3/4" dogs in 20mm dog holes

[Mike Holbrook]

I have been reading old posts on this subject. One post seems to indicate that 3/4" .75" dogs work in 20mm (.7874" holes). I am still wondering how well. I invested years ago in: Veritas Surface Clamp, a Veritas Hold Down, Veritas Bench Anchors, Veritas Round Bench Dog, Veritas Wonder Dog, all 3/4". I also have a Festool MFT table and Festool clamps which of course uses 20mm.

To make things worse I drilled holes in my compact Hammer workbench using my Wood Owl marked 3/4" Ultra Smooth drill bit, which as it turns out is actually 19mm (.748"). The holes I drilled are just a little too tight for my Veritas clamps and dogs, especially the ones with the long posts.

I hope to remedy the situation by buying either the Veritas UJK Parf Guide Drilling System or a 20mm Dog Bushing with 25mm bit to drill the hole for the bushing and 20mm drill bit designed to be used with the bushing. I am hoping to drill out the old holes with one of the jigs designed to make "perfect" 20mm holes.

The Veritas 20mm Bushing (& bit for it) look like they would be more accurate at drilling through the 3 1/2 and 2 1/2" sections of my workbench but the Parf Guide looks better at laying out holes. I have plans to build other workbenches too, and would like to standardize on the 20mm holes so I can use Parf & Qwas dogs and my Festool clamps.

[lowell holmes]

I might take a round file to the holes. A rasp might work as well, but it will be more aggressive.

[Bryan Lisowski]

I would bring a caliper to the big box store and find a dowel that is a little thin and then wrap a piece of sand paper around and sand until fit is right.

[Mike Holbrook]

So far my Iwasaki rasp and rat tail file have been very slow at reaming 3 1/2 & 2 1/2 inch deep holes in hardwood. I have a few dowels that are lesser diameter, may try that on the existing holes.

I am interested in a system to drill future 20mm holes with too though. Part of the issue may be that the holes are not exactly straight. I just tried doing it like chair legs with a sliding bevel & square to approximate 90 degrees. I was wondering if those who have used the Parf Guide Drilling System and or the Veritas 20mm bushing and bit might comment on how they worked?

[Lee Schierer]

Can you borrow a 3\4" reamer from a machine shop.

[Dave Zellers]

To add to Bryan's thought, I fixed my too- tight dog hole problem by cutting a thin kerf down lengthwise 3" in a 1/2" dowel then inserting a long strip of 80 grit sandpaper and wrapping tightly until it just fits in the hole, cut the sandpaper at that point, then chuck that in a drill. It works rather quickly.

[Mike Holbrook]

I have dowels and sticky 80 grit paper so I am sure I can rig something up to "ream" the 19mm Wood Owl bit holes out to 3/4".

I am actually more interested in the best way to drill very straight, exactly 20mm holes, in a properly spaced pattern, probably using the Festool 96mm spacing pattern. The problem I see with the Veritas Bushing and drill system and the Parf Guide Drilling system is neither is designed to drill through 3+ inch

[Peter Kuhlman]

You probably know this ----
Need to know that all the L clamps used for tops like Festool's MFT only work with a top no more than 3/4" thick. Any thicker and you can't rotate the bottom of the L to stand the clamp up.

[Andy Giddings]

Parf guide system works extremely well, accurate and vertical. Of course this was drilling holes in 3/4 MDF not into 3 1/2 inch hardwood :-)

[Mike Holbrook]

I am trying to get an order for some parts in at LV before the free shipping sale ends. I do not currently have a 20mm bit to test with. Wood Owl apparently makes a 19 and 21mm (7 1/2" long) drill bit but not a 20, which seems odd.The actual issue is most drill bits will not drill through a 3" bench top after fitting through a guide system.

My issue with the Parf Guide Drilling System is it appears to be oriented towards drilling holes in material around 3/4" thick which may or may not help drilling 3+" holes. The information I am looking at does not even say how long the shaft of the drill bit is. The Guide Bushings drill bits are 6" long with 3 5/8" of fluting. The Bushing drill bits work in Bushings designed to fit in 1 1/2" stock, which means they will only drill a hole a little over 2" deep. It may be that once a 2" hole is drilled, the 6" bit can be placed in the 2 inch hole, using the hole as the guide, to drill out the remaining 1".

