SOlid TC versus other bits

[BobL]

Anyone have experience in using Double Flute Solid Carbide Straight Bits like http://www.timbecon.com.au/products/freud-router-bits-520_0.aspx

I was routing some 20mm deep x 1/4" wide blind slots in Jarrah last weekend and although I was attempting to do this in two passes I still managed to snap the bit. As I'm going to have to buy another I was thinking - is it worth it going to something tougher like the solid carbide bit?

[Ashore]

Not double flute ones but I do ust a solid tugnsten carbide single flute bit 3.6mm for cutting slots for perspex to slide in on some display boxes
Did have a normal one at 4mm and snapped it doing 5mm deep cuts in tassi oak, but so far the solid TC has been great,

Rgds

[Rocker]

Anyone have experience in using Double Flute Solid Carbide Straight Bits like http://www.timbecon.com.au/products/freud-router-bits-520_0.aspx

I was routing some 20mm deep x 1/4" wide blind slots in Jarrah last weekend and although I was attempting to do this in two passes I still managed to snap the bit. As I'm going to have to buy another I was thinking - is it worth it going to something tougher like the solid carbide bit?

BobL,

I always use solid carbide spiral upcut bits for routing mortices. Although it is possible to use straight bits for this job, if you take very shallow passes, spiral upcut bits clear the waste much more efficiently. Even with spiral upcut bits, I only rout a maximum depth of 6 mm in each pass. 10 mm passes are much too deep for a straight bit, so I am not surprised that you broke one attempting it. You will find that 8 mm and 9.5 mm spiral upcut bits cut mortices far more easily and effectively than straight bits of the same diameter.

You can get solid carbide spiral upcut bits from Mcjing, http://www.mcjing.com.au/routerbits/index.htm , or from Carbatec.

Rocker

[outback]

I'm with Mister Rocker on this, 10mm is a heap of pressure on a lil 1/4 bit. SPiral upcuts are the way to go, heaps gooder than normal ones. However they won't take too well to big deep cuts like 10mm though.

[BobL]

Thanks Guys, I clearly expecting too much from using such a bit in jarrah. Rocker, thanks for the Mcjing link, their prices seem about half of prices here in the West.

One more question, what's the difference between downcut and upcut bits? Reading around I think it has something to do with the direction of waste ejection. Upcutters pull the material towards the shank and downcuts push it towards the tip? Does this mean that upcutters are better for blind slots and downcutters are better for open slots if you want the waste ejected at the tip?

Thanks again

[Greg Q]

In theory, yes. In practice, from what I have seen, if there is any plunging required the upcuts are very much better. I use carbide upcuts with no problems EXCEPT solid 1/4" bits, two of which I had snap under what I thought was normal use. (Freud). No issues with larger Freud or CMT bits.

Greg

[BobL]

In theory, yes. In practice, from what I have seen, if there is any plunging required the upcuts are very much better. I use carbide upcuts with no problems EXCEPT solid 1/4" bits, two of which I had snap under what I thought was normal use. (Freud). No issues with larger Freud or CMT bits.

Greg

Thanks Greg.

Checking prices on (1/4" diam x 1" cutting length) upcutters here in the West I see prices of between $42 and $58. Then McJing has these for $22 ???

[Greg Q]

I'm not familiar with McJing, so I can't comment. Another option to consider is buying surplus industrial cutters on eBay. Last year I snagged a lifetime supply of Titanium Nitrate coated end mills for about $2.00
each shipped (in a lot of 50 from the America.). These are surprisingly durable and strong. Earlier this year I cut 300 mortises with no visible wear on the bit. (Yet they too will sometimes snap when trying to mill too fast sideways.) These same bits will plunge rapidly into an aluminium billet and take aggressive sideways cuts after plunging 30-40 mm.

I recall now that the times I have had problems was when I plunged in several locations along the length of the slot, then tried to take a clean-up pass. The bits don't like trying to go from material to void repeatedly-you are better plunging to a moderate depth (15 mm ?) and taking a sideways pass, then stepping down to the next depth, etc. SEE TERMITE"S TIP BELOW: 2/3 BIT DIA MAX DEPTH OF PLuNGE
One more thing: Make sure that your collet is in good shape and clean. Spiral upcuts or endmills will try to pull out of the collet because of the thrust generated by the flutes. One of these bad boys pulling out of the collet at 18,000 rpm will get your undivided attention.

[BobL]

Thanks Greg, the tip about the material-void passes agrees with my limited experience, as does the sideways pressure / cutter climbing up out of the collet. A couple of weeks ago my 5/16 jumped out but it was decidedly undramatic. It just danced about a bit between the material and the fence for a few seconds - maybe it would have been more dramatic if it had hit some metal.

[Greg Q]

Yeah, if the bit is in a slot when it leaves the collet it's merely fascinating, and sometimes insulting to the work piece. My little incident happened when I was using a collar for edge trimming-the bit ricocheted around the shop too fast to see.

One thing that I forgot to mention is that end mills come in four flute variety too, which is not what you want for woodworking as the chip clearance rate isn't good enough. If you go looking, try Melin brand 2-flute. They're high quality, and while the new cost is $25.00-$50.00, the eBay surplus price is a fraction of that.

Greg

[Termite]

Rule of thumb for cutting with a straight bit is:- depth of cut no more that 2/3 of cutter diameter. If cutting MDF then cut that down to 1/2 diameter.

[mat]

Bob

Not all solid carbide bits are equal. McJings are chinese. I believe the generic carbatecs are also. Northwood's are made in Taiwan and then others such as LV are Onsruds made in the US. CMT's probably Italian.
Carbitool in Voctoria also have solid carbides - not sure if they are locally made.

[Wizened of Oz]

Solid carbide bits are extremely brittle, as a few above have indicated.
Having snapped a few I've given up on solid carbide upcut spiral in the 1/4" size and got HSS ones from Lee Valley. Still use 3/8" and 1/2" solid carbide(very carefully).

[Greg Q]

Rule of thumb for cutting with a straight bit is:- depth of cut no more that 2/3 of cutter diameter. If cutting MDF then cut that down to 1/2 diameter.


Thanks Termite. I was just going to go back and correct my 15 mm advice above. I don't know what I was thinking, but it sure wasn't metric.:eek:

[BobL]

Thanks guys, all good info to store away in the old noggin!


Rule of thumb for cutting with a straight bit is:- depth of cut no more that 2/3 of cutter diameter. If cutting MDF then cut that down to 1/2 diameter.

Crikey! no wonder I was having problem with my 9 mm jarrah passes using a 6.4mm bit. Me thinks I may have spent too much time routing crapiata.

Out of interest, why is your recommendation for MDF LESS than other timber, I would have though that something like red gum would be much harder on a router bit than MDF?

[Greg Q]

MDF produces very fine dust which doesn't eject from the cut very well, and this can choke and overheat the cutter.

[Termite]

MDF produces very fine dust which doesn't eject from the cut very well, and this can choke and overheat the cutter.
Yep, and MDF is full of glue and this overheats the cutter as well.