Min Shank Length

**HeadScratcher** · 9th May 2012, 08:25 PM

Just wondering what the minimum shank length required to hold a router bit firmly in the chuck we be.

Just received my new brass router guides today and the equivelant brass one is longer than the Makita one I bought locally.

In the picture I have roughly 20mm of cutter exposed, with a guide height of 13mm (33mm total to base) I am guessing that will still leave me about 5mm short when using an 18mm template and cutting 18mm MDF.

Carefully undoing the nut and measuring how much is being held, I measure 13mm being gripped on a 1/2" shank dia router bit.

My reckoning would be I need to buy a longer cutter... agree? disagree?

**hilton** · 9th May 2012, 09:37 PM

Cheaper to just cut the new guide bush but this may mess with the concentricity (ap?) of the bush.

It does look a bit long hey? You do get longer bits but they are mostly made for Leigh Dovetail Jigs.

**HeadScratcher** · 9th May 2012, 10:30 PM

The thought crossed my mind to cut the guide but that wont gain me anything since the length of the guide (13mm) is shorter than the thickness of the template (18mm), only if the guide was bottoming out on the material below would it help to shorten the guide.

I could make a thinner template but that would mean buying more MDF which also costs money.

**Template Tom** · 9th May 2012, 11:16 PM

Now you can see the reason for the 40mm Guide as the chuck will penetrate through to give you greater depth

**hilton** · 9th May 2012, 11:28 PM

Originally Posted by HeadScratcher

The thought crossed my mind to cut the guide but that wont gain me anything since the length of the guide (13mm) is shorter than the thickness of the template (18mm), only if the guide was bottoming out on the material below would it help to shorten the guide.

I could make a thinner template but that would mean buying more MDF which also costs money.

Essentially you've chosen the incorrect thickness of material for template making. I think you have three options;

1. Thinner template material
2. Longer shank/cutter
3. Router collet extension (I don't know if this will work specifically with your guide bush though)

**Template Tom** · 10th May 2012, 09:49 AM

Longer shank cutters are available from Carb-I-Tool here in Australia Long series, Solid carbide (single flute)3.2mm,4mm,4.8mm,5mm,6,mm.6.35mm

**HeadScratcher** · 10th May 2012, 10:39 AM

Originally Posted by Template Tom

Now you can see the reason for the 40mm Guide as the chuck will penetrate through to give you greater depth

The router tightening nut actually goes inside the guide, so not sure how much more I could gain from going deeper. I only pushed down as far as it stopped perhaps I could rotate the 3 step screw thing to allow it to go lower.

Getting back to the original question (because there are a few solutions, including making a new thinner template) but how much of the cutter shaft needs to be in the chuck to be considered safe?

**Breezy** · 10th May 2012, 03:00 PM

Originally Posted by HeadScratcher

Getting back to the original question (because there are a few solutions, including making a new thinner template) but how much of the cutter shaft needs to be in the chuck to be considered safe?

Read point 2 here CARB-I-TOOL Safety

**HeadScratcher** · 10th May 2012, 03:47 PM

Thanks Breezy

Great link, also told me what router speed I need as well.

Thread: Min Shank Length

Thread Tools

Search Thread

Min Shank Length

Similar Threads

8mm and 6mm shank router bits

Ring Shank Nails

Hex shank drill bits

Shank Size?

different router bit Shank size

Tags for this Thread

Posting Permissions