gear to the table, but I think I have an idea on that. No more shop time tonight so I'll have to try it tomorrow.

 

[Guster]

Probably would have run that operation with a boring head instead. Bit more control to sneak up on your dimension and no problems with work holding in this case.

 

[lukedwag]

Mount the gear on the Chuck and then hold the tool on the table. Use it like a lathe

 

[A_Pmech]

Remember that you must make the axis of gear concentric with the axis of the rotary table, NOT the machine spindle, to bore the gear correctly.

An indicator mounted in the spindle resting on the gear bore while rotating the rotary table with the worm disengaged is sufficient.

 

[matt_i]

Probably would have run that operation with a boring head instead. Bit more control to sneak up on your dimension and no problems with work holding in this case.

This would be my thought also, if you desire a precision fit/size.

Also, a lathe would do the job quickly and more reliably...but understand you might not have one.

 

[m32825]

... a lathe would do the job quickly and more reliably...but understand you might not have one.

Educate me on this. How would you securely mount the gear on the lathe? Same question for the earlier suggestion to mount it on the chuck. Not taking issue with the approach, just trying to learn a new trick. Thanks!

 

[Guster]

Educate me on this. How would you securely mount the gear on the lathe? Same question for the earlier suggestion to mount it on the chuck. Not taking issue with the approach, just trying to learn a new trick. Thanks!

If it fits the lathe, one option and probably the fastest would be a square piece of flat stock with two or more holes matching the bolt holes in the gear. Chucked up in a four jaw and then dialed in both running concentric to the hub and planar to the surface of the gear. Bore away...

Plenty of other options.

 

[ER70S-2]

Probably would have run that operation with a boring head instead. Bit more control to sneak up on your dimension and no problems with work holding in this case.

Definitely. Clamp it to the table, center the spindle with a DTI, and bore it. You could have been done a long time ago. This is not a job for a rotary table IMO.

 

[ER70S-2]

Educate me on this. How would you securely mount the gear on the lathe?

Faceplate.

 

[m32825]

Thanks for the tips, Guster & ER70S-2! I get to play in the machine shop enough to know that half the job is figuring out the right way to fixture things. Now I've got something new to try!

-- Carl

 

[Doug Arthurs]

I would bolt that to the table and use a boring head as well. Too much work getting the rotab set up and then the gear concentric with the rotab. Plus my rotab is way too heavy I avoid it as much as possible. If you must use the rotab then bolt a block of steel or alum to it and drill and tap holes to bolt the gear down to the block.

 

[Doug Arthurs]

You are probably about to tell me you don't have a boring head. I get it. But you have bought a Bridgeport so you need to start thinking like a Bridgeport owner.

In the past a job would come along and you would think "how can I do this with the tools I have." This is the old way of thinking. Now that you have a mill you need to revise your way of thinking.

The new milling machine owner way of thinking is "what new tooling, accessory or cutter can I buy to accomplish this job". Once you conform to this life will get better. Stop resisting. When you get to the point where you can no longer find new tooling to accomplish the job, you know you have arrived at the point where you need to upgrade your mill to one that is Less worn, or has more bells and whistles.

 

[ER70S-2]

"what new tooling, accessory or cutter can I buy to accomplish this job".

Or what new tooling, accessory or cutter you can make to accomplish this job.

 

[buildyourown]

Use a pair of kant twist clamps to hold the gear down to a bar of aluminum that fits in your vise. Dial the hole in with a test indicator. You should have one. Its one of the most common setup tools for a manual or cnc machinist. Gets your vise square, finds holes, edges, plates, centers of shafts, etc.
Then use a boring head to make your hole. You can get them pretty cheap on ebay.

 

[manwithtools]

You are probably about to tell me you don't have a boring head. I get it. But you have bought a Bridgeport so you need to start thinking like a Bridgeport owner.

In the past a job would come along and you would think "how can I do this with the tools I have." This is the old way of thinking. Now that you have a mill you need to revise your way of thinking.

The new milling machine owner way of thinking is "what new tooling, accessory or cutter can I buy to accomplish this job". Once you conform to this life will get better. Stop resisting. When you get to the point where you can no longer find new tooling to accomplish the job, you know you have arrived at the point where you need to upgrade your mill to one that is Less worn, or has more bells and whistles.

LOL, this is so true. I just about split my sides reading this.

 

[manwithtools]

What you really need to insure it's properly located is a "Haimer 3D-Sensor",

 

[A_Pmech]

What you really need to insure it's properly located is a "Haimer 3D-Sensor",

Everybody needs a 3-D taster!

