Lathe question

[Guest]

I just dont really know how the owners of the machine shop where BSB works would feel about him coming to work with a film crew and start turning some BSB Racing Razors out instead of working on what they want him to do....LOL..

Somehow that would not fly. I work for the world's largest plastic card manufacturer. It is very high security. NO CAMERAS past the turnstile. Somebody gets a cell phone out on the production floor, out the door they go! There are over 100 security cameras inside and outside the place. Employee badges have an RF chip in them and every door I go through it has to be swiped or it doesn't open up. Soooooooo, a camera crew is out of the question. I have a Taig at home and although it's rinky dink, it gets the job done.

 

[Vitamin K]

Well, I'll just throw out some questions for the red hot lathers. Some of these questions have been answered by a few of you, but not all of them. Answer if you feel like it /images/boards/smilies/smile.gif

- What sort of mandrel do you use to hold the wheels while you work on them? If you use a friction/press-fit mandrel, how do you accommodate differences in bore sizes (assuming BSA wheels). Do you ream bores to a standard size before mounting on the lathe?

- Do you re-chuck existing mandrels when you need to re-setup your lathe, or do you cut a new one to fit the wheels you plan to work? If you re-chuck existing mandrels, what method do you use to center the mandrels in the chuck?

- What kind of device do you prefer to hold stock? 3-jaw chuck? 4-jaw chuck? Collet?

- What do you consider an acceptable amount of runout on a finished set of wheels?

- What criteria (if any) do you have for selecting wheels to turn?

 

[derby freak]

Im by no mean a red hot "lather" but ill try to answer your questions
1...Depends on type of wheel you are working with
2...Rechuck...Insert mandrel into collet and tighten it down
3...Collet type chuck
4...If you spin the wheel on an axle and you see it wobbling its junk
5...Make sure the wheelbores are in good condition and try to pair up the casting numbers

 

[derby freak]

Sorry I need to be more specific on question one...Press fit mandrel...No i dont ream bores..if you get a wheel that the bore fits much looser on your axles than therest mark it by a method of your choosing and use it as the non contacting wheel on your ss car or trash it

 

[pony express]

I have never been able to get a good wheel by my lathe skills. I have not found a good enough mandrel. The best I could do is placing the inside hub in the jaws of my chuck that I mount in the jaws of the lathe chuck. I can't get the wheel perfectly motionless as the cutting tool does its thing. The best cutting tool I've gotten so far is a router bit. I need to take a class I think.

 

[Vitamin K]

I have never been able to get a good wheel by my lathe skills. I have not found a good enough mandrel. The best I could do is placing the inside hub in the jaws of my chuck that I mount in the jaws of the lathe chuck. I can't get the wheel perfectly motionless as the cutting tool does its thing. The best cutting tool I've gotten so far is a router bit. I need to take a class I think.

Don't most people turn their own mandrels?

What kind of lathe are you using? Have you measured the chuck's inherent runout?

 

[pony express]

I use a Micro Mark lathe and one of those wheel mandrels availble at most sites. It does not work.
I don't know how to lathe a mandrel so I just chuck the inside hub of the wheel. It works better than the mandrel. My wheels I make are good for the NDFW only.

 

[Vitamin K]

I use a Micro Mark lathe and one of those wheel mandrels availble at most sites. It does not work.
I don't know how to lathe a mandrel so I just chuck the inside hub of the wheel. It works better than the mandrel. My wheels I make are good for the NDFW only.

Yeah, would not expect to get good results from a typical screw-fit mandrel.

I'd like some experienced lathe-users to set me straight here if my understanding is flawed. From what I've seen, a typical PWD lathe mandrel is a rod of metal (aluminum?) in which a section has been cut down to be a pin of a diameter sufficient to hold the bore of a wheel snug while spinning, but not so snug that it deforms the bore.

The challenge that I seem to understand is that it is very hard to center a piece of stock perfectly in a chuck. The act of turning down the stock gives you a centered piece (and, thus, a centered mandrel), but as soon as you remove the piece from the chuck, you risk not being able to get it dead on center again. Hence, for the best accuracy, you'd turn a new mandrel each time you set up the lathe again...or, perhaps just turn a mandrel and never take it out of the chuck!

