Tips/Techniques Hold down kit usage

[Hruul]

Good video on how to use a hold down kit and some accessories that can be made to help hold things to the t-slot table.

 

[David]

I just watched that the other night

 

[skippyelwell]

I like his swarf catch box at 14:50

 

[Susquatch]

I like low key videos like this, but it's unfortunate that he missed the opportunity to explain how and why table tearout occurs. In so doing, he leaves his viewers at risk of badly damaging the T-Slots on their machine tables.

Anyone not already familiar with the overall issues of compression and tension loading of cast iron might benefit from reading this thread and the ones it links to.

Post in thread 'Proper mill cutter and technique'

Jan 22, 2025

Cuts for the angle were very light since it was only held by one clamp. One tight clamp but still only one.

I "THINK" that you might have a problem with your clamping arrangements. You probably won't find this info in a book or a video. You learn about this by personal experience (to be avoided) or by hearing about the mistakes of others.

1. Never allow the bolt to extend below the T-Nut.

2. Always try to achieve compression (columnar) loading of the T-slot clamping system. Tensile loading should be avoided.

3. Avoid over-torqueing a T-Nut and bolt.

Here is a photo of the Mill...

• Susquatch

• 

 

[djberta]

I like low key videos like this, but it's unfortunate that he missed the opportunity to explain how and why table tearout occurs. In so doing, he leaves his viewers at risk of badly damaging the T-Slots on their machine tables.

Anyone not already familiar with the overall issues of compression and tension loading of cast iron might benefit from reading this thread and the ones it links to.

Post in thread 'Proper mill cutter and technique'

Jan 22, 2025

Cuts for the angle were very light since it was only held by one clamp. One tight clamp but still only one.

I "THINK" that you might have a problem with your clamping arrangements. You probably won't find this info in a book or a video. You learn about this by personal experience (to be avoided) or by hearing about the mistakes of others.

1. Never allow the bolt to extend below the T-Nut.

2. Always try to achieve compression (columnar) loading of the T-slot clamping system. Tensile loading should be avoided.

3. Avoid over-torqueing a T-Nut and bolt.

Here is a photo of the Mill...

• Susquatch

• 

I made my own t nuts for a couple different sizes. I followed a couple videos to make them. On one video they staked the bottom of the t nut, so I did as well. In that video they explained the same issue if the bolt jacks up under the t nut your tables done.

 

[Susquatch]

I made my own t nuts for a couple different sizes. I followed a couple videos to make them. On one video they staked the bottom of the t nut, so I did as well. In that video they explained the same issue if the bolt jacks up under the t nut your tables done.

I don't disagree. What I was complaining about is the missing science that explains WHY it happens.

It's one thing to say that a screw that reaches the bottom of the slot can jack the nut and can easily break the T-slot.

It's another thing to explain that cast iron has very low ultimate tensile strength (fracture/breaking point) compared to steel, but is very strong in compression.

Jacking the lip of the slot tries to bend the lip. It can't bend, so it easily breaks. Tightening a nut up below the lip without anything above the lip also tries to bend the lip so it easily breaks that way too.

A proper clamping setup clamps the lip between the nut and the work which creates a compressive load that cast iron handles very well.

What is missing in every video I have seen is both the science and the objective. The objective is to clamp the lip and the work together in a compressive column. Don't pull up on the lip, bend the lip, or jack it with tensile (bending) loads.

Last, but not least, if you absolutely must clamp an unsupported load, be very mindful of how much force (torque) you use to tighten the clamp. There is no need to gronk on a T-Nut bolt. Even a very modest amount of torque will apply a crap load of force to the clamp.

 

[Tomc938]

Couple of useful tips there that I likely never would have thought of on my own, but will definitely use.

Thanks @Hruul!