T-slot table clamps

[JohnCoker]

I like the "machinists clamp" style hold-downs, but I'm not sure which set is the correct size. Anyone know how T-slots are measured? The narrowest width of the slots is 11/32", which doesn't seem to correspond to the available sizes.
Grizzly 1/2" clamp kit (http://www.amazon.com/Grizzly-3400-3501-Clamping-T-slots-58-Piece/dp/B0000DD0D2/ref=sr_1_1?s=hi&ie=UTF8&qid=1391316448&sr=1-1&keywords=t-slot+clamps)

If you use the T-slots for clamps, what sort have you found work well?

[Burkhardt]

I think the machinist type clamps are a bit overkill for a router and not that convenient to use. Inevitable bit collisions have the bits on the losing end.

The Incra clamps are O.K. but actually I prefer the Rockler t-slot clamps. Usually I replace the cheap steel bolts with bronze carriage bolts that don't dig into the aluminum t-rails. At some point I started making my own low profile hardwood clamps but since I got the vacuum pods to work properly I rarely use any clamps at all.

No matter how you do it, the clamping will stress and warp the wood somewhat.

[JohnCoker]

You mean these "Rockler Deluxe Hold Down Clamp"?
http://www.amazon.com/Rockler-Deluxe-Hold-Down-Clamp/dp/B002MMMSTU/ref=sr_1_3?ie=UTF8&qid=1391357411&sr=8-3&keywords=Rockler+clamp

http://ecx.images-amazon.com/images/I/41WN1i0fGYL._SX425_.jpg

That seems like a lot of height above the surface being machined to get in the way of the moving carriage.

On the Alpha, I would screw my sacrificial board (usually ¼" Masonite) down to the MDF surface, but I was trying to avoid an extra surface with the Desktop to preserve the range of the Z axis travel.

[curtiss]

These clamps work well but will not out-perform a bit...

[scottp55]

shop fox clamps? Think this is Bob E's

[bearcat]

As an alternative, I use large fender washers with 1/4"-20 bolts / T-nuts and a matching thickness shim blocks.

Ed

[Burkhardt]

You mean these "Rockler Deluxe Hold Down Clamp"?

http://ecx.images-amazon.com/images/I/41WN1i0fGYL._SX425_.jpg

That seems like a lot of height above the surface being machined to get in the way of the moving carriage.

Almost. I use the regular variety without the plastic shoes with 5/16" bolt. The ones that come with the clamp are O.K. and better than the Incra hex head bolts. But as mentioned before I throw them away and buy bronze carriage bolts from McMaster, available in various lengths. They slide better in the slots, don't dent them inside and usually don't break the bit if it happens to hit the bolt

I have a full surface extruded t-slot table (80/20 system, 1.5" thick) but no spoilboard. I cut a bunch of 2"x2"x0.75" plywood square "pucks" with non-slip drawer sheet on both sides that I place between the work piece and the table under the clamps when there is a risk of going through. The anodized table surface is so slick the bit will shove the work piece around without anti-slip.

The homemade low-profile hardwood clamps look like the pic below. They can clamp from the top of the work piece or you can insert a Spax screw that goes into the side. The clamps are made in full 3d on the indexer and given the machine time they are kind of expensive :rolleyes:

After all, I wish I had started the vacuum pod experiments much earlier. If the part can hold the vacuum and does not cut into the pod area this is by far the best and easiest method.

https://lh5.googleusercontent.com/-q5vKRez7ZNs/UTbJ1Ths-sI/AAAAAAAADx0/fhN1cqMTUw0/w800-h600-no/DSC01348.JPG

https://lh4.googleusercontent.com/-68gE_3ZopzI/UTbJ2Xt_HfI/AAAAAAAADx8/I1OjfGDwdW8/w800-h600-no/DSC01350.JPG

[khaos]

I like the "machinists clamp" style hold-downs, but I'm not sure which set is the correct size. Anyone know how T-slots are measured? The narrowest width of the slots is 11/32", which doesn't seem to correspond to the available sizes.
Grizzly 1/2" clamp kit (http://www.amazon.com/Grizzly-3400-3501-Clamping-T-slots-58-Piece/dp/B0000DD0D2/ref=sr_1_1?s=hi&ie=UTF8&qid=1391316448&sr=1-1&keywords=t-slot+clamps)

If you use the T-slots for clamps, what sort have you found work well?

