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Tips of the Trade

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
I'm holding the tap with two hands and pressing downwards slightly and drawing the part towards me. It is cutting but very minimum, actually more like scraping.

I am gunna try this ASAP! Love it!

Is there any issue with the orientation (let's call it clocking) of the tap? Cutting edge straight down, flat edge down, etc?
 

thestelster

Ultra Member
Premium Member
Is there any issue with the orientation (let's call it clocking) of the tap? Cutting edge straight down, flat edge down, etc?
It's by feel. By clocking the tap, you'll feel when its cutting or just rubbing. Just put even downward pressure. Or if its tighter on one end, put more pressure on that end. Similar to hand honing a wood chisel on a bench stone.
 

Susquatch

Ultra Member
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Moderator
Premium Member
It's by feel. By clocking the tap, you'll feel when its cutting or just rubbing. Just put even downward pressure. Or if its tighter on one end, put more pressure on that end. Similar to hand honing a wood chisel on a bench stone.

That makes great practical sense. I'll be trying that trick very soon!
 

thestelster

Ultra Member
Premium Member
In the similar vain, to slightly enlarge an internal thread. Stick a wood skewer, or tooth pick, or wooden dowel into one or two of the flutes of the tap. It will put more pressure on the opposite side and cut a little deeper.
 

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Susquatch

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I like that too!

Sometimes I just rotate the nut in the vise 3 times - ie every other face. This distorts the nut a bit and sometimes that's just enough to enlarge the thread a wee bit. I suppose that might bite me someday but the only time it did was when I forgot to use a sharpy to keep track of which faces I had done. I ended up doing every face and then the nut was too loose!

It's sort of the opposite of squeezing or expanding an outside thread die.
 

thestelster

Ultra Member
Premium Member
You have a part to machine, but it is so irregular in shape there's no easy way to hold it securely. You could epoxy the part onto a plate, but then removing the epoxy afterwards can be troublesome. So what do you do? You use a fusible alloy. Low melting temperature metals. One specifically is Cerrosafe. Its formulated to melt slightly below the boiling temperature of water. Find or make a metal box that will hold your part to be machined, and position the part in the box. Put that box in a pan or tray to catch the drippings. Put the Cerrosafe in a pot and some water, put the pot on a hot plate. As the metal warms up, it will melt into a liquid. The water is there only to keep the temperature down. Once completely melted pour the Cerrosafe into the box holding your part. Pour enough Cerrosafe to completely surround your part. Let everything cool. Once cool, put the box in your vice or chuck, and machine away. Once you're finished the machining, put the whole box into a container with water, and put on the hot plate. Let it come up to temperature, the Cerrosafe melts the part comes out, use a brush to clean off any excess Cerrosafe left on the part. Remove from the boiling water, dry, and oil. Pour the melted Cerrosafe into the pot, and reuse as often as you want. A couple caveats. When machining your part, keep it cool. Remember, the Cerrosafe melts at 90°C, or there abouts, so you don't want your part coming loose. The other caveat is not to hold smooth, regular shaped parts, it could spin in the Cerrosafe.
 

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thestelster

Ultra Member
Premium Member
Here is another example of fixturing with fusible metal. With these 2-part boxes, assemble the boxes, put the part in the box, pour the melted Cerrosafe into the box. Once cool, remove the bottom and chuck in your four jaw lathe chuck.
 

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PeterT

Ultra Member
Premium Member
Very useful thanks. I was reading another application related to filling thin walled tubing with Cerrosafe. They said to give the ID surface a light pre-coating with oil. But they didn't say why. Maybe related to squish deformation in this application but I also wondered if it was like a release agent after re-melting for removal. Have you found this to be the case where the alloy leaves a thin 'plating' to the surface? (you mention brush clean).

Do you think he boiling water is more about controlling maximum temperature or maybe also has to do with allowing any cutting oil or similar 'impurities' to come to surface (lower density)?
 

thestelster

Ultra Member
Premium Member
Very useful thanks. I was reading another application related to filling thin walled tubing with Cerrosafe. They said to give the ID surface a light pre-coating with oil. But they didn't say why. Maybe related to squish deformation in this application but I also wondered if it was like a release agent after re-melting for removal. Have you found this to be the case where the alloy leaves a thin 'plating' to the surface? (you mention brush clean).

Do you think he boiling water is more about controlling maximum temperature or maybe also has to do with allowing any cutting oil or similar 'impurities' to come to surface (lower density)?
Hi Peter, yes, I use the water to control the temperature, plus you know visually that the Cerrosafe is molten when the water is just starting to boil. The Cerrosafe will leave a skim coat on the part, but while its still in the boiling water, just brushing it will remove it. The added aspect is that while the part is still warm, the pores are open and readily absorbs oil to prevent it from rusting. I'm not so sure about using it in a tube prior to bending, like you would sand or a mandrel, Cerrosafe doesn't give much. You can't indent it with a fingernail like you could lead.
 

