New tool

[Steve Little]

[Steve Little]

I know I'm gonna be late to the show and everyone has one of these in their toolbox.
I bought a couple more BT brake backing plates at a swap meet recently and the guy selling them was kind enough to tell me that one of them was warped. I have had problems of this nature before but I just toss them back in the box and pick another on. The box is getting down to slim pickings so I need one of these tools.



I used the turning tool as a run out guide and put it up against the backing plate.



In case its not quite clear...I have rotated the plate around and it is 1/4" out.

[gharper]

Steve,

Nice tool! Once you gt the plates straightened, you can use that as a mandrel to turn the plate with brake shoes in place and turn them to fit your drum for perfect brake operation.

[exeric]

Steve, these are before, and after pictures of the front backing plate on my '48FL. I was wondering why it wouldn't hold on a hill.

[Steve Little]

Hi Harper. Thanks for the tip. I didnt think of that application.
Eric. Nice visual shots of the distortion and correction.



I took this back plate off a 46 Knuckle I'm building, and checked it. It was also a 1/4" out. I gave it some measured whacks with a nylon hammer and told it to smarten up its attitude .
Then I had a bit of a think about the coincidence of both being 1/4" out at the same point.
The distortion of these two plates was at the slide locator.
I think it comes from people not getting the locating tab into the slot. If the half shaft is done up with the locator tab sitting against the slide area of the slot instead of being in it, this type of distortion could happen.

[exeric]

Steve, what were your speeds, and feeds. I would have to think your speed would be slow to avoid chatter. . . And, that reminds me of the old bastard in the machine shop that would look over your shoulder and tell you to speed it up, or slow it down. No matter what you did, it was always wrong, and he would be the first to let you know

[exeric]

Oh, wait a minute; you're just using the cutter to see run-out, and where you need to bend the backing plate. I saw all the chips, and cutting fluid and assumed you were taking cuts. They say there are no stupid questions, but I can prove that is not true

[Steve Little]

he he Thanks Eric.
I was wondering if one of the machinists on the forum would pick up the fluffy finish on the spigot.
I turned the short spigot first and couldn't wait to try the tool out, so I put the chrome backing plate on and checked it. When I had straightened it, I checked the radial run out. There was an area that had been rubbing against the brake drum. It had rubbed a big groove around the edge and created a protruding lip. I spun the lip off, and noticed sparks coming off. The steel for these backing plates is robust and I think I took the nose off the tip. I then turned up the second spigot, but didn't rotate the tip for a fresh edge.
Speeds and Feeds. I roughed the shaft at 300rpm at “Fast” feed, and did the last pass at Slowest feed but it still left a fluffy finish. It was ripping not cutting.

A little bit of back ground info.
I'm a Tradesman in Boilermaking & Structual steel.
I got my basic knowledge of turning while looking over the shoulder of the Tool room machinists I used to employ.

I like good quality tools and solid machinery so I like to buy machinery from an age when they were good quality, and made to last.
Sorry China. I don't subscribe to your policy of “Its cheap. Just buy another one”
I bought my first lathe for the frame business, and it was a Harrison of English renown.
I only had it for a couple of years and had to sell it for a lathe that would take 1 ½'' tube.
I did some research before replacing the Harrison. I found that Mazak lathes hold a well respected reputation for excellent quality. Not sure if they are well known in the US but the 1960's Mazaks are very sought after here. They were made in Japan until 1969 and then cost cutting saw them made in Taiwan, now...mainland China.
1960's Japanese Mazaks are very sought after and collectable. Taiwan and China models...not so much.
My Mazak spent most of its life in a high production workshop. The previous operator must have had an allergic reaction to an oil gun. When I first bought it, I pulled it down to the main bed and cleaned out the hardened gum in the oil ways. I need to replace the nuts and screws to get better accuracy and fine finish as it makes micro jumps during feed.
I promise to try cut out my tardy turning and pick my game up.

[ryan]

Great tool and pictures. Thanks for sharing them with us! I do have a couple of questions, without criticism I must add. First I noticed you are using a 3 jaw chuck without turning the o.d. of your shaft at the same time you turned down the shoulder of your spigot. Unless you have a perfect 3 jaw, your spigot will not repeat when used again. It would not repeat anyway with using a 3 jaw. Did you happen to check the concentricity of the shaft with the area turned? I know a couple of thousands does not matter much in this case, but I have seen a lot of 3 jaws out of whack.
Also, why is your plate sticking out of the jaw that much, run out adds up rather quickly. I assume for hammering room. Plus, being out so far will add to chatter.

Without posting the formula, here is a link to a simple feed and speed calculator.

http://littlemachineshop.com/mobile/speeds_feeds.php



Thanks again

[Steve Little]

Hi Ryan.
Thanks for contributing with your knowledge.
I usually keep the material close to the jaws because my 3 jaw chuck has 007” (I think the term is concentric run out). But on this occasion I was going to be brave and try to do all the turning in one set up. But I ended up wimping out half way through, and parted off and turned the job around.
It didn't matter to me because I just needed the tool to check the distortion of the front, and rear, brake backing plate but in truth...I err... well you see... umm... I don't know what I'm doing.
But I'm the only person here these days, so I get away with it. Until now!

I used to employ Tool room machinists, who I can say, are a testy funch of buckers.
They turned their noses at this Chinese 3 jaw which is 9 1/2” diam. They mostly used the four jaw chuck. But it is 12” diam and I cant lift it in and out of the lathe these days, so I leave the easy one in.