The actual measurement has to allow some clearance for movement. That is to say a 5/8s T nut will be undersized. If its a little tight take a file and sander to it. The results are worth the time. Also, don't just use a bolt head. It does not spread the load properly and can burr the underside of your slot.

Look for drawings like this one when you order to be sure:
http://www.te-co.com/Images/tooling-components/t-slot-nuts.jpghttp://www.te-co.com/Images/tooling-components/t-slot-nuts-la.jpg

I hopped over to grizzly.com and here is a linkto some tnuts with the measurements. http://www.grizzly.com/products/T-Slot-Nuts-pk-of-4-7-16-Slot-3-8-16/G9511

Be sure to click the second image @ grizzly !!

Hope this helps.

[dlcw]

Here's my simple, small parts hold down system. Bought the t-tracks and knobs from Rockler, t-bolts at local Ace Hardware and everything else made in the shop.

Bits win every time they collide with a clamp. :D

[ssflyer]

I use and like the ShopFox cam clamps that Scott mentioned, because they clamp down and in at the same time, on the edge, giving great holding power. I got my T-Track off 8020's eBay surplus store for a good price, and I use rather odd T-Nuts - they are round on the backside, so you can insert them anywhere, without sliding them in from the end. Then I just use a magnet to pull 'em out when I'm done. Pretty slick, I think :D I think they are called, "Roll In" or "Drop In" T-Nuts...

[scottp55]

Ron, bought some of these because the looked easier on the T-track- never realized they were also drop-in! Haven't used yet,but just looking look at very good quality and machining.

[scottp55]

Darn, no link.http://www.fastenal.com/web/products/details/0957140;jsessionid=VsvxSjtJRC3hGHcX4ZbYpt1JHWJ1LnH Lbygkyd3m61wF6DRRrW0p!-396863484!259453287?searchMode=productSearch&zipcode=&filterByStore=&filterByVendingMachine=

[adrianm]

Here's what I use (pictures are of my old top, it's now full width).

In the latest set I've made I've switched the insert to a flush nylon nut and I use nylon bolts in the t-track as well.

[scottp55]

Adrian, Nylon wonderful idea, any problems with "Oomphing them tight"? Do you use a washer on the bolt head? Thanks for the .zip.

[bleeth]

Hey Adrian:
Did you ever think of lining the inside edge of your corner board with aluminum and using a custom x-y zeroing program?

[adrianm]

Hey Adrian:
Did you ever think of lining the inside edge of your corner board with aluminum and using a custom x-y zeroing program?

Dave, see my post in this thread :) - http://www.talkshopbot.com/forum/showthread.php?t=19057

Scott, no issues with tightening them down enough with the nylon bolts. I don't use washers now but I did use them with the steel and aluminium bolt versions as they could get really hard to undo without the washers. I use a slightly different design of knob now (attached). Machined with a 1/4" bit an M8 nylon nut fits really tightly.

[scottp55]

Thanks Adrian

[JohnCoker]

All great suggestions, thanks!

I just realized that the aluminum T-slot track is too low for the reach of the Desktop Z with normal straight bits, so for the short term I'll be screwing down to the MDF board supplied with the unit.

[scottp55]

John, If you're like me, you'll soon find your 0,0 corner looking like swiss cheese. I found VCarving a very LIGHT(.02" Vbit) grid on the spoilboard lets me reference easily to different locations for screw holes. Recently someone told me Bondo works well in the screw hole when they get really bad, but I've had pretty good luck with sawdust and superglue. an 8 oz. deadblow hammer to knock the dimples down followed by a cabinet scraper seems to work better than sanding flush. 2 cents

[bob_s]

Scott
just a few hold down comments

I got tired of hitting screws with $40 bits, so I put threaded inserts in and started using nylon bolts with baltic birch hold downs. this is a link to Vectric site where I posted a file for the hold down clamps
http://forum.vectric.com/viewtopic.php?f=35&t=10338&p=72363&hilit=Bob_s+Insert#p72363

I now buy the nylon bolts and longer lengths nylon of threaded rod from Amazon as well. There are times when small pieces of 1/2" Baltic ply with a single hole and a 3/8 dado on the edge also work well to hold down small pieces.
I have found that it's just as important to prevent sliding as it is to hold it straight down, so I use a lot of edge blocking in combination with hold downs
Bob

[scottp55]

Thanks Bob, Darn it! Aspire files don't open in VCP:(

[bob_s]

Scott
I saved it as a VCP file
The vectors should be there the area where I did a 3d cut maybe a flute would do it
let me know if this opens

[scottp55]

Got it Bob. Thanks!:)

[Burkhardt]

I was in the garage today with the camera and took a picture of my clamp setup. Nowadays I prefer the vacuum pods for parts larger than 5"x5". But for smaller parts and if they have holes I use the Rockler clamps with spacers.

