# What are these (woodworking?) clamps for? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [September 15, 2020, 5:18pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710 "2020-09-15T17:18:23Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [September 15, 2020, 5:18pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/1 "2020-09-15T17:18:23Z")
I bought a bunch of clamps on craigslist. Most of them are C clamps or F clamps or bar clamps. Stuff that I understand. And then, there’s these ones. What are they for? [[Album] Clamps ![](https://i.imgur.com/axODrN1.jpeg?fb "Clamps") ](https://imgur.com/a/Ahn7tWB) ---
**Author:** ![mikecurtis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikecurtis/32/3284_2.png) [@mikecurtis](https://boards.straightdope.com/u/mikecurtis)\ **Post date:** [September 15, 2020, 5:36pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/2 "2020-09-15T17:36:55Z")
Those are jig clamps. They’re designed to hold the material to a work table. The 2 with the thumb screws attach to a piece of flat bar, such as a flat bar clamp. And the other one is a bench dog clamp. ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [September 15, 2020, 5:40pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/3 "2020-09-15T17:40:01Z")
And similar versions fit onto a miter saw to hold down short pieces. > **[Clamp Hold Down Assembly \[JMS10SCMS-194\] for Jet Power Tools | eReplacement...](https://www.ereplacementparts.com/clamp-hold-down-assembly-p-453065.html)** > > Buy a Jet Clamp Hold Down Assembly \[JMS10SCMS-194\] for your Jet Power Tool - We have the parts and diagrams to make your repairs easy. ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [September 15, 2020, 5:42pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/4 "2020-09-15T17:42:56Z")
Ok, I see how the two with the thumb screws would work, but I’m still a little fuzzy on the other one. I’m used to bench dog clamps having a longer circular (or less commonly, square) bar that extends below the bench surface into the dog hole. But this one just has a flat bottom. How does it attach to the bench/dog hole? ---
**Author:** ![mikecurtis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikecurtis/32/3284_2.png) [@mikecurtis](https://boards.straightdope.com/u/mikecurtis)\ **Post date:** [September 15, 2020, 5:45pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/5 "2020-09-15T17:45:44Z")
It doesn’t. It slides into a groove. ---
**Author:** ![mikecurtis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikecurtis/32/3284_2.png) [@mikecurtis](https://boards.straightdope.com/u/mikecurtis)\ **Post date:** [September 15, 2020, 5:54pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/6 "2020-09-15T17:54:32Z")
Most likely those were specialized clamps that were part of a system designed to do a specific job. They’re not really general purpose clamps. ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [September 15, 2020, 5:57pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/7 "2020-09-15T17:57:40Z")
Yeah, I can see how I could slide the one clamp into a T-track or something, but it’s awkward that it doesn’t rotate. I could only clamp something in line with the track. I’ll probably just give it away. The other two might be useful to provide clamping pressure to the middle of a large piece? If I can run a bar clamp across and slot into it. I’ll have to see if they’ll fit onto the bars of any of my F-clamps. ---
**Author:** ![mikecurtis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikecurtis/32/3284_2.png) [@mikecurtis](https://boards.straightdope.com/u/mikecurtis)\ **Post date:** [September 15, 2020, 6:19pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/8 "2020-09-15T18:19:41Z")
No. it rotates. there’s a piece missing. there should be a holddown bolt. basically a two headed cam that slides in the track and fits into the clamp. This one shows the bolt going all the way thru, but ive seen them as just a non adjustable bolt. > **[Jorgensen - Style No. 1800 Hold-Down Clamps 18340 4-1/4" Jorgensenhold-Down C:...](https://www.amazon.com/Jorgensen-Hold-Down-Jorgensenhold-Down-018-1834-jorgensenhold-down/dp/B00462EIZG)** > > Jorgensen - Style No. 1800 Hold-Down Clamps 18340 4-1/4" Jorgensenhold-Down C: 018-1834 - 18340 4-1/4" jorgensenhold-down c - Bench Clamps - Amazon.com ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [September 15, 2020, 6:33pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/9 "2020-09-15T18:33:46Z")
It’s all coming together now. Thanks! ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 15, 2020, 6:37pm UTC](https://boards.straightdope.com/t/what-are-these-woodworking-clamps-for/920710/10 "2020-09-15T18:37:20Z")
Right, the T-nut portion is missing. These probably fit standard T-tracks. The T-nut diameter or long axis is likely 9/16". [Here is a .pdf showing common dimensions.](http://go.rockler.com/tech/RTD10000592AA.pdf)