Standard Die Sets & Hydraulic Presses FAQs

Using your Die Set

What is the max load for my die? You can find the maximum recommended load on the individual product page. The steel we use has a very high yield strength of over 80,000 psi (550 MPa). We recommend a 50% safety margin. Loads for each die set should be carefully considered before using the die to ensure safe operation. This is of particular concern with smaller inner diameter (ID) dies, where you can reach the yield strength of the steel with just a few pumps of the hydraulic press.

Do note that using high pressing force does not guarantee a denser pellet. If you press too hard, you will most likely surpass the fracture stress of the compact well before you reach the yield stress of the material. The stress in your pellet will concentrate at the top side of your pellet, and you will likely see cracking or "capping" at the top of your powder compact.

Do I need the prepare the die set in any way? We store our dies with a water-resistant lubricant. When you receive it, simply give it a good clean with detergent before use. If you are storing your die for a long period or if it will be exposed to moisture or humidity, you can spray it with WD-40 or a similar product before storing.

Can I heat up my die set? Our standard D2 Tool Steel die sets cannot be heated because the metal has been heat-treated; heating it will compromise the heat treatment, making it softer, weaker, and quickly leading to oxidation. Our 440C Stainless Steel die sets can be heated to around 250°C (480°F).

What is the thickest pellet I can make with my die set? As a general rule of thumb, your pellet height should not greatly exceed its diameter. Going thicker than the diameter leads to non-uniform compaction throughout the pellet, where the top experiences more stress concentration than the bottom (non-moving surface). That being said, all materials behave differently, so you can treat this rule as a flexible guideline. The maximum height of pellets you can make using our standard range (50 mm height die sleeve) die sets is between 0.6 and 1.0 inch, depending on the material you are pressing and your loading method.

Tips:

If you are pressing long pellets (relative to their diameter), consider lubricating your die.
Try adding a rubber O-ring (or similar flexible material) between the base plate and the die sleeve. This allows movement of both the top and bottom plungers, improving stress uniformity throughout the pellet.
For making pellets with very long aspect ratios, other methods such as cold isostatic pressing (CIP) may be more suitable.

Operating & Technical FAQs

What height opening does my press need to be? Our standard range die sets have a 50 mm height die sleeve and a similar length plunger. Your press will need a clearance of about 100–150 mm (4–6 inches), depending on the specific die set and the amount of powder you are using. Clearance for loading the die set depends on the minimum die set height, the amount of powder added, and whether or not you are using spacers. If you are limited on space, you do not need to press with spacers.

The minimum height needed is the assembled die set height with no spacers (found on the website's product page) plus the height of the powder added into the sleeve.

If the piston travel distance is 30 mm, can it accommodate a 90 mm high pellet press die set? Travel distance is usually not an issue for larger sets because you can compress the sample, release the pressure, lower the threaded top pressing surface, and press again. However, the daylight (the total gap between the top and bottom pressing surfaces) is more critical. If you require 90 mm of clearance, we can supply a press with a larger gap. Please send us a quote request or an email with your specifications.

Can I use organic solvents with my die set? Organic solvents cannot be used with our standard D2 Tool Steel die sets. For our standard 440C Stainless Steel sets, you would need to verify that your specific solvents are compatible.

Do I need to use lubricants or binders? For most materials, you do not need to lubricate your die before use, nor do you have to use binders. However, some users prefer applying a small amount of lubricant to the die walls, as this area experiences the highest friction during pressing and ejection, which can lead to cracking. Likewise, certain applications and materials call for binders as standard processing protocol. Both lubricants and binders can be burned out during post-sintering above 700°C (1290°F), leaving behind minimal residual carbon residue.

Lubricants you might consider: WD-40, paraffin wax, stearic acid (which also helps bind very fine powders), oleic acid, polyglycols, graphite, boron nitride, and stearates (aluminum stearate, butyl stearate, lithium stearate, magnesium stearate, sodium stearate, zinc stearate).

Will my die rust? The D2 tool steel we use for our standard die sets offers high strength and high hardness for demanding tooling applications; it is not stainless steel. If left wet or stored without drying, it will rust. If rust occurs, it is generally easy to clean off.