I used to put a complete "spoil board" under the work piece when clamping but at some point it dawned on me that it is only needed under the actual clamping point. So I cut a handful of square and angle shaped spacers, and stuck thin anti-slip mat on them. If I see a good chance to not get stuck I let the cut out parts just fall down onto the table. If they are really small and may jam with the bit I use tabs. You can also see some battle scars on the clamps when I was too stingy and set the clamps too close.
https://lh3.googleusercontent.com/-aLQcg3JxGC4/Uv2bKNjJqLI/AAAAAAAAEmI/UmVovGAtdnw/w698-h842-no/DSC02226.JPG

[JohnCoker]

I used to put a complete "spoil board" under the work piece when clamping but at some point it dawned on me that it is only needed under the actual clamping point.
Interesting idea (but only if you're working with thick stock that doesn't droop).

[steve_g]

Ha! I blew on my screen to clear away the sawdust so I could get a better view!
SG

[Burkhardt]

Interesting idea (but only if you're working with thick stock that doesn't droop).

Sure, this is only for rigid sheets. With 3/4" material you can easily hold parts 2-3 feet in size (or bigger?). But I use that method only for smaller parts.

If you have a sloppy large thin sheet clamping may not be the best idea, anyway. A contiguous spoil board and downcut bits should make it manageable though.

[Burkhardt]

Ha! I blew on my screen to clear away the sawdust so I could get a better view!
SG

I have only a 1hp dust collector. It removes the chips well until the bit goes through the material. But it is not too bad. The black anodized table makes it look worse than it is.

[steve_g]

I was mocking myself, not suggesting you had a messy shop! I can’t cast that first stone! Actually it’s a testament to your clear photography…
SG

[Joe Porter]

Besides the excellent tips and clear photos, I am glad to see other people have some scarred-up clamps also....joe

[Burkhardt]

Forgot to mention something....if you look close at the little right angle spacers in the previous picture, you will see a small nub on the corner of the angle. That has actually a purpose. I can also set the spacer upright with that nub fitting snugly into a t-slot and then it becomes a fencing spacer or spacing fence for repeated work.




Besides the excellent tips and clear photos, I am glad to see other people have some scarred-up clamps also....joe
Oh yes. Ample scars.....usually the bits survive
https://lh6.googleusercontent.com/-WiKBWsWh4-8/UvcSQyJDvKI/AAAAAAAAEkM/M7DMaBbO-wc/w920-h811-no/DSC02208.JPG

[Bob Eustace]

The perfect clamp to me would be a Kevlar version of the ShopFox cam clamp complete with a Kevlar bolt. Now this isnt tooooo far fetched as they are just starting to 3D print in Kevlar and similar stranded materials for the aero industry. Now matter how carefull we all have clamp collisions from time to time - just hurts when its a tapered ball mill and the job has no margin or worse is a freebie!

[jerry_stanek]

My perfect clamp would be a smart one that jumped out of the way and reclamp when the spindle is going to hit it.

[gundog]

For me vacuum was the answer. If the part is too small to hold by vacuum then I throw on a piece of plywood screw or clamp it there with toggle clamps and hold the plywood with vacuum. Very few projects won't hold on my vacuum table by just using scrap material to block off the part of the vacuum zone not being used.

Using vacuum to hold parts is like going from a hand held router with jigs to a CNC IMHO.

These are the toggle clamps I am talking about screwed to plwood and use a block of scrap between the toggle clamp and the machined part to stop from hitting the clamp. http://www.harborfreight.com/catalogsearch/result?q=toggle+clamp

[gundog]

HF used to have a straight line or push toggle clamp but I don't see them on their site. You can always mount them on their side to a board to push horizontally but the clamp made to do this works great with a sacrificial board between the clamp and the work project. I have also made cam clamps from plastic HDPE but any more I vary rarely need anything but vacuum.

Sorry I just realized I posted on the Desk Top section and I am not sure about vacuum on that size machine.

Mike