Shortly after buying this Mazak, I remember a machinist was turning up some parts on the 3 jaw and I heard him swear and turn off the lathe. I went over to see if I could help, and he just waived me away. I dropped my head and shoulders and dragged my toes back to the office.
Much to my angst he proceeded to take parts off the lathe, even though we were trying to get an order finished.
He pulled the 3 jaw apart, at which point I weaseled my way back into the operation by offering to clean the parts in the parts washer (as you know I did the most important part of the job) while he reconnected the 3 jaw face plate to the lathe and checked it for run out.
It was running out 003” on the face at 9” diam. He refaced it, then lubed all the parts and put it back together.
He then put the 4 jaw chuck on the machine and put a long piece of ground round bar in the chuck and drilled a center in both ends.
As long as I kept my manic breathing under control I was allowed to stay and help.
He removed the 4 jaw and put the big dead center in the quill of the head stock, and another one in the tail stock and then put the round bar in and dialed the tail stock to the head. When all this was done, he refitted the 3 jaw and checked it. The teeth were...and still are, running out at 007”
We didn't have a tool post grinder to fix the jaws.
I do now, so I will do it soon.
Thanks again.
Regards Steve

[ryan]

Hi Ryan.
Thanks for contributing with your knowledge.
I usually keep the material close to the jaws because my 3 jaw chuck has 007” (I think the term is concentric run out). But on this occasion I was going to be brave and try to do all the turning in one set up. But I ended up wimping out half way through, and parted off and turned the job around.
It didn't matter to me because I just needed the tool to check the distortion of the front, and rear, brake backing plate but in truth...I err... well you see... umm... I don't know what I'm doing.
But I'm the only person here these days, so I get away with it. Until now!

I used to employ Tool room machinists, who I can say, are a testy funch of buckers.
They turned their noses at this Chinese 3 jaw which is 9 1/2” diam. They mostly used the four jaw chuck. But it is 12” diam and I cant lift it in and out of the lathe these days, so I leave the easy one in.

Shortly after buying this Mazak, I remember a machinist was turning up some parts on the 3 jaw and I heard him swear and turn off the lathe. I went over to see if I could help, and he just waived me away. I dropped my head and shoulders and dragged my toes back to the office.
Much to my angst he proceeded to take parts off the lathe, even though we were trying to get an order finished.
He pulled the 3 jaw apart, at which point I weaseled my way back into the operation by offering to clean the parts in the parts washer (as you know I did the most important part of the job) while he reconnected the 3 jaw face plate to the lathe and checked it for run out.
It was running out 003” on the face at 9” diam. He refaced it, then lubed all the parts and put it back together.
He then put the 4 jaw chuck on the machine and put a long piece of ground round bar in the chuck and drilled a center in both ends.
As long as I kept my manic breathing under control I was allowed to stay and help.
He removed the 4 jaw and put the big dead center in the quill of the head stock, and another one in the tail stock and then put the round bar in and dialed the tail stock to the head. When all this was done, he refitted the 3 jaw and checked it. The teeth were...and still are, running out at 007”
We didn't have a tool post grinder to fix the jaws.
I do now, so I will do it soon.
Thanks again.
Regards Steve

Steve,
Again, I was not trying to shoot down your process. I was a mold maker at one time. Please let me know when you decide the grind in your jaws, I can explain the correct procedure. All I see on YouTube only have the process half right and come out worse than they started.

Take care,
Ryan

[harleytoprock]

Ryan, I'd be curious as to your method of grinding jaws as well. The tricky part is for the jaws to be in position as to a mimic as if the jaws are closed down on a piece of round stock. I've seen a few methods and I'd like to hear yours. Thanks.

[ryan]

The people are using the jaw threads to locate instead of using the jaw itself to locate off of. There is play or clearance in the bolt hole threads that bolt the jaw on. The threads do not locate the jaw itself, causing everything to go out of whack. There is a tool called an anti-backlash ring or a jaw boring ring that locks into the counterbore of the jaw itself, this will keep the jaws true going in both directions, clamping on the o.d. of the stock and clamping on the I.d. of the stock.

There are some inexpensive ones out there, so do not panic, I will help look for some as well.
Take care

[Steve Little]

Hi.
Seems like there are a few interested machinists on the forum, so here is a little wall break in the thread with some ideas for your deliberation and discussion:
I've been trolling through You tube for fix it ideas on 3 jaw chucks.
Here are some methods that might have plausible merit:

Method 1.
Thick machined ring placed over external steps on jaws. Open jaws onto ring for uniform outward pressure.
Grind face of teeth to achieve a uniform face.
My question on this method is: Does this method (pressure on jaws is reverse to working action)) invite error because slop in scroll might cause jaw misalignment?





Method 2
Place small precision V plates between each jaw and screw down jaws to capture plates between the jaws to trap the plates at the end and cause pressure. The V in the plates creates clearance for the grinder tool to pass through. This method has a downward pressure on the jaws.




Look forward to reading the discussion.
Regards Steve

[Steve Little]

Hi Ryan.
Terms or job references mean different things in different countries. I'm making a guess that (Mold Maker) may not mean the same thing over here as it does over there. It reads like you are making a reference to machining.
I think a mold maker over here means a guy working in a foundry who boxes up patterns and fills them with sand to make a mold.
To help cross the international divide, what does a Mold Maker do in the States?

Not making any disrespect for your job. Just like to learn different terminologies in different countries
Regards Steve