Minimum grip on stock while in vise?

[slow-poke]

For milling situations where your mounting a thin piece of stock on parallels so the top surface is above the jaws. Obviously if there is not enough material in the vise, it will be inclined to come loose and things could turn ugly. The question is how much is enough?

Assume a good quality milling vise Is being used.

 

[Susquatch]

Assuming you are not doing crazy things like our pros do, then I find a tenth (0.100) is usually enough.

I prefer more though - 1/4" in general for most things I do. But the last thing I want is for the work to come out of the vise. Bad stuff happens then.

If you are pushing the limits of your machine, you might need a lot more.

 

[little ol' e]

I have some 3d to run over these 4 blocks. I've got about 1/4" in the vice.
This material is just 1018 for soft tooling try outs.
I use emery paper alot when doing this type of machining with multiple blocks.
Toe clamping on a fixture plate just wouldn't work in this case.
Hope it helps some,

@Susquatch, pay no mind to the brass hammer, I recall you mentioning that you would never have a brass hammer on your mill.
I often break the codes and laws of machining when needed .
I call this hammer a QS, TE code hammer just to keep it in line with the standards...

 

[Dabbler]

@little ol' e Can I ask for more specifics. Depending on what exactly you are trying to do there are several remedies to try.

For instance: you have a 3" X 3" X .250 aluminum you have to face mill in your vise to get it to .210 thickness. I that case I would super glue it to a substrate and put that steel backing plate in the vice.

Can you be more specific as to your circumstance?

 

[Dan Dubeau]

Certain situations I'll use my thin parallels and grip on 1/16". I also made some diy talon grips in soft jaws that will hold onto 0.06" and absolutely trust those to grip and rip away. They've never flung a part, but they do mark them. I've got a set of old starrett vise hold downs too, but rarely use then anymore outside of a a few rare instances every couple of years. When you reduce your grip on the part you must also reduce your cuts/toolpressure you're exerting on it as well. Good sharp tooling, smaller cutters etc, should net you good results and reduce tool pressure.

I also use 2 way tape, or super glue for thin non ferrous stuff that needs to stay flat, but get thinner. It's tough trying to hold that stuff in a vise because any pressure you put on it to hold it, bows it up in the middle.

As a general all purpose rule I am more comfortable in the 1/4-3/4" grip range. My 1" and 1.5" parallels are the most used in my tray, as they will let me hold about 80% of the things I need to machine by letting me hold onto 0.75" and 0.25" respectively (6"kurt style vise with 1.75"jaws). Anything thinner than that say 1/8" and down, and I start adjusting my machining approach accordingly.

 

[Susquatch]

@Susquatch, pay no mind to the brass hammer, I recall you mentioning that you would never have a brass hammer on your mill.

I don't remember saying that like that. If I did, I was having a senior moment.

More likely what I said (or at least what I should have said) is that I don't NEED and RARELY USE a brass hammer on my lathe or my mill. I do keep one in the area for those few times when the odd part needs an attitude adjustment or disassembly.

On the mill, I dont need a brass hammer to tap down work on my vise. My vise has prismatic jaws that pull the work down as they tighten. No need for tapping with a hammer of any kind.

I also don't use a metal hammer on my R8 drawbar. Instead, I use a hard plastic mallet. There is something about the hard plastic that makes things come loose without the need for muscle or force. One very light rap with the plastic mallet and the R8 tool drops immediately. The bonus is no damage to the top of the drawbar.

I may have also said that I use the same plastic mallet to remove the chucks on my D1-5 lathe spindle. It works just as well on the chucks as it does on the spindle. One light tap and it's off. Ya, there is something magic about that plastic mallet.

Some might want to say I prolly don't tighten them adequately. While it's true that I don't gronk on them like I've seen some guys do, it helps to remember that I'm a big guy and they are definitely not what anyone else would ever call loose. It used to take several sharp raps with the brass mallet till I accidentally discovered how well the plastic one works.

Edit - here is a photo of both mallets with a #2 Philips screwdriver for perspective. Although bigger, the plastic mallet is prolly about half the weight of the brass one.

 

[little ol' e]

@little ol' e Can I ask for more specifics. Depending on what exactly you are trying to do there are several remedies to try.

For instance: you have a 3" X 3" X .250 aluminum you have to face mill in your vise to get it to .210 thickness. I that case I would super glue it to a substrate and put that steel backing plate in the vice.

Can you be more specific as to your circumstance?

Sure,
Material is C1018 that doesn't need to see the surface grinder. If I try to machine the 3d profile over the top in a smile type shape, going down to about .02 off vice jaws through the middle 2 blocks, the blocks will have a tendency to move.
These blocks will be installed in assembly afterwards. If I did these 1 at a time.... I would have some clean up and blending to do within the shape on assembly.

Without the emery paper , I know, at least 1 could pull away and shoot out the vise. Then it could/would be a domino effect after that. I've done that before lol..

Saw another guy doing this at another shop several years back and thought dam, that's pretty slick, so I stuck with it.
Since doing this, I haven't taken the side window out of this mill yet lol.

I never considered super glue. That sounds pretty slick as well.

 

[whydontu]

I don't remember saying that like that. If I did, I was having a senior moment.

More likely what I said (or at least what I should have said) is that I don't NEED and RARELY USE a brass hammer on my lathe or my mill. I do keep one in the area for those few times when the odd part needs an attitude adjustment or disassembly.

