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Unistrut, have I got the correct lag/coach screw ?

 
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incova




Joined: 27 Nov 2006
Posts: 789
Location: london


PostLink    Posted: Mon May 03, 2010 2:29 am    Post subject: Unistrut, have I got the correct lag/coach screw ? Reply with quote


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Hi guys going to mount my Ampro 4600 and I was wondering if I have the correct lag/coach screws/bolts, i have a set of M8 coach/lag screws that are,

1 inch diameter(25mm) and 5 1/8 (130mm)of a inch long, just double checking if these correct to go into the joists, thanks.

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Nashou66




Joined: 12 Jan 2007
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Location: West Seneca NY


PostLink    Posted: Mon May 03, 2010 2:41 am    Post subject: Reply with quote

Those are huge!!! I used 3/8 inch by 4 inch.

Athanasios

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incova




Joined: 27 Nov 2006
Posts: 789
Location: london


PostLink    Posted: Mon May 03, 2010 2:45 am    Post subject: er oops Reply with quote

I was told to use m8!

should I just look for some smaller screws man? I dont want to use bolts that are to big lol!

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Tom.W




Joined: 09 Mar 2006
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PostLink    Posted: Mon May 03, 2010 3:41 am    Post subject: Reply with quote

M8 bolts are about 5/16 of an inch in diameter. 4 inches long should be just fine.
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garyfritz




Joined: 08 Apr 2006
Posts: 12023
Location: Fort Collins, CO


PostLink    Posted: Mon May 03, 2010 4:15 am    Post subject: Reply with quote

I also used 3/8" x 4" (about 10mm x 100mm). 4 bolts in each strut and it held my 180lbs without even noticing it. I'm quite sure my whole family (total weight about 600lbs) AND my projector could hang from those 8 bolts and be well within the safety limits.
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JustGreg




Joined: 07 Mar 2006
Posts: 3098
Location: Kenosha, WI


PostLink    Posted: Mon May 03, 2010 7:41 am    Post subject: Reply with quote

Yeah I also used ~3/8" x 4" lag bolts. Drill a pilot hole first and liberally apply soap to the bolts. You can use liquid soap if that's all you have. (A friend of mine used a lube that was more, erm, made for his wife. Embarassed OK...bring on the jokes! Thumbs Up )

The pilot hole keeps you from splitting the joist. Just don't drill a hole the same size as the bolt! Shocked I would recommend drilling a hole that's 2/3rds the diameter of the UNTHREADED part of the lag bolt. And when you drill the hole, do it in steps, eg, drill half the depth and back the bit out with the drill running and then drill the second half the depth. Use your drill motors highest speed and a sharp bit. This keeps the wood in the bore from becoming distressed. Let the drill do all the work...don't lean into it more than you have to to keep it going in.

I'd also use some thick washers on the bolts to help the bolt head share the load. You don't need lock washers but can use them if it makes you more comfortable sitting under it. Razz
I cut some thick and thin washers to use as shims to level the frame (Unistrut). Just cut a notch out of one side (of the washer). You can use a hacksaw but I used a vice and an electric grinder with a cutoff wheel.
I used those between the Unistrut and the joist to level the base of the frame. I didn't use turnbuckle nuts (hex shaped, ~2-3" long) one end with right hand thread, the other end with left hand thread) and 3/8" all-thread on the Unistrut bolted to the pj for leveling. My HT ceiling height required me to be a bit more creative.

If the ceiling isn't finished yet now would be a good time to install an inexpensive electric winch. I can't believe I muscled my Marquee 8500 up and down as many times as I did with nothing but chains and S hooks. The winch takes 'most' of the trepidation out of the process. You'll also be more likely to take it down and give the innards a good cleaning now and then if it isn't such a scary process.

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incova




Joined: 27 Nov 2006
Posts: 789
Location: london


PostLink    Posted: Mon May 03, 2010 11:22 am    Post subject: ok they are too big! Reply with quote

wow, ok, thanks for the information, not sure why I was recommended M8, they look something that belongs in a gun somewhere! I suppose if I did use them the pj would be very safe though? I will look at the M5 bolts that seems to be the size others are using so sounds sensible, I thought M8s would be the same size as the lags recommecnded on Curts write up about mounting pjs but once I got them it was clear they were not............................All I do is communicate with you guys its ridiculous I dont even know the size of bolts in the UK! I may as well be from the U.S or Canada lol! thanks again guys for the info, Tom I swear these are a inch in diameter do you think I got sent the wrong set?
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AnalogRocks
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Joined: 08 Mar 2006
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Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Mon May 03, 2010 4:33 pm    Post subject: Re: ok they are too big! Reply with quote

incova wrote:
.....All I do is communicate with you guys its ridiculous I don't even know the size of bolts in the UK!

