Machining Setup's with Few Comments

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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo » Tue Aug 14, 2018 6:49 pm

Turning a long slender shaft using a simple shop made backrest.

Another job where I had to turn down a 1/8" dia. bar to 0.107" dia. where the turned length was 1-1/8" long and the 1/8" dia. bar stuck out from the collet 1-5/8". The resulting shaft had to be on size without any taper and have a good finish.

Some sort of support is needed for a job like this if ever one hopes to achieve the above.

The cutting tool has to be exactly on center height and needs to be extremely sharp. Take extremely light cuts (0.002") and several passes may be required to eliminate taper.

All credit goes to Dave Powell of TSME who first showed me how it is done.
Attachments
394 Turning Down a Long Slender Shaft Using a Simple Shop Made Backrest.jpg

RET
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Re: Machining Setup's with Few Comments

Post by RET » Thu Aug 16, 2018 9:06 am

Hi Don,

Essentially, what you are doing is using a follower rest to support the work. About 30 years ago, I needed to do the same thing when I was working on the German 88mm. gun model. I needed to turn down a 3/16" dia. shaft to 0.10 dia. so I could thread it for #4-40 NC. I had a proper follower rest for my lathe and I found out that if you used the right setup, it was VERY easy. By the way, the shaft was stainless.

The setup I used was to hold the shaft in a 3/16" collet with at least 6" sticking out. This is necessary so that the headstock doesn't influence what you are doing at the steady rest. As Don says, the tool must be sharp and it needs to be positioned right at the edge of the steady fingers. Its best if the little burr that the tool sometimes throws up just clears the edge of the steady fingers. The fingers must run on the full shaft dia. and the complete cut must be taken in one pass. If you don't, the turned section can become slightly triangular in shape. Take a couple of very short test cuts to get the diameter right and run the lathe slowly. You may have to guide the rod into the follower until the tool starts to cut.

As I said above, it was surprising how well the setup worked.

Richard Trounce.

Magicniner
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Re: Machining Setup's with Few Comments

Post by Magicniner » Thu Aug 16, 2018 10:38 am

Build or buy a Roller Box instead, a couple of 1/8" long test cuts on your chosen stock to set the roller box up and then the job is a single pass, for as many parts as you need from the same stock ;-)

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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo » Thu Aug 23, 2018 5:16 pm

Some quick and dirty slotting with a side tooth slotting saw in my small horizontal mill.

The vise used has horizontal and vertical vee grooves cut into the vise jaws to aid in holding and squaring round work.

The problem is how does one quickly and accurately center the cutter over the work to cut a center slot in it?

With the method I use, the only requirement is the vee grooves in the vise all have to be the same size.

First center the cutter by eye over the work.

See the pile of different thickness feeler gauges in the first photo. Make a thickness selection so that the feeler gauge pile is a nice light push fit between the cutter side teeth and one vise jaw. Then try it on the other side of the cutter. If the fit on the other side of the cutter is loose move the cutter very slightly towards the loose fit side and adjust the pile thickness until there is the same very light push fit on either side of the cutter. For larger diameter work, substitute a small adjustable parallel for the feeler gauge pile.

It can be done faster than describing what to do.

In the second photo, one can see the quick and dirty depth gauge for checking the slot depth. One can use an eye loupe to set the scale graduations if greater accuracy is required.
Attachments
143 Slotting a Leaf Spring End Keeper Blank.jpg
144 After Slotting.jpg

Harold_V
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Re: Machining Setup's with Few Comments

Post by Harold_V » Fri Aug 24, 2018 3:30 am

Assuming the V grooves are identical, that's a quick way to get where you're going. However, there's no guarantee that they will be the same size. That said, once the vise is dialed in, you can achieve the same thing (finding center) by using a longer piece, which protrudes from the vise. Mic the cutter, so you know the exact width, and mic the material you use to make the setup. It should be the same diameter as the parts to be machined.

With both dimensions recorded, add them together, and divide by two. Next, pick up the edge of the part (either edge) with the cutter, which you can do by running the cutter backwards, and using a piece of paper (thickness doesn't matter. I use writing paper, and measure so I can correct by the paper thickness) then move over the amount calculated previously. That should put you on center.

Many insist that using cigarette paper is a necessity. I say it isn't, and that it's dangerous, especially when picking up a cutter. It gets you dangerously close because it's too short to allow clearance. By using a longer strip of paper, you can insert the paper safely. By running the cutter in reverse, it doesn't cut the paper when it makes contact. The thicker paper also gives you a little fudge factor, in case you over feed when picking up. Cigarette paper is too thin to provide any protection, so you can easily mark the part you're trying to pick up.

Remember to run the cutter the opposite direction when you take the cut.

