Vicmarc VM120 standard jaws - dovetail angles different

[Alan Heffernan]

The inside dovetail (for tenons) on the standard jaws is 10 degrees. The outside dovetail (for recess/mortise) is 14 degrees. Does someone know why they are different?

I am preparing a short safety discussion on properly sized tenons (and mortises) for a club meeting and this question comes to mind. I sent Vicmarc an email but they are closed for though January for an extended holiday period.

EDIT: the larger dovetail jaws they sell have 13 degree angles on both sides.

 

[Steve Tiedman]

I did not know this, and I've had a Vicmarc chuck for over 20 years. May I speculate?

10 degrees on the inside also has the benefit of the wood tenon grab being in compression, giving a lot of holding power.

14 degrees on the outside of the jaw, now the wood is being placed under tension, or shear (spread out away from itself), so maybe the greater dovetail angle is helping to lock the wood to the jaws to make up for the lesser amount of force being put onto the wood. Put the same force into a mortise grab as you would on a tenon grab and you'll run the risk of breaking the wood, especially if the general shape of your piece is already established in that area.

These are my guesses anyway.

 

[Alan Heffernan]

I did not know this, and I've had a Vicmarc chuck for over 20 years. . . . . . . .

Here are the actual dimensions I took from the set on my VM120. This "sketch" is a snippet from within a Fusion 360 model I made to print a gauge. BTW, another piece of info I found in measuring was the saw kerf on the jaws at ~1.5mm. In other words, at a perfect circle, the kerf between jaws is about 1.5mm. I have always wondered about that so I measured it as well. Also attaching a rendering of the gauge I am printing.

 

[hockenbery]

The inside dovetail (for tenons) on the standard jaws is 10 degrees. The outside dovetail (for recess/mortise) is 14 degrees. Does someone know why they are different?

You did a nice diagram.

This is what is on the vicmark web site.
The sizes indicated on the drawing are when the jaws form a perfect circle. VM120 and VM150 chucks provide approx. 48mm of expansion beyond these specified sizes. The Standard Jaws have an internal dovetail angle of 10 degrees for clamping and an external dovetail angle of 14 degrees for expanding.

 

[Alan Heffernan]

You did a nice diagram.

This is what is on the vicmark web site.
The sizes indicated on the drawing are when the jaws form a perfect circle. VM120 and VM150 chucks provide approx. 48mm of expansion beyond these specified sizes. The Standard Jaws have an internal dovetail angle of 10 degrees for clamping and an external dovetail angle of 14 degrees for expanding.

Thanks, my actual measurements (taken at perfect circle) are slightly different than Vicmarc's drawing but within a few tenths of mm. We are dealing with wood here and I am not surprised their tolerances are not that tight. It is interesting that this "standard jaw" has different angles on the dovetails. The larger dovetails are all 13 degrees.

 

[Dean Center]

So, how are you going to present the Nova jaws? Some are dovetails, some are the dovetail-looking 'beak' jaws.

 

[Karl Loeblein]

Here are the actual dimensions I took from the set on my VM120. This "sketch" is a snippet from within a Fusion 360 model I made to print a gauge. BTW, another piece of info I found in measuring was the saw kerf on the jaws at ~1.5mm. In other words, at a perfect circle, the kerf between jaws is about 1.5mm. I have always wondered about that so I measured it as well. Also attaching a rendering of the gauge I am printing.


View attachment 59654

How are these being used? Just wondering how using these might differ compared to using these flatter gauges below on thingiverse?

https://www.thingiverse.com/thing:4042358

 

[Dave Landers]

How are these being used? Just wondering how using these might differ compared to using these flatter gauges below on thingiverse?

https://www.thingiverse.com/thing:4042358

Trent Bosch sells something similar for various jaws. Here's a screen shot from one of his product videos

 

[Alan Heffernan]

So, how are you going to present the Nova jaws? Some are dovetails, some are the dovetail-looking 'beak' jaws.

Dean, I am not going to work on the Nova's. My favorite is Vicmarc with Oneway my next go to.

BTW, as I understand it, the Nova intends to crush the wood fiber when using a tenon.

How are these being used? Just wondering how using these might differ compared to using these flatter gauges below on thingiverse?

https://www.thingiverse.com/thing:4042358
View attachment 59694

Thanks for pointing these out. I had not seen them. They appear to be half circle (180º) vs 1/4 (90º) for what I have modeled. For me, that makes them a bit more difficult to check the profile of the dovetail on a slightly oversize tenon. They also don't offer a profile check for the mortise/recess side.

 

[Alan Heffernan]

@Karl Loeblein
Here's my printed gauge. As compared to Trent's, I put a stalk on mine for handling. I am still wondering why the difference angles on the faces of the dovetails for these particular jaw. Guess we will have to wait on a response from Vicmarc.

 

[Karl Loeblein]

@Karl Loeblein
Here's my printed gauge. As compared to Trent's, I put a stalk on mine for handling. I am still wondering why the difference angles on the faces of the dovetails for these particular jaw. Guess we will have to wait on a response from Vicmarc.

View attachment 59700

Seems easy enough to sketch out these dovetail jaws after the basic measurements are captured and entered into a parametric CAD program like Fusion360 or OnShape that can extrude the shape around a circle. Thanks for sharing because it’s nice seeing how our 3d printers can be used for making useful shop items.

Fwiw, here’s another free 3d item for the Nova chucks on Thingiverse that combines the two styles into one:


Don’t mean to hijack your question, but while we’re on the subject of 3d printing. Here’s a hanging mount that my son created in OnShape today for holding a Temptop Air Quality monitor in the shop. The monitor came with a built-in stand on the back, but that‘s useless whIle the usb is plugged into the bottom. This mount allows the monitor to remain safely upright so the screen can be read while it’s plugged in.

 

[Dean Center]

Here’s a hanging mount that my son created in OnShape today for holding a Temptop Air Quality monitor in the shop. This mount allows the monitor to remain safely upright so the screen can be read while it’s plugged in.
View attachment 59713

How soon can your son get to work on lower cost joint replacements?

 

[Lance Mirrer]

To those creating 3d gauges, are any of you willing/able to create a set to sell? I am interested in them for VM120 & Nova.
Thanks,

 

[Bill Blasic]

I have a Bambu P1P on the way. I have been checking out all woodturning items for ideas. I bought it (as I explained to my wife) to make 1 thing for my CNC router that I needed for use with my turnings. Don't you know someone has already made it and they gave it away. Thank you as it will be one of the first things I make.

 

[Alan Heffernan]

To those creating 3d gauges, are any of you willing/able to create a set to sell? I am interested in them for VM120 & Nova.
Thanks,

Trent Bosch sells individual and sets at a reasonable price. You have the option to pick only the ones you want.

 

[robo hippy]

I never noticed that the jaws were different angles, and this is after maybe 30 years..... I know with dove tail joinery, they use a 7 to 1 and 8 to one ratio for different hardwoods. Don't even know which is for which. I just use the same one....

robo hippy

 

[Scott Hoefs]

IMO I have never paid much attention to the angle for either the mortis or tenon. I swag both and have never had an issue with either. I'm not goanna say I haven't lost a piece or two, but when it does happen it's because I was too aggressive. I use the tail stock whenever possible for support until the center. Finesse for turning is key especially towards the end. The last thing I need is to toss a piece across the room because I'm in a hurry. Even on larger pieces, 16" plus I only cut a recess of 1/8"- 1/4"