 

[zeebzob]

I have a Harbor Freight lathe. I bought a cheap collet chuck and I at times need to remove the spindle. I then have to rechuck it when I turn wheels again. When I do, I indicate it with a test indicator. It's a pain in the arse, I typically have to remove it, spin it slightly and reclamp down on it until it has .0005 runout or less. It's tedious and takes a bit of luck, but I can usually get it in about 10 minutes or less. I try nit to remove it unless it's necessary.

 

[cycrunner]

I have a Central Machinery (Harbor Freight) lathe with a 3 jaw chuck. Here is what I do to get a "no runout wheel" :

Turn a plastic mandrel (I use Delrin) with the OD just under the wheel OD size. Face it so it has a pin long enough and a diameter that just has a tight slip fit for the bore of the stock BSA wheel. You now have a mandrel face truly perpendicular to the pin.

Apply double stick tape to the mandrel face and mount your wheel with the letter side tightly against the mandrel face. Turn the OD to clean up and to the size you want. Use light cuts to keep the wheel from coming off the mandrel face.

Depending on the class/division machine the wheel to the width required and machine off the wheel bumps, if allowed, or just true that side to the edge of the bumps. You now have both the inner and outer edges of the wheel diameter parallel to each other.

I then turn the inner hub OD to a diameter and length that I want. Using a fine file I radius the hub and polish it and the outer wheel OD. Make all your wheel hubs you are working on the same OD as these will be mounted to the mandrel bored hole when you turn around the wheels for machining the other side.

If allowed, machine the inner wheel ID and inner face to reduce weight while still on the mandrel.

Remove the wheel from the mandrel and do your other wheels the same way. Do not remove the mandrel from the chuck until all your wheels are ready for the next step.

Next machine off the mandrel pin and drill and bore a mounting hole for the wheel's hubs. You need to allow for the longer hub to fully enter the mandrel hole.
Boring the drilled hole preserves concentricity. You should have tight slip fit on the wheel's hubs ODs you machined previously.

Mount the wheels with the inside faced edge against the mandrel face. - I use some stretchy electrical tape over the mandrel and wheel OD to hold the wheel against the mandrel. You now have the wheel bore, the hub OD and the wheel OD concentric with each other.

I then machine the outer axel bore step and reverse cone it with a lathe bit, and the BSA letters if allowed, then polish the outer axel bore step and any other part of the wheel as desired.
Note - to remove the wheels from the mandrel that has the double sick tape I apply some alcohol to loosen the tape. Then clean off any residue and apply new tape for each of the other wheels.

 

[Vitamin K]

Cycrunner, thanks for that awesome write-up!

I had been curious about the possibility of using delrin for mandrel stock, but was loathe to ask about it, lest my ignorance be mocked. Glad to know that it is a viable option! The double-stick tape also sounds clever!

 

[cycrunner]

I neglected to add that I also use a live or dead center in the tailstock lightly against the hub to help keep the wheel firmly against the double stick tape when turning the OD and width.

 

[GDH Racing]

When we make parts on a CNC lathe and have extremely tight tolerances we do not use permanent work holding fixtures like Zeebob discusses. We load a rough fixture in the chuck and use the lathe to machine it into the tolerance needed to hold the work piece. That ensures the fixture is true. When the fixture is removed it is trashed and a new fixture made specifically for the next part (it's actually more complex but this is the basics of the process) The repeatability of removing and replacing work holding fixtures just is not possible without a lot of effort, so it's cheaperand faster to use this method and less room for error. This is medium volume extremely tight tolerance work in a production plant so I am not sure if it would be applicable. I thought I would pass it along.

 

[GravityX]

I can understand what you are saying here GDH. There are always other solutions to bring things back to "center" for repeatability. Take a look at this video below, for instance. I understand this may not work for all situations, but it is another option for those making their own wheels to get the wheel fixture running true again. If you never have to remove the wheel fixture you would not need this adjustable collet, as it would stay centered, unless the headstock bearings wear out.

[video]https://youtu.be/2PidQxTYP7k[/video]