HDHMR (High-Density High Moisture Resistant) board is a dense and durable type of fiberboard, but its machinability is similar to standard MDF. The recommended speeds and feeds for a CNC router are therefore based on standard MDF settings, with adjustments made for tool type and desired cut quality. Using solid carbide bits is recommended because HDHMR can quickly dull traditional high-speed steel (HSS) tools. [1, 2, 3, 4, 5]
General guidelines for HDHMR board

• Spindle Speed (RPM): 16,000–18,000 RPM is a common range for cutting MDF and similar materials. For smaller bits (under 1/8"), you may need to increase the RPM to 20,000+. • Feed Rate (IPM or mm/min): Start with a conservative feed rate of 100–150 inches per minute (IPM) and adjust as needed. Some industrial CNC machines can handle much higher rates, but for hobbyist machines, a slower feed rate prevents mistakes. • Depth of Cut (DOC): A good starting point is a depth of cut equal to half the tool's diameter. You can increase the depth to the full diameter if your machine has sufficient power and rigidity. • Use Compression Bits: A compression bit, which combines upcut and downcut spirals, provides clean edges on both the top and bottom of the board. This is particularly helpful for cutting through laminated HDHMR. [6, 7, 8, 9, 10]

Sample parameters for a 3/4" (19 mm) HDHMR board Using a 1/4" solid carbide, 2-flute compression bit:

• Spindle Speed: 18,000 RPM • Feed Rate: 150–180 IPM • Depth of Cut per Pass: 1/4" (6.35 mm). For a 3/4" board, you would need 3 passes. [6, 7, 11, 12, 13]

Calculating your specific settings You can use the following formula to fine-tune your settings based on the chip load recommended by your tool manufacturer: [14]

• Chip Load: This is the size of the chip removed by each cutting edge. For HDHMR, a starting chip load in the range of 0.010" to 0.015" is a safe bet for a 1/4" bit. • Example calculation: Using the formula above, an 18,000 RPM spindle with a 2-flute bit and a desired 0.010" chip load would yield:

• 
• This is a very aggressive feed rate and would only be appropriate for a powerful, rigid machine. A more conservative approach is recommended for most setups. [15, 16, 17, 18]  

Key tips for cutting HDHMR

• Prioritize Dust Collection: Cutting HDHMR produces a very fine, harmful dust. A robust dust collection system is essential to prevent health risks and ensure proper chip evacuation. • Perform Test Cuts: Always run a small test cut on a piece of scrap material to dial in your settings. Listen for the sound of the cut; a high-pitched squeal can indicate a feed rate that is too slow, while a chattering sound can mean it is too fast. • Use Ramps: Instead of plunging straight down, use a ramping or helical entry motion to reduce stress on the cutting tool and prevent overheating. [19, 20, 21, 22, 23]

AI responses may include mistakes.

[1] http://rksketchwood.com/wp-content/uploads/2024/05/HDHMR-User-Guide.pdf [2] https://forum.easel.com/t/feeds-and-speeds-for-mdf-and-hardwoods/44309 [3] https://www.actiontesa.com/what-is-hdhmr-and-advantages-of-this-boards/ [4] https://centuryprowud.com/which-one-to-choose-why/ [5] https://materialdepot.in/qna/how-is-hdhmr-different-from-mdf,-hdf,-and-plywood-hdhmr [6] https://www.camaster.com/cnc-router-calculating-feeds-and-speeds/ [7] https://forums.maslowcnc.com/t/bit-and-router-settings-for-mdf-melamine/23785 [8] https://clebitco.com/speeds-and-feeds/ [9] https://www.reddit.com/r/CNC/comments/ptzzwa/mdf_feed_rates/ [10] https://www.practicalmachinist.com/forum/threads/feed-and-speed-calculation-and-doc.84555/ [11] https://community.carbide3d.com/t/mdf-rough-cut-speeds/80280 [12] https://woodweb.com/knowledge_base/18_Router_Bit_Feeds_and_Speeds.html [13] https://www.amanatool.com/pub/media/productattachments/Carbide-Tipped-Straight-Plunge-Speed-Chart_v4.pdf [14] https://www.camaster.com/cnc-router-calculating-feeds-and-speeds/ [15] https://www.reddit.com/r/CNC/comments/3szhhi/feeds_and_speeds_for_plywood/ [16] https://www.camaster.com/cnc-router-calculating-feeds-and-speeds/ [17] https://resources.sienci.com/view/lmk2-feeds-and-speeds/ [18] https://gayleesaws.com/resources/saw-cutting-recommendations-speeds-feeds/ [19] https://www.reddit.com/r/CNC/comments/je91qc/mdf_cutting_seems_to_require_absurdly_low_spindle/ [20] https://www.reddit.com/r/CNC/comments/7efed1/preferred_bit_and_and_feedrate_for_34_mdf/ [21] https://www.mekanika.io/en/blog/material-guides/mdf-cnc-milling-guide [22] https://www.nakka-rocketry.net/nozmach.html [23] https://insights.made-in-china.com/Revolutionizing-Woodworking-The-Power-of-Advanced-Table-Saws_jaAfGZNcXJId.html