Shop Made Tools

[DennisCA]

Made some hold down clamps





Enlarging the screw holes a little (1mm larger) in the old chuck, to aid with being able to loosen the screws a little and knocking the chuck around to fine adjust it. Hoping to get some more life out of this worn old chuck that way. The screws where really a tight fit in the bore so adjustment was tricky, now I should have half a mm in either direction.

[rcaffin]

Just a thought about those clamps. I always put the support block further away from the bolt so that most of the force is on the job being held. But my support blocks are usually a bit more generic and not an exact match to the job height.

Cheers
Roger

[DennisCA]

I figured this way I minimize any distortion of the clamps. I tested the hold and it was really good. Those where just some pieces of aluminum which happened to fit almost exactly.

[BCRider]

Roger is still right though. A clamp is a simple lever and the clamping force will be shared between the two support points based on the ratio of the arms. Your setup is roughly even by the looks of things and for what you're doing you didn't need much so it worked fine of course.

But for other setups we're better off keeping the bolts in tight to the work piece and keep the supports as far as is tidy from the bolts. Not only does this focus more of the pressure on the item being held down but because more pressure is where it needs to be we don't need as much torque on the nut. And that means a lesser and more kindly load on the poor overworked T slot overhangs. Ya, the thinner nature of those clamps will let them flex more than others. But I'd suggest that the better way to deal with that is use a taller support or a shim under the far end and let them flex. They'll still focus the pressure according to the leverage ratio but with a bit of a spring in their nature is all.

I like the strap clamps you have. Shop made? They are thinner than ideal if we compare them to the usual commercial ones. But I bet the thin nature comes in handy a lot of the time. I could use one or two like that done in some 3/8 x 2 metal on occasion.

[DennisCA]

They were thinner than I wanted to but it's the stock I had easily at hand. I have another piece so I am thinking I will make two more, thin clamps can come in handy after all. Will make thicker ones in the future.

[Baz]

No I disagree with the long gap to support in this case. By snugging up the support the top surface of the T slot is under the support block and the job so it is all in compression, not being pulled upwards.

[rcaffin]

all in compression, not being pulled upwards.
Well, I see the point, but I don't torque the bolts that hard myself.

Cheers
Roger

[Toolguy]

One thing you really want to be careful of is that the bolts don't go through the T nut to the bottom of the T slot. It's fairly easy to break out the T slot if the bolt is acting as a jack screw in the bottom of the T slot. Most people here probably already know about this, but some may not.

[Cenedd]

One thing you really want to be careful of is that the bolts don't go through the T nut to the bottom of the T slot. It's fairly easy to break out the T slot if the bolt is acting as a jack screw in the bottom of the T slot. Most people here probably already know about this, but some may not.

It's astoundingly easy to prevent this happening with shop-made T nuts. Was watching a Blondihacks video on making T nuts. I've previously made some but was bored and it turns out you can always learn new twists. She pointed out that you can simply deform the last thread with a centre punch to stop the bolt threading all the way through. Brilliantly simple once it's been pointed out!

[Arcane]

One thing you really want to be careful of is that the bolts don't go through the T nut to the bottom of the T slot. It's fairly easy to break out the T slot if the bolt is acting as a jack screw in the bottom of the T slot. Most people here probably already know about this, but some may not.

Wouldn't the problem be running out of thread on the stud at the top end?

[Toolguy]

Wouldn't the problem be running out of thread on the stud at the top end?

That depends on the stackup height of the part being clamped, the strap clamp thickness, the height of the nut, etc. plus the length of the bolt.

[Arcane]

That depends on the stackup height of the part being clamped, the strap clamp thickness, the height of the nut, etc. plus the length of the bolt.

I think you are missing the point. When you run out of threads at the top, the nut jams against the unthreaded portion and it turns the stud into a bolt and when some ham fisted operator who is using the wrong length of stud keeps cranking on the wrench trying to tighten the clamp down and the bottom end of the stud gets forced through the deformed threads at the bottom of the T-nut it can bottom out in the T-slot. Once that happens no amount of wrenching will make the clamp tighten down on the workpiece but it will generate a ton of upward force on the T-slot.

[rcaffin]

If the bolt is too long, damage will happen.
I usually check the bolt length without the nut in place. If it hits the bottom of the slot - a change happens. A couple of extra washers can work wonders.

Cheers
Roger

[The Metal Butcher]

I think you are missing the point. When you run out of threads at the top, the nut jams against the unthreaded portion and it turns the stud into a bolt and when some ham fisted operator who is using the wrong length of stud keeps cranking on the wrench trying to tighten the clamp down and the bottom end of the stud gets forced through the deformed threads at the bottom of the T-nut it can bottom out in the T-slot. Once that happens no amount of wrenching will make the clamp tighten down on the workpiece but it will generate a ton of upward force on the T-slot.

1. Don't allow ham-fisted operators in your shop. :P
2. All thread.

[DennisCA]

I'm aware of not letting the thread go through the T-nut. I should do what Cenedd suggests though to eliminate the chance..