Holdfast holes - is there really much science behind palcement?

[shafiq]

Hi all. After many many moons just getting away with workholding using Irwin clamps, my Zeiss, Sheffield Tool Co, Axminster QR and sometimes my Stabila 1m level... or whatever else comes to hand. I've finally got a couple of nice Holdfasts from the UKW forum. Apparently made by an ex forum member or something like that and spoken highly of by WoodHaven shop.

Sorry for the background. So, I'm going to buy a 19mm auger type bit for my drill and have read briefly the piece by Chris Schwarz. But, do I really need to overthink where I make my holes! I'll eventually (maybe, but assume for benchdogs the holes don't go all the way through the bench!?) buy some 19mm benching to multipurpose the holes and also add a side platform to the joist/bench.

Any info is good info

 

[shafiq]

That's my outdoorsy bench (now slightly warped from a winter of outdoors) and these are the holdfasts. I'm going to get a 19mm bit now unless someone stops me.

I was thinking about 3 holes for now and there's 2 holdfasts being delivered this afternoon.

Thread 'Holdfasts'

Mar 15, 2023

Could someone please measure the diameter of the shaft of their holdfast. I have a local blacksmith who has proven to be extremely cheap and good, and I want to get a price from him for making one or two.

• Mike G
• Replies: 18
• Forum: General Woodworking

 

[Accipiter]

Not fully answering your question but... I bought an MFT top, pre drilled, yet to use/fit... the holes go all the way through. Admittedly it's 19mm or 25mm thick but would have to check for you if you want?

Some MFT tops have 20mm holes - some 19mm. Confusing...

 

[shafiq]

Not fully answering your question but... I bought an MFT top, pre drilled, yet to use/fit... the holes go all the way through. Admittedly it's 19mm or 25mm thick but would have to check for you if you want?

Some MFT tops have 20mm holes - some 19mm. Confusing...

Hmmm. That answers it nicely thanks Accipter sir. I need to get this log processed (with the human milling machine - me... I feel rather poorly after getting about 4 boards out of it and a Disston saw already) as its getting in the way of my bike riding. Can't handle it sat outdoors for another year!! 2 or 3 more massive logs to process after this, but when I've recovered.

 

[Accipiter]

Here's a photo of the MFT top... it's 19mm thick and follows the 96mm centres for the holes. For some more information regarding such tops and the 'bench dog' fittings there are plenty of videos on YouTube to give the visual information of making such (should you choose) and the different size holes/dogs and reaming out if you 19mmholes but get 20mm dogs...

Good job I went to take the photo... I'd put some eggs on to boil... and *forgot* - until I walked into the kitchen... guess they're now well HARD boiled

 

[shafiq]

Thanks Accipiter. Yes, I guess a 19mm drill bit is a good shout. Going to buy now.

 

[Accipiter]

Normally it would be a 19mm router cutter so making sure the holes are vertical... how good are you with a drill and bit for getting verticals? . Either way have fun

 

[shafiq]

Normally it would be a 19mm router cutter so making sure the holes are vertical... how good are you with a drill and bit for getting verticals? . Either way have fun

I usually measure thrice, cut twice. This time I plan yo make a jig to go with the roofers square and other square. I'm gonna get it straight, first time

 

[Steve Maskery]

I suggest that you try it on a piece of scrap first. A 19mm top seems very thin to me. Holdfastds work by racking between the top of the hole and the bottom, and if these two points are very close together, there is nothing to rack against.
I'm not saying they won't work, they may work fine, but just check first.
S

 

[Accipiter]

I mentioned 'thickness' in relation to the *MFT* top holes Steve.. @shafiq hasn't stated a thickness of/or the *material* he may use. I understood he was asking in respect of the size of hole - and if they go all the way through.

Hold fasts are usually used on solid wood workbenches. I know that the MFT top I posted a pic of wouldn't stand up to such usage being MDF.

 

[shafiq]

I suggest that you try it on a piece of scrap first. A 19mm top seems very thin to me. Holdfastds work by racking between the top of the hole and the bottom, and if these two points are very close together, there is nothing to rack against.
I'm not saying they won't work, they may work fine, but just check first.
S

Steve. I think you misunderstood. 19mm hole in a joist type top. Its about 70mm thick so that hows far I will drill down Steve.

 

[shafiq]

Anyway, holdfasts are here. 19mm thick auger bought from Wickes. Will double check thickness, make a squaring jig and get em made.

 

[Woodbloke]

I suggest that you try it on a piece of scrap first. A 19mm top seems very thin to me. Holdfastds work by racking between the top of the hole and the bottom, and if these two points are very close together, there is nothing to rack against.
I'm not saying they won't work, they may work fine, but just check first.
S

Agreed Steve. I'd also add that MDF of any denomination is probably too soft so continued use by a big lumpy iron holdfast in the holes is liable to distort or damage them. Better I fancy in a thick (as you say) hardwood bench top.

I have no experience of these bad boys having always used a Record one wot sits in an iron collar in the bench top - Rob

 

[AndyP]

Does this help.
19mm holes spaced a just a little less than the reach of the holdfast which are also the ones made by a member on UKW many years ago. Top is made form two sheets of MRMDF and one chipboard ex-office desk and lipped with beech

 

[shafiq]

Before I start drilling into my joist/bench. Just to confirm that my holdfasts are 18mm Richard James (or whatever the UKW guy was who made them back then).

I'm assuming then that a 19mm hole would be quite appropriate and I'll do a test run/fit shortly. Have made a 'squaring up' jig but won't use it just yet as I had to glue it up rather than pilot holes and screws!!

 

[shafiq]

Does this help.
19mm holes spaced a just a little less than the reach of the holdfast which are also the ones made by a member on UKW many years ago. Top is made form two sheets of MRMDF and one chipboard ex-office desk and lipped with beech
View attachment 54697

Thanks for this btw Andy. Helps alot.