Hold fasts problems

[AdamAronson]

All,

 

Been loving my Roubo! Thanks again to Marc and and the fellow Guild members for the help.

 

I'm looking for suggestions on how to get to actually make use of my hold fasts. Simply put ... they don't hold. I can't get them to grip in the holes I drilled in my 4" thick Ash top.

 

I drilled the holes by hand with a power drill and a 3/4" brad point bit. As a result some of my holes are not 100% square to the top and some are slightly irregular. Could this be the problem? If so, would the best remedy be to plug the holes with 3/4" Ash dowels and glue and then re-drill with a guide?

 

I've tried sanding the shanks of the hold fasts with 80 grit paper... not helping. Any other suggestions? Could the hand drilling of the holes have caused me this much trouble?

 

The other thing I wondered... could the inside of the holes be burnished smooth preventing the hold fasts from "sticking"?

 

Thanks,

Adam

[thewoodwhisperer]

This may be a dumb question but how hard are you hitting them? I was never a big holdfast user until my Roubo and I was actually a little surprised by how hard I have to hit them. But when they grab, they REALLY grab. 

[jhl.verona]

I think the 4" thickness may be the problem. Though you didn't specify which holdfasts you're using, the Gramercy holdfasts specify a thickness of 2". Any thicker and they suggest counter boring a larger hole underneath (see the video on the page linked).

 

Although a simple tool, they do need some play in the hole to be able to grip properly, too much and they'll pop out under force, too little and they simply won't grip. 

 

HTH

 

John

[AdamAronson]

Interesting video. My top is 4" think and yes, I am using the Gramercy Holdfasts. Has anyone else tried the counterbore with any success? The idea of drilling an inch from the bottom of each hole from underneath my bench brings tears of joy to my eyes.

 

I'm not hitting them lightly but I'm also not sledgehammering at them.

 

Is there no concern from the peanut gallery re: the slightly oversized and/or skewed holes?

 

A

[Eric.]

I also have to pound the hell out of mine to get them stuck.  But once they're stuck, ain't goin' nowhere.

[Trip]

==> My top is 4" think and yes, I am using the Gramercy Holdfasts. Has anyone else tried the counterbore with any success?

 

if you read CS's blog, he recommends a 1" counter-bore in a 4" top.  Gramercy also recommends this.  It also came-up in Marc's interview with Chris.  

 

I used the counterbore technique and don't have to really pound the holdfast -- more of a "sharp rap" to set.

[duckkisser]

if i understand the physics right your basicly just taping on the holdfast to nock the end at an angle in the hole.  if there is no where for the end to angle it cant hold.  imagine using a wedge in a door except its not a wedge its just a piece of flat wood that slide under the door.  not realy going to wedge itself to the door now is it.

[jhl.verona]

Well I don't have Gramercy holdfasts, actually mine are in wood, but the principle is the same. Duckkisser has it right, the longer the hole, the harder you'll have to hit the holdfast to get it to grip. There is a minimum too, of course. I have no idea what scale to use for hammering, light tap, to heavy blow perhaps? Anyway, Mr Underhill has it about right to me... a smart rap perhaps?

 

[Edit] Just saw hhh's post - so there you are then, the official 'required force' is a sharp rap, or smart rap if you prefer metric... [/Edit]

John

[Barron]

I drilled up from the bottom with a 1" bit and they work great. I hit them at the top a curve with a sharp rap to set them and hit them on the side ( the straight part) to loosen. It can take a couple of raps to get them loose. Try drilling one hole 1" diameter about an inch in from the bottom and see how it works.

[RenaissanceWW]

The skewed holes shouldn't be a problem and let me second some of the above with the sharp rap.  If you have to really pound them then you risk damaging the work in the process.  For that matter that harder you have to work to set them the harder you have to hit them to release.  I have used the Gramercy holdfasts in material 6" thick with no problem.  I wonder if they have changed the shape since the initial run when I got mine.

[skiback46]

I just got a pair of the Gramercy hold fasts, for use in my 4" thick maple top.  They didn't hold.  I used some 120 or 150 sandpaper sanding around (not up and down) the shaft and they hold great.  So if you sanded up and down I would first try sanding around the shaft before counterboring.

[AdamAronson]

Thanks much for all the responses. This past weekend I tried a combination of sanding the shafts of the holdfasts with 80 grit and counterboring from underneath with a 1" forstner. The combination of the two made all the difference. This makes me wonder if it wouldn't be worthwhile to have the holdfast shafts toothed a bit more.

 

Eh, in the mean time... I'm good.

 

Thanks again!

[SeventyFix]

I just received a pair of Gramercy holdfasts and other than a final sanding and Danish oil, my bench is finished.  My bench is made from hard maple. The bench top is 1/16" shy from the full 4" plans.  My holdfast holes are decent but far from perfect.  They were done with a spade bit.

 

Upon first use, the holdfasts wouldn't hold anything, no matter how hard I hit them (I dinged the benchtop while at it; it's first blemish).  I did not counter bore the 3/4" holes from the underneath as Gramercy suggests. 

 

I took a quarter sheet of 60 grit sandpaper and I wrapped it around the holdfast, twisting the stem in the paper 50 times.  Please note that you need to sand around the stem, not up and down.  You're removing some metal with this operation - expect to see a good amount of fine steel filings in the paper.  After a few minutes of sanding around each shaft, I tried it again.  This time it worked as it should and held firm.  Yes, a good whack from a leftover section of hard maple was required to set and release the holdfast.

 

One of the holdfasts held on the first try.  The other required additional sanding.  In the end, both worked well.  In conclusion, sand the stems circumferentially with rough grit sand paper first.  Do not counter bore the holdfast holes until you've decided that it's your only option.  In my case, a few minutes of sanding was enough to get the holdfasts to work properly.

[Coop]

Mine aren't Gramercy but they too didn't hold. I used a Forstner bit to drill the first two holes. After investigating, I saw that the holes were not straight by any means. It looked like a mole hole. I bought a dog hole bushing and 3/4" brad pt bit from Lee Valley and it made all the difference. Straight holes!