If I buy both the Parf Guide Drilling system and a 20mm Bushing guide and 6" 20mm drill bit I am still not sure I will be able to drill 3" holes without yet a third 20mm drill bit with a longer shaft.....which so far I have not been able to locate. I think the Parf Guide drill bit's, round undersized, shaft is what rides in the Guide bushing, which I believe means the 6" Bushing Guide drill bit or any other longer bit will probably not work in it. Using the Parf Guide to mark/drill 3mm holes, then drill 3/4" deep 20mm holes with the guide and carbide drill just gets me 3/4" deep. Then having to come back with a 20mm bushing guide to get the hole 2" deep, then remove the bushing to drill the extra inch seems a little complicated.

[Andy Giddings]

Mike, Peter Parfitt (the inventor of the Parf guide system) is active over on the Festool Owners Group concerning the product. I suspect if you asked a question over there you'd get some input (thread is here http://festoolownersgroup.com/festool-jigs-tool-enhancements/parf-guide-system-review/)

[Mike Holbrook]

Thanks for that link Andy. I just found a YouTube video Peter did which suggests that one can actually make a minimum 1" deep hole with his stock drill bit. He suggests that the bottom of deeper holes can be "carefully" bored out using the top part of the hole as the guide. The top of the hole is where the hole needs to be accurate.

I was very interested in the Medite Smartply, moisture resistant (MR) MDF he uses in his demos. Instead of making a bunch os sawdust when drilled it actually makes round/solid shavings, like a hand plane does. Problem is it looks like it is only sold in Europe. I guess I have multiple questions to ask at the Festool Owners Group. I have posted there years ago should have thought of that option.

[Andy Giddings]

If you want moisture resistant MDF in the US, I know that Medex is available (at least in the DFW area)

[lowell holmes]

I would probably try enlarging the hole with a 3/4" auger bit in my brace,

[Steven Hosler]

If you have the Festool LR 32 system (drilling guide and guide rails), you can make very accurate MFT replicas. There are several videos on YouTube on how to do this. I used the method that uses guide dogs you attach to the guide rail. Every third hole in the LR 32 guide rails are exactly 96 mm apart. I ran straight edges down the rows and columns (12 rows, 9 columns) and they were dead on. I also checked the 90 degree accuracy at several places and it was also dead on. Depending on the plunge capability of your router, it may be able to make the 3" depth. I just used 3/4" MDF.

[Rick Potter]

I bought one of those Armor 1 1/2" thick predrilled tables from Rockler. Turns out the holes were about 1/32" shy of being 3/4 (sorry, don't speak metric). A true 3/4" dowel would not go in the hole, but a HD metric 3/4" dowel fits. I ended up using a 3/4" metal working twist bit, and ran it through a few of the holes, came out fine. My drill bit was a cheapie, from a show, and has about 3-4" useable depth.

You might consider doing every other hole, to keep options open.

[David J Blackburn]

Can't you go as deep as possible with the parf system (or whatever), then drill a narrower hole in the middle of what remains, and then take a long trim/pattern router bit (I always forget - whichever one has the bearing on the top) to flush the roughed out/narrow bottom to the correct sized smooth top of the hole?

Even if you don't have a long enough bit, you could then finish it from the bottom with the other type of bit (pattern/trim).

I mean, that's tedious I suppose but it'd work.

[Mike Holbrook]

The LV 20mm that says it is 6" long with 3 5/8' of fluting may work if it actually is 20mm, but it is $34.80. I can buy two Wood Owl Ultra smooths, 7.5" fluted more of the way for less. The 18" Wood Owls around that size are less too. 20mm is about .787" so it isn't far from .75. 19mm (.748) is very close to .75. Some of my Veritas hardware sort of work in the 19mm holes, will work better with use/work on the holes. Longer shafts seem to have more trouble.