.....I may as well be from the U.S or Canada lol!


......I swear these are a inch in diameter do you think I got sent the wrong set?


Are you sure you didn't get bolts that you swear are 254mm in diameter EH? Mr. Green

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incova




Joined: 27 Nov 2006
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Location: london


PostLink    Posted: Mon May 03, 2010 4:38 pm    Post subject: these? Reply with quote

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280374624592&ssPageName=ADME:B:EOIBSA:GB:1123
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AnalogRocks
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PostLink    Posted: Mon May 03, 2010 4:40 pm    Post subject: Reply with quote

Shouldn't there be a grade rating on those e.g. grade 5 grade 8? OR are the metric bolts rated as M5, M8 etc?
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garyfritz




Joined: 08 Apr 2006
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Location: Fort Collins, CO


PostLink    Posted: Mon May 03, 2010 5:02 pm    Post subject: Re: ok they are too big! Reply with quote

AnalogRocks wrote:
incova wrote:
......I swear these are a inch in diameter do you think I got sent the wrong set?

Are you sure you didn't get bolts that you swear are 254mm in diameter EH? Mr. Green

Ah, how about 25.4mm Jeremy?? Mr. Green

incova, I'm a metric-knownothing USian, but http://euler9.tripod.com/bolt-database/22.html says M-series metric screws are specified by nominal major diameter, i.e. the outermost diameter of the threads -- thus an M10 screw should have a 10mm diameter. So if your screws look like they're an inch in diameter, they are most definitely not M8 screws!

I'd look for something more like M10, 100mm long.

And definitely follow Greg's advice to rub soap on the screw before torquing it in! It makes them go in MUCH easier. Without the soap you can snap off the screw if the hole is a bit too small. BTW I'd recommend normal bar soap, not wife lube. Laughing
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incova




Joined: 27 Nov 2006
Posts: 789
Location: london


PostLink    Posted: Mon May 03, 2010 5:59 pm    Post subject: thats what I thought! Reply with quote

thats what I thought!, ergo m6 m8 m10 etc! so how the hell I ended up with m25! I dunnoI am sure they have the order wrong now...........................
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Tom.W




Joined: 09 Mar 2006
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PostLink    Posted: Mon May 03, 2010 6:46 pm    Post subject: Reply with quote

Metric conversion chart...

http://mdmetric.com/tech/cvtcht.htm
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AnalogRocks
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Joined: 08 Mar 2006
Posts: 26690
Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Mon May 03, 2010 11:50 pm    Post subject: Re: ok they are too big! Reply with quote

garyfritz wrote:
AnalogRocks wrote:
incova wrote:
......I swear these are a inch in diameter do you think I got sent the wrong set?

Are you sure you didn't get bolts that you swear are 254mm in diameter EH? Mr. Green

Ah, how about 25.4mm Jeremy?? Mr. Green


Ooops missed my period Embarassed

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garyfritz




Joined: 08 Apr 2006
Posts: 12023
Location: Fort Collins, CO


PostLink    Posted: Tue May 04, 2010 2:46 am    Post subject: Reply with quote

Not touching that one... Laughing
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Tom.W




Joined: 09 Mar 2006
Posts: 6637



PostLink    Posted: Tue May 04, 2010 5:48 am    Post subject: Reply with quote

Child support ?

Wink
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JustGreg




Joined: 07 Mar 2006
Posts: 3098
Location: Kenosha, WI


PostLink    Posted: Tue May 04, 2010 7:27 am    Post subject: Re: ok they are too big! Reply with quote

AnalogRocks wrote:
garyfritz wrote:
AnalogRocks wrote:
incova wrote:
......I swear these are a inch in diameter do you think I got sent the wrong set?

Are you sure you didn't get bolts that you swear are 254mm in diameter EH? Mr. Green

Ah, how about 25.4mm Jeremy?? Mr. Green


Ooops missed my period Embarassed

Wow! He gets a laugh AND another post. Thumbs Up

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"Is it ignorance or apathy? Hey, I don't know and I don't care!" --Jimmy Buffett
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