Low profile workholders

[homebrewed]

I finished up some low-profile workholders for my mill today. They are based on another H-M thread here, started by @Janderso . I liked the idea, a lot, so decided to make some for myself -- but, of course, "customizing" them according to my tastes.

Here's a photo sowing both sides.



And a photo of the moveable "jaw" of the setup:



The aluminum bar is just there to show how it works. The two-piece movable jaw has the same 5 degree taper as described in the link I provided above. The right-hand component is drilled at a 5 degree angle because I thought that would produce a bit more mechanical advantage because the screw is oriented parallel to the taper angle -- it won't apply any force to the fixed side to increase any frictional load. I thought I was being original but closer examination of a similar low profile clamp design on Harold Halls's web site showed he had done the same thing. Nothing new under the sun, huh. BTW, I made tee nuts with a matching 5 degree angle so the clamping load was evenly distributed across the table.

But I didn't machine dovetails, just a simple slot and boss arrangement. I didn't think the added machining complexity was needed, considering what the clamps are for. Plus, it took a lot less time to make them compared to two dovetails.

The 5 degree angle has a huge mechanical advantage. It feels like it should be able to apply a very high clamping force.

 

[brino]

Very nice!

I'm guessing the blocks are just under an inch thick.
Is there enough meat in the thickness to counter-bore those socket head cap screws, to provide an even lower profile?

Thanks,
Brian

 

[homebrewed]

Very nice!

I'm guessing the blocks are just under an inch thick.
Is there enough meat in the thickness to counter-bore those socket head cap screws, to provide an even lower profile?

Thanks,
Brian

Yes, they ended up just under 1" X 1" after cleaning up the hot-roll scale. I chose not to counter-bore because in my experience they and the socket head screw cavities fill up with swarf. So there is enough "meat" there to counter-bore, if I find a need to do it.

If I was going to use these to clamp items to a lathe faceplate I definitely would counter-bore them.

 

[great white]

I think I'd consider making a set that has the socket heads countersunk to go along with the ones standing proud. I would think with them standing proud like that would make it a bit difficult to use something like a fly cutter on the whole work piece.

 

[homebrewed]

I think I'd consider making a set that has the socket heads countersunk to go along with the ones standing proud. I would think with them standing proud like that would make it a bit difficult to use something like a fly cutter on the whole work piece.

I've been considering that. I had the thought of attaching sacrificial jaws to them so I can machine material that's thinner than the workkholder body, maybe they also could be used to move the screw heads further back. There would be limits to that -- I suspect that making the sacrificial pieces a lot wider would substantially reduce their holding power.

On the other hand, having a variety of workholders on hand makes sense. I have enough raw material to make another set.....

 

[Rob Thule]

Nice

I use low profile holders on my mini surface grinder. I also angled the fixed jaw to keep part firmly in contact with table.

 

[JohnDB]

Ought to be a big help with low amounts of z travel.

 

[brino]

I had the thought of attaching sacrificial jaws to them so I can machine material that's thinner than the workkholder body

Sacrificial jaws are a great idea!!!

There would be limits to that -- I suspect that making the sacrificial pieces a lot wider would substantially reduce their holding power.

From all your post history, you are obviously both very knowledgeable and very comfortable with physics..... but I don't' understand this statement.
Are you concerned that the wide sacrificial jaw gets pulled to the table (in the z-direction) more than it "pushes" in the horizontal (y-direction)?
Or maybe concerned about the flex of a thin, sacrificial (maybe aluminum) jaw?...especially if the hold down bolt ends up relatively far from the jaw/work interface.....

I see this idea as equivalent to common mill vise hold-down clamps like the Starrett 54A, etc.
https://www.lighttoolsupply.com/54a/

hmmmm, I wonder if these two ideas could be combined......

Thanks in advance for any guidance!
Brian

 

[Provincial]

Does anyone else use foam ear plugs to keep hex drive pockets (and other recesses and holes) from getting plugged up? If the foam stands proud, just grab it to remove it. If it doesn't stick up, use an O-ring pick to get it out.

I also use Q-tips to keep the mason bees from plugging the holes in my air tool plugs. I cut them in half, which leaves plenty of handle to remove/replace them.

 

[homebrewed]

Sacrificial jaws are a great idea!!!



From all your post history, you are obviously both very knowledgeable and very comfortable with physics..... but I don't' understand this statement.
Are you concerned that the wide sacrificial jaw gets pulled to the table (in the z-direction) more than it "pushes" in the horizontal (y-direction)?
Or maybe concerned about the flex of a thin, sacrificial (maybe aluminum) jaw?...especially if the hold down bolt ends up relatively far from the jaw/work interface.....

I see this idea as equivalent to common mill vise hold-down clamps like the Starrett 54A, etc.
https://www.lighttoolsupply.com/54a/

hmmmm, I wonder if these two ideas could be combined......

Thanks in advance for any guidance!

I was in fact concerned about the situation where the hold down is a good distance from the work. Also, having three pieces under horizontal compression and no direct restraint on the Z axis doesn't seem all that stable to me, especially for thin pieces. One way to address that concern would be to screw the sacrificial jaws to the hold downs.

I think I will add that option to my hold downs. There's plenty of "meat" there to do it.