 

[manwithtools]

They are pricey, but once you use one, you can understand why.

 

[WhoWhatNow]

Thanks for all the help guys.

Just a few pictures of what I did to move this project along.

Since this was the first time using a rotary table, I did not have any T-nuts. So I had to make a pair. Not sure what type of steel I pulled out of the scrap bin, but I couldn’t tap them to save my life. The studs got welded so I could move on to the actual task at hand.

I got the table centered and then used little creative clamping to keep the gear off the table surface (I love Unistrut). The gear was centered next. I did a quick turn without turning the mill on to make sure everything was positioned correctly. Everything went pretty smoothly. And it fits perfectly. I welded a few studs to the gear and then the studs to the blower shoot.

So everything is together, but it isn’t working properly unfortunately. It rotates smoothly without the chain attached but once the chain is placed on both gears, it gets very hard to turn and the hydraulics can’t move it. Not sure exactly what is wrong yet. I am guessing something is misaligned.

I do actually have a boring head. Learning to use that will be for the next project.

 

[WhoWhatNow]

Thanks for all the help guys.

Just a few pictures of what I did to move this project along.

Since this was the first time using a rotary table, I did not have any T-nuts. So I had to make a pair. Not sure what type of steel I pulled out of the scrap bin, but I couldn’t tap them to save my life. The studs got welded so I could move on to the actual task at hand.

I got the table centered and then used little creative clamping to keep the gear off the table surface (I love Unistrut). The gear was centered next. I did a quick turn without turning the mill on to make sure everything was positioned correctly. Everything went pretty smoothly. And it fits perfectly. I welded a few studs to the gear and then the studs to the blower shoot.

So everything is together, but it isn’t working properly unfortunately. It rotates smoothly without the chain attached but once the chain is placed on both gears, it gets very hard to turn and the hydraulics can’t move it. Not sure exactly what is wrong yet. I am guessing something is misaligned.

I do actually have a boring head. Learning to use that will be for the next project.

 

[WhoWhatNow]

Th chain was slack for the last picture.

 

[WhoWhatNow]

Th chain was slack for the last picture.

 

[helterskelter]

It's hard to tell from your pictures but it looks like only one small clamp is holding the enter of the gear? Your endmills will be much happier if you had secured it more rigidly.

Also this is definitely better as a lathe job if you've got one.

 

[WhoWhatNow]

It's hard to tell from your pictures but it looks like only one small clamp is holding the enter of the gear? Your endmills will be much happier if you had secured it more rigidly.

Also this is definitely better as a lathe job if you've got one.

I used a clamp during the final part of the cut to make sure the center section did not move after being cut free. The gear is held on the perimeter (at 12 and 6 in the picture.)

My lathe is only an 8” so it was too small for this job.

 

[ER70S-2]

That's what you wanted to do? You should have said that you wanted to take out almost all of the center! I was imagining that you only wanted to open up the center hole a little bit. What you did wasn't really a job for a boring bar as I originally thought. Putting the gear on a faceplate on a lathe would have probably been a little easier, but what you did was fine!

 

[NitroShark]

I've bored lots of sprockets with a manual Bridgeport.. For that job with your setup No indicators are needed just a plate of aluminum bolted to your rotary table (face plate).

Going off the sprocket pitch diameter would of been the most accurate but in your case I would have done this using the sprocket OD as a reference.


1) Bolt aluminum face plate to rotary table.
2) counter bore the plate 3/4 thicknesses of your sprocket using just an endmill.
3) clamp sprocket down in counterbore.
4) using endmill---now just cut out you socket bore with the rotary table as you did before.

 

[homebuilt burner]

Good job. Looks like you solved your own problem. It is always good to hear others ideas as sometimes we overlook the obvious. The more machining I do the more I find I don’t know.

 

[66cj225]

By its title the scope of this project is limited but the next thought should be the radial outside and inside cuts for the guard that protects you and your grandchildren from the pinch points. Hydraulics aren't really forgiving.

 

[66cj225]

And I do recognize that JD grillguard!!

 

[OccupantRJ]

Check your flow control valve. The way you have it on one side of the hydraulic motor likely would have speed of movement in one rotation direction, but almost lock up in the other direction as this type valve usually controls flow in one direction only. It would need to be installed before your directional valve to control the speed of the motor equally in both directions.

Nice work on the sprocket. Ya done good.
BTW, your mill is a 1957 model