Janger

(John)
Administrator
Vendor
Removing dowel pins from blind holes. I googled this and found a lot of BS. The best answer I cane up with is to attach a drill chuck to the pin and then lever up on the chuck with a rounded lever - back side of channel lock pliers. This works. I removed the pins easily which were not coming out. The holes in the fixture plate are touch small and I have to tap them in with a hammer. So they are in too tight to pull with fingers or pliers.

807525C9-6C2D-443E-B35B-413D1AACD9B3.jpeg 7CE6DBF9-3D27-4E6F-85AB-6A7D9C9914EB.jpeg
 

Everett

Super User
That is a slick idea, I always wondered how flywheel dowel pins get removed from blind holes when they got sent out for resurfacing.
 

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
Very useful thanks. I was reading another application related to filling thin walled tubing with Cerrosafe. They said to give the ID surface a light pre-coating with oil. But they didn't say why. Maybe related to squish deformation in this application but I also wondered if it was like a release agent after re-melting for removal. Have you found this to be the case where the alloy leaves a thin 'plating' to the surface? (you mention brush clean).

Do you think he boiling water is more about controlling maximum temperature or maybe also has to do with allowing any cutting oil or similar 'impurities' to come to surface (lower density)?

I have found that it prefers to stick to itself rather than to anything else.

But then again, I have not tried boiling water to remove it. I've always just used its early contraction factor to separate the parts.

To be totally truthful, I've never used it with boiling water at all. That's another new trick for me. I like the fact the cerrosafe sinks but any oil floats. That might extend the life of my cerrosafe considerably as it tends to collect garbage in it over time otherwise.

You can cut cerrosafe easily with wire cutters or heavy snips. But it is more brittle than it is malleable. I doubt bending it would be very effective. Then again, a few cracks or even breaks might not hurt a thin wall pipe bending exercise very much at all. I dunno - might be worth a try.
 

PeterT

Ultra Member
Premium Member
Removing dowel pins from blind holes. I googled this and found a lot of BS. The best answer I cane up with is to attach a drill chuck to the pin and then lever up on the chuck with a rounded lever - back side of channel lock pliers. This works. I removed the pins easily which were not coming out. The holes in the fixture plate are touch small and I have to tap them in with a hammer. So they are in too tight to pull with fingers or pliers.
The only problem I see with that is you are probably still putting a bit of lateral bend force into the dowel & plate with the levering action, so not great for either component if its a lot of re-assembly. There are 2 other styles to be aware of, internally threaded which you can latch onto & pull axially. And external end thread, but the jig plate typically has a reamed section (for alignment) and threaded section (for retention).
 

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Susquatch

Ultra Member
Administrator
Moderator
Premium Member
Automotive machine shops use a collet chuck attached to a slide hammer. Works slick.


I made a collet to pull blind hole bearings using a slide hammer. The concept would work just as well with dowel pins. And no worries about pulling at the wrong angle either. Just reverse the collet and button. So the inside part is slotted instead of the outside The slide hammer would actually tighten the collet.

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You have a part to machine, but it is so irregular in shape there's no easy way to hold it securely. You could epoxy the part onto a plate, but then removing the epoxy afterwards can be troublesome. So what do you do? You use a fusible alloy. Low melting temperature metals. One specifically is Cerrosafe. Its formulated to melt slightly below the boiling temperature of water. Find or make a metal box that will hold your part to be machined, and position the part in the box. Put that box in a pan or tray to catch the drippings. Put the Cerrosafe in a pot and some water, put the pot on a hot plate. As the metal warms up, it will melt into a liquid. The water is there only to keep the temperature down. Once completely melted pour the Cerrosafe into the box holding your part. Pour enough Cerrosafe to completely surround your part. Let everything cool. Once cool, put the box in your vice or chuck, and machine away. Once you're finished the machining, put the whole box into a container with water, and put on the hot plate. Let it come up to temperature, the Cerrosafe melts the part comes out, use a brush to clean off any excess Cerrosafe left on the part. Remove from the boiling water, dry, and oil. Pour the melted Cerrosafe into the pot, and reuse as often as you want. A couple caveats. When machining your part, keep it cool. Remember, the Cerrosafe melts at 90°C, or there abouts, so you don't want your part coming loose. The other caveat is not to hold smooth, regular shaped parts, it could spin in the Cerrosafe.
Nice two stage trigger cover.
 
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