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

pete
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Re: Machining Setup's with Few Comments

Post by pete » Fri Aug 24, 2018 2:36 pm

I use the cigarette paper trick myself sometimes even though I've got some more modern tooling to do the same. But if the cutting tool is rotating? Then that's what needle nose pliers are for and as Harold mentions I wouldn't ever get my hands and fingers in that close. Good edge finders should be more accurate, repeatable and probably quicker if the working faces were properly lapped. But the paper can edge find on some work better than anything else I've got since it can pick up any minor tool runouts on blade type cutting tools, endmills etc. If it's just needing to take a few more thou on the lathe and you've forgotten what your dial settings were, that paper can do what no other tool can do there. Those old machinist's who figured out that trick were a damned smart bunch. I keep a package of Zig Zags right next to my 3D Taster and for the right situation I think there worth having in your tool box.

The only reason I do use the rolling papers is there a known almost exact .001" thickness. Thicker paper works fine but could still compress a bit before it rips with a non rotating tool so sometimes isn't quite as accurate. I figure if the cigarette paper does rip I should be somewhere within about 5/10ths. Feeler gauges or shim stock also works, I still think the paper is a bit better method and even more so while checking cutting tools while there rotating. Oddly with the hundreds of Youtube videos I've watched it seems few know about it since I've only seen the method used a couple of times there. Those thin rolling papers can even be used as a quick and dirty check for part flatness on a surface plate. Put one under each corner of the part and if none can be pulled without the paper ripping it should be fairly flat.

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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo » Mon Aug 27, 2018 2:34 pm

A difficult holding job.

The part shown in the previous post was next setup for a 3/32" drilled/reamed cross hole and then both ends of the part were sloped at 45 degrees to finish the part.

The cross drilling operation was not particularly difficult but holding the part to slope both ends of it was a different story. The part could not be held in any conventional way in the mill's vise and still have enough clamping force to do the end milling and yet not distort the part due to the clamping pressure.

Sometimes, one has to come up with something a little different.

The simple holding fixture shown in the third photo did the job superbly but to make it was an exercise in itself.
Attachments
145 Cross Drilling a New Leaf Spring End Keeper.jpg
146 Machining the Leaf Spring Keeper Sloped Ends.jpg
147 The Holding Clamping Fixture.jpg

Harold_V
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Re: Machining Setup's with Few Comments

Post by Harold_V » Mon Aug 27, 2018 3:36 pm

Carrdo wrote:
Mon Aug 27, 2018 2:34 pm
The part could not be held in any conventional way in the mill's vise and still have enough clamping force to do the end milling and yet not distort the part due to the clamping pressure.
You can circumvent that problem by simply installing a spacer of the identical thickness on the opposite end of the vise. That forces the jaws to grip parallel, and adds surface area, so the part isn't crushed or otherwise distorted. I've used this method with success for years. I specialized in small work when I ran my commercial shop, so I was forced to learn what works, and what doesn't. Small work is very unlike large stuff, with work holding often a challenge.

H
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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo » Sun Sep 02, 2018 12:26 pm

Harold,

The part which I was machining was half round so no matter how it was held lengthwise (and it needed to be held lengthwise to machine the sloped ends) in the vise there was only a line contact between the vise jaws which was not enough to resist the milling forces so it had to be mounted on the base plate so as to give the vise jaws the necessary gripping force.

John Hasler
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Re: Machining Setup's with Few Comments

Post by John Hasler » Sun Sep 02, 2018 12:40 pm

Carrdo wrote:
Sun Sep 02, 2018 12:26 pm
Harold,

The part which I was machining was half round so no matter how it was held lengthwise (and it needed to be held lengthwise to machine the sloped ends) in the vise there was only a line contact between the vise jaws which was not enough to resist the milling forces so it had to be mounted on the base plate so as to give the vise jaws the necessary gripping force.
I use v-grooved vise jaws for that. You can also use a v-block.

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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo » Sun Sep 02, 2018 12:48 pm

A semi universal multi angle square or round tool bit grinding fixture to grind miniature slotting tool bits and many other types of multi angled cutting tools in my surface grinder. The fixture will rotate 360 degrees in two separate planes set 90 degrees apart and nod more than 45 degrees forwards or backwards all at the same time to enable multiple angles to be ground on the tool bit all at one setting.

I sweated bricks and mortar to come up with this fixture which is adapted from two separate commercial tools (a combination of a South Bend tool bit grinding block coupled with a small, no name toolmakers rotating, swivelling vise (precision ground and hardened).

Its small size is perfect for the type of work I do.
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395 Semi Universal Multi Angle Toolbit Grinding Fixture.jpg
396 Semi Universal Multi Angle Toolbit Grinding Fixture.jpg

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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo » Wed Sep 05, 2018 5:59 pm

Producing a 1/8" wide slotting tool bit utilizing the semi universal multi angle tool bit grinding fixture illustrated previously.
Attachments
98 Setup to Grind the Tool Bit Top Rake.jpg
102 Checking Finished Tool Bit Tip Width.jpg
103 A Perfect Fit.jpg
105 Finished Slotting Tool Bit.jpg

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