best sprial upcut bit for MDF

[gychang]

I use 1/4" diameter spiral upcut bit to cut out speaker holes on 3/4" MDF. Only after 4 holes it started to smoke and burn...

The bit turns black, and hot, ended up putting the new one in. It seems either I am being too aggressive with my router (I used other bits which seems to last from HD) or the bit could be better $15 /each from a reputbable web site...

Could someone recommend a good spiral bit, that last a while, especially with MDF.

thanks,

gychang

[drumpriest]

I wonder why you chose a spiral bit for mdf anyway, were you getting a lot of torn up mdf with a straight bit? Have you tried a shear angle bit? I think they would last longer, and are more easily sharpened. MDF is going to be hard on any of these bits, due to the glue content.

I use whiteside spirals for most things, solid carbide, but I occasionally use high speed steel for 1/4", less likely to break. I pay about 11$ for the steel bit (less if my timing is correct). Is yours steel or carbide??

[hermit]

I agree with Keith. I have found straight bits actually work better with mdf than spiral bits.

Todd

[cgallery]

The obvious question, I guess: You are you using solid carbide spirals and hot HSS, right?

2nd obvious question: You aren't cutting the entire thickness of MDF in a single pass, right?

[gychang]

The obvious question, I guess: You are you using solid carbide spirals and hot HSS, right?

2nd obvious question: You aren't cutting the entire thickness of MDF in a single pass, right?

am newbie to woodworking, what is HSS?, I pay $15 /each at MCLC?, may not be carbide I guess.

2nd answer: takes me about 6-8 different passes to get thru 3/4" thick MDF...

gychang

[gychang]

I am fairly new to this, I use the bit for Jasper router jig (to cut circles), and it must be 1/4" size bit. Can anyone recommend a particular router bit (sounds like may be carbide will last longer)?

should I be using straight or spiral bit?

thanks,

gychang

[drumpriest]

gychang, I'd use a straight bit, only caveat is that you need to ensure that there is a bit of cutter exposed at the top, so that it's a plungable bit. 1/4" can be tricky, as these smaller bits can break if you stress them too much. Solid carbide spirals would indeed stay sharp longer than HSS (high speed steel), but at the expense of being more brittle, and can therefore snap when being used too aggressively.

It's unfortunate that your jig only allows 1/4", 1/2" would be better, safer anyway. Spiral cutters are best for deep plunges, such as mortise routing, or shelf pin hole routing. They are also good for cutting curly materials that are prone to chip out. In MDF, you certainly don't need to use a spiral cutter to get what you want done.

[LCHIEN]

I'm going to toss in my 2 cents worth.

Burning usually occurs when the feed speed is too slow. If you take too deep a cut you will have to feed slower, burn the bit and wood, and possibly break the bit.

You should be taking less than 1/8", no more, per pass. Which when you say 6-8 passes per 3/4" material, sounds just about right.

The next thing is you should be feeding pretty rapidly, too slow and again you can burn the bit. I would guess a 8" diameter circle taking 1/8" deep cuts I would be spinning the router around the circle in about 3-5 seconds. I personally spin the router around the circle 2-3 times just to make sure the cut is clean.

Can't recall having cut larger circles in MDF, but as far as using a spiral upcut bit, that's what I would have chosen because I think the MDF edge would fuzz up otherwise, and because the spiral upcuts always have a bottom cutter making them plungable for the 1/8" increment on the depth.

[LinuxRandal]

am newbie to woodworking, what is HSS?, I pay $15 /each at MCLC?, may not be carbide I guess.

2nd answer: takes me about 6-8 different passes to get thru 3/4" thick MDF...

gychang

HSS that I haven't seen addressed is High Speed Steel. Your gonna ask/see lot's of abreviations, and since I believe I've seen you post over at Sawmill, I know they have a section with terms/abreviations. I am sure there is one here to, just don't know where (faq's maybe).

[RodKirby]

What Loring said..

[gychang]

I'm going to toss in my 2 cents worth.

Burning usually occurs when the feed speed is too slow. If you take too deep a cut you will have to feed slower, burn the bit and wood, and possibly break the bit.

You should be taking less than 1/8", no more, per pass. Which when you say 6-8 passes per 3/4" material, sounds just about right.

Can't recall having cut larger circles in MDF, but as far as using a spiral upcut bit, that's what I would have chosen because I think the MDF edge would fuzz up otherwise, and because the spiral upcuts always have a bottom cutter making them plungable for the 1/8" increment on the depth.

thanks for very helpful tips. I checked again and I use the carbide tip, sounds like spiral upcut tip is OK for my needs.

I need to to make sure feed is reasonable speed and clean up the groove frequently to rid of the dust as others have suggested. I will also try another brand whiteside bit to see if it is better than my MLCS bit.

gychang

[GaryA]

This certainly doesnt come from a place of knowing better, but why wouldn't you just use a jig saw in this scenario? Is this a through cut?

[Stormbringer]

This certainly doesnt come from a place of knowing better, but why wouldn't you just use a jig saw in this scenario? Is this a through cut?

Exactly. Why not just cut the holes with the jigsaw and clean up the edge with a straight bit? MUCH quicker and much less wear on your bit. As noted, MDF resin can be very hard on cutting edges. Just make a template for your router to butt against (kinda like an edge guide for a circle) and your home free...for a lot less $$$.

Good luck,
Greg

[gychang]

Exactly. Why not just cut the holes with the jigsaw and clean up the edge with a straight bit? MUCH quicker and much less wear on your bit. As noted, MDF resin can be very hard on cutting edges. Just make a template for your router to butt against (kinda like an edge guide for a circle) and your home free...for a lot less $$$.

Good luck,
Greg

I use the Jasper for different speaker projects and making a different jig each time is not practical. I will try jigsaw first and see if I can be relatively accurate, thanks much for the suggestion.

gychang

[drumpriest]

To use the router, you'd need a template, after you've jigsawed it away. Circle cutting jigs mount at the center of the circle, if you've cut away that center, there's nothing to attach to.