On the mill, I dont need a brass hammer to tap down work on my vise. My vise has prismatic jaws that pull the work down as they tighten. No need for tapping with a hammer of any kind.

I also don't use a metal hammer on my R8 drawbar. Instead, I use a hard plastic mallet. There is something about the hard plastic that makes things come loose without the need for muscle or force. One very light rap with the plastic mallet and the R8 tool drops immediately. The bonus is no damage to the top of the drawbar.

I may have also said that I use the same plastic mallet to remove the chucks on my D1-5 lathe spindle. It works just as well on the chucks as it does on the spindle. One light tap and it's off. Ya, there is something magic about that plastic mallet.

Some might want to say I prolly don't tighten them adequately. While it's true that I don't gronk on them like I've seen some guys do, it helps to remember that I'm a big guy and they are definitely not what anyone else would ever call loose. It used to take several sharp raps with the brass mallet till I accidentally discovered how well the plastic one works.

Edit - here is a photo of both mallets with a #2 Philips screwdriver for perspective. Although bigger, the plastic mallet is prolly about half the weight of the brass one.

View attachment 31228

Best persuader in my shop:

Dead-Blow Mallet - Lee Valley Tools

www.leevalley.com

 

[slow-poke]

I need to get a dead blow hammer. I have a smaller nylon one, have not tried that on my MT3 drawbar, brass one works well.

 

[140mower]

I use a chunk of lead....

For a lot of things. Time to re-pour this one soon.

 

[kstrauss]

I agree with Dan and wouldn't be without my Talon grips. They are pricey but essential for holding stock with all but 0.075 or even less available for machining. I often then flip the half-completed part and grip in a vise on parallels or, depending on the shape, in custom soft jaws to remove the 0.075 from the back of the piece.

Thin stock bows and can't really be held in a vise directly. Coolant tends to destroy the grip of double sided tape. Crazy glue to a substrate sorta works but I haven't found a completely satisfactory solution.

When cutting thin plastic I mostly use very thin double sided tape (https://www.amazon.ca/Nitto-Permacel-P-02-WI07536-Double/dp/B000QC48UU/ Not cheap but it works really well.) to attach it to an aluminum or even a MDF substrate.

 

[Mcgyver]

One of the best things for solidly holding work with minimal depth is a set of holds downs. Makes the minimum say .030" and you will never need to tap the work down. They are what people did before angle locks, and while not as convenient, are arguably more effective.

If you study the angles in the photos their ways should reveal itself. They sit flat on the parallels until tightened at which point the jaws push them up a bit so they are angle down slightly toward the work.

They should be hardened to stand up, all the ones I have are, but soft would work toward getting you out of a bind. They were a common apprentice project, I have Bill Hope's from almost a 100 years ago and some Starretts and Luftkins (different sizes). Starrett still makes them I believe. I'm using them below because they work better than a Kurt when you only want to grip a small bit of metal solidly and want zero lift (a T shape is being made out of this, irrc for metric to imperial key.)

 

[Former Member]

Thin grip ht worries less that thin stock. Why....thin stock can flex unexpectantly and when it does there are surprises, generally not good.

This falls under don't ask.

 

[Susquatch]

Best thing is a set of holds downs.

Never saw those before. Very cool. I was going to ask if the backs were vertical but I see clearly that they are not. This helps keep the nose down.

Is it necessary to use two blocks under the work? Wouldn't one suffice? Or are the blocks angled slightly too?

 

[Janger]

. I also made some diy talon grips in soft jaws that will hold onto 0.06" and absolutely trust those to grip and rip away.

DIY talon grips … a few pics of those Don?

 

[Dan Dubeau]

I'm about ready to make another batch, so I'll start a thread when I do. IMO they're actually a relatively easy shop project, but I did make a quick fixture for them to mill the tooth profile. We've got a bit of a slow period coming up, so there will be a few make work projects like that going on. I've got an idea to try and make them on the lathe too, and if it works it'll be much easier and quicker to crank them out on a bar pulled lathe in one go.

 

[Mcgyver]

Is it necessary to use two blocks under the work? Wouldn't one suffice? Or are the blocks angled slightly too?

They are just parallels, one would work the same.

I was going to ask if the backs were vertical but I see clearly that they are not. This helps keep the nose down.

thats the key to it. When the bottom surface rest on the parallels before tightening, the jaw and that wider edge side are not parallel, they're at slight angle. tightening forces them parrallel and lifts the hold up up slight on the jaw side so its bottom is not longer parallel to the parallel. Too many double words....I was hoping the pics would explain

 

[Janger]

I use a chunk of lead....
View attachment 31231
For a lot of things. Time to re-pour this one soon.

Impact Poly Hammers

Professional Grade Soft Faced Dead-Blow Hammers. With increased steel frame construction, fully welded heads, and lifetime warranty.

impactpolyhammers.com

I bought a very nice dead blow hammer from a guy who makes them in Lethbridge, Alberta. See above. They cost a little more and are very well made.

 

[Susquatch]

They cost a little more and are very well made.

I'm interested.

How well do they work releasing an R8 collet or a d1-x lathe chuck?

 

[Dabbler]

I bought a very nice dead blow hammer from a guy who makes them in Lethbridge, Alberta.

thanks for the comment - I've never seen them before - very nice (Iwatched both their videos on the construction. very impressive.

One of the best things for solidly holding work with minimal depth is a set of holds downs.

My mentor never mentioned them. they look very handy.