How do I clean and store my die set? After each use, ensure the die set is thoroughly cleaned and completely dry. It is normal for small amounts of powder to remain on the surfaces after pressing. The die set must be thoroughly cleaned before the next use, as the tolerance/gap between the plunger and sleeve is very narrow.

If storing your die long-term or exposing it to humidity, spray it with WD-40 or a similar protective product. For thorough cleaning, we recommend using 3M™ Crème Cleanser. This cream can be applied with water and contains a gentle abrasive to help remove chemical residues from the surface. Use a scourer-coated sponge for best results on outer surfaces, and an appropriately sized nylon brush for the inner surface of the die sleeve.

I scratched the inside of my die sleeve or rod. Can I fix this? Potentially, yes. For small scratches, you can attach a cylinder flex hone tool to a drill and hone the inside of your die sleeve or rod using honing oil. You only need to remove the high points of the scratch that cause interference. Scratches near the edges can often be smoothed with a fine file or fine-grit paper. Avoid using rough abrasives, as they will permanently alter the surface finish; removing more than 0.0005 inches will noticeably affect the fit of the parts.

Powder Handling & Performance FAQs

Do you have some advice for making good pellets?
There are several key considerations:

Press safely: Always think through the force you intend to apply beforehand and never exceed the maximum recommended force for your die. Wear safety glasses with side shields, use a protective guard between yourself and the press, keep the press bed clear of extraneous items, and verify that all parts are correctly aligned before applying pressure.
Check alignment & gauges: Verify that your press plates are parallel and that your sample is level prior to pressing. Ensure your pressure/force gauge is operational and accurate, checking your target force against the maximum load limits listed on our product page for your specific die diameter.
Avoid overfilling: Overfilling the die sleeve with powder will prevent the plunger from locating correctly.
Clean prior to use: Always clean your die before loading. This prevents cross-contamination and reduces friction, allowing the die to operate smoothly.
Optimize force: Higher force is not always better. If your pellet is cracking, try reducing the force before increasing it. Ensure all operators adhere to the recommended limits and that your pressure gauge is calibrated.
Troubleshooting difficult materials: If a material is challenging to press, consider drying the powder, modifying its particle size via additional grinding, or tapping the assembled die gently with a rubber mallet before pressing to help the powder settle evenly. You can also experiment with lubricants or binders to assist with pellet release.

Can I use more than the recommended max force? Exceeding the recommended maximum force removes your safety margin and poses a risk of component failure. Even if the plunger handles the force initially, repeated overloading significantly increases the risk of fatigue failure. Metal does not always display visible warnings before fracturing under excessive loads. Always use a safety guard and follow standard laboratory safety guidelines.

What is the minimum powder particle size? Our die sets accommodate powders with particle sizes down to approximately 10–20 microns. You can use nanopowders, but be aware that fine particles may escape into the clearance gap between the plunger and sleeve. While this can cause temporary seizing or jamming, the components can generally be freed and cleaned.

Is the pressure shown on the hydraulic press pressure gauge the same as the pressure inside the die? No. The pressure gauge reads the hydraulic pressure within the press cylinder itself.

If your gauge displays units of force (e.g., tons, kN, lbs), that value represents the force applied directly to the plunger.
If your gauge displays pressure units (e.g., psi, bar), that reading reflects the hydraulic pressure beneath the press ram.

To determine the stress applied to your powder, calculate the force using the effective area of your press ram (refer to your press manual), then divide that force by the cross-sectional area of your die's plunger

My pellets have issues with density — what can I do? Pellet density depends not only on the applied pressure and pressing conditions, but also on the characteristics of the powder itself. Factors such as particle size and grain size distribution play a significant role in how densely the material can compact. We recommend reviewing our pellet preparation guidelines to ensure all best practices are being followed. In some cases, lightly lubricating the die sleeve (for example, with a small amount of WD-40 or similar light lubricant) can help reduce wall friction, allowing particles to rearrange more effectively and potentially improve final pellet density.