getting clean straight cuts in MDF

[thetyreman]

hi,

I've been working with a full 8 x 4' sheet of MDF and want to get perfectly straight and clean cuts, it's important the edge is dead straight, I have been using a hardpoint saw and then followed by a power planer, it looks like I might need to purchase a guide rail and circular saw, is there a way I could do it without? also seen that some people use a guide rail and router, any thoughts?

cheers,

tyreman.

 

[Inspector]

Use the edge of another sheet. Factory edges are usually pretty good if they haven't been dragged around on them. Let the edge of the saw/router ride against it.

Pete

 

[Molynoox]

Track saw is the obvious answer but a cheaper alternative would be a home made rail for a circular saw. Like Pete mentioned, the factory edges on boards are straight and can be used as the 'guiding' part of your home made rail.
I probably have a picture of mine somewhere if you are interested.
Martin

 

[MikeK]

Use the edge of another sheet. Factory edges are usually pretty good if they haven't been dragged around on them. Let the edge of the saw/router ride against it.

Pete

That's the method I used with a long forgotten circular saw for plywood and MDF cuts slightly shorter than a full sheet. In my experience, the reference edge must extend beyond the board being cut at both ends in order to ensure the saw is stable before and after the cut. However, this was definitely an outside task since the dust collection on the circular saw is almost non-existent.

When I got tired of using the cumbersome (for me) straightedge method, I bought a Bosch circular saw and pair of 1600mm FSN rails. This was still an outside task, but there was no longer any doubt where the cut would be and I could use two rails joined together for full sheet rips or one rail for full sheet crosscuts.

Finally, I migrated to a tracksaw, vacuum, and set of rails. Now I can cut MDF inside with very little cleanup. I have the 3000mm rail and multiples of the 1400mm and 800mm rails. Some machines came bundled with rails.

You certainly could use a router and rail, but if this is a through cut instead of a trim cut, I think the process will not be as clean as a plunge or track saw. With a trim cut, it is possible to have a dust shroud on the bottom of the router base to assist with the dust collection, but I can't think of a way to collect the dust from the bottom of a through cut.

 

[Inspector]

Mike I get that a track saw is the ultimate short of a big slider or a panel saw but I got the impression the OP has a budget constraint.

Seems lots of people use a sheet of styrofoam to cut sheet goods as it supports the sheet and with the blade buried the dust is contained and vacuumed up by the saw. I haven't done it, mostly because I am loathe to buy a sheet of foam that I'm not using for insulation. The foam will reduce the dust flying around from the bottom.

Pete

 

[MikeK]

Pete, I use a sheet of 15mm OSB for my sacrificial cutting board when the cut is not over the edge of my table. In my area, two half sheets of OSB are less expensive than the equivalent size of foam board. However, beer is less expensive than bottled water, so it is a strange market.

When I don't use the sacrificial board, very little dust escapes from the track saw housing. The exception is when the start of the cut is a plunge into the wood. Then there is some dust until the leading edge of the blade is doing all of the cutting. However, with the open circular saw, very little (if any) dust makes it to the vacuum and a foam or OSB board would not make any difference other than provide more flying dust.

@petermillard reviewed two plunge saws from Lidl and Screwfix:

 

[pgrbff]

I used to cut by hand and clean up with a router with a straight edge made from a scrap of ply. I have finally bought a tracksaw and it makes the whole job fare simpler.

 

[petermillard]

Easiest/cheapest way would be to get the suppliers to cut it to size, though I appreciate that ship may have sailed; can’t beat a panel saw that costs more than you car, and someone else doing the work, though…

There’s a few ways you could so this, but if you’re making more than one or two cuts then a cheap tracksaw will make life much easier, cleaner and healthier. I’ve done this all different ways - rough cut then trim with a router, circ. saw with a DIY saw board etc… and even the cheapest tracksaw beats them hands down if you’re making more then the occasional cut.

 

[Fergie 307]

hi,

I've been working with a full 8 x 4' sheet of MDF and want to get perfectly straight and clean cuts, it's important the edge is dead straight, I have been using a hardpoint saw and then followed by a power planer, it looks like I might need to purchase a guide rail and circular saw, is there a way I could do it without? also seen that some people use a guide rail and router, any thoughts?

cheers,

tyreman.

I have certainly used a level as a straight edge to guide both saw and router. Depends which way you are cutting, ie nave you got something long enough.

 

[Ollie78]

A compression router bit in a decent router will give a very nice cut, they are a bit pricey though. Track saw is pretty close second.
For clean routing or sawing good extraction is important.

Ollie

 

[thetyreman]

thankyou, I think I'll try a router bit on the edge,

on a side note I think I may have a serious allergy to MDF, it makes me feel really awful, mainly with a really bad flu like cough, even with wearing a mask, vac and ambient air extractor running. I will only work with it outside from now on!

 

[TRITON]

Nothing worse than getting a paper type cut off a freshly cut sheet of mdf. Those edges are like razor blades.

 

[Inspector]

Mask as in cartridge? A proper fitting cartridge mask with fresh organic vapour cartridges should keep the dust and glue vapours out of your nose. Don't take it off until you vacuum off yourself and remove the dusty clothes.

Pete

 

[thetyreman]

Mask as in cartridge? A proper fitting cartridge mask with fresh organic vapour cartridges should keep the dust and glue vapours out of your nose. Don't take it off until you vacuum off yourself and remove the dusty clothes.

Pete

yes it's a 3m 7500 mask with P100 pink filters, I am not used to power tool woodworking but I did have a nasty flu last week so that doesn't help, was tested and it wasn't covid, I'll be more careful in future.

 

[Lefley]

I used 8 foot level Two clamps and router for years, until I broke down and bought a track saw. Wish I’d bought it years and